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side stitch

Side stitch

When running or exercising, a side stitch is an intense stabbing pain under the lower edge of your ribcage although it may occur in any region of your abdomen 1. Side stitch is also referred to as exercise related transient abdominal pain 2 or ‘side ache’ 3. This pain is caused by the internal organs (like the liver and stomach) pulling downwards on the diaphragm. Side stitch is therefore more likely to occur in sports involving up and down actions – like running, jumping and horse riding  4.

Approximately 70% of runners report experiencing the pain in the past year and in a single running event approximately one in five participants can be expected to suffer exercise related transient abdominal pain. Side stitch (exercise-related transient abdominal pain) is a localized pain that is most common in the lateral aspects of the mid abdomen along the costal border, although it may occur in any region of the abdomen. Side stitch (exercise-related transient abdominal pain) may also be related to shoulder tip pain, which is the referred site from tissue innervated by the phrenic nerve.

Side stitch (exercise-related transient abdominal pain) tends to be sharp or stabbing when severe, and cramping, aching, or pulling when less intense. Side stitch is exacerbated by the postprandial (after meal) state, with hypertonic beverages being particularly provocative 4. Side stitch (exercise-related transient abdominal pain) is most common in the young but is unrelated to sex or body type. Well trained athletes are not immune from the condition, although they may experience it less frequently.

Several theories have been presented to explain the mechanism responsible for the pain, including ischemia of the diaphragm; stress on the supportive visceral ligaments that attach the abdominal organs to the diaphragm; gastrointestinal ischemia or distension; cramping of the abdominal musculature; ischemic pain resulting from compression of the celiac artery by the median arcuate ligament; aggravation of the spinal nerves; and irritation of the parietal peritoneum. Of these theories, irritation of the parietal peritoneum best explains the features of side stitch; however, further investigations are required.

Strategies for managing the pain are largely anecdotal, especially given that its cause remains to be fully elucidated. Commonly purported prevention strategies include avoiding large volumes of food and beverages for at least 2 hours prior to exercise, especially hypertonic compounds; improving posture, especially in the thoracic region; and supporting the abdominal organs by improving core strength or wearing a supportive broad belt. Techniques for gaining relief from the pain during an episode are equivocal.

Side stitch key points

  • Side stitch (exercise-related transient abdominal pain)is a well known and common condition that, until a spate of investigations over the past 15 years, has historically received limited research attention.
  • The characteristics of side stitch (exercise-related transient abdominal pain) are reasonably well understood but the mechanism responsible for the pain remains to be fully elucidated.
  • Further studies are required to determine the etiology of side stitch (exercise-related transient abdominal pain)so as to inform effective strategies for managing the condition.

Side stitch prevalence and incidence

Morton and Callister 1 surveyed 965 participants from six sports and reported 61 % had experienced side stitch (exercise-related transient abdominal pain) in the past year. The prevalence of side stitch (exercise-related transient abdominal pain) in these sports was as follows:

  • swimming (75 %, N = 103),
  • running (69 %, N = 439),
  • horse riding (62 %, N = 100),
  • aerobic group fitness (52 %, N = 126),
  • basketball (47 %, N = 121) and
  • cycling (32 %, N = 76).

In a study of 110 triathletes, Sullivan 5 reported a similar prevalence of side stitch (exercise-related transient abdominal pain)for running (68 %), but lower rates for swimming (15 %) and cycling (8 %). The disparity in the reported prevalence of side stitch (exercise-related transient abdominal pain) in swimming might be explained by the swimmers surveyed by Morton and Callister 1 being very young, which increases susceptibility to the pain. When age and other personal characteristics known to affect side stitch (exercise-related transient abdominal pain) were controlled for, Morton and Callister 6 found running and horse riding to be most provocative of the pain, and cycling the least. side stitch (exercise-related transient abdominal pain)was 10.5 and 9 times more common in running and horse riding than cycling, respectively 6.

The incidence of side stitch (exercise-related transient abdominal pain) during a single running event has been reported by Morton et al. 7 (N = 848) and ter Steege and Kolkman 8 (N = 1,254) as 27 and 17 %, respectively. While Morton et al. 7 questioned participants immediately after completing the event, ter Steege and Kolkman 8 administered an online questionnaire within 48 hours following the event, to which some participants did not respond to for several weeks. Consequently, inaccuracies in recall may have misrepresented the incidence reported by ter Steege and Kolkman 9. A further explanation for the differing incidences of side stitch (exercise-related transient abdominal pain) reported in the two studies may be that ter Steege et al. 9 asked only about side stitch (exercise-related transient abdominal pain) of ‘moderate’ or greater severity. Therefore, the subjects in this study may not have reported less intense experiences of side stitch. Smaller studies have reported the incidence of side stitch (exercise-related transient abdominal pain)to be 21 % for a 10-km event 10 and 19 % for a 67-km ultramarathon 3. Hence, the body of evidence suggests that approximately one in five participants in a running event may be expected to experience side stitch.

