Review Article
Sports Medicine 9 (3): 159-172, 1990 011 2-1642/90/0003-0159/$07.00/0 © ADIS Press Limited All rights reserved. SPORT2259.
The Effect of Exercise on the Gastrointestinal Tract 1 Frank M. Moses Gastroenterology Service, Walter Reed Army Medical Center, Washington, D.C., USA
Contents
Summary ............................................................................................ ....................................... 159 I. Early Reports and Surveys .............................................................................. ............... ..... 160 2. Oesophagus .................................... .. .. ............................................................................ ....... 163 3. Stomach ................................................ ................................................................................. 164 4. Intestines .................................... ............................................................. ........ .. .................... 165 5. Liver ............................................. ....... ......................................................... ......................... 167 6. Gastrointestinal Bleeding "" "." """.""" ..""".""""""."""".""."".""""""""""."""""""". 168 7. Conclusion .......... ................ ............ .. .......... .. .... ............................................... ..................... 170
Summary
Surveys of athletes, primarily runners, have shown that digestive disorders are common, associated both with training and racing. Women, in particular, seem to suffer most commonly. Nearly half have loose stools and nausea and vomiting occur frequently after hard runs. Diarrhoea, incontinence and rectal bleeding occur with surprising frequency. Runners may use medications prophylactically to minimise some of these symptoms. Upper digestive symptoms seem to occur more commonly in multisport events such as triathlons or enduro. The published literature is difficult to analyse and the basic intestinal physiology not well studied. Most gastroenterologists are accustomed to evaluating the fasting patient at rest and exercise physiologists are seldom experienced with digestive techniques. Digestive symptoms occurring with exercise referable to the oesophagus include chest pain, gastro-oesophageal reflux symptoms, or symptoms related to alterations in motility. While little is known of the oesophageal physiology during exercise, it is believed that only minimal changes occur in most subjects. Gastro-oesophageal reflux occurs more frequently with exercise than at rest and may produce symptoms of chest pain suggestive of ischaemic disease. Acid exposure may be reduced by pretreatment with histamine H2receptor antagonists. Oesophageal symptoms, though common, are rarely disabling to the athlete, and the clinical importance lies in confusion with ischaemic disease. Cases of acute gastric stasis following running have been reported and gastric physiology during exercise, particularly bicycling, has been more actively investigated. Gastric emptying during exercise is subject to a number of factors including calorie count, meal osmolality, meal temperature and exercise conditions. However, it is generally accepted
I The opinions or assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.
Sports Medicine 9 (3) 1990
160
that light exercise accelerates liquid emptying, vigorous exercise delays solid emptying and has little effect upon liquid emptying until near exhaustion. Gastric acid secretion probably changes little with exercise although some have postulated that ulcer patients may increase secretion with exercise. Some exercise-associated digestive symptoms, such as diarrhoea and abdominal pain, have been attributed to changes in intestine function. Small bowel transit is delayed by exercise when measured by breath hydrogen oral caecal transit times and motility may be reduced as well. Intestinal absorption during exercise has not been well evaluated but probably changes little in ordinary circumstances. Passive absorption of water, electrolytes and xylose are not affected by submaximal effort. Colonic transit and function is even more difficult to evaluate and published results have been conflicting. However, it is likely that many of the lower digestive complaints of runners such as diarrhoea and lower abdominal cramps are due to direct effects of exercise upon the colon. Gastrointestinal bleeding is the most dramatic digestive disorder associated with exercise. While 'runner's anaemia' may often represent a pseudonaemia from expanded plasma volume, runners may develop haematemesis or melaena after competitive or training events or present only with symptoms of profound iron deficiency and anemia. Many surveys have demonstrated that approximately 20% of marathon runners will convert to guaiac positivity following the race. While cases of presumed ischaemic colitis occur and anorectal sources of bleeding have been identified, by far the most frequently reported lesion of running associated bleeding has been haemorrhagic gastritis. The aetiology is felt to be ischaemic though other possibilities have not been excluded. The lesion is transient, resolves quickly with rest, and is not recognised if endoscopy is not done within 72 hours of the event. While exercise-associated intestinal bleeding is common, individual cases must be evaluated clinically. Exercise, while of obvious benefit to the general health of many, does not offer assurance against other, more mundane causes of intestinal bleeding. The study of the digestive tract during the stress of exercise is in Its mtancy. It IS hoped that the awareness of symptoms and clinical difficulties encountered by active subjects will provoke additional study of the GI physiology of the active individual in health and disease.
Abdominal discomfort, diarrhoea and other digestive disorders are frequent among athletes. Although these symptoms are oflow intensity in most, they may be an occasion of great disability. Perhaps the most dramatic digestive disorder associated with exercise is that of gastrointestinal (GI) haemorrhage. After winning a marathon in record time, Derek Clayton was quoted as saying: 'Two hours later, the elation had worn off. I was urinating quite large clots of blood, and I was vomiting black mucus and had black diarrhea. I don't think too many people can understand what I went through for the next 48 hours' (Clayton 1979). Other leading runners have been slowed by refractory iron deficiency anaemia. The symptoms of gastric stasis and diarrhoea similarly limit athletic performance. However, despite several excellent reviews (Brouns
et al. 1987; Keeffe et al. 1984; Riddoch & Trinick 1988; Sullivan 1984; Worobetz & Gerrard 1985) little formal attention has been devoted towards these problems and only now are investigators attempting to unravel the physiology ofthe digestive system during exercise. This article reviews recent published series and personal observations and summarises the more common and more serious conditions encountered by physicians caring for athletes.
1. Early Reports and Surveys Interest in exercise physiology of the digestive tract dates back at least to William Beaumont who observed the permanent gastric fistula of Alexis St. Martin. He differentiated the effects of moderate
Effect of Exercise on the GI Tract
and severe exercise after meals and seemed quite aware that fatiguing exercise retarded digestion (Beaumont 1838). Some years later the effects of exercise upon gastric secretion and digestion were again studied and it was said that exercise which produced no discomfort helped digestion and exercise which produced discomfort delayed it (Campbell et al. (928). However, interest in athletic-associated, primarily running-associated, digestive disorders was renewed by a series of reports in the early part of this decade. A letter describing 'athletes' diarrhoea in distance runners (Scobie 1978) was followed by a report of 2 cases of GI disturbances in runners: a young long distance runner who suffered abdominal pain and loose bowel movements with running, and a young medical student and distance runner with a history of bloody diarrhoea and crampy abdominal pain following hard runs (Fogoros (980). Next, a letter detailing a survey of a recreational runners' club reported heartburn in 10% of runners and common complaints of abdominal cramps, the urge to have a bowel movement, and a decrease in appetite following a race (Sullivan 1981). Later that year another report appeared of 2 runners, one who suffered abdominal pain and bloody diarrhoea and presumed to have ischaemic colitis and a second who also suffered bloody diarrhoea with running in whom no aetiology was found (Cantwell (981). In 1984 a survey of 707 respondents in a marathon run noted frequent GI symptoms. Nearly half had occasional loose stools and 13% had 3 or more bowel movements per day. Nausea and vomiting were more frequent following hard runs. Abdominal cramps occurred during and after running in 14% and nearly 2% had bloody bowel movements. Women suffered GI tract symptoms more frequently than men and some runners thought that conditioning lessened their GI disturbances (Keeffe et al. 1984). Similar findings were noted by Priebe and Priebe (1984) who found that runners could prevent diarrhoea with prophylactic medications and confirmed more recently in a larger series (Riddoch & Trinick 1988). In 1985 a survey of the GI symptoms during an
161
enduro multisport event (an 800m harbour swim, a 25km cycle, a 5km canoe paddle, and a 12km run) found a prevalence of GI symptoms similar to previous studies in runners (Worobetz & Gerard 1985). 81 % of respondents claimed at least an occasional symptom. The most prevalent were lower GI complaints ranging from the urge to have a bowel movement to incapacitating diarrhoea. Also noted was an adaptation phenomena with lower GI symptoms being more prevalent during the first few weeks of training. Upper GI symptoms including nausea, vomiting and heartburn were prevalent, but rarely disabling. Upper abdominal symptoms may be more frequent in triathlon or other multisport endurance athletic events. In a survey of an international distance triathlon we noted dyspeptic symptoms such as the loss of appetite, heartburn, nausea, and bloating occurring in 25 to 35% of participants. Lower GI symptoms such as cramps or diarrhoea were less frequent (see table I). Triathletes in general tend to eat and drink more during their races than runners and the type of meal and fluid replacement may effect the nature of the digestive symptoms. In a military group undergoing prolonged high intensity physical and mental training, those individuals who received water rather than a glucose polymer solution as oral rehydration suffered less dyspeptic and reflux-related symptoms, possibly due to gastric emptying differences (unpublished data, Human Performance Laboratory, Uniformed Services University, Bethesda). Abdominal symptoms such as nausea or vomiting may also be manifestations of dehydration or hyperthermia and, in the appropriate clinical setting, conditions such as these should be suspected. This literature review is summarised in table I and indicates that lower GI symptoms are more common than upper GI symptoms and that the urge to defecate is among the most common reported symptoms. Bowel movements and even diarrhoea are frequent after running and may often interrupt a run. Bloody bowel movements are associated with running. All lower GI symptoms are more common in women and probably more common in younger runners. Upper GI symptoms such
Table I. Incidence of gastrointestinal symptoms associated with exercise Reference
Subjects (no.)
0'\ IV
Symptoms (% of athletes) loss of appetite
oesophageal
508
10
heartburn
gastric chest pain
belching
nausea
vomiting
intestinal abdominal cramps
colon or rectal
25 8
30
19.38
urge to have bowel movement
bowel movement with exercise
diarrhoea rectal bleeding
36
13
10
2.4
67
63
51
30e
12
54
44
26
...-.........-.... Sullivan (1981)
Running club (57)
6
11.68
9.58
Keefe et al. (1984) Marathon (707) Priebe & Priebe (1984)b
Runners (425)
Worobetz & Gerard (1985)
Enduro (70)
41
Riddoch & Trinick (1988)
Marathon (536)
288
Worme et al. (1989)
Triathlon (67)
12
11
8
18
1.88
36
21
4
30
20
4
31 8
42
12
6
2
5
27
Sports Medicine 9 (3): 159-172, 1990 011 2-1642/90/0003-0159/$07.00/0 © ADIS Press Limited All rights reserved. SPORT2259.
The Effect of Exercise on the Gastrointestinal Tract 1 Frank M. Moses Gastroenterology Service, Walter Reed Army Medical Center, Washington, D.C., USA
Contents
Summary ............................................................................................ ....................................... 159 I. Early Reports and Surveys .............................................................................. ............... ..... 160 2. Oesophagus .................................... .. .. ............................................................................ ....... 163 3. Stomach ................................................ ................................................................................. 164 4. Intestines .................................... ............................................................. ........ .. .................... 165 5. Liver ............................................. ....... ......................................................... ......................... 167 6. Gastrointestinal Bleeding "" "." """.""" ..""".""""""."""".""."".""""""""""."""""""". 168 7. Conclusion .......... ................ ............ .. .......... .. .... ............................................... ..................... 170
Summary
Surveys of athletes, primarily runners, have shown that digestive disorders are common, associated both with training and racing. Women, in particular, seem to suffer most commonly. Nearly half have loose stools and nausea and vomiting occur frequently after hard runs. Diarrhoea, incontinence and rectal bleeding occur with surprising frequency. Runners may use medications prophylactically to minimise some of these symptoms. Upper digestive symptoms seem to occur more commonly in multisport events such as triathlons or enduro. The published literature is difficult to analyse and the basic intestinal physiology not well studied. Most gastroenterologists are accustomed to evaluating the fasting patient at rest and exercise physiologists are seldom experienced with digestive techniques. Digestive symptoms occurring with exercise referable to the oesophagus include chest pain, gastro-oesophageal reflux symptoms, or symptoms related to alterations in motility. While little is known of the oesophageal physiology during exercise, it is believed that only minimal changes occur in most subjects. Gastro-oesophageal reflux occurs more frequently with exercise than at rest and may produce symptoms of chest pain suggestive of ischaemic disease. Acid exposure may be reduced by pretreatment with histamine H2receptor antagonists. Oesophageal symptoms, though common, are rarely disabling to the athlete, and the clinical importance lies in confusion with ischaemic disease. Cases of acute gastric stasis following running have been reported and gastric physiology during exercise, particularly bicycling, has been more actively investigated. Gastric emptying during exercise is subject to a number of factors including calorie count, meal osmolality, meal temperature and exercise conditions. However, it is generally accepted
I The opinions or assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense.
Sports Medicine 9 (3) 1990
160
that light exercise accelerates liquid emptying, vigorous exercise delays solid emptying and has little effect upon liquid emptying until near exhaustion. Gastric acid secretion probably changes little with exercise although some have postulated that ulcer patients may increase secretion with exercise. Some exercise-associated digestive symptoms, such as diarrhoea and abdominal pain, have been attributed to changes in intestine function. Small bowel transit is delayed by exercise when measured by breath hydrogen oral caecal transit times and motility may be reduced as well. Intestinal absorption during exercise has not been well evaluated but probably changes little in ordinary circumstances. Passive absorption of water, electrolytes and xylose are not affected by submaximal effort. Colonic transit and function is even more difficult to evaluate and published results have been conflicting. However, it is likely that many of the lower digestive complaints of runners such as diarrhoea and lower abdominal cramps are due to direct effects of exercise upon the colon. Gastrointestinal bleeding is the most dramatic digestive disorder associated with exercise. While 'runner's anaemia' may often represent a pseudonaemia from expanded plasma volume, runners may develop haematemesis or melaena after competitive or training events or present only with symptoms of profound iron deficiency and anemia. Many surveys have demonstrated that approximately 20% of marathon runners will convert to guaiac positivity following the race. While cases of presumed ischaemic colitis occur and anorectal sources of bleeding have been identified, by far the most frequently reported lesion of running associated bleeding has been haemorrhagic gastritis. The aetiology is felt to be ischaemic though other possibilities have not been excluded. The lesion is transient, resolves quickly with rest, and is not recognised if endoscopy is not done within 72 hours of the event. While exercise-associated intestinal bleeding is common, individual cases must be evaluated clinically. Exercise, while of obvious benefit to the general health of many, does not offer assurance against other, more mundane causes of intestinal bleeding. The study of the digestive tract during the stress of exercise is in Its mtancy. It IS hoped that the awareness of symptoms and clinical difficulties encountered by active subjects will provoke additional study of the GI physiology of the active individual in health and disease.
Abdominal discomfort, diarrhoea and other digestive disorders are frequent among athletes. Although these symptoms are oflow intensity in most, they may be an occasion of great disability. Perhaps the most dramatic digestive disorder associated with exercise is that of gastrointestinal (GI) