The dreaded stitch revisited
Issue: Volume 28 Number 3
In 2001, Coaches’ Edge (www.coachesedge.com) reported on some cutting-edge research into the causes of the dreaded ‘stitch’, or what scientists call Exercise-related Transient Abdominal Pain (ETAP).
That research suggested ETAP could be caused by the dehydration of the parietal peritoneum, the membrane lining the entire abdominal wall, extending up under the diaphragm. It also identified a possible link between ETAP and the carbohydrate levels in the fluids drunk before and during exercise.
This article reveals new research findings.
Overview
It appears there is nothing simple about the stitch. In fact, this new research indicates there could be several causes for ETAP:
- Firstly, the new investigations reinforce the belief that high-carbohydrate drinks, such as fruit juice, ingested before and during exercise, are more likely to provoke ETAP than lower-carbohydrate fluids (such as water or Gatorade ).
- Secondly, it appears that ETAP is not actually a muscle cramp, as is often thought, and is not as a result of a diaphragm disorder.
- Thirdly, and perhaps most surprisingly, a new study has linked the curvature of an athlete’s spine to the onset and the severity of ETAP.
Study 1: are carbs linked to ETAP?
After the findings of the initial research it was necessary to further investigate the link between carbohydrate levels in various drinks and the onset of ETAP.
To do this, three different beverages were compared (Morton, Aragon–Vargas and Callister 2001); these were flavoured water (0 per cent carbohydrate), Gatorade sports drink (6 per cent carbohydrate) and a reconstituted fruit juice (11 per cent carbohydrate). As a control, a test was also carried out on subjects who were not given any fluid.
Forty subjects consumed a given volume of the beverage being trialled 20 minutes before starting to run on a treadmill. The subjects then drank a portion of the beverage at regular intervals during the run. Symptoms of ETAP and other gastrointestinal complaints were monitored every two minutes.
Unremarkably, drinking no fluid produced the fewest symptoms of ETAP. However, dehydration can be far more debilitating to performance than experiencing a bout of ETAP and should be avoided.
The results for the three carbohydrate drinks show a marked difference. Unequivocally, the reconstituted fruit juice resulted in greater symptoms of ETAP. When drinking reconstituted fruit juice, the subjects developed ETAP more quickly during exercise, and when they persisted with the exercise, the pain grew to a greater severity.
Interestingly, when the subjects were consuming flavoured water and Gatorade sports drink there was no significant difference in the severity of ETAP observed.
Previous research (Murray et al. 1997) established that high-carbohydrate fluids pass slowly through the stomach, and this study confirmed that the reconstituted fruit juice certainly resulted in greater feelings of abdominal bloating and discomfort. What is interesting, however, is that the data analysis indicates that the ETAP-provocative nature of the reconstituted fruit juice was independent of its affect on abdominal bloating. In other words, high-carbohydrate beverages appear to cause ETAP for reasons other than just making your stomach distended. This may be due to the slowing effect that high-carbohydrate drinks have on fluid absorption in the intestine, but further exploration is needed.
The study concluded that flavoured waters and Gatorade sports drink are preferable choices for preventing ETAP during exercise, when compared to higher-carbohydrate beverages. Of course a sports drink has several benefits over water — it provides a source of energy that is rapidly absorbed while also replacing electrolytes that are lost through perspiration.
Study 2: are we looking at muscle cramps?
A second study looked at whether ‘stitch’ pain is associated with abdominal cramping or diaphragm disorders (Morton and Callister 1999). The study was somewhat peculiar in that the subjects were asked to do anything they felt would provoke an episode of the pain.
When ETAP did develop to a satisfactory severity, skin electrodes were used to measure the electrophysiological activity at the site of the pain.
During a muscle cramp, which is an intense muscular contraction, electrophysiological activity is very high. However, it was found that essentially no such activity was taking place at the ETAP site, indicating that ETAP is not a muscular cramp.
Researchers then measured lung performance before and during an episode of ETAP, and found there was no change. Lung function is dependant to a great extent on the diaphragm, so it would make sense that disorders of the diaphragm would result in compromised lung function.
Hence, it appears evident that ETAP is not related specifically to the diaphragm.
Study 3: spinal involvement
The third of the new studies has discovered that an athlete’s spine may play an important function in the development of ETAP (Morton and Aune 2001). This investigation was sparked by an earlier study into the stitch, dating back to the 1940s, which made an anecdotal observation that individuals with increased curvature of the upper and lower spine (referred to as kyphosis and lordosis, respectively) seemed more likely to report the pain.
In order to investigate this more thoroughly, a comprehensive posture analysis was conducted on more than 150 individuals. These findings were then compared to their experience of ETAP. It was found that while the extent of lordosis had no bearing on ETAP, the degree of kyphosis showed a direct and overwhelming relationship. Those individuals who had increased kyphosis were far more inclined to suffer from ETAP. Additionally, it was found that abnormal sideways curvature of the spine (scoliosis) was related to the severity of the pain experienced by the subjects.
This study indicates that it is likely the spinal nerves arising from the thoracic (chest) region are involved in ETAP. Spinal nerves arising from the lower portions of the thoracic spine innervate the abdominal area. Subsequent tests have indicated that, in some individuals who suffer from ETAP, palpating the nerves adjacent to specific vertebral joints can reproduce the pain. It was deduced that if a particular spinal nerve is aggravated, it might contribute to ETAP (Morton, Aune and Callister 1999).
From a prevention viewpoint, this means that athletes who regularly suffer from ETAP might benefit from getting their spine examined by a physiotherapist for abnormalities such as joint hypermobility.
So the quest for the solution to the simple ‘stitch’ continues, but it seems that there are now two avenues to pursue. The first is to find out exactly why high-carbohydrate beverages often produce ETAP, and the second is to determine the extent to which the configuration of the spine is responsible for the pain.
Practical tips to avoid the common ‘stitch’
• Avoid high-carbohydrate drinks such as fruit juice (for example, greater than 6 per cent carbohydrates) before and during exercise
• Ensure the athlete is well hydrated for 24 hours leading up to an event. This will minimise the risk of dehydrating the parietal peritoneum as explored in Coaches' Edge, August 2001
• Where possible, avoid excessive torso movement when exercising
• If you or your athletes regularly experience a ‘stitch’, get your thoracic spine examined by a physiotherapist
References
Morton, DP, Aragon–Vargas, LF and Callister, R 2001, ‘Effect of ingested fluid composition on the experience of exercise-related transient abdominal pain’, Australian Conference of Science and Medicine in Sport Proceedings, Perth.
Morton, DP and Aune, T 2001, ‘Role of the thoracic spine in the experience of exercise related transient abdominal pain’, Australian Conference of Science and Medicine in Sport Proceedings, Perth.
Morton DP, Aune, T and Callister, R 1999, ‘Influence of body type and posture on the experience of “stitch”’, Fifth International Olympic Committee World Congress on Sport Sciences — Book of Abstracts, p. 226.
Morton, DP and Callister, R 1999, ‘Electromyography and spirometry measurements during “stitch”’, Fifth International Olympic Committee World Congress on Sport Sciences Book of Abstracts, p. 226.
Murray, R, Bartoli, WP, Eddy, DE and Horn, MK 1997, ‘Gastric emptying and plasma deuterium accumulation following ingestion of water and two carbohydrate-electrolyte beverages’, International Journal of Sports Nutrition, 7, pp. 144–215.
This article is reproduced with the permission of the editorial team at Coaches’ Edge, a free web-based newsletter that publishes the latest research in hydration, nutrition, training, injury management and mental preparation, among others. To join Coaches’ Edge, log on to www.coachesedge.com.au.
