What is ZMA supplement

ZMA is short for zinc magnesium aspartate (ZMA). ZMA supplement is a commercial supplement containing zinc monomethionine aspartate, magnesium aspartate, and vitamin B-6 (ZMA). ZMA supplementation is based upon the rationale that zinc and magnesium deficiency may reduce the production of testosterone and insulin like growth factor (IGF-1) ¹. Consequently, ZMA supplementation is advocated for its ability to increase testosterone and IGF-1, which is further suggested to promote recovery, anabolism, and strength during training.

Two studies with contrasting outcomes have examined the ability of acute ZMA administration to increase anabolic hormone concentrations. Initially, Brilla and Conte ² reported that a zinc-magnesium formulation increased testosterone and IGF-1 (two anabolic hormones) leading to greater strength gains in football players participating in spring training while Koehler et al. ³ reported that ZMA supplementation increased serum zinc and excretion, but failed to change free and total testosterone levels. Wilborn et al. ⁴ had resistance trained males ingest a ZMA supplement or placebo in a double-blind fashion and resistance train for 8 weeks and found no change in free or total testosterone, strength or fat-free mass (via DXA). It is noted that previous deficiencies in zinc may negatively impact endogenous production of testosterone secondary to its role in androgen metabolism and steroid receptor interaction ⁵. To this point, Brilla and Conte ² did report depletions of both zinc and magnesium, thus increases in testosterone levels could have been attributed to deficient nutritional status rather than a pharmacologic effect. More research is needed to further evaluate the role of ZMA on body composition and strength during training before definitive conclusions can be drawn. These findings are in contrast with the notion that ZMA supplementation can increase zinc and magnesium status, anabolic hormone status, and/or strength gains during training. These findings refute claims that ZMA supplementation in the amount and manner investigated provides performance enhancing effect to experienced resistance trained athletes. Whether higher levels of ZMA is needed to promote these adaptations in experienced resistance-trained males; ZMA supplementation may influence zinc and magnesium status and/or training adaptations in individuals with low zinc and magnesium status; and/or, whether ZMA supplementation may have therapeutic and/or performance enhancing effect in other populations (e.g., untrained, females, elders, etc) remains to be determined.

Zinc is an essential trace element involved in a range of vital biochemical processes and is required for the activity of more than 300 enzymes ⁴. Zinc-containing enzymes participate in many components of macronutrient metabolism, particularly cell replication. In addition, zinc-containing enzymes such as carbonic anhydrase and lactate debydrogenase are involved in exercise metabolism while superoxide dismutase protects against free radical damage. Zinc deficiencies have been shown to be higher in athletes and/or individuals who recreationally train ⁶. Zinc deficiencies in athletes have been suggested to contribute to impaired immune function and decreased performance ⁷.

Magnesium is a ubiquitous element that plays a fundamental role in many cellular reactions. More than 300 metabolic reactions require magnesium as a cofactor ⁴. Some important examples include glycolysis, fat and protein metabolism, adenosine triphosphate synthesis, and second messenger system. Magnesium also serves as a physiological regulator of membrane stability and in neuromuscular, cardiovascular, immune, and hormonal function. It also appears that there is a relationship between magnesium levels and cortisol, which has been reported to have negative effects on strength gains and muscle mass during training. A 1984 ⁸ study found that 14 days of magnesium supplementation decreased cortisol which would theoretically reduce catabolism during training. Another study reported similar results concluding that magnesium supplementation reduced the stress response without affecting competitive potential ⁹.

Athletes have been reported to have lower levels of zinc and magnesium possibly due to increased sweating while training or inadequate intake in their diets ¹⁰. Additionally, zinc and magnesium supplementation has been reported to have positive effects on resistance training athletes ¹¹. Theoretically, zinc and magnesium supplementation may enhance anabolic hormonal profiles, reduce catabolism, improve immune status, and/or improve adaptations to resistance training. In support of this theory, Brilla and Conte ¹¹ reported that ZMA supplementation during off-season football resistance training promoted significant increases in testosterone, IGF-1, and muscle strength. However, it is clear that more research is needed before conclusions can be drawn.

Lastly, companies selling nutritional supplements or promoting exercise, diet or supplementation protocols should develop scientifically based products, conduct research on their products, and honestly market the results of studies so consumers can make informed decisions.

Does ZMA work?

The major findings of this study was that dietary supplementation of a commercially available ZMA supplement resulted in a non-significant 12–17% increase in serum zinc levels but did not appear to effect anabolic or catabolic responses to resistance training, body composition, or training adaptations ⁴. These findings do not support contentions that ZMA supplementation during training increases muscle mass and/or enhances training adaptations. The following provides additional insight to results observed.

Zinc and Magnesium Status

Athletes have been reported to have low zinc and magnesium levels which have been found to negatively impact performance ¹². Brilla and Conte ¹¹ reported that ZMA supplementation (i.e., 30 mg zinc monomethionine aspartate, 450 mg magnesium aspartate, and 10.5 mg vitamin B-6) promoted a 30% increase in plasma zinc levels (0.8 ± 0.1 to 1.04 ± 0.14 μg/mL) and a 6.1% increase in plasma magnesium levels (19.43 ± 1.2 to 20.63 ± 0.73 μg/mL). In the a study by Wilborn and colleagues (subjects from Baylor University and the American College of Sports Medicine: age 27 ± 9 years; height 178 ± 8 cm, average weight 85.15 kg, and 18.6 ± 6% body fat) ⁴, fasting zinc and magnesium levels were within normal ranges (1.04 ± 0.24 to 1.08 ± 0.2 μg/mL) and training did not negatively impact on zinc or magnesium status. ZMA supplementation promoted only a modest but non-significant increase in plasma zinc levels (12–17%) while magnesium levels were not significantly affected. These findings indicate that within the population and sample tested, ZMA supplementation had no discernable effects on plasma zinc or magnesium status. While the present study did not assess tissue levels of these minerals, these findings suggest that ZMA supplementation may not be needed or beneficial in this population of athletes. In support of this finding, Lukasi ⁶ concluded that although some studies ¹³ have suggested that zinc and magnesium levels are diminished in athletes, most athletes get adequate dietary intake of booth zinc and magnesium.

Training Adaptations

ZMA supplementation has been purported to increase zinc and magnesium status, anabolic hormones, and promote greater gains in strength during training. In support of this contention, Brilla and Conte ¹¹ reported that ZMA supplementation significantly increased free testosterone, IGF-1, and isokinetic strength gains during training. However, the results of another study do not support these findings ⁴. In this regard, ZMA supplementation had no significant effects on total and free testosterone, IGF-1, growth hormone, cortisol, the ratio of cortisol to testosterone, or muscle and liver enzymes in response to training ⁴. Moreover, no significant effects were observed between groups in changes in 1-RM strength, upper or lower body muscle endurance, or anaerobic sprint capacity. Interestingly, while some contend that ZMA supplementation may increase muscle mass during training, the Brilla and Conte ¹¹ paper reported that ZMA supplementation had no effect on body mass changes during training. Results of the this study support these findings in that ZMA supplementation had no significant effects on body mass or DEXA determined body composition values ⁴. However, it should be noted that some potentially favorable trends were observed in fat free mass, fat mass, and body fat that deserve additional study.

What works?

Strong evidence to support efficacy and apparently safe

ß-alanine

ß-alanine, a non-essential amino acid, has physical performance enhancing (ergogenic) potential based on its role in carnosine synthesis ¹⁴. Carnosine is a dipeptide comprised of the amino acids, histidine and ß-alanine, that naturally occur in large amounts in skeletal muscles. Carnosine is believed to be one of the primary muscle-buffering substances available in skeletal muscle. Studies have demonstrated that taking four to 6 grams of ß-alanine orally, in divided doses, over a 28-day period is effective in increasing carnosine levels ¹⁵, while more recent studies have demonstrated increased carnosine and efficacy up to 12 grams per day ¹⁶. According to the International Society of Sports Nutrition (ISSN) position statement, evaluating the existing body of ß-alanine research suggests improvements in exercise performance with more pronounced effects on activities lasting one to 4 minutes; improvements in neuromuscular fatigue, particularly in older subjects, and lastly; potential benefits in tactical personnel ¹⁷. Other studies have shown that ß-alanine supplementation can increase the number of repetitions one can do ¹⁸, increase lean body mass ¹⁹, increase knee extension torque ²⁰, and increase training volume ¹⁸. In fact, one study also showed that adding ß-alanine to creatine improves performance over creatine alone ²¹. While it appears that ß-alanine supplementation can improve performance, other studies have failed to demonstrate a performance benefit ²².

Caffeine

Caffeine is a naturally derived stimulant found in many nutritional supplements typically as guarana, bissey nut, or kola. Caffeine can also be found in coffee, tea, soft drinks, energy drinks, and chocolate. Caffeine has also been shown to be an effective performance enhancing (ergogenic) aid for aerobic and anaerobic exercise with a documented ability to increase energy expenditure and promote weight loss ²³. Research investigating the effects of caffeine on time trial performance in trained cyclists found that caffeine improved speed, peak power, and mean power ²⁴. Similar results were observed in a recent study that found cyclists who ingested a caffeine drink prior to a time trial demonstrated improvements in performance ²⁵. Studies indicate that ingestion of caffeine (e.g., 3–9 mg/kg taken 30–90 min before exercise) can spare carbohydrate use during exercise and thereby improve endurance exercise capacity ²⁶. In addition to the apparent positive effects on endurance performance, caffeine has also been shown to improve repeated sprint performance benefiting the anaerobic athlete ²⁷. Research examining caffeine’s ability to increase maximal strength and repetitions to fatigue are largely mixed in their outcomes. For example, Trexler, et al. ²⁷ reported that caffeine can improve repeated sprint performance but failed to impact maximal strength and repetitions to fatigue using both upper-body and lower-body exercises. In agreement, Astorino and colleagues ²⁸ revealed no change in upper-body and lower-body strength after resistance trained males ingested 6 mg/kg of caffeine. Similarly, Beck and investigators ²⁹ provided resistance trained males with 201 mg caffeine (2.1–3.0 mg/kg) and reported no impact on lower-body strength, lower-body muscular endurance or upper-body muscular endurance. Maximal upper-body strength, however, was improved. In contrast, other studies have indicated that caffeine may favorably impact muscular performance. For example, Goldstein et al. ³⁰ reported that caffeine ingestion (6 mg/kg) significantly increased bench press strength in a group of women but did not impact repetitions to fatigue. Studies by Duncan and colleagues ³¹ have examined the impact of caffeine on strength and endurance performance as well various parameters of mood state while performing maximal resistance exercise. Briefly, these authors have reported improvements in strength and repetitions to failure using the bench press ³² and other exercises ³¹. In addition to potential ergogenic impact, these authors also reported that caffeine significantly improved various indicators of mood state ³³, lowered ratings of perceived exertion and decreased perception of muscle pain ³¹ when acute doses of caffeine (5 mg/kg) were provided before maximal resistance exercise. As illustrated, when evaluating the research on caffeine for its ability to impact strength and muscular performance, the findings are equivocal, and, subsequently, more research is needed to better determine what situations may best predict caffeine’s ability to impact strength performance. For example, trained subjects have demonstrated more ergogenic effects compared to untrained subjects ³⁴. Also, people who drink caffeinated drinks regularly, however, appear to experience less ergogenic benefits from caffeine ³⁵. Some concern has been expressed that ingestion of caffeine prior to exercise may contribute to dehydration, although several studies have not supported this concern ³⁶. Caffeine, from anhydrous and coffee sources are both equally ergogenic ²⁷. Caffeine doses above 9 mg/kg can result in urinary caffeine levels that surpass the doping threshold for many sport organizations. In summary, consistent scientific evidence is available to indicate that caffeine operates as an ergogenic aid in several sporting situations.

Carbohydrate

One of the best ergogenic aids available for athletes and active individuals alike, is carbohydrate. Optimal carbohydrate in the diet on a daily basis, in the hours leading up to exercise, throughout exercise and in the hours after exercise can ensure endogenous glycogen stores are maintained and support many types of exercise performance ³⁷. In this respect, athletes and active individuals should consume a diet high in carbohydrate (e.g., 55–65% of calories or 5–8 g/kg body weight per day) to maintain muscle and liver carbohydrate stores ³⁸. Research has clearly identified carbohydrate as an ergogenic aid that can prolong exercise ³⁸. For example, Below and colleagues ³⁹ provided research that ingesting carbohydrate throughout a time to exhaustion protocol after nearly an hour of moderate intensity cycling can significantly extend the time cycling is performed. Moreover, Widrick et al. ⁴⁰ systematically examined all four possible combinations of high and low pre-exercise intramuscular glycogen levels with and without carbohydrate provision before a standard bout of cycling exercise. When carbohydrate was provided, performance was improved. In addition to traditional endurance exercise models, Williams and Hawley ⁴¹ summarized the literature involving carbohydrate delivery and performance of team sports that are typically characterized by variable intensities and intermittent periods of heavy exertion and concluded that carbohydrate intake can increase performance. Pochmuller et al. ⁴² and Colombani et al. ⁴³ have critically pointed to the duration of the involved exercise bout, the intensity of exercise involved, and the fasting status of the individuals as key factors that may impact exercise performance. Further, Burke and colleagues ⁴⁴, Hawley et al. ³⁷ and Rodriguez et al. ⁴⁵ have all emphasized the importance of optimal carbohydrate delivery throughout various types of sport and recovery scenarios to support performance. Beyond ingestion, a growing body of literature has drawn attention to the potential impact of carbohydrate mouth rinsing as an ergogenic strategy. Initial work by Carter and colleagues ⁴⁶ where they demonstrated an increase in time to exhaustion performance while cycling after rinsing (but not swallowing) the oral cavity with a carbohydrate solution versus a no carbohydrate rinse revealed that receptors in the brain might be linked to the mere presence of carbohydrate in the mouth, which subsequently can work to improve various types of exercise performance. While this concept is still emerging, some ⁴⁷ but not all ⁴⁸ of the studies have supported the ability of carbohydrate mouth rinsing to increase performance. Another carbohydrate manipulation strategy has included utilizing high molecular weight carbohydrates solutions, in contrast to traditional low molecular weight beverages, to theoretically accelerate glucose absorption and energy availability. Importantly, the majority of the literature suggests that utilizing a high molecular weight solution can impart changes in oxidized substrates, or patterns of fuel usage, but appears to have no ergogenic effect on performance in males or females ⁴⁹.

Creatine monohydrate

Creatine supplementation is a well-supported strategy to increase muscle mass and strength during training. However, creatine has also been reported to improve exercise capacity in a variety of settings ⁵⁰. Specifically, and as discussed by Kreider et al. ⁵¹, studies have documented improvements in: a) single and multiple sprints, b) work completed across multiple sets of maximal effort, c) anaerobic threshold, d) glycogen loading, e) work capacity, f) recovery, and g) greater training tolerance. Consequently, team sports, individual activities or sports that consist of high intensity, intermittent exercise such as soccer, tennis, basketball, lacrosse, field hockey and rugby can all benefit from creatine use ⁵². Moreover, a 2009 study found that in addition to high intensity interval training creatine improved critical power ⁵⁰. Less research is available involving creatine supplementation and endurance exercise, but creatine’s ability to promote glycogen loading ⁵³ and storage of carbohydrate ⁵⁴, key fuels during endurance exercise, may translate into improved endurance exercise performance. Indeed, a 2003 study found that ingesting 20 g of creatine for 5 days improved endurance and anaerobic performance in elite rowers ⁵⁵. Since creatine has been reported to enhance interval sprint performance, creatine supplementation during training may improve training adaptations in endurance and anaerobic athletes, anaerobic capacity, and allow athletes to complete greater volumes of training at or above anaerobic threshold ⁵⁶. Notably, for athletes who struggle to maintain their body mass throughout their competitive season, creatine use may help athletes in this respect. Importantly and in addition to creatine being an effective ergogenic aid in a wide variety of sports, studies have documented these outcomes (improvements in acute exercise capacity, work completed during multiple sets and training adaptations) in adolescents ⁵⁷, younger adults ⁵⁸, and older individuals ⁵⁹. Regarding creatine and athletic performance, there appears to be a misunderstanding that creatine may result in muscle cramps and dehydration. However, based on many available studies, there is no clinical evidence that creatine supplementation will increase susceptibility of dehydration, muscle cramps, or heat related illness ⁶⁰.

Sodium bicarbonate (baking soda)

During high intensity exercise, acid (H+) and carbon dioxide (CO2) accumulate in the muscle and blood. The bicarbonate system is the primary means the body rids itself of the acidity and CO2 via their conversion to bicarbonate prior to subsequent removal in the lungs. Bicarbonate loading (e.g., 0.3 g per kg taken 60–90 min prior to exercise or 5 g taken two times per day for 5 days) as sodium bicarbonate has been shown to be an effective way to buffer acidity during high intensity exercise lasting one to 3 minutes in duration ⁶¹. Matson et al. ⁶² reported improvements in exercise capacity in events like the 400–800 m run while Lindh and colleagues ⁶³ reported that bicarbonate can improve 200 m freestyle swimming performance in elite male swimmers. Similarly, studies have reported the ability of bicarbonate to improve 3 km cycling time trials ⁶⁴. Marriott et al. ⁶⁵ published findings that sodium bicarbonate significantly improved intermittent running performance by 23% and reduced perceived exertion in male team-sport athletes. Interestingly, Percival and investigators ⁶⁶ reported that sodium bicarbonate supplementation resulted in significantly higher levels of PGC-1-α, a key protein known to drive mitochondrial adaptations. Finally, a meta-analysis by Peart and investigators ⁶⁷ involving sodium bicarbonate reported the overall treatment effect to be moderate at improving performance with nearly all measured ergogenic outcomes being influenced by the training status of the participants.

In addition, other studies have examined the potential additive benefit of ingesting sodium bicarbonate with either caffeine or beta-alanine. In this respect, Kilding et al. ⁶⁴ reported significant independent effects of caffeine and bicarbonate on three-kilometer cycling time trial performance, but no additive benefit. Alternatively, Tobias and associates ⁶⁸ also reported a significant improvement in upper-body power production in trained martial arts athletes after ingesting either beta-alanine or sodium bicarbonate, but noted a distinct synergistic improvement in upper-body power and performance when beta-alanine and sodium bicarbonate were ingested together. In contrast, Danaher et al. ⁶⁹ had eight healthy males supplement with either beta-alanine, sodium bicarbonate or their combination for 6 weeks in a crossover fashion before completing a repeated sprint ability test while cycling. While buffering capacity was increased, performance was only improved when beta-alanine was provided. Due to the mixed outcomes and relative lack of available studies, more research is recommended examining the synergistic impact of sodium bicarbonate and other ingredients. It is important to highlight that a common complaint surrounding the ingestion of sodium bicarbonate is gastrointestinal distress, thus athletes should experiment with its use prior to performance to evaluate tolerance.

Sodium phosphate

Phosphate is best known as an essential mineral found in many common food sources (e.g., red meat, fish, dairy, cereal, etc.) with key functions in bone, cell membranes, RNA/DNA structure and as backbones of phosphocreatine and various nucleotides. In addition, phosphate has been suggested to operate in an ergogenic fashion due to its potential to improve oxygen transport through modulation of 2,3-diphosphoglycerate (DPG) and other lactic-acid-buffering components. Sodium phosphate (NaPO4) supplementation has been reported in multiple studies to improve aerobic capacity by 5–12% ⁷⁰, anaerobic threshold by 5–10% ⁷¹, mean power output ⁷⁰ and intermittent running performance ⁷². Collectively these studies have employed a dosing regimen that required 1 g of NaPO4 to be taken four times daily for three to 6 days. Not all studies, however ⁷³, have reported ergogenic outcomes while factors that impact phosphate absorption, training status and gender posed as potential reasons why supplementation has not universally impacted performance. Brewer and colleagues ⁷⁴ reported modest (non-significant) effects of NaPO4 supplementation on repeated supplementation regimens in trained cyclists completing a time trial. Furthermore, West and investigators ⁷⁵ used a mixed gender cohort and concluded no change in VO2Max resulted after supplementation. Buck et al. ⁷⁶ were the first to solely examine the impact of NaPO4 in female athletes when they had 13 trained female cyclists complete a 500-kJ time trial after supplementing with either 25, 50, or 75 mg/kg of NaPO4 in a randomized, double-blind manner. No significant impact of supplementation was seen at any dosage leading the authors to conclude that females may not respond in the same manner as men. However, the same authors on two occasions ⁷⁷ examined the impact of NaPO4 in female team sport athletes completing repeated bouts of sprint running and found that NaPO4 significantly improved best and total sprint times when compared to a placebo. Consequently, the impact of gender on the ergogenic potential of NaPO4 remains unclear with consistent benefits in females when repeated sprints are performed but no such benefits during time-trial work.

Water and sports drinks

Adopting strategies to limit the loss of body mass due to sweating is critical to maintain exercise performance (particularly in hot/humid environments). People engaged in intense exercise or work in the heat are commonly recommended to regularly ingest water or sports drinks (e.g., 12–16 fluid ounces every 10–15 minutes) with the overarching goal being to minimize the loss of body mass commonly seen as a result of exercising in a hot and humid environment ⁷⁸. Below and colleagues ³⁹ demonstrated the independent ability of both fluid (no carbohydrate) and carbohydrate ingestion to significantly increase cycling performance. Moreover, when the two treatments were combined a synergistic impact on performance was observed. Studies show that ingestion of sports drinks during exercise in hot/humid environments can help prevent dehydration and improve endurance exercise capacity ⁷⁹. Of note and like carbohydrate, it appears that exercise factors such as the duration and intensity of the exercise bout operate as strong predictors of cycling time-trial performance ⁸⁰. Consequently, frequent ingestion of water and/or sports drinks during exercise is one of the easiest and most effective ergogenic aids due to its ability to support thermoregulation and reduce cardiovascular strain during prolonged bouts of exercise, particularly when completed in hot and humid conditions ⁷⁸.
Limited or mixed evidence to support efficacy

L-alanyl-L-glutamine

Operating under the same theoretical framework as glutamine, interest in supplementing with L-alanyl-L-glutamine has increased in recent years. The ingredient has two parts: L-alanine and L-glutamine, both of which are amino acids that are mainstays in the transamination processes involving amino acids. Rogero and colleagues ⁸¹ supplemented rats with L-alanyl-L-glutamine for the final 21 days of a six-week exercise training program. Supplementation did not impact time to exhaustion performance, but higher levels of glutamine were found when compared to a control group. Cruzat and Tirapequi ⁸² also reported increases in plasma and intramuscular glutamine along with an improved antioxidative profile in blood, muscle and liver tissue samples of laboratory rats. These results were extended in 2010 to also report an attenuation of inflammation and plasma creatine kinase levels in laboratory rats after exercise training ⁸².

Since 2010, five peer-reviewed studies have been published using human subjects. Hoffman and colleagues ⁸³ reported, in a group of ten physically active males, that L-alanyl-L-glutamine increased time to exhaustion on a cycle ergometer when exposed to mild dehydration stress. Two years later, the same research group reported that rehydration with L-alanyl-L-glutamine after 2.3% dehydration in a basketball scrimmage led to an improvement in basketball skill performance and visual reaction time when compared to water ⁸⁴. A 2016 study indicated that L-alanyl-L-glutamine maintained reaction time in an upper and lower-body activities after an exhaustive bout of treadmill running ⁸⁵. Finally, a 2015 paper determined that L-alanyl-L-glutamine significantly improved treadmill running performance when compared to no hydration ⁸⁶. Collectively this research indicates that L-alanyl-L-glutamine at dosages ranging 300–1000 mg per 500 mL of fluid can favorably influence hydration status and performance when compared to no fluid ingestion or water only ingestion.

Arachidonic acid

Arachidonic acid is a long-chain polyunsaturated fatty acid (20:4, n-6) that resides within the phospholipid bi-layer of cell membranes at concentrations that are dependent upon dietary intake ⁸⁷. Arachidonic acid is not found in high amounts in the typical American diet ⁸⁸. However, as little as 1.5 g per day of supplementation over a 50-day period has been shown to increase tissue cell membrane stores of arachidonic acid ⁸⁹. In skeletal muscle, there is evidence that arachidonic acid drives some of the inflammatory response to strength training via enhanced prostaglandin signalling ⁹⁰. Specifically, exercise liberates arachidonic acid from the muscle cell membrane via phospholipase A2 activation. Resultant free intracellular arachidonic acid is subsequently converted into certain prostaglandins (i.e., PGE2 or PGF2α) via cyclooxygenase (COX) enzymes ⁹¹, and these prostaglandins can signal associated receptors in an autocrine and paracrine manner to up-regulate signalling associated with increases in muscle protein synthesis. Roberts and colleagues ⁹² were the first group to examine the impact of arachidonic acid supplementation on changes in strength and body composition. Over an eight-week period, resistance-trained, college-aged males were supplemented in a double-blind fashion with either a placebo or arachidonic acid at a dosage of 1 g per day in conjunction with 90 g/day of whey protein. A significant increase in anaerobic peak power was found in the arachidonic acid group, but no other changes in strength or body composition were found. The second study by DeSouza et al. ⁹³ investigated the effects of arachidonic acid supplementation (0.6 g/day vs. placebo) in strength-trained college-aged males for 8 weeks with concomitant resistance training and without protein supplementation. These authors reported that lean body mass (2.9%), upper-body strength (8.7%), and anaerobic peak power (12.7%) significantly increased only in the arachidonic acid group. Mitchell and colleagues ⁹⁴ have also published data in 19 resistance-trained men who supplemented, in a double-blind, placebo-controlled fashion, with 1.5 g per day of arachidonic acid for 4 weeks and found that arachidonic acid supplementation did not impact acute changes in muscle protein synthesis and other mechanistic links to protein translation. The authors concluded that arachidonic acid supplementation did not support a mechanistic link between arachidonic acid supplementation and short-term anabolism, but may increase translation capacity. Given the limited human data and inconsistent nature (two positive outcomes, one negative outcome) of the findings regarding the efficacy of arachidonic acid, it is too early to recommend arachidonic acid at this time. In this respect, more chronic human studies testing different doses of arachidonic acid supplementation are needed to fully examine its safety and potential efficacy as a performance enhancing or muscle building aid. From a safety perspective and due to arachidonic acid being a known pro-inflammatory fatty acid, use of arachidonic acid may be contraindicated in populations that have compromised inflammatory health (i.e., inflammatory bowel syndrome, Chron’s disease, etc.).

Branched chain amino acids (BCAA)

Ingestion of BCAA (e.g., 6–10 g per hour) with sports drinks during prolonged exercise has long been suggested to improve psychological perception of fatigue (i.e., central fatigue). Accordingly, Mikulski and investigators ⁹⁵ used 11 endurance trained men to examine the impact of ingesting 16 g of BCAAs and 12 g of ornithine aspartate over a 90-minutes cycling exercise bout and found that the amino acid combination significantly improved reaction time, but no ergogenic impact was seen when BCAAs were ingested independently. Although a strong rationale and data exist to support an ergogenic outcome, mixed outcomes currently prevail as other studies have failed to report an ergogenic impact of BCAAs ⁹⁶. Consequently, more research is needed to fully determine the ergogenic impact, if any, of BCAAs. An important point to highlight surrounding BCAAs is the growing body of literature supporting their ability to mitigate outcomes surrounding muscle damage. In this respect, multiple studies have investigated and offered support for BCAA’s ability to promote recovery, mitigate soreness and attenuate losses in force production ⁹⁶, ⁹⁷.

Citrulline

Citrulline (2-Amino-5-(carbamoylamino)pentanoic acid or L-Carnitine) is endogenously produced from ornithine and carbamoyl phosphate in the urea cycle. In the body, citrulline is efficiently recycled into arginine for subsequent nitric oxide production through the citrulline-nitric oxide cycle ⁹⁸. Unlike arginine, citrulline catabolism is limited in the intestines ⁹⁹ as well as its extraction from hepatic tissue ¹⁰⁰ resulting in the majority of citrulline passing into systemic circulation before conversion to arginine [542]. Due to this and its non-competitive uptake for cell transport ¹⁰¹, oral citrulline supplementation has been shown to be more effective in increasing arginine ¹⁰² and activation of nitric oxide synthase (NOS) ¹⁰² as well as various biomarkers of nitric oxide ¹⁰³. Multiple studies have employed aerobic exercise models to examine citrulline’s impact on performance. Suzuki et al. ¹⁰⁴ showed that 2.4 g/day of L-citrulline for 7 days increased plasma nitric oxide metabolites, plasma arginine and 4-km time trial performance. Using a finger flexor exercise model and P31 nuclear magnetic resonance spectroscopy, Bailey and colleagues ¹⁰⁵ reported that 7 days of citrulline (6 g/day) significantly increased plasma arginine and nitrite levels and significantly improved VO2 kinetics and exercise performance. However, not all studies reported an ergogenic effect whereby Cunniffe et al. ¹⁰⁶ reported no impact of 12 g of citrulline malate on the performance of a single bout of high-intensity cycling. In addition to aerobic exercise research, three studies examined the impact of an 8-g citrulline dose while resistance training on various performance outcomes ¹⁰⁷. One study ¹⁰⁸ evaluated the effects on the number of repetitions performed for chin-ups, reverse chin-ups, and push-ups to failure in trained males. A second study ¹⁰⁹ evaluated the effect of citrulline supplementation on the number of repetitions performed for five sequential sets (60% 1RM) to failure on the leg press, hack squat, and leg extension exercises in trained males. The third study ¹⁰⁷ evaluated the effects of citrulline supplementation on the number of repetitions performed during six sets each of bench press and leg press exercises to failure at 80% 1RM in trained females. In all three studies, citrulline malate was shown to significantly increase performance during upper- and lower-body multiple-bout resistance exercise performance. Alternatively, Cultrufello and colleagues ¹¹⁰ reported that a 6 g dose of L-citrulline failed to impact both aerobic and anaerobic indicators of exercise performance. The role of malate in combination with citrulline is largely undetermined. Since malate is an important tricarboxylic acid cycle intermediate, this could possibly account for improvements in muscle function ¹¹¹. Therefore, it is presently unclear whether these benefits can be solely attributed to citrulline, as well as what role citrulline may play in aerobic and anaerobic performance.

Essential amino acids (EAA)

Research exploring the impact of essential amino acids with various forms of exercise has exploded. To date, it is well accepted that ingestion of at least 2 g of the essential amino acid, leucine, is required to stimulate cellular mechanisms controlling muscle hypertrophy ¹¹² and that ingestion of 6–12 g of a complete essential amino acid mixture are needed to maximize muscle protein synthesis ¹¹³. However, their impact on performance remains largely unexplored. While sound theoretical rationale exists and multiple acute study designs provide supportive evidence, it is currently unclear whether following this strategy would lead to greater training adaptations and/or whether essential amino acid supplementation would be better than simply ingesting carbohydrate and a quality protein following exercise. Moreover, very little research is available that has examined the ability of essential amino acids to impact exercise performance. For these reasons, many authors and review articles have encouraged the prioritization of intact protein sources over ingestion of free form amino acids ¹¹⁴ to promote accretion of fat-free mass, but, as mentioned, the impact of this recommendation on performance changes remains undetermined.

Glycerol

Ingesting glycerol with water has been reported to increase fluid retention, and maintain hydration status ¹¹⁵. Theoretically, this should help athletes prevent dehydration and improve thermoregulatory and cardiovascular changes. Although studies indicate that glycerol can significantly enhance body fluid, results are mixed on whether it can improve exercise capacity ¹¹⁶. Regarding endurance performance Coutts and investigators ¹¹⁷ had ten trained endurance athletes complete an Olympic distance triathlon under both placebo and glycerol hyperhydration (1.2 g/kg) + 25 mL/kg fluid solution) 2 hours before completion of each triathlon and reported that completion time was significantly improved with glycerol hyperhydration over placebo. These findings were corroborated by Goulet et al. ¹¹⁷ when they had six endurance-trained subjects hyperhydrate with glycerol or water 2 hour before a prolonged (2 hour) bout of cycling at 65% VO2max in hot conditions (26-27 °C) followed two-minute intervals at 80% VO2max and concluded that glycerol hyperhydration significantly improved performance. In contrast, Marino et al. ¹¹⁸ reported that a similar glycerol hyperhydration protocol did not improve the total distance covered when moderately trained cyclists completed a variable-intensity cycling protocol. Additionally, Goulet et al. ¹¹⁹ combined a hyperhydration strategy (1.2 g/kg glycerol + 26 mL/kg water) 2 h before commencing a two-hour cycling bout at 66% VO2max and 25 °C with consuming (500 mL/hour) a sports drink and reported that glycerol hyperhydration failed to impact cardiovascular or thermoregulatory functions as well as endurance performance. McKenna and investigators ¹²⁰ were one of the only research groups to examine glycerol’s potential to impact anaerobic power after glycerol hyperhydration. After following a double-blind hyperhydration protocol, male collegiate wrestlers lost 3% of their body mass from fluid and completed an anaerobic test where no impact on performance was found. Variable outcomes surrounding glycerol continue to undermine its potential and the ability to offer a recommendation for its use. Consequently, as pointed out by Goulet et al. ¹²¹, it is concluded that more research needs to be completed to work through the nuance surrounding glycerol’s potential efficacy, a key point previously summarized by Nelson et al. ¹²².

β-hydroxy β-methylbutyrate (HMB)

For several years, beta-hydroxy-beta-methyl-butyrate (HMB) has received interest for its ability to enhance training adaptations and performance while also delaying or preventing muscle damage ¹²³. Initial work by Nissen and colleagues ¹²⁴ showed significant increases in lean body mass and strength with doses 1.5 and 3 g/day in untrained males, with the 3 g dose showing additional benefits over the lower dose. Gallagher and colleagues ¹²⁵ indicated that a dose of 38 mg/kg/day (approximately 3 g/day) promoted improvements in fat-free mass, peak isometric force and isokinetic torque production, while no changes in maximal strength were seen. In agreement, Thomson and researchers ¹²⁶ had 22 resistance trained men supplement, in a double-blind fashion, with either HMB or placebo for 9 weeks and concluded that HMB was responsible for a significant increase in lower-body strength. Not all studies, however, have provided support. For example, Kreider et al. ¹²⁷ used a dose-response, placebo-controlled approach and concluded that three or 6 g of calcium-HMB did not impact body composition or strength adaptations in individuals experienced with resistance exercise after 4 weeks of supplementation and resistance training. Similarly, Hoffman and colleagues ¹²⁸ reported that HMB supplementation failed to improve anaerobic power production in collegiate football players, a conclusion which aligns with other previous studies ¹²⁹. Differences in training regimens (intensities), randomization, and supervision varied in the initial studies and may have contributed to the mixed results. HMB appears to have the greatest effects on performance when training intensity is maximized.

While many of the previous studies have examined, with mixed results, the ergogenic potential of calcium-HMB supplementation in active, recreationally active individuals, Durkalec-Michalski and colleagues completed three investigations ¹³⁰ that all sought to determine the impact of calcium-HMB supplementation in different athlete types. For instance, HMB supplementation (3 g/day) in elite rowers over a 12-week period significantly improved aerobic (VO2max, time to reach ventilatory threshold) performance markers and decreased fat mass when compared to changes seen with placebo ¹³¹. Later, Durkalec-Michalski and Jeszka ¹³² required 58 highly trained males to supplement with calcium-HMB (3 g/day) for 12 weeks. In this study, fat-free mass increased and fat mass decreased along with multiple markers of aerobic capacity when HMB was provided in comparison to a placebo. Most recently, HMB supplementation over 12 weeks in highly-trained combat sport athletes significantly increased (in comparison to placebo) several indicators of aerobic and anaerobic exercise performance ¹³⁰. The recent studies by Durkalec-Michalski and colleagues confirmed earlier works by Vukovich ¹³³ and Lamboley ¹³⁴ that HMB does have a positive effect on increasing aerobic capacity.

HMB is available as calcium-HMB and as free acid. In comparison to calcium HMB, HMB-free acid shows greater and faster absorption (approx. 30 min vs. 2–3 h) ¹³⁵. Much of the initial research used calcium-HMB with largely mixed outcomes while studies using the free acid form are more limited. Studies by Wilson and colleagues using the free acid form have indicated robust changes in strength, vertical jump power and skeletal muscle hypertrophy while heavy resistance training alone ¹³⁶ and in combination with supplemental ATP ¹³⁷, but others have critically questioned these outcomes ¹³⁸. A recent systematic review by Silva and investigators ¹³⁹ concluded that the free acid form of HMB may improve muscle and strength and attenuate muscle damage when combined with heavy resistance training but stated that more research is needed before definitive conclusions can be determined.

Nitrates

Nitrate supplementation has received much attention due to their effects on vasodilation, blood pressure, improved work efficiency, modulation of force production, and reduced phosphocreatine degradation ¹⁴⁰ all of which can potentially improve sports performance. Nitrate supplementation is most commonly consumed two to 3 h prior to exercise as beetroot juice or sodium nitrate ¹⁴¹ and is prescribed in both absolute and relative amounts ranging from 300 to 600 mg ¹⁴¹ or 0.1 mmol per kilogram of body mass per day, respectively ¹⁴². These dosing amounts appear to be well tolerated when consumed as both supplemental ¹⁴³ and supplemental sources ¹⁴⁴ without significant alterations in hemodynamics or clinical boundaries of hepatorenal and muscle enzyme status ¹⁴⁵. Supplementing highly trained cyclists with sodium nitrate (10 mg per kilogram of body mass) significantly reduced VO2peak without influencing time to exhaustion or maximal power outputs ¹⁴⁶. Additionally, 600 mg of nitrate supplementation (given 2 h prior) non-significantly improved the performance of a 500-m time trial performance in elite-level kayak athletes by 2 s ¹⁴⁷. Of practical significance, it should be noted that first place and last place in the 2008 Beijing Olympics, was separated by 1.47 s in the 500-m men’s canoe/kayak flatwater race. Amateur cyclists at simulated altitude (~ 2500 m) observed improved 16.1 km time trial performance with a concomitant decrease in oxygen consumption after beetroot juice (310 mg nitrate) supplementation ¹⁴⁸. Not all findings, however, have reported performance benefits with nitrate supplementation. Nitrate supplementation (~ 385 mg nitrate) 2.5 h before a 50-mile time trial in well-trained cyclists failed to improve performance ¹⁴⁹, which was also reported by MacLeod et al. ¹⁵⁰ after examining nitrate supplementation (~ 400 mg nitrate) on 10-km time trial performance in normoxia or simulated altitude (~ 2500 m). In well-trained runners, nitrate supplementation (~ 430 mg nitrate) did not improve performance during an incremental exercise test to exhaustion (simulated altitude 4000 m) or a 10-km time trial (simulated altitude, 2500 m) ¹⁵¹ and Nyakayiru et al. ¹⁵² reported no impact of nitrate supplementation on changes in VO2 and time trial performance in highly trained cyclists. Other studies have also reported an additive or synergistic effects of high-intensity intermittent exercise, endurance exercise, or resistance training when nitrate supplementation is combined with sodium phosphate ¹⁵³, caffeine ¹⁵⁴, or creatine ¹⁵⁵, respectively. It is important to mention that dietary nitrates have a health benefit in some, but not all populations ¹⁵⁶. Daily consumption of beetroot juice (~ 320–640 mg nitrate/d) significantly decreased resting systolic blood pressure in older adults by approximately 6 mmHg ¹⁵⁷. Nitrate supplementation (560 mg – 700 mg nitrate) significantly increased blood flow to working muscle and exercise time in older adults with peripheral artery disease ¹⁵⁸ as well as significantly improved endothelial function via increased flow-mediated dilation and blood flow velocity in older adults with risk factors of cardiovascular disease ¹⁵⁹. Collectively, these results indicate that nitrate supplementation may improve aerobic exercise performance and cardiovascular health in some populations.

Post-exercise carbohydrate and protein

Ingesting carbohydrate with protein following exercise has been a popular strategy to heighten adaptations seen as part of a resistance training program. The rationale behind this strategy centers upon providing an energy source to stimulate muscle protein synthesis via key signal transduction pathways. Additionally, carbohydrate intake will impact insulin status which could promote muscle protein synthesis, limit protein breakdown or both ¹⁶⁰. Furthermore, combining carbohydrate with protein can heighten glycogen resynthesis rates, particularly when carbohydrate intake is not optimal ¹⁶¹ and can improve muscle damage responses after exhaustive exercise ¹⁶². A key point for readers to consider when interpreting findings from this literature is the amount of protein, essential amino acids or leucine being delivered by the protein source ¹¹⁴. In the last few years many studies have agreed that post workout supplementation is vital to recovery and training adaptations ¹⁶³. However, the need for adding carbohydrate to protein to maximize hypertrophic adaptations continues to be questioned. For example, Staples and investigators ¹⁶⁴ used an acute study design involving stable isotope methodology to investigate the impact of adding 50 g of carbohydrate to 25 g of whey protein ingestion after a single bout of lower body resistance exercise. The authors concluded that the combination of carbohydrate and protein was no more effective at stimulating muscle protein synthesis or blunting rates of muscle protein breakdown than protein alone. Furthermore, Hulmi and colleagues ¹⁶⁵ had participants resistance train for 12 weeks and supplement with equivalent doses of whey protein, carbohydrate or whey protein + carbohydrate while having strength and body composition assessed. Overall, changes in strength were similar in all groups while changes in fat-free mass were greater in the protein group when compared to the carbohydrate group. Fat mass was found to significantly decrease in both groups that contained protein in comparison to carbohydrate, but no differences between the two protein-containing groups were noted. In conclusion, these findings underscore the importance of ingesting adequate protein to stimulate resistance training adaptations. Whether or not the addition of carbohydrate can heighten these changes at the current time seems unlikely. This outcome, however, should not distract the reader from appreciating the fact that optimal carbohydrate delivery will absolutely support glycogen recovery, aid in mitigating soreness and inflammation and fuel other recovery demands.

Quercetin

Quercetin is a flavonoid commonly found in fruits, vegetables and flowers, and is known for having some health benefits with therapeutic use. In addition, quercetin has been purported in both animal and human models to improve endurance performance. In this respect, Cureton and colleagues ¹⁶⁶ supplemented 30 recreationally active, but not highly trained men in a double-blind fashion to ingest either quercetin (1 g/day) or placebo. No changes in total work performed, substrate utilization, or perception of effort were found after supplementation. Similarly, Bigelman and investigators ¹⁶⁷ supplemented ROTC cadets with either 1 g of quercetin or a placebo and concluded that VO2max was unchanged as a result. These results correspond with the outcomes of other studies that failed to document ergogenic potential for quercetin ¹⁶⁸. In contrast, Nieman et al. ¹⁶⁹ supplemented untrained adult males with 1 g of quercetin in a double-blind fashion for 2 weeks and reported that treadmill performance and markers of mitochondrial biogenesis were improved. Similarly, Patrizio et al. ¹⁷⁰ used a resistance exercise model and reported quercetin may improve neuromuscular performance while Davis et al. ¹⁷¹ had 12 study participants supplement with either quercetin and placebo and found that quercetin may improve VO2max and endurance capacity. A meta-analysis was completed by Pelletier and researchers ¹⁷² to summarize the potential impact of quercetin supplementation on endurance performance. This analysis involved seven published studies representing 288 research participants. Only in untrained participants was quercetin found to significantly increase endurance performance. A 2011 meta-analysis by Kressler et al. Kressler J, Millard-Stafford M, Warren GL. Quercetin and endurance exercise capacity: a systematic review and meta-analysis. Med Sci Sports Exerc. 2011;43(12):2396–2404. doi: 10.1249/MSS.0b013e31822495a7 drew a similar conclusion whereby they indicated quercetin does have benefit, but the size of this effect is trivial and small. Consequently, more research needs to be completed to better identify what situations may exist that support quercetin’s ability to impact exercise performance.

Taurine

Taurine is an amino acid found in high abundance in human skeletal muscle ¹⁷³ derived from cysteine metabolism that plays a role in a wide variety of physiological functions ¹⁷⁴. Studies have indicated that training status (higher in trained vs. untrained muscle, reviewed in [624]) and fiber type (higher in type I vs. type II) impact the amount of taurine found in muscle. It has been reported in some ¹⁷⁵ but not all studies ¹⁷⁶ that taurine may improve exercise performance and mitigate recovery from damaging and stressful exercise ¹⁷⁷. In recent years, many studies have examined the impact of taurine ingestion on various types of exercise performance. In accordance with previous work, ergogenic outcomes related to taurine administration continue to be mixed. Milioni and investigators ¹⁷⁸ failed to show an improvement in performance with a 6 g dose of taurine while completing high-intensity treadmill running. Similarly, Balshaw et al. ¹⁷⁵ indicated that taurine failed to positively impact 3-km running performance in trained runners. In contrast, a 2017 study by Warnock et al. ¹⁷⁹ reported that a 50 mg/kg dose of taurine outperformed caffeine, placebo and caffeine + taurine on performance changes after repeated Wingate anaerobic capacity tests. Finally, a 2018 meta-analysis by Waldron et al. ¹⁸⁰ reported that single daily dosages ranging from one to 6 g for up to 2 weeks can significantly improve endurance exercise performance in a range of study participants. Two studies ¹⁸¹, ¹⁸² have been completed that examined taurine’s ability to mitigate decrements associated with muscle damage and resistance exercise performance. Notably, oral ingestion at a dosage of 50 mg/kg for 14 days prior to damage and for 7 days after damage significantly increased strength, and decreased soreness and markers of muscle damage ¹⁸². Finally, studies have also supported the ability of taurine to function in an anti-oxidative role, which may promote an improved cellular environment to tolerate exercise stress ¹⁸³. While more research continues to be published involving taurine, the consensus of these outcomes continue to be mixed regarding taurine’s potential to enhance physical performance.

Supplements to promote general health

Although daily vitamin and mineral supplementation has not been found to improve exercise capacity in athletes, it may make sense to take a daily vitamin supplement for health reasons. Vitamin D is often recommended to athletes, especially those participating in indoor sports or in cloudy geographies ¹⁸⁴. Although direct evidence linking vitamin D with performance is equivocal, it is clear that vitamin D has a role in regulating immune function, cardiovascular health, and growth and repair. Dosing should be dependent upon baseline levels, which can be measured by any physician ¹⁸⁵. Glucosamine and chondroitin have been reported to slow cartilage degeneration and reduce the degree of joint pain in active individuals which may help athletes postpone and/or prevent joint problems ¹⁸⁶. Meanwhile, other ingredients including undenatured type II collagen (UC-II) may be helpful as well although more research is needed involving athletic applications ¹⁸⁷. Supplemental vitamin C, glutamine, echinacea, quercetin, and zinc have been reported to enhance immune function ¹⁸⁸. However, consuming carbohydrate during prolonged strenuous exercise attenuates rises in stress hormones and appears to limit the degree of exercise-induced immune depression [699]. Similarly, although additional research is necessary, vitamin E, vitamin C, selenium, alpha-lipoic acid and other antioxidants may help restore overwhelmed antioxidant defenses exhibited by athletes ¹⁸⁹. One countering argument against higher doses is the potential for these to interfere with adaptive responses to training ¹⁹⁰. Finally, the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapantaenoic acid (EPA), in supplemental form, are now endorsed by the American Heart Association for heart health in certain individuals stemming from initial scientific statements made in 2002 ¹⁹¹. This supportive supplement position stems from: 1) an inability to consume cardio-protective amounts by diet alone; and, 2) the mercury contamination sometimes present in whole-food sources of DHA and EPA found in fatty fish. For general health, dosing recommendations range from 3000 mg-5000 mg daily of deep, cold water fish ¹⁹². Consequently, prudent use of these types of nutrients at various times during training may help athletes stay healthy and/or tolerate training to a greater degree.

High intensity exercise can compromise an athlete’s immune health. Infection risk and exercise workload follow a J-Shape curve with moderate intensity exercise reducing the infection risk, and high intensity exercise actually increasing the risk of infection ¹⁹³. Immune suppression in athletes further worsens by the psychological stress, foreign travel, disturbed sleep, environmental extremes, exposure to large crowds or an increase exposure to pathogens due to elevated breathing during exercise or competition. Athletes have several nutritional options to reduce the risk and symptoms of upper respiratory tract infections, including probiotics and baker’s yeast beta-glucan. Beta-glucan is a natural gluco polysaccharide derived from the cell walls of highly purified yeast (Saccharomyces cerevisiae) and has been shown to significantly decrease upper-respiratory tract infection symptoms in men and women participating in the Carlsbad marathon ¹⁹⁴. Probiotics, often referred to as “friendly” or “good” bacteria, are live microorganisms which when administered in adequate amounts confer a health benefit on the host. An estimated 70% of our immune system is located in your digestive system indicating the importance of a balanced gut microflora on immune health. Probiotics have been shown to reduce the number, duration and severity of upper-respiratory tract infections and gastrointestinal distress in the general population and in athletes, certain strains of probiotics have been shown to significantly reduce the number of upper-respiratory tract infection episodes a well as their severity ¹⁹⁵. Health benefits of probiotics are strain specific and dose dependent, and some strains have failed to show beneficial effects in athletes ¹⁹⁶. Also, consuming carbohydrate during prolonged strenuous exercise attenuates rises in stress hormones and appears to limit the degree of exercise-induced immune depression ¹⁸⁸.

Conclusion

Several factors operate as cornerstones to enhance athletic performance and optimize training adaptations including the consumption of a balanced, nutrient and energy dense diet, prudent training, and obtaining adequate rest. Use of a limited number of nutritional supplements that research has supported to improve energy availability (e.g., sports drinks, carbohydrate, creatine, caffeine, β-alanine, etc.) and/or promote recovery (carbohydrate, protein, essential amino acids, etc.) can provide additional benefit in certain instances ¹. Dietitians and sport nutritionists should stay up to date on current research regarding the role of nutrition on exercise so they can provide honest and accurate information to their students, clients, and/or athletes about the role of nutrition and dietary supplements on performance and training. Furthermore, these professionals should actively participate in exercise nutrition research, write unbiased scholarly reviews for journals and lay publications, and help disseminate the latest research findings to the public. Through these actions, consumers and other professionals can make informed decisions about appropriate methods of exercise, dieting, and/or whether various nutritional supplements can affect health, performance, and/or training. In all situations, individuals are expected and ethically obligated to disclose any commercial or financial conflicts of interest during such promulgations. Finally, companies selling nutritional supplements or promoting exercise, diet or supplementation protocols should develop scientifically based products, conduct research on their products, and honestly market the results of studies so consumers can make informed decisions.

References

1. Kerksick CM, Wilborn CD, Roberts MD, et al. ISSN exercise & sports nutrition review update: research & recommendations. Journal of the International Society of Sports Nutrition. 2018;15:38. doi:10.1186/s12970-018-0242-y. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6090881/
2. Brilla L, Conte V. Effects of a novel zinc-magnesium formulation on hormones and strength. J Exerc Physiol Online. 2000;3:26–36.
3. Koehler K, Parr MK, Geyer H, Mester J, Schanzer W. Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement. Eur J Clin Nutr. 2009;63(1):65–70. doi: 10.1038/sj.ejcn.1602899
4. Wilborn CD, Kerksick CM, Campbell BI, et al. Effects of Zinc Magnesium Aspartate (ZMA) Supplementation on Training Adaptations and Markers of Anabolism and Catabolism. Journal of the International Society of Sports Nutrition. 2004;1(2):12-20. doi:10.1186/1550-2783-1-2-12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2129161/
5. Om AS, Chung KW. Dietary zinc deficiency alters 5 alpha-reduction and aromatization of testosterone and androgen and estrogen receptors in rat liver. J Nutr. 1996;126(4):842–848. doi: 10.1093/jn/126.4.842.
6. Lukasi HC. Micronutrients (magnesium, zinc, and copper): are mineral supplements needed for athletes? International Journal of Sport Nutrition. 1995;5:74–83.
7. Nieman DC, Pedersen BK. Exercise and immune function. Recent developments. Sports Med. 1999;27:73–80. doi: 10.2165/00007256-199927020-00001
8. Golf SW, Happel O, Graef V, Seim KE. Plasma aldosterone, cortisol and electrolyte concentrations in physical exercise after magnesium supplementation. J Clin Chem Clin Biochem. 1984;22:717–721.
9. Golf SW, Bender S, Gruttner J. On the Significance of Magnesium in Extreme Physical Stress. Cardiovascular Drugs and Therapy. 1998;12:197–202. doi: 10.1023/A:1007708918683.
10. Konig D, Weinstock C, Keul J, et al. Zinc, iron, and magnesium status in athletes – influence on the regulation of exercise-induced stress and immune function. Exerc Immunol Rev. 1998;4:2–21.
11. Brilla LR, Conte V. Effects of a novel zinc-magnesium formulation on hormones and strength. J Exerc Physiol Online. 2000;3:26–36.
12. Gleeson M, Nieman DC, Pedersen BK. Exercise, nutrition and immune function. J Sport Science (London) 2004;22:115–125. doi: 10.1080/0264041031000140590
13. Cordova A, Navas FJ. Effect of training on zinc metabolism: changes in serum and sweat zinc concentrations in sportsmen. Ann Nutr Metab. 1998;42:274–282. doi: 10.1159/000012744
14. Trexler ET, Smith-Ryan AE, Stout JR, Hoffman JR, Wilborn CD, Sale C, Kreider RB, Jager R, Earnest CP, Bannock L, Campbell B, Kalman D, Ziegenfuss TN, Antonio J. International society of sports nutrition position stand: Beta-alanine. J Int Soc Sports Nutr. 2015;12:30. doi: 10.1186/s12970-015-0090-y.
15. Harris RC, Tallon MJ, Dunnett M, Boobis L, Coakley J, Kim HJ, Fallowfield JL, Hill CA, Sale C, Wise JA. The absorption of orally supplied beta-alanine and its effect on muscle carnosine synthesis in human vastus lateralis. Amino Acids. 2006;30(3):279–289. doi: 10.1007/s00726-006-0299-9
16. Church DD, Hoffman JR, Varanoske AN, Wang R, Baker KM, La Monica MB, Beyer KS, Dodd SJ, Oliveira LP, Harris RC, Fukuda DH, Stout JR. Comparison of two beta-alanine dosing protocols on muscle carnosine elevations. J Am Coll Nutr. 2017;36(8):608–616. doi: 10.1080/07315724.2017.1335250
17. Trexler ET, Smith-Ryan AE, Stout JR, Hoffman JR, Wilborn CD, Sale C, Kreider RB, Jager R, Earnest CP, Bannock L, Campbell B, Kalman D, Ziegenfuss TN, Antonio J. International society of sports nutrition position stand: Beta-alanine. J Int Soc Sports Nutr. 2015;12:30. doi: 10.1186/s12970-015-0090-y
18. Hoffman JR, Ratamess NA, Faigenbaum AD, Ross R, Kang J, Stout JR, Wise JA. Short-duration beta-alanine supplementation increases training volume and reduces subjective feelings of fatigue in college football players. Nutr Res. 2008;28(1):31–35. doi: 10.1016/j.nutres.2007.11.004
19. Smith AE, Walter AA, Graef JL, Kendall KL, Moon JR, Lockwood CM, Fakuda DH, Beck TW, Cramer JT, Stout JR. Effects of beta-alanine supplementation and high-intensity interval training on endurance performance and body composition in men; a double-blind trial. J Int Soc Sports Nutr. 2009;6(1):5. doi: 10.1186/1550-2783-6-5.
20. Derave W, Ozdemir MS, Harris RC, Pottier A, Reyngoudt H, Koppo K, Wise JA, Achten E. Beta-alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters. J Appl Physiol. 2007;103(5):1736–1743. doi: 10.1152/japplphysiol.00397.2007
21. Hoffman J, Ratamess N, Kang J, Mangine G, Faigenbaum A, Stout J. Effect of creatine and beta-alanine supplementation on performance and endocrine responses in strength/power athletes. Int J Sport Nutr Exerc Metab. 2006;16(4):430–446. doi: 10.1123/ijsnem.16.4.430.
22. Smith AE, Moon JR, Kendall KL, Graef JL, Lockwood CM, Walter AA, Beck TW, Cramer JT, Stout JR. The effects of beta-alanine supplementation and high-intensity interval training on neuromuscular fatigue and muscle function. Eur J Appl Physiol. 2009;105(3):357–363. doi: 10.1007/s00421-008-0911-7
23. Goldstein ER, Ziegenfuss T, Kalman D, Kreider R, Campbell B, Wilborn C, Taylor L, Willoughby D, Stout J, Graves BS, Wildman R, Ivy JL, Spano M, Smith AE, Antonio J. International society of sports nutrition position stand: caffeine and performance. J Int Soc Sports Nutr. 2010;7(1):5. doi: 10.1186/1550-2783-7-5
24. Wiles JD, Coleman D, Tegerdine M, Swaine IL. The effects of caffeine ingestion on performance time, speed and power during a laboratory-based 1 km cycling time-trial. J Sports Sci. 2006;24(11):1165–1171. doi: 10.1080/02640410500457687
25. Ivy JL, Kammer L, Ding Z, Wang B, Bernard JR, Liao YH, Hwang J. Improved cycling time-trial performance after ingestion of a caffeine energy drink. Int J Sport Nutr Exerc Metab. 2009;19(1):61–78. doi: 10.1123/ijsnem.19.1.61.
26. Graham TE. Caffeine and exercise: metabolism, endurance and performance. Sports Med. 2001;31(11):785–807. doi: 10.2165/00007256-200131110-00002
27. Trexler ET, Smith-Ryan AE, Roelofs EJ, Hirsch KR, Mock MG. Effects of coffee and caffeine anhydrous on strength and sprint performance. Eur J Sport Sci. 2016;16(6):702–710. doi: 10.1080/17461391.2015.1085097
28. Astorino TA, Rohmann RL, Firth K. Effect of caffeine ingestion on one-repetition maximum muscular strength. Eur J Appl Physiol. 2008;102(2):127–132. doi: 10.1007/s00421-007-0557-x
29. Beck TW, Housh TJ, Schmidt RJ, Johnson GO, Housh DJ, Coburn JW, Malek MH. The acute effects of a caffeine-containing supplement on strength, muscular endurance, and anaerobic capabilities. J Strength Cond Res. 2006;20(3):506–510.
30. Goldstein ER, Jacobs PL, Whitehurst M, Penhollow T, Antonio J. Caffeine enhances upper body strength in resistance-trained women. J Int Soc Sports Nutr. 2010;7(1):18. doi: 10.1186/1550-2783-7-18
31. Duncan MJ, Stanley M, Parkhouse N, Cook K, Smith M. Acute caffeine ingestion enhances strength performance and reduces perceived exertion and muscle pain perception during resistance exercise. Eur J Sport Sci. 2013;13(4):392–399. doi: 10.1080/17461391.2011.635811
32. Duncan MJ, Oxford SW. Acute caffeine ingestion enhances performance and dampens muscle pain following resistance exercise to failure. J Sports Med Phys Fitness. 2012;52(3):280–285
33. Duncan MJ, Smith M, Cook K, James RS. The acute effect of a caffeine-containing energy drink on mood state, readiness to invest effort, and resistance exercise to failure. J Strength Cond Res. 2012;26(10):2858–2865. doi: 10.1519/JSC.0b013e318241e124
34. Woolf K, Bidwell WK, Carlson AG. The effect of caffeine as an ergogenic aid in anaerobic exercise. Int J Sport Nutr Exerc Metab. 2008;18(4):412–429. doi: 10.1123/ijsnem.18.4.412
35. Tarnopolsky MA, Atkinson SA, Macdougall JD, Sale DG, Sutton JR. Physiological responses to caffeine during endurance running in habitual caffeine users. Med Sci Sports Exerc. 1989;21(4):418–424. doi: 10.1249/00005768-198908000-00013
36. Armstrong LE. Caffeine, body fluid-electrolyte balance, and exercise performance. Int J Sport Nutr Exerc Metab. 2002;12(2):189–206. doi: 10.1123/ijsnem.12.2.189
37. Hawley JA, Leckey JJ. Carbohydrate dependence during prolonged, intense endurance exercise. Sports Med. 2015;45(Suppl 1):S5–12. doi: 10.1007/s40279-015-0400-1
38. Cermak NM, Van Loon LJ. The use of carbohydrates during exercise as an ergogenic aid. Sports Med. 2013;43(11):1139–1155. doi: 10.1007/s40279-013-0079-0
39. Below PR, Mora-Rodriguez R, Gonzalez-Alonso J, Coyle EF. Fluid and carbohydrate ingestion independently improve performance during 1 h of intense exercise. Med Sci Sports Exerc. 1995;27(2):200–210. doi: 10.1249/00005768-199502000-00009
40. Widrick JJ, Costill DL, Fink WJ, Hickey MS, Mcconell GK, Tanaka H. Carbohydrate feedings and exercise performance: effect of initial muscle glycogen concentration. J Appl Physiol. 1993;74(6):2998–3005. doi: 10.1152/jappl.1993.74.6.2998
41. Williams C, Rollo I. Carbohydrate nutrition and team sport performance. Sports Med. 2015;45(Suppl 1):S13–S22. doi: 10.1007/s40279-015-0399-3
42. Pochmuller M, Schwingshackl L, Colombani PC, Hoffmann G. A systematic review and meta-analysis of carbohydrate benefits associated with randomized controlled competition-based performance trials. J Int Soc Sports Nutr. 2016;13:27. doi: 10.1186/s12970-016-0139-6
43. Colombani PC, Mannhart C, Mettler S. Carbohydrates and exercise performance in non-fasted athletes: a systematic review of studies mimicking real-life. Nutr J. 2013;12:16. doi: 10.1186/1475-2891-12-16
44. Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci. 2011;29(Suppl 1):S17–S27. doi: 10.1080/02640414.2011.585473
45. Rodriguez NR, Dimarco NM, Langley S, American Dietetic A, Dietitians Of C, American College of Sports Medicine N. Athletic P. Position of the american dietetic association, dietitians of Canada, and the american college of sports medicine: nutrition and athletic performance. J Am Diet Assoc. 2009;109(3):509–527. doi: 10.1016/j.jada.2009.01.005
46. Carter JM, Jeukendrup AE, Jones DA. The effect of carbohydrate mouth rinse on 1-h cycle time trial performance. Med Sci Sports Exerc. 2004;36(12):2107–2111. doi: 10.1249/01.MSS.0000147585.65709.6F.
47. Kasper AM, Cocking S, Cockayne M, Barnard M, Tench J, Parker L, Mcandrew J, Langan-Evans C, Close GL, Morton JP. Carbohydrate mouth rinse and caffeine improves high-intensity interval running capacity when carbohydrate restricted. Eur J Sport Sci. 2016;16(5):560–568. doi: 10.1080/17461391.2015.1041063
48. Dolan P, Witherbee KE, Peterson KM, Kerksick CM. Effect of carbohydrate, caffeine, and carbohydrate + caffeine mouth rinsing on intermittent running performance in collegiate male lacrosse athletes. J Strength Cond Res. 2017;31(9):2473–2479. doi: 10.1519/JSC.0000000000001819
49. Mock MG, Hirsch KR, MNM B, Trexler ET, Roelofs EJ, Smith-Ryan AE. Post-exercise ingestion of low or high molecular weight glucose polymer solution does not improve cycle performance in female athletes. J Strength Cond Res. 2018; 10.1519/JSC.0000000000002560
50. Kendall KL, Smith AE, Graef JL, Fukuda DH, Moon JR, Beck TW, Cramer JT, Stout JR. Effects of four weeks of high-intensity interval training and creatine supplementation on critical power and anaerobic working capacity in college-aged men. J Strength Cond Res. 2009;23(6):1663–1669. doi: 10.1519/JSC.0b013e3181b1fd1f
51. Kreider RB, Kalman DS, Antonio J, Ziegenfuss TN, Wildman R, Collins R, Candow DG, Kleiner SM, Almada AL, Lopez HL. International society of sports nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr. 2017;14:18. doi: 10.1186/s12970-017-0173-z
52. Kreider RB. Effects of creatine supplementation on performance and training adaptations. Mol Cell Biochem. 2003;244(1–2):89–94. doi: 10.1023/A:1022465203458
53. Green AL, Hultman E, Macdonald IA, Sewell DA, Greenhaff PL. Carbohydrate ingestion augments skeletal muscle creatine accumulation during creatine supplementation in humans. Am J Phys. 1996;271(5 Pt 1):E821–E826
54. Eijnde BO’T, Richter EA, Henquin JC, Kiens B, Hespel P. Effect of creatine supplementation on creatine and glycogen content in rat skeletal muscle. Acta Physiol Scand. 2001;171(2):169–176. doi: 10.1046/j.1365-201x.2001.00786.x.
55. Chwalbinska-Moneta J. Effect of creatine supplementation on aerobic performance and anaerobic capacity in elite rowers in the course of endurance training. Int J Sport Nutr Exerc Metab. 2003;13(2):173–183. doi: 10.1123/ijsnem.13.2.173
56. Nelson AG, Day R, Glickman-Weiss EL, Hegsted M, Kokkonen J, Sampson B. Creatine supplementation alters the response to a graded cycle ergometer test. Eur J Appl Physiol. 2000;83(1):89–94. doi: 10.1007/s004210000244
57. Juhasz I, Gyore I, Csende Z, Racz L, Tihanyi J. Creatine supplementation improves the anaerobic performance of elite junior fin swimmers. Acta Physiol Hung. 2009;96(3):325–336. doi: 10.1556/APhysiol.96.2009.3.6
58. Volek JS, Ratamess NA, Rubin MR, Gomez AL, French DN, Mcguigan MM, Scheett TP, Sharman MJ, Hakkinen K, Kraemer WJ. The effects of creatine supplementation on muscular performance and body composition responses to short-term resistance training overreaching. Eur J Appl Physiol. 2004;91(5–6):628–637. doi: 10.1007/s00421-003-1031-z.
59. Wiroth JB, Bermon S, Andrei S, Dalloz E, Hebuterne X, Dolisi C. Effects of oral creatine supplementation on maximal pedalling performance in older adults. Eur J Appl Physiol. 2001;84(6):533–539. doi: 10.1007/s004210000370
60. Sobolewski EJ, Thompson BJ, Smith AE, Ryan ED. The physiological effects of creatine supplementation on hydration: a review. Am J Lifestyle Med. 2011;5(4):320–327. doi: 10.1177/1559827611406071
61. Mcnaughton L, Backx K, Palmer G, Strange N. Effects of chronic bicarbonate ingestion on the performance of high- intensity work. Eur J Appl Physiol Occup Physiol. 1999;80(4):333–336. doi: 10.1007/s004210050600.
62. Matson LG, Tran ZV. Effects of sodium bicarbonate ingestion on anaerobic performance: a meta-analytic review. Int J Sport Nutr. 1993;3(1):2–28. doi: 10.1123/ijsn.3.1.2.
63. Lindh AM, Peyrebrune MC, Ingham SA, Bailey DM, Folland JP. Sodium bicarbonate improves swimming performance. Int J Sports Med. 2008;29(6):519–523. doi: 10.1055/s-2007-989228
64. Kilding AE, Overton C, Gleave J. Effects of caffeine, sodium bicarbonate, and their combined ingestion on high-intensity cycling performance. Int J Sport Nutr Exerc Metab. 2012;22(3):175–183. doi: 10.1123/ijsnem.22.3.175
65. Marriott M, Krustrup P, Mohr M. Ergogenic effects of caffeine and sodium bicarbonate supplementation on intermittent exercise performance preceded by intense arm cranking exercise. J Int Soc Sports Nutr. 2015;12:13. doi: 10.1186/s12970-015-0075-x
66. Percival ME, Martin BJ, Gillen JB, Skelly LE, Macinnis MJ, Green AE, Tarnopolsky MA, Gibala MJ. Sodium bicarbonate ingestion augments the increase in pgc-1alpha mRNA expression during recovery from intense interval exercise in human skeletal muscle. J Appl Physiol. 2015;119(11):1303–1312. doi: 10.1152/japplphysiol.00048.2015
67. Peart DJ, Siegler JC, Vince RV. Practical recommendations for coaches and athletes: a meta-analysis of sodium bicarbonate use for athletic performance. J Strength Cond Res. 2012;26(7):1975–1983. doi: 10.1519/JSC.0b013e3182576f3d
68. Tobias G, Benatti FB, De Salles PV, Roschel H, Gualano B, Sale C, Harris RC, Lancha AH, Jr, Artioli GG. Additive effects of beta-alanine and sodium bicarbonate on upper-body intermittent performance. Amino Acids. 2013;45(2):309–317. doi: 10.1007/s00726-013-1495-z
69. Danaher J, Gerber T, Wellard RM, Stathis CG. The effect of beta-alanine and nahco3 co-ingestion on buffering capacity and exercise performance with high-intensity exercise in healthy males. Eur J Appl Physiol. 2014;114(8):1715–1724. doi: 10.1007/s00421-014-2895-9
70. Folland JP, Stern R, Brickley G. Sodium phosphate loading improves laboratory cycling time-trial performance in trained cyclists. J Sci Med Sport. 2008;11(5):464–468. doi: 10.1016/j.jsams.2007.04.004
71. Kreider RB, Miller GW, Williams MH, Somma CT, Nasser TA. Effects of phosphate loading on oxygen uptake, ventilatory anaerobic threshold, and run performance. Med Sci Sports Exerc. 1990;22(2):250–256. doi: 10.1249/00005768-199004000-00596
72. Kopec BJ, Dawson BT, Buck C, Wallman KE. Effects of sodium phosphate and caffeine ingestion on repeated-sprint ability in male athletes. J Sci Med Sport. 2016;19(3):272–276. doi: 10.1016/j.jsams.2015.04.001
73. Brewer CP, Dawson B, Wallman KE, Guelfi KJ. Effect of sodium phosphate supplementation on cycling time trial performance and vo2 1 and 8 days post loading. J Sports Sci Med. 2014;13(3):529–534.
74. Brewer CP, Dawson B, Wallman KE, Guelfi KJ. Effect of repeated sodium phosphate loading on cycling time-trial performance and vo2peak. Int J Sport Nutr Exerc Metab. 2013;23(2):187–194. doi: 10.1123/ijsnem.23.2.187
75. West JS, Ayton T, Wallman KE, Guelfi KJ. The effect of 6 days of sodium phosphate supplementation on appetite, energy intake, and aerobic capacity in trained men and women. Int J Sport Nutr Exerc Metab. 2012;22(6):422–429. doi: 10.1123/ijsnem.22.6.422
76. Buck CL, Dawson B, Guelfi KJ, Mcnaughton L, Wallman KE. Sodium phosphate supplementation and time trial performance in female cyclists. J Sports Sci Med. 2014;13(3):469–475
77. Buck CL, Henry T, Guelfi K, Dawson B, Mcnaughton LR, Wallman K. Effects of sodium phosphate and beetroot juice supplementation on repeated-sprint ability in females. Eur J Appl Physiol. 2015;115(10):2205–2213. doi: 10.1007/s00421-015-3201-1
78. Mcdermott BP, Anderson SA, Armstrong LE, Casa DJ, Cheuvront SN, Cooper L, Kenney WL, O’connor FG, Roberts WO. National athletic trainers’ association position statement: fluid replacement for the physically active. J Athl Train. 2017;52(9):877–895. doi: 10.4085/1062-6050-52.9.02
79. Von Duvillard SP, Arciero PJ, Tietjen-Smith T, Alford K. Sports drinks, exercise training, and competition. Curr Sports Med Rep. 2008;7(4):202–208. doi: 10.1249/JSR.0b013e31817ffa37
80. Goulet ED. Dehydration and endurance performance in competitive athletes. Nutr Rev. 2012;70(Suppl 2):S132–S136. doi: 10.1111/j.1753-4887.2012.00530.x
81. Rogero MM, Tirapegui J, Pedrosa RG, Castro IA, Pires IS. Effect of alanyl-glutamine supplementation on plasma and tissue glutamine concentrations in rats submitted to exhaustive exercise. Nutrition. 2006;22(5):564–571. doi: 10.1016/j.nut.2005.11.002
82. Cruzat VF, Rogero MM, Tirapegui J. Effects of supplementation with free glutamine and the dipeptide alanyl-glutamine on parameters of muscle damage and inflammation in rats submitted to prolonged exercise. Cell Biochem Funct. 2010;28(1):24–30. doi: 10.1002/cbf.1611
83. Hoffman JR, Ratamess NA, Kang J, Rashti SL, Kelly N, Gonzalez AM, Stec M, Anderson S, Bailey BL, Yamamoto LM, Hom LL, Kupchak BR, Faigenbaum AD, Maresh CM. Examination of the efficacy of acute l-alanyl-l-glutamine ingestion during hydration stress in endurance exercise. J Int Soc Sports Nutr. 2010;7:8. doi: 10.1186/1550-2783-7-8
84. Hoffman JR, Williams DR, Emerson NS, Hoffman MW, Wells AJ, Mcveigh DM, Mccormack WP, Mangine GT, Gonzalez AM, Fragala MS. L-alanyl-l-glutamine ingestion maintains performance during a competitive basketball game. J Int Soc Sports Nutr. 2012;9(1):4. doi: 10.1186/1550-2783-9-4
85. Pruna GJ, Hoffman JR, Mccormack WP, Jajtner AR, Townsend JR, Bohner JD, La Monica MB, Wells AJ, Stout JR, Fragala MS, Fukuda DH. Effect of acute l-alanyl-l-glutamine and electrolyte ingestion on cognitive function and reaction time following endurance exercise. Eur J Sport Sci. 2016;16(1):72–79. doi: 10.1080/17461391.2014.969325
86. Mccormack WP, Hoffman JR, Pruna GJ, Jajtner AR, Townsend JR, Stout JR, Fragala MS, Fukuda DH. Effects of l-alanyl-l-glutamine ingestion on one-hour run performance. J Am Coll Nutr. 2015;34(6):488–496. doi: 10.1080/07315724.2015.1009193
87. Ayre KJ, Hulbert AJ. Dietary fatty acid profile influences the composition of skeletal muscle phospholipids in rats. J Nutr. 1996;126(3):653–662. doi: 10.1093/jn/126.3.653
88. Zhou L, Nilsson A. Sources of eicosanoid precursor fatty acid pools in tissues. J Lipid Res. 2001;42(10):1521–1542.
89. Kelley DS, Taylor PC, Nelson GJ, Mackey BE. Arachidonic acid supplementation enhances synthesis of eicosanoids without suppressing immune functions in young healthy men. Lipids. 1998;33(2):125–130. doi: 10.1007/s11745-998-0187-9
90. Helge JW, Wu BJ, Willer M, Daugaard JR, Storlien LH, Kiens B. Training affects muscle phospholipid fatty acid composition in humans. J Appl Physiol. 2001;90(2):670–677. doi: 10.1152/jappl.2001.90.2.670
91. Kulmacz RJ, Pendleton RB, Lands WE. Interaction between peroxidase and cyclooxygenase activities in prostaglandin-endoperoxide synthase. Interpretation of reaction kinetics. J Biol Chem. 1994;269(8):5527–5536
92. Roberts MD, Iosia M, Kerksick CM, Taylor LW, Campbell B, Wilborn CD, Harvey T, Cooke M, Rasmussen C, Greenwood M, Wilson R, Jitomir J, Willoughby D, Kreider RB. Effects of arachidonic acid supplementation on training adaptations in resistance-trained males. J Int Soc Sports Nutr. 2007;4:21. doi: 10.1186/1550-2783-4-21
93. De Souza EO, Lowery RP, Wilson JM, Sharp MH, Mobley CB, Fox CD, Lopez HL, Shields KA, Rauch JT, Healy JC, Thompson RM, Ormes JA, Joy JM, Roberts MD. Effects of arachidonic acid supplementation on acute anabolic signaling and chronic functional performance and body composition adaptations. PLoS One. 2016;11(5):e0155153. doi: 10.1371/journal.pone.0155153
94. Mitchell CJ, D’souza RF, Figueiredo VC, Chan A, Aasen K, Durainayagam B, Mitchell S, Sinclair AJ, Egner IM, Raastad T, Cameron-Smith D, Markworth JF. Effect of dietary arachidonic acid supplementation on acute muscle adaptive responses to resistance exercise in trained men: a randomized controlled trial. J Appl Physiol. 2018;124(4):1080–1091. doi: 10.1152/japplphysiol.01100.2017
95. Mikulski T, Dabrowski J, Hilgier W, Ziemba A, Krzeminski K. Effects of supplementation with branched chain amino acids and ornithine aspartate on plasma ammonia and central fatigue during exercise in healthy men. Folia Neuropathol. 2015;53(4):377–386. doi: 10.5114/fn.2015.56552
96. Negro M, Giardina S, Marzani B, Marzatico F. Branched-chain amino acid supplementation does not enhance athletic performance but affects muscle recovery and the immune system. J Sports Med Phys Fitness. 2008;48(3):347–351
97. Greer BK, Woodard JL, White JP, Arguello EM, Haymes EM. Branched-chain amino acid supplementation and indicators of muscle damage after endurance exercise. Int J Sport Nutr Exerc Metab. 2007;17(6):595–607. doi: 10.1123/ijsnem.17.6.595
98. Haines RJ, Pendleton LC, Eichler DC. Argininosuccinate synthase: at the center of arginine metabolism. Int J Biochem Mol Biol. 2011;2(1):8–23
99. Wu G. Urea synthesis in enterocytes of developing pigs. Biochem J. 1995;312(Pt 3):717–723.
100. Van De Poll MC, Siroen MP, Van Leeuwen PA, Soeters PB, Melis GC, Boelens PG, Deutz NE, Dejong CH. Interorgan amino acid exchange in humans: consequences for arginine and citrulline metabolism. Am J Clin Nutr. 2007;85(1):167–172. doi: 10.1093/ajcn/85.1.167
101. Curis E, Nicolis I, Moinard C, Osowska S, Zerrouk N, Benazeth S, Cynober L. Almost all about citrulline in mammals. Amino Acids. 2005;29(3):177–205. doi: 10.1007/s00726-005-0235-4
102. Wijnands KA, Vink H, Briede JJ, Van Faassen EE, Lamers WH, Buurman WA, Poeze M. Citrulline a more suitable substrate than arginine to restore no production and the microcirculation during endotoxemia. PLoS One. 2012;7(5):e37439. doi: 10.1371/journal.pone.0037439
103. Mckinley-Barnard S, Andre T, Morita M, Willoughby DS. Combined l-citrulline and glutathione supplementation increases the concentration of markers indicative of nitric oxide synthesis. J Int Soc Sports Nutr. 2015;12:27. doi: 10.1186/s12970-015-0086-7
104. Suzuki T, Morita M, Kobayashi Y, Kamimura A. Oral l-citrulline supplementation enhances cycling time trial performance in healthy trained men: double-blind randomized placebo-controlled 2-way crossover study. J Int Soc Sports Nutr. 2016;13:6. doi: 10.1186/s12970-016-0117-z
105. Bailey SJ, Blackwell JR, Lord T, Vanhatalo A, Winyard PG, Jones AM. L-citrulline supplementation improves o2 uptake kinetics and high-intensity exercise performance in humans. J Appl Physiol. 2015;119(4):385–395. doi: 10.1152/japplphysiol.00192.2014
106. Cunniffe B, Papageorgiou M, O’brien B, Davies NA, Grimble GK, Cardinale M. Acute citrulline-malate supplementation and high-intensity cycling performance. J Strength Cond Res. 2016;30(9):2638–2647. doi: 10.1519/JSC.0000000000001338
107. Glenn JM, Gray M, Wethington LN, Stone MS, Stewart RW, Jr, Moyen NE. Acute citrulline malate supplementation improves upper- and lower-body submaximal weightlifting exercise performance in resistance-trained females. Eur J Nutr. 2017;56(2):775–784. doi: 10.1007/s00394-015-1124-6
108. Wax B, Kavazis AN, Luckett W. Effects of supplemental citrulline-malate ingestion on blood lactate, cardiovascular dynamics, and resistance exercise performance in trained males. J Dietary Suppl. 2016;13(3):269–282. doi: 10.3109/19390211.2015.1008615
109. Wax B, Kavazis AN, Weldon K, Sperlak J. Effects of supplemental citrulline malate ingestion during repeated bouts of lower-body exercise in advanced weightlifters. J Strength Cond Res. 2015;29(3):786–792. doi: 10.1519/JSC.0000000000000670
110. Cutrufello PT, Gadomski SJ, Zavorsky GS. The effect of l-citrulline and watermelon juice supplementation on anaerobic and aerobic exercise performance. J Sports Sci. 2015;33(14):1459–1466. doi: 10.1080/02640414.2014.990495
111. Wagenmakers AJ. Muscle amino acid metabolism at rest and during exercise: role in human physiology and metabolism. Exerc Sport Sci Rev. 1998;26:287–314. doi: 10.1249/00003677-199800260-00013
112. Pasiakos SM, Mcclung JP. Supplemental dietary leucine and the skeletal muscle anabolic response to essential amino acids. Nutr Rev. 2011;69(9):550–557. doi: 10.1111/j.1753-4887.2011.00420.x
113. Tipton KD, Wolfe RR. Exercise, protein metabolism, and muscle growth. Int J Sport Nutr Exerc Metab. 2001;11(1):109–132. doi: 10.1123/ijsnem.11.1.109
114. Jager R, Kerksick CM, Campbell BI, Cribb PJ, Wells SD, Skwiat TM, Purpura M, Ziegenfuss TN, Ferrando AA, Arent SM, Smith-Ryan AE, Stout JR, Arciero PJ, Ormsbee MJ, Taylor LW, Wilborn CD, Kalman DS, Kreider RB, Willoughby DS, Hoffman JR, Krzykowski JL, Antonio J. International society of sports nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. doi: 10.1186/s12970-017-0177-8.
115. Van Rosendal SP, Osborne MA, Fassett RG, Coombes JS. Physiological and performance effects of glycerol hyperhydration and rehydration. Nutr Rev. 2009;67(12):690–705. doi: 10.1111/j.1753-4887.2009.00254.x
116. Magal M, Webster MJ, Sistrunk LE, Whitehead MT, Evans RK, Boyd JC. Comparison of glycerol and water hydration regimens on tennis-related performance. Med Sci Sports Exerc. 2003;35(1):150–156. doi: 10.1097/00005768-200301000-00023
117. Coutts A, Reaburn P, Mummery K, Holmes M. The effect of glycerol hyperhydration on olympic distance triathlon performance in high ambient temperatures. Int J Sport Nutr Exerc Metab. 2002;12(21):105–119. doi: 10.1123/ijsnem.12.1.105
118. Marino FE, Kay D, Cannon J. Glycerol hyperhydration fails to improve endurance performance and thermoregulation in humans in a warm humid environment. Pflugers Arch. 2003;446(4):455–462. doi: 10.1007/s00424-003-1058-3
119. Goulet ED, Robergs RA, Labrecque S, Royer D, Dionne IJ. Effect of glycerol-induced hyperhydration on thermoregulatory and cardiovascular functions and endurance performance during prolonged cycling in a 25 degrees c environment. Appl Physiol Nutr Metab. 2006;31(2):101–109. doi: 10.1139/h05-006
120. Mckenna ZJ, Gillum TL. Effects of exercise induced dehydration and glycerol rehydration on anaerobic power in male collegiate wrestlers. J Strength Cond Res. 2017;31(11):2965–2968. doi: 10.1519/JSC.0000000000001871
121. Goulet ED, Rousseau SF, Lamboley CR, Plante GE, Dionne IJ. Pre-exercise hyperhydration delays dehydration and improves endurance capacity during 2 h of cycling in a temperate climate. J Physiol Anthropol. 2008;27(5):263–271. doi: 10.2114/jpa2.27.263
122. Nelson JL, Robergs RA. Exploring the potential ergogenic effects of glycerol hyperhydration. Sports Med. 2007;37(11):981–1000. doi: 10.2165/00007256-200737110-00005
123. Rowlands DS, Thomson JS. Effects of beta-hydroxy-beta-methylbutyrate supplementation during resistance training on strength, body composition, and muscle damage in trained and untrained young men: a meta-analysis. J Strength Cond Res. 2009;23(3):836–846. doi: 10.1519/JSC.0b013e3181a00c80
124. Nissen S, Sharp R, Ray M. Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance exercise testing. J Am Physiol. 1996;81:2095–2104
125. Gallagher PM, Carrithers JA, Godard MP, Schulze KE, Trappe SW. Beta-hydroxy-beta-methylbutyrate ingestion, part i: effects on strength and fat free mass. Med Sci Sports Exerc. 2000;32(12):2109–2115. doi: 10.1097/00005768-200012000-00022
126. Thomson JS, Watson PE, Rowlands DS. Effects of nine weeks of beta-hydroxy-beta- methylbutyrate supplementation on strength and body composition in resistance trained men. J Strength Cond Res. 2009;23(3):827–835. doi: 10.1519/JSC.0b013e3181a00d47
127. Kreider RB, Ferreira M, Wilson M, Almada AL. Effects of calcium beta-hydroxy-beta-methylbutyrate (hmb) supplementation during resistance-training on markers of catabolism, body composition and strength. Int J Sports Med. 1999;20(8):503–509. doi: 10.1055/s-1999-8835.
128. Hoffman JR, Cooper J, Wendell M, Im J, Kang J. Effects of beta-hydroxy beta-methylbutyrate on power performance and indices of muscle damage and stress during high-intensity training. J Strength Cond Res. 2004;18(4):747–752
129. O’connor DM, Crowe MJ. Effects of beta-hydroxy-beta-methylbutyrate and creatine monohydrate supplementation on the aerobic and anaerobic capacity of highly trained athletes. J Sports Med Phys Fitness. 2003;43(1):64–68
130. Durkalec-Michalski K, Jeszka J, Podgorski T. The effect of a 12-week beta-hydroxy-beta-methylbutyrate (hmb) supplementation on highly-trained combat sports athletes: a randomised, double-blind, placebo-controlled crossover study. Nutrients. 2017;9,7
131. Durkalec-Michalski K, Jeszka J. The efficacy of a beta-hydroxy-beta-methylbutyrate supplementation on physical capacity, body composition and biochemical markers in elite rowers: a randomised, double-blind, placebo-controlled crossover study. J Int Soc Sports Nutr. 2015;12:31. doi: 10.1186/s12970-015-0092-9
132. Durkalec-Michalski K, Jeszka J. The effect of beta-hydroxy-beta-methylbutyrate on aerobic capacity and body composition in trained athletes. J Strength Cond Res. 2016;30(9):2617–2626. doi: 10.1519/JSC.0000000000001361
133. Vukovich MD, Dreifort GD. Effect of beta-hydroxy beta-methylbutyrate on the onset of blood lactate accumulation and v(o)(2) peak in endurance-trained cyclists. J Strength Cond Res. 2001;15(4):491–497.
134. Lamboley CR, Royer D, Dionne IJ. Effects of beta-hydroxy-beta-methylbutyrate on aerobic-performance components and body composition in college students. Int J Sport Nutr Exerc Metab. 2007;17(1):56–69. doi: 10.1123/ijsnem.17.1.56
135. Fuller JC, Jr, Sharp RL, Angus HF, Baier SM, Rathmacher JA. Free acid gel form of beta-hydroxy-beta-methylbutyrate (hmb) improves hmb clearance from plasma in human subjects compared with the calcium hmb salt. Br J Nutr. 2011;105(3):367–372. doi: 10.1017/S0007114510003582
136. Wilson JM, Lowery RP, Joy JM, Andersen JC, Wilson SM, Stout JR, Duncan N, Fuller JC, Baier SM, Naimo MA, Rathmacher J. The effects of 12 weeks of beta-hydroxy-beta-methylbutyrate free acid supplementation on muscle mass, strength, and power in resistance-trained individuals: a randomized, double-blind, placebo-controlled study. Eur J Appl Physiol. 2014;114(6):1217–1227. doi: 10.1007/s00421-014-2854-5
137. Lowery RP, Joy JM, Rathmacher JA, Baier SM, Fuller JC, Jr, Shelley MC, 2nd, Jager R, Purpura M, Wilson SM, Wilson JM. Interaction of beta-hydroxy-beta-methylbutyrate free acid and adenosine triphosphate on muscle mass, strength, and power in resistance trained individuals. J Strength Cond Res. 2016;30(7):1843–1854. doi: 10.1519/JSC.0000000000000482
138. Phillips SM, Aragon AA, Arciero PJ, Arent SM, Close GL, Hamilton DL, Helms ER, Henselmans M, Loenneke JP, Norton LE, Ormsbee MJ, Sale C, Schoenfeld BJ, Smithryan AE, Tipton KD, Vukovich MD, Wilborn C, Willoughby DS. Changes in body composition and performance with supplemental hmb-fa+atp. J Strength Cond Res. 2017;31(5):e71–e72. doi: 10.1519/JSC.0000000000001760
139. Silva VR, Belozo FL, Micheletti TO, Conrado M, Stout JR, Pimentel GD, Gonzalez AM. Beta-hydroxy-beta-methylbutyrate free acid supplementation may improve recovery and muscle adaptations after resistance training: a systematic review. Nutr Res. 2017;45:1–9. doi: 10.1016/j.nutres.2017.07.008
140. Larsen FJ, Schiffer TA, Borniquel S, Sahlin K, Ekblom B, Lundberg JO, Weitzberg E. Dietary inorganic nitrate improves mitochondrial efficiency in humans. Cell Metab. 2011;13(2):149–159. doi: 10.1016/j.cmet.2011.01.004
141. Hoon MW, Johnson NA, Chapman PG, Burke LM. The effect of nitrate supplementation on exercise performance in healthy individuals: a systematic review and meta-analysis. Int J Sport Nutr Exerc Metab. 2013;23(5):522–532. doi: 10.1123/ijsnem.23.5.522
142. Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Dietary nitrate reduces maximal oxygen consumption while maintaining work performance in maximal exercise. Free Radic Biol Med. 2010;48(2):342–347. doi: 10.1016/j.freeradbiomed.2009.11.006
143. Hord NG, Tang Y, Bryan NS. Food sources of nitrates and nitrites: the physiologic context for potential health benefits. Am J Clin Nutr. 2009;90(1):1–10. doi: 10.3945/ajcn.2008.27131.
144. Webb AJ, Patel N, Loukogeorgakis S, Okorie M, Aboud Z, Misra S, Rashid R, Miall P, Deanfield J, Benjamin N, Macallister R, Hobbs AJ, Ahluwalia A. Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite. Hypertension. 2008;51(3):784–790. doi: 10.1161/HYPERTENSIONAHA.107.103523
145. Joy JM, Lowery RP, Falcone PH, Mosman MM, Vogel RM, Carson LR, Tai CY, Choate D, Kimber D, Ormes JA, Wilson JM, Moon JR. 28 days of creatine nitrate supplementation is apparently safe in healthy individuals. J Int Soc Sports Nutr. 2014;11(1):60. doi: 10.1186/s12970-014-0060-9
146. Bescos R, Rodriguez FA, Iglesias X, Ferrer MD, Iborra E, Pons A. Acute administration of inorganic nitrate reduces vo(2peak) in endurance athletes. Med Sci Sports Exerc. 2011;43(10):1979–1986. doi: 10.1249/MSS.0b013e318217d439
147. Peeling P, Cox GR, Bullock N, Burke LM. Beetroot juice improves on-water 500 m time-trial performance, and laboratory-based paddling economy in national and international-level kayak athletes. Int J Sport Nutr Exerc Metab. 2015;25(3):278–284. doi: 10.1123/ijsnem.2014-0110
148. Muggeridge DJ, Howe CC, Spendiff O, Pedlar C, James PE, Easton C. The effects of a single dose of concentrated beetroot juice on performance in trained flatwater kayakers. Int J Sport Nutr Exerc Metab. 2013;23(5):498–506. doi: 10.1123/ijsnem.23.5.498
149. Wilkerson DP, Hayward GM, Bailey SJ, Vanhatalo A, Blackwell JR, Jones AM. Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists. Eur J Appl Physiol. 2012;112(12):4127–4134. doi: 10.1007/s00421-012-2397-6
150. Macleod KE, Nugent SF, Barr SI, Koehle MS, Sporer BC, Macinnis MJ. Acute beetroot juice supplementation does not improve cycling performance in normoxia or moderate hypoxia. Int J Sport Nutr Exerc Metab. 2015;25(4):359–366. doi: 10.1123/ijsnem.2014-0129.
151. Arnold JT, Oliver SJ, Lewis-Jones TM, Wylie LJ, Macdonald JH. Beetroot juice does not enhance altitude running performance in well-trained athletes. Appl Physiol Nutr Metab. 2015;40(6):590–595. doi: 10.1139/apnm-2014-0470
152. Nyakayiru JM, Jonvik KL, Pinckaers PJ, Senden J, Van Loon LJ, Verdijk LB. No effect of acute and 6-day nitrate supplementation on vo2 and time-trial performance in highly trained cyclists. Int J Sport Nutr Exerc Metab. 2017;27(1):11–17. doi: 10.1123/ijsnem.2016-0034.
153. Buck C, Guelfi K, Dawson B, Mcnaughton L, Wallman K. Effects of sodium phosphate and caffeine loading on repeated-sprint ability. J Sports Sci. 2015;33(19):1971–1979. doi: 10.1080/02640414.2015.1025235
154. Lane SC, Hawley JA, Desbrow B, Jones AM, Blackwell JR, Ross ML, Zemski AJ, Burke LM. Single and combined effects of beetroot juice and caffeine supplementation on cycling time trial performance. Appl Physiol Nutr Metab. 2014;39(9):1050–1057. doi: 10.1139/apnm-2013-0336
155. Galvan E, Walker DK, Simbo SY, Dalton R, Levers K, O’connor A, Goodenough C, Barringer ND, Greenwood M, Rasmussen C, Smith SB, Riechman SE, Fluckey JD, Murano PS, Earnest CP, Kreider RB. Acute and chronic safety and efficacy of dose dependent creatine nitrate supplementation and exercise performance. J Int Soc Sports Nutr. 2016;13:12. doi: 10.1186/s12970-016-0124-0.
156. Gilchrist M, Winyard PG, Aizawa K, Anning C, Shore A, Benjamin N. Effect of dietary nitrate on blood pressure, endothelial function, and insulin sensitivity in type 2 diabetes. Free Radic Biol Med. 2013;60:89–97. doi: 10.1016/j.freeradbiomed.2013.01.024
157. Jajja A, Sutyarjoko A, Lara J, Rennie K, Brandt K, Qadir O, Siervo M. Beetroot supplementation lowers daily systolic blood pressure in older, overweight subjects. Nutr Res. 2014;34(10):868–875. doi: 10.1016/j.nutres.2014.09.007
158. Kenjale AA, Ham KL, Stabler T, Robbins JL, Johnson JL, Vanbruggen M, Privette G, Yim E, Kraus WE, Allen JD. Dietary nitrate supplementation enhances exercise performance in peripheral arterial disease. J Appl Physiol. 2011;110(6):1582–1591. doi: 10.1152/japplphysiol.00071.2011
159. De Oliveira GV, Morgado M, Pierucci AP, Alvares TS. A single dose of a beetroot-based nutritional gel improves endothelial function in the elderly with cardiovascular risk factors. J Functional Foods. 2016;26:301–308. doi: 10.1016/j.jff.2016.08.017
160. Koopman R, Beelen M, Stellingwerff T, Pennings B, Saris WH, Kies AK, Kuipers H, Van Loon LJ. Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. Am J Physiol Endocrinol Metab. 2007;293(3):E833–E842. doi: 10.1152/ajpendo.00135.2007
161. Zawadzki KM, Yaspelkis BB, 3rd, Ivy JL. Carbohydrate-protein complex increases the rate of muscle glycogen storage after exercise. J Appl Physiol. 1992;72(5):1854–1859. doi: 10.1152/jappl.1992.72.5.1854
162. Romano-Ely BC, Todd MK, Saunders MJ, Laurent TS. Effect of an isocaloric carbohydrate-protein-antioxidant drink on cycling performance. Med Sci Sports Exerc. 2006;38(9):1608–1616. doi: 10.1249/01.mss.0000229458.11452.e9
163. Kreider RB, Earnest CP, Lundberg J, Rasmussen C, Greenwood M, Cowan P, Almada AL. Effects of ingesting protein with various forms of carbohydrate following resistance-exercise on substrate availability and markers of anabolism, catabolism, and immunity. J Int Soc Sports Nutr. 2007;4:18. doi: 10.1186/1550-2783-4-18
164. Staples AW, Burd NA, West DW, Currie KD, Atherton PJ, Moore DR, Rennie MJ, Macdonald MJ, Baker SK, Phillips SM. Carbohydrate does not augment exercise-induced protein accretion versus protein alone. Med Sci Sports Exerc. 2011;43(7):1154–1161. doi: 10.1249/MSS.0b013e31820751cb
165. Hulmi JJ, Laakso M, Mero AA, Hakkinen K, Ahtiainen JP, Peltonen H. The effects of whey protein with or without carbohydrates on resistance training adaptations. J Int Soc Sports Nutr. 2015;12:48. doi: 10.1186/s12970-015-0109-4
166. Cureton KJ, Tomporowski PD, Singhal A, Pasley JD, Bigelman KA, Lambourne K, Trilk JL, Mccully KK, Arnaud MJ, Zhao Q. Dietary quercetin supplementation is not ergogenic in untrained men. J Appl Physiol. 2009;107(4):1095–1104. doi: 10.1152/japplphysiol.00234.2009
167. Bigelman KA, Fan EH, Chapman DP, Freese EC, Trilk JL, Cureton KJ. Effects of six weeks of quercetin supplementation on physical performance in rotc cadets. Mil Med. 2010;175(10):791–798. doi: 10.7205/MILMED-D-09-00088
168. Scholten SD, Sergeev IN. Long-term quercetin supplementation reduces lipid peroxidation but does not improve performance in endurance runners. Open Access J Sports Med. 2013;4:53–61. doi: 10.2147/OAJSM.S39632.
169. Nieman DC, Williams AS, Shanely RA, Jin F, Mcanulty SR, Triplett NT, Austin MD, Henson DA. Quercetin’s influence on exercise performance and muscle mitochondrial biogenesis. Med Sci Sports Exerc. 2010;42(2):338–345. doi: 10.1249/MSS.0b013e3181b18fa3
170. Patrizio F, Ditroilo M, Felici F, Duranti G, De Vito G, Sabatini S, Sacchetti M, Bazzucchi I. The acute effect of quercetin on muscle performance following a single resistance training session. Eur J Appl Physiol. 2018;118(5):1021–1031. doi: 10.1007/s00421-018-3834-y.
171. Davis JM, Carlstedt CJ, Chen S, Carmichael MD, Murphy EA. The dietary flavonoid quercetin increases vo(2max) and endurance capacity. Int J Sport Nutr Exerc Metab. 2010;20(1):56–62. doi: 10.1123/ijsnem.20.1.56
172. Pelletier DM, Lacerte G, Goulet ED. Effects of quercetin supplementation on endurance performance and maximal oxygen consumption: a meta-analysis. Int J Sport Nutr Exerc Metab. 2013;23(1):73–82. doi: 10.1123/ijsnem.23.1.73.
173. Pierno S, Liantonio A, Camerino GM, De Bellis M, Cannone M, Gramegna G, Scaramuzzi A, Simonetti S, Nicchia GP, Basco D, Svelto M, Desaphy JF, Camerino DC. Potential benefits of taurine in the prevention of skeletal muscle impairment induced by disuse in the hindlimb-unloaded rat. Amino Acids. 2012;43(1):431–445. doi: 10.1007/s00726-011-1099-4
174. Schaffer SW, Jong CJ, Ramila KC, Azuma J. Physiological roles of taurine in heart and muscle. J Biomed Sci. 2010;17(Suppl 1):S2. doi: 10.1186/1423-0127-17-S1-S2
175. Balshaw TG, Bampouras TM, Barry TJ, Sparks SA. The effect of acute taurine ingestion on 3-km running performance in trained middle-distance runners. Amino Acids. 2013;44(2):555–561. doi: 10.1007/s00726-012-1372-1
176. Rutherford JA, Spriet LL, Stellingwerff T. The effect of acute taurine ingestion on endurance performance and metabolism in well-trained cyclists. Int J Sport Nutr Exerc Metab. 2010;20(4):322–329. doi: 10.1123/ijsnem.20.4.322
177. Mcleay Y, Stannard S, Barnes M. The effect of taurine on the recovery from eccentric exercise-induced muscle damage in males. Antioxidants (Basel). 2017;6,4
178. Milioni F, Malta Ede S, Rocha LG, Mesquita CA, De Freitas EC, Zagatto AM. Acute administration of high doses of taurine does not substantially improve high-intensity running performance and the effect on maximal accumulated oxygen deficit is unclear. Appl Physiol Nutr Metab. 2016;41(5):498–503. doi: 10.1139/apnm-2015-0435
179. Warnock R, Jeffries O, Patterson S, Waldron M. The effects of caffeine, taurine, or caffeine-taurine coingestion on repeat-sprint cycling performance and physiological responses. Int J Sports Physiol Perform. 2017;12(10):1341–1347. doi: 10.1123/ijspp.2016-0570
180. Waldron M, Patterson SD, Tallent J, Jeffries O. The effects of an oral taurine dose and supplementation period on endurance exercise performance in humans: a meta-analysis. Sports Med. 2018;48(5):1247–1253. doi: 10.1007/s40279-018-0896-2
181. Da Silva LA, Tromm CB, Bom KF, Mariano I, Pozzi B, Da Rosa GL, Tuon T, Da Luz G, Vuolo F, Petronilho F, Cassiano W, De Souza CT, Pinho RA. Effects of taurine supplementation following eccentric exercise in young adults. Appl Physiol Nutr Metab. 2014;39(1):101–104. doi: 10.1139/apnm-2012-0229.
182. Ra SG, Akazawa N, Choi Y, Matsubara T, Oikawa S, Kumagai H, Tanahashi K, Ohmori H, Maeda S. Taurine supplementation reduces eccentric exercise-induced delayed onset muscle soreness in young men. Adv Exp Med Biol. 2015;803:765–772. doi: 10.1007/978-3-319-15126-7_61
183. Zembron-Lacny A, Szyszka K, Szygula Z. Effect of cysteine derivatives administration in healthy men exposed to intense resistance exercise by evaluation of pro-antioxidant ratio. J Physiol Sci. 2007;57(6):343–348. doi: 10.2170/physiolsci.RP009307
184. Krzywanski J, Mikulski T, Krysztofiak H, Mlynczak M, Gaczynska E, Ziemba A. Seasonal vitamin d status in polish elite athletes in relation to sun exposure and oral supplementation. PLoS One. 2016;11(10):e0164395. doi: 10.1371/journal.pone.0164395
185. Close GL, Hamilton DL, Philp A, Burke LM, Morton JP. New strategies in sport nutrition to increase exercise performance. Free Radic Biol Med. 2016;98:144–158. doi: 10.1016/j.freeradbiomed.2016.01.016
186. Braham R, Dawson B, Goodman C. The effect of glucosamine supplementation on people experiencing regular knee pain. Br J Sports Med. 2003;37(1):45–49. doi: 10.1136/bjsm.37.1.45
187. Lugo JP, Saiyed ZM, Lane NE. Efficacy and tolerability of an undenatured type ii collagen supplement in modulating knee osteoarthritis symptoms: a multicenter randomized, double-blind, placebo-controlled study. Nutr J. 2016;15:14. doi: 10.1186/s12937-016-0130-8
188. Gleeson M. Nutritional support to maintain proper immune status during intense training. Nestle Nutr Inst Workshop Ser. 2013;75:85–97. doi: 10.1159/000345822
189. Lowery L, Berardi JM, Ziegenfuss T. Antioxidants. In: Antonio J, Stout J, editors. Sports supplements. Baltimore: Lippincott, Williams & Wilkins; 2001. pp. 260–278.
190. Gleeson M. Nutritional support to maintain proper immune status during intense training. Nestle Nutr Inst Workshop Ser. 2013;75:85–97. doi: 10.1159/000345822.
191. Kris-Etherton PM, Harris WS, Appel LJ, American Heart Association. Nutrition C Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation. 2002;106(21):2747–2757. doi: 10.1161/01.CIR.0000038493.65177.94
192. Hill AM, Buckley JD, Murphy KJ, Howe PR. Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors. Am J Clin Nutr. 2007;85(5):1267–1274. doi: 10.1093/ajcn/85.5.1267
193. Nieman DC. Risk of upper respiratory tract infection in athletes: an epidemiologic and immunologic perspective. J Athl Train. 1997;32(4):344–349
194. Talbott S, Talbott J. Effect of beta 1, 3/1, 6 glucan on upper respiratory tract infection symptoms and mood state in marathon athletes. J Sports Sci Med. 2009;8(4):509–515.
195. Cox AJ, Pyne DB, Saunders PU, Fricker PA. Oral administration of the probiotic lactobacillus fermentum vri-003 and mucosal immunity in endurance athletes. Br J Sports Med. 2010;44(4):222–226. doi: 10.1136/bjsm.2007.044628
196. Gleeson M, Bishop NC, Oliveira M, Mccauley T, Tauler P, Lawrence C. Effects of a lactobacillus salivarius probiotic intervention on infection, cold symptom duration and severity, and mucosal immunity in endurance athletes. Int J Sport Nutr Exerc Metab. 2012;22(4):235–242. doi: 10.1123/ijsnem.22.4.235