Side stitch causes

The etiology of side stitch (exercise-related transient abdominal pain) remains speculative, although progress has been made within the past 15 years regarding potential mechanisms. While some long-standing theories seem unlikely in the light of more recent findings, other novel theories have emerged. Indeed, determining the cause of side stitch (exercise-related transient abdominal pain) is the first step towards developing procedures to manage the ailment, if at all possible.

Many of the characteristics of side stitch (exercise-related transient abdominal pain) are consistent with irritation of the parietal peritoneum, and while speculative, friction on this tissue might be a plausible explanation for side stitch (exercise-related transient abdominal pain) 11.

Numerous theories have been proposed to explain the mechanism responsible for side stitch (exercise-related transient abdominal pain), however, many are based on case studies or anecdotal reports. The recent spate of investigations over the past 15 years have provided a better understanding of the characteristics of side stitch (exercise-related transient abdominal pain) and factors relating to its provocation, allowing an evidence-based approach for appraising previously proposed theories and generating alternative explanations 12. Interestingly, long-held theories that have now been convincingly discredited still commonly appear in the literature 13. Importantly, the consistent characteristics of side stitch (exercise-related transient abdominal pain) reported in widely differing individuals and sporting activities suggests a single cause 14.

Diaphragmatic ischemia

In 1941, Capps 15 proposed that side stitch (exercise-related transient abdominal pain) was caused by ischemia of the diaphragm. In support of this theory are sensations associated with innervation of the diaphragm. The diaphragm is mostly innervated by the phrenic nerve, which refers pain to the shoulder tip region, but the peripheral portions of the diaphragm are supplied by the lower six intercostal nerves, which could account for sharp and well localized pain in the subcostal region 16.

The main evidence against this theory is that side stitch (exercise-related transient abdominal pain) can be induced by activities of low respiratory demand, such as horse, camel, and motorbike riding, where ischemia of the diaphragm is improbable 1. Further, this theory does not account for side stitch (exercise-related transient abdominal pain) in regions of the abdomen other than the subcostal border. Finally, it has been questioned whether in non-diseased individuals the diaphragm muscle would become ischemic and fatigue before the muscles of the limbs, as this would imply central fatigue precedes peripheral fatigue 17.

Interestingly, in a study that predated Capps’ theory, diaphragmatic movements were monitored during an episode of side stitch (exercise-related transient abdominal pain) using a fluoroscopic technique and were found to be full and unrestricted 18. More recently, Morton and Callister 19 required subjects to perform a flow-volume loop while experiencing side stitch (exercise-related transient abdominal pain) and found no compromise in any spirometry measures. They had hypothesized that lung function would be impaired, especially inhalation, if the diaphragm was ischemic 19. In conclusion, diaphragmatic ischemia is an unlikely etiology of side stitch (exercise-related transient abdominal pain) .

Mechanical stress on the visceral ligaments

Historically, the most widely accepted theory on the causation of side stitch (exercise-related transient abdominal pain) has centred on mechanical stress being placed upon the visceral ligaments that support the abdominal viscera, especially the liver and stomach, via attachments to the diaphragm. The theory was first proposed at least as far back as the 1920s 20, but was popularized by Sinclair 2 in 1951.

This theory explains several features of side stitch (exercise-related transient abdominal pain), most notably the high prevalence of side stitch (exercise-related transient abdominal pain) in activities that are ‘jolting’ in nature yet of low respiratory demand such as horse riding 21. Further, consuming food and fluid prior to exercise could provoke side stitch (exercise-related transient abdominal pain) by the increased gastric mass loading the visceral ligaments 2. Plunkett and Hopkins 22 argued that increased gastric mass would also result when consuming hypertonic beverages 23 due to these fluids slowing gastric emptying and thereby maintaining a larger gastric mass. As the visceral ligaments attach to the diaphragm, the theory could also explain the experience of shoulder tip pain. Less well established observations that lend credibility to the visceral ligament theory include the alleged therapeutic effect of body inversion or wearing a supportive belt around the abdomen 22.

While the visceral ligament theory accounts for many of the characteristics of side stitch (exercise-related transient abdominal pain) , it has been argued that there are several aspects of the pain that the theory cannot explain 24. The observation of side stitch (exercise-related transient abdominal pain) low in the abdomen is not consistent with the theory. Further, it is unclear why side stitch (exercise-related transient abdominal pain) would be prevalent in swimming as this activity is not ‘jolting’ in nature and occurs in a prone position 1. It would be expected that increasing adipose stores within the greater and lesser omentum would contribute to an increased susceptibility to side stitch (exercise-related transient abdominal pain) , as these structures attach via mesentery directly to the stomach [34], yet side stitch (exercise-related transient abdominal pain) appears unrelated to body mass index 7 or endomorphy 12. Finally, as the ligaments are extensions of the abdominal viscera, pain arising from them would likely be visceral in nature, which is typically dull, medial and poorly localized 25, in contrast to side stitch (exercise-related transient abdominal pain) , which is mostly sharp, lateral and well localized 7.

In conclusion, the visceral ligament theory explains several features of side stitch (exercise-related transient abdominal pain) such as its high prevalence in ‘jolting’-type activities and its relation to the post-prandial state. However, the theory has shortcomings relating to the documented pain distribution and characteristics, as well as the observation that side stitch (exercise-related transient abdominal pain) can occur in non-‘jolting’ activities.

Gastrointestinal disturbances

side stitch (exercise-related transient abdominal pain) has been commonly referred to as a gastrointestinal disturbance 26 and is commonly the most prevalent symptom reported in studies of gastrointestinal complaints during exercise 3. Despite being labeled a gastrointestinal disturbance, the etiology of the pain from a gastrointestinal perspective is poorly defined 27.

The few reports that have offered a gastrointestinal explanation for side stitch (exercise-related transient abdominal pain) have focused on the pain originating from gut ischemia 8 or distension 21. Supportive of an ischemic explanation for the pain, splanchnic blood flow decreases by up to 80 % during exercise 8. Gut ischemia has been observed in otherwise healthy subjects, but only during maximal exercise 28, unlike side stitch (exercise-related transient abdominal pain) which can occur during lower intensity activities.

The main reason side stitch (exercise-related transient abdominal pain) has been labeled a gastrointestinal disturbance is due to its association with the post-prandial state 1, yet the pain is commonly experienced when no food or drink is consumed for several hours before exercise 23. More importantly, the established characteristics of side stitch (exercise-related transient abdominal pain) are dissimilar to gastrointestinal pain, which is typically described as medial, diffuse and colicky 25. Silen 25 observed that people with gastrointestinal discomfort tend to writhe the torso to obtain pain relief, which is unlike side stitch (exercise-related transient abdominal pain) that is relieved by reducing movement 7.

In conclusion, while side stitch (exercise-related transient abdominal pain) is commonly considered a gastrointestinal complaint, elements of the pain are not consistent with a gastrointestinal origin.

Muscular cramp

In the two large epidemiological studies by Morton and colleagues 7, approximately one in four sufferers of side stitch (exercise-related transient abdominal pain) described the sensation of the pain as ‘cramping’. They suggested that a muscular cramp could explain several of the features of side stitch (exercise-related transient abdominal pain) , such as the pain occurring throughout the abdomen, and suggested the theory warranted further investigation. Subsequently, Morton and Callister 29 measured localized electromyographic (EMG) activity while side stitch (exercise-related transient abdominal pain) was present, as muscular cramp is associated with high levels of EMG activity 30. EMG activity was not elevated at the site of side stitch (exercise-related transient abdominal pain) during an episode of the pain, which convincingly discredited the muscular cramp theory.

Median arcuate ligament syndrome

Side stitch (exercise-related transient abdominal pain) has been referred to in the literature as median arcuate ligament syndrome 31. The median arcuate ligament is a fibrous arch that unites the crura of the diaphragm on either side of the aortic hiatus. In some people, the ligament inserts low and crosses the proximal portion of the celiac axis, which can cause compression and ischemic-related epigastric pain, especially post-prandially and during expiration 32. While the condition does not explain several of the characteristic of side stitch (exercise-related transient abdominal pain) , such as its manifestation in other regions of the abdomen, the anatomical abnormality leading to the syndrome is surprisingly common, being present in approximately 16 % of individuals and 30 % of young people 33.

Neurogenic Pain

The experience of side stitch (exercise-related transient abdominal pain) appears to be affected by poor posture, especially in the thoracic region 12. Kugelmass 34 was the first to make this observation and he suggested that poor posture might affect side stitch (exercise-related transient abdominal pain) by altering the mechanics of the abdominal structures responsible for the pain. However, Morton and Aune 35 noted that palpating specific vertebrae in the T8–12 region, which innervates the abdominal wall, could reproduce symptoms of side stitch (exercise-related transient abdominal pain). Side stitch (exercise-related transient abdominal pain) could be exactly reproduced in 8 of 17 subjects assessed, and the site at which the subjects reported side stitch (exercise-related transient abdominal pain) corresponded to the dermatome arising from the nerve root being palpated. Hence, they suggested that a neurogenic origin of side stitch (exercise-related transient abdominal pain) should be considered.

Other reports of side stitch (exercise-related transient abdominal pain) – like symptoms in the literature have implicated the nervous system. For example, slipping rib syndrome, in which hypermobility of the eighth, ninth and/or tenth rib results in trauma to the adjacent intercostal nerve, is a documented but often undiagnosed source of upper abdominal pain similar in nature to side stitch (exercise-related transient abdominal pain) 36. Similarly, abdominal wall nerve entrapment, in which the anterior cutaneous branch of an intercostal nerve is compressed at the site at which it reflexes sharply and pierces the abdominal musculature, can produce pain with similar features to side stitch (exercise-related transient abdominal pain) 37. Finally, spinal tumors and facet joint cysts have been known to produce similar symptoms to side stitch (exercise-related transient abdominal pain) as a result of compressive forces being placed on the intercostal nerves 38.

While a neurogenic explanation does not account for all features of side stitch (exercise-related transient abdominal pain) , such as its relation to the post-prandial state, it is notable that the intercostal nerves can be rendered vulnerable to compression as a result of a reduction in intervertebral disk height that can occur during repetitive, dynamic torso movements such as running 39.

Irritation of the parietal peritoneum

After studying approximately 600 sufferers of side stitch (exercise-related transient abdominal pain), Morton and Callister 1 suggested that side stitch (exercise-related transient abdominal pain) might be caused by irritation of the parietal peritoneum, which is the outer layer of the peritoneum that adheres to the abdominal wall and underside of the diaphragm. They presented the following evidence for side stitch (exercise-related transient abdominal pain) arising from this tissue: aggravation of the portion of the parietal peritoneum that adheres to the abdominal wall causes sharp, well localized pain similar in nature to side stitch (exercise-related transient abdominal pain) 40; the portion of the parietal peritoneum that underlays the diaphragm is innervated by the phrenic nerve and gives rise to shoulder tip pain when aggravated 41; pain arising from the parietal peritoneum is accentuated by movement 25; the parietal peritoneum traverses the entire abdominal wall which could account for the widespread distribution of side stitch (exercise-related transient abdominal pain) 16; the parietal peritoneum is most firmly adhered to the abdominal wall along the linear alba and the greatest potential for movement is therefore in the lateral aspects of the abdomen 16; the tension in the parietal peritoneum is increased with the torso in an extended posture; children have a proportionally larger peritoneal surface area than that of adults which might explain the high prevalence of side stitch (exercise-related transient abdominal pain) in the young 42; and pain arising from the parietal peritoneum relieves quickly on removal of the stimulus 43 which is similar to that observed for side stitch (exercise-related transient abdominal pain) when activity is ceased 19.

In addition to these observations, several case reports describing side stitch (exercise-related transient abdominal pain) have implicated the parietal peritoneum 44. Dimeo et al. 44 reported the case of a 29-year-old national class distance runner with severe, recurrent side stitch (exercise-related transient abdominal pain) in the upper right abdominal quadrant during exertion. Laparoscopy showed congenital supernumerary ligaments binding the gallbladder to the abdominal wall. Symptoms of side stitch (exercise-related transient abdominal pain) resolved after cholecystectomy and resection of the adhesions. Similarly, Lauder and Moses 45 reported adhesions between the ascending colon and anterior abdominal wall to be the cause of recurrent side stitch (exercise-related transient abdominal pain) in a 28-year-old triathlete. The pain resolved following surgical intervention. Several authors have also suggested that side stitch (exercise-related transient abdominal pain) is caused by a ‘cecal slap syndrome’ in which the caecum slaps against the anterior abdominal wall during repetitive jolting actions such as running 46.

Morton and Callister 1 suggested that side stitch (exercise-related transient abdominal pain) might result from increased friction between the parietal peritoneum attached to the abdominal wall and the visceral peritoneum that overlays the abdominal viscera. They argued that friction might be increased by the visceral and parietal layers of the peritoneum being forced more firmly together by distension of the stomach, as occurs in the postprandial state, or other abdominal organs such as the liver or large intestine. Further, they suggested that exercise-mediated changes in the quantity or viscosity of the lubricating serous fluid contained within the peritoneal cavity might increase friction. The serous fluid within the peritoneal cavity is in a constant state of flux 47, being derived from splanchnic blood flow, which decreases during exercise 8, and draining into the lymphatic system, which is facilitated by movement of the diaphragm 48. Interestingly, the fluid in the peritoneal cavity is highly responsive to osmotic gradients between it and its vascular supply 47, which might explain the provocative effect of consuming hypertonic beverages on side stitch (exercise-related transient abdominal pain) 23. Results of the study by Morton et al. 23 indicated that consuming hypertonic beverages provoked side stitch (exercise-related transient abdominal pain) for reasons other than just increasing gastric mass due to slowing of gastric emptying.

Recently, Mole et al. 49 found that individuals symptomatic to side stitch (exercise-related transient abdominal pain) had significantly thinner transversus abdominis and poorer functional core stability than asymptomatic individuals. The authors argued that better strength and activation of the abdominal musculature, especially the transversus abdominis, might reduce abdominal content mobility leading to lesser symptoms of side stitch (exercise-related transient abdominal pain). This observation may lend further support to the parietal peritoneum theory, although it would also support the visceral ligament theory as better core stability might reduce loading on the visceral ligaments.

Factors influencing the experience of side stitch

Personal characteristics

In an article that appeared in the British Medical Journal in 1945 50, the author asserted that some individuals are more susceptible to side stitch (exercise-related transient abdominal pain) than others, which could be attributed to anatomical, physiological, or mechanical factors. Subsequently, investigations of a variety of personal characteristics on the experience of side stitch (exercise-related transient abdominal pain) have been conducted 12.

Several studies have demonstrated that the young are most susceptible to side stitch (exercise-related transient abdominal pain) 1. Morton and Callister 6 reported 77 % of active individuals under the age of 20 years experienced the pain compared with only 40 % of individuals over the age of 40 years. Both the prevalence and severity of side stitch (exercise-related transient abdominal pain) have been shown to significantly decrease with increasing age 7. Confounding the observation that side stitch (exercise-related transient abdominal pain) decreases with increasing age might be a reduction in activity levels, however these studies targeted an active population. While the young appear more susceptible to the pain, Kugelmass 34 reported it to be relatively uncommon before the age of 10 years.

Conflicting reports exist regarding the influence of sex on side stitch (exercise-related transient abdominal pain) . side stitch (exercise-related transient abdominal pain) was reported four times more frequently by females in a study by ter Steege et al. 9 of gastrointestinal complaints during long distance running. Other studies of gastrointestinal symptoms during running have also reported a higher prevalence of side stitch (exercise-related transient abdominal pain) among females 51. Rehrer et al. 3 reported 41 % of females experienced side stitch (exercise-related transient abdominal pain) during an ultra-marathon event compared with only 17 % of males, although the difference was not statistically significant as only 12 females participated in the event. Conversely, two studies by Morton and colleagues 7 found no gender differences in the experience of side stitch (exercise-related transient abdominal pain) when other potentially confounding factors such as age were controlled for. As the studies by Morton and colleagues 7 involved a comparably larger number of cases, the weight of the current evidence suggests that there is little or no effect of gender on side stitch (exercise-related transient abdominal pain) .

A high level of physical conditioning may decrease the experience of side stitch (exercise-related transient abdominal pain) 15; however, the ailment is not unknown among well trained and even elite athletes 7. Morton and Callister 1 observed well conditioned individuals to be as likely to report experiencing side stitch (exercise-related transient abdominal pain) within the past year as less conditioned individuals and also to report pain of a similar severity, although better conditioned individuals reported experiencing the pain less frequently. Hence, training status might have some prophylactic benefits but in some athletes the possibility of experiencing side stitch (exercise-related transient abdominal pain) cannot be eliminated 15.

The influence of body type and posture on side stitch (exercise-related transient abdominal pain) has been investigated in several studies 7. Body mass index was not related to side stitch (exercise-related transient abdominal pain) in either of the large epidemiological studies conducted by Morton and colleagues 7. Recognizing the limitations of body mass index as a surrogate for body type, Morton and Callister 12 investigated the relationship between somatotype and the experience of side stitch (exercise-related transient abdominal pain) in 159 active young people (mean age = 18.6 years). side stitch (exercise-related transient abdominal pain) was unrelated to somatotype, which conflicted with an early report by Kugelmass 34, who observed children with an ectomorphic disposition to be most afflicted by the pain. However, the two studies 12 did concur that individuals with poor postural alignment were more predisposed to the pain. Morton and Callister 12 found individuals with kyphosis were more susceptible to side stitch (exercise-related transient abdominal pain) and the extent of kyphosis and lordosis influenced the pain severity. The implications of these observations are discussed below when considering the etiology of the pain.

Mode of exercise

As described previously, the experience of side stitch (exercise-related transient abdominal pain) varies for different sporting activities, with running consistently being reported as most provocative of the condition 7. It has been concluded that side stitch (exercise-related transient abdominal pain) is most prevalent in activities that involve repetitive torso movement, involving either vertical translation or longitudinal rotation, especially when the torso is in an extended posture 52. These conditions are all met in running, which explains the high prevalence of side stitch (exercise-related transient abdominal pain) in this activity. Swimming extends the torso and involves repetitive rotation with the torso extended, accounting for a modest prevalence of side stitch (exercise-related transient abdominal pain) . Cycling, in which the prevalence of side stitch (exercise-related transient abdominal pain) is comparatively low, flexes the torso and involves relatively little movement.

Exercise intensity has been suggested to influence side stitch (exercise-related transient abdominal pain) 53 although the pain can clearly occur during activities of low intensity such as horse riding 1. Morton et al. 7 reported 31 % of runners experienced the pain during a walk/run event compared with only 16 % of walkers. Controlling for factors such as the age of the participants, the runners were 3.5 times more likely to report the pain than the walkers. As running also differs from walking in its movement characteristics, this would confound the potential effect of exercise intensity. Among the runners in this study, the occurrence or severity of side stitch (exercise-related transient abdominal pain) was unrelated to the time to complete the event, suggesting exercise intensity was not important 7.

Pre-exercise ingestion

Consuming food or drink before exercise has consistently been reported to evoke side stitch (exercise-related transient abdominal pain) 7. Consequentially, laboratory-based studies that have endeavoured to take measurements of the pain have required subjects to eat and/or drink before exercise to provoke its manifestation 29.

Fifty-two percent of respondents surveyed by Morton and Callister 1 perceived eating before exercise to provoke side stitch (exercise-related transient abdominal pain) and 38 % claimed that drinking before exercise provoked the pain. Sinclair 2 reported that the postprandial state could induce side stitch (exercise-related transient abdominal pain) in 30 out of 35 cases compared with only 19 cases when prior feeding did not occur. Approximately half of the individuals who reported developing side stitch (exercise-related transient abdominal pain) during the run/walk event studied by Morton et al. 7 claimed the pain developed shortly after ingesting fluid at a drink station. Further, an analysis of the pre-event meal of the 848 participants in this event showed a positive relationship between the volume of food and drink consumed relative to body weight and the experience of side stitch (exercise-related transient abdominal pain) . Interestingly, side stitch (exercise-related transient abdominal pain) was unrelated to the nutritional content of the pre-event meal with regards to carbohydrate (sugar and starch), fat, protein, water, or total energy. However, a limitation of this study was that participants were not asked whether they periodically experienced the pain and so analyses could not be performed on the symptomatic individuals only.

Two studies have shown that the composition of ingested fluid influences the experience of side stitch (exercise-related transient abdominal pain) , with hypertonic fluids being most provocative 23. Plunkett and Hopkins 22 compared the consumption of large volumes of water, an isotonic solution, and a hypertonic solution on the experience of side stitch (exercise-related transient abdominal pain) during treadmill running. They found that the isotonic solution evoked fewer symptoms of side stitch (exercise-related transient abdominal pain) than water but the hypertonic trial was more provocative than both. Similarly, Morton et al. 23 found a hypertonic beverage to be significantly more provocative of side stitch (exercise-related transient abdominal pain) than isotonic and hypotonic beverages, with 83 % of subjects developing the pain after consuming the hypertonic solution compared with 70 % in the other two trials. Other studies have suggested a connection between the carbohydrate content of ingested fluid and the experience of side stitch (exercise-related transient abdominal pain) 53.

While fluid consumption appears to provoke side stitch (exercise-related transient abdominal pain), fluids may be better tolerated with practice. Reliability testing conducted by Morton et al. 23, which involved subjects exercising on several occasions after consuming large volumes of fluid, found that the experience of side stitch (exercise-related transient abdominal pain) decreased in the later trials. Just as the gut may be trainable with regards to digesting and absorbing fluids during exercise 54, this may suggest that sufferers of side stitch (exercise-related transient abdominal pain) might benefit from practicing fluid consumption during exercise.

Inadequate warm-up and cold ambient conditions

Inadequate warm-up prior to exercise and cold ambient conditions have been suggested to provoke side stitch (exercise-related transient abdominal pain) 7; however, these claims are based on anecdotal observations. For example, Capps 15 claimed that 40 out of 60 competitors in a cross-country running event that occurred in an ambient temperature of −9 °C were forced out of the event due to side stitch (exercise-related transient abdominal pain) . Morton et al. 7 reported that equal numbers of competitors developed side stitch (exercise-related transient abdominal pain) during the first, middle, and final third of a 14-km running event, suggesting that inadequate warm-up was not an important contributor. At this time, the influence of these factors is inconclusive and requires further clarification.

Side stitch symptoms

While conflicting reports of the pain characteristics of side stitch (exercise-related transient abdominal pain) appeared in early studies 4, more recent larger studies have demonstrated that the manifestation of the pain is remarkably similar between individuals 7 and in different sporting activities 6. This is an important qualification as it indicates that side stitch (exercise-related transient abdominal pain) is mostly a single condition, rather than a cluster of ailments 1. Further, this suggests a single cause 55.

Pain sensation and severity

Morton and Callister 1 studied almost 600 cases of side stitch (exercise-related transient abdominal pain) and observed that the sensation of the pain was significantly related to its severity. The pain was described as sharp or stabbing when severe, and cramping, aching, or pulling when less intense. Progression to sharp and stabbing pain with increasing pain severity has been observed subsequently in other epidemiological studies 7, clinical trials 19, and case reports 56.

When Morton and Callister questioned individuals from six sports about their experience of side stitch (exercise-related transient abdominal pain) in the past year, symptomatic individuals reported the severity as 5.6 ± 0.2 out of 10 at its worst, resulting in 76 % having to reduce their exercise intensity when the pain was present and 12 % to stop exercise altogether 1. In a study that targeted a single running event, sufferers rated the pain as 3.6 ± 0.1 out of 10, forcing 36 % to slow down and 6 % to stop entirely 7. Although the pain is mostly benign, it can clearly be detrimental to performance and may compromise sports participation for some individuals 7.

Pain location

In approximately 80 % of cases, the pain is described as localized rather than vague and diffuse 7. While the pain is mostly localized during an episode, it may occur in any region of the abdomen 7, with pain in the mid- to upper-abdomen, especially along the costal border, being the most common site as shown in Figure 1. Right side pain has been reported as up to twice as common as left side pain 19, although left side pain may be more prevalent among the young 6.

Figure 1. Side stitch pain location

Footnote: The location of side stitch or exercise-related transient abdominal pain (ETAP) reported by the combined symptomatic subjects (N = 818) in the studies by Morton and Callister 1 and Morton et al. [7. Note, some respondents reported side stitch (exercise-related transient abdominal pain) in more than one position. L = left, R = right

[Source  4 ]

Intra-individual frequency and pain reproducibility

Approximately half of the 600 symptomatic individuals surveyed by Morton and Callister 1 claimed side stitch (exercise-related transient abdominal pain) occurred in less than 10 % of exercise sessions, and 82 % indicated it occurred no more than 20 % of the time.

The reproducibility of side stitch (exercise-related transient abdominal pain) has been explored in two laboratory-based studies 23. Plunkett and Hopkins 22 reported poor reproducibility of the condition, although only ten subjects were involved in the study. Morton et al. 23 exercised 23 symptomatic individuals on a treadmill on two different days after consuming large volumes of fluid and found 64 % experienced side stitch (exercise-related transient abdominal pain) in both trials, 23 % experienced side stitch (exercise-related transient abdominal pain) in one trial, and only 13 % did not experience side stitch (exercise-related transient abdominal pain) on either occasion. The intra-class correlation between the two trials was significant for the mean pain severity but not peak severity. The authors suggested that the between-days reliability of the pain was acceptable for repeated measure design studies, but they acknowledged that the subjective, transient, and partially unpredictable nature of the phenomenon makes studying the condition challenging 29.

Shoulder tip pain

As far back as 1951, Sinclair 2 reported an association between side stitch (exercise-related transient abdominal pain) and shoulder tip pain. In his observations on 123 athletes, 28 (23 %) reported shoulder tip pain in association with side stitch (exercise-related transient abdominal pain) and in all but one case the shoulder tip pain was on the same side of the torso as side stitch (exercise-related transient abdominal pain). The significance of this observation is that the shoulder tip region—extending from the lateral third of the trapezius border to the acromion process—is the referred site for pain arising from tissue innervated by the phrenic nerve 43, which includes the diaphragm and neighboring structures.

While difficult to delineate as referred pain, Morton and Callister 1 questioned individuals about ‘non-injury-related’ shoulder pain in their study of side stitch (exercise-related transient abdominal pain) in six sports. Fourteen percent reported experiencing sharp, well localized pain in the shoulder tip region characteristic of referred shoulder tip pain 43, and those who were susceptible to side stitch (exercise-related transient abdominal pain) were significantly more likely to report shoulder tip pain. Further, shoulder tip pain was most common in the same sports as side stitch (exercise-related transient abdominal pain) , albeit approximately 4–5 times less common than side stitch (exercise-related transient abdominal pain) 6. shoulder tip pain was only reported by 5 % of the 848 participants questioned by Morton et al. 7 at a running event, as compared with 27 % for side stitch (exercise-related transient abdominal pain), but the two conditions were significantly related. In both studies, shoulder tip pain was rated as more severe than side stitch (exercise-related transient abdominal pain) but was not related to side stitch (exercise-related transient abdominal pain) in a particular region of the torso.

Side stitch treatment

Many techniques and strategies have been proposed for preventing side stitch (exercise-related transient abdominal pain) from occurring and/or gaining relief from the pain when it is present. However, as the cause of the pain has not been well understood, many of the documented management strategies are anecdotal 11.

To prevent side stitch (exercise-related transient abdominal pain), large volumes of food and drink should be avoided at least 2 hours before exercise 7, possibly 3–4 hours 57 for those more vulnerable. During exercise, small but regular volumes of fluid might be better tolerated 14. Hypertonic beverages should be avoided 23.

Techniques that support, or restrict movement in, the torso might be helpful 22. This may be achieved by wearing a wide, supportive belt around the waist 14, but improving functional core stability is more desirable 49. Spitznagle and Sahrmann 58 reported two case studies in which exercises tailored to improve dynamic trunk stability were effective for preventing the occurrence of side stitch (exercise-related transient abdominal pain).

Kugelmass 34 reported that improving posture reduced symptoms of side stitch (exercise-related transient abdominal pain) in the children he studied. Similarly, two case studies have reported symptoms of side stitch (exercise-related transient abdominal pain) improving through a treatment regimen that aimed to improve spinal alignment and function 56.

As the frequency of side stitch (exercise-related transient abdominal pain) occurrence may decrease with improved fitness level 1, physical conditioning might be considered a prevention strategy. Failing these strategies, McCrory 59 comically advocated: “grow old, as stitches are less common with aging”.

To gain relief from side stitch (exercise-related transient abdominal pain) when the pain is present, the most common techniques reported by almost 600 sufferers questioned by Morton and Callister 1 were deep breathing (40 %), pushing on the affected area (31 %), stretching the affected site (22 %) and bending over forward (18 %). Deep breathing has been reported to relieve side stitch (exercise-related transient abdominal pain) by other authors 2 although Plunkett and Hopkins 22 found that breathing shallowly but with more air in the lungs throughout the breathing cycle relieved the pain in their subjects. Pushing on the affected site might conceivably support the abdominal organs or restrict their movement and is not dissimilar to tightening a wide belt around the waist, which was reported by Plunkett and Hopkins 22 to relieve the pain. Reports of bending over forward 1 and stretching the affected site 1 seem contradictory, which questions the efficacy of these maneuvers.

In conclusion, it is disappointing that the despite the recent research interest in the condition, innovative methods for managing the well known, potentially debilitating pain have not been determined. Indeed, the most effective strategy for relieving side stitch (exercise-related transient abdominal pain) remains to stop exercising 19, which is not always practical or desirable.

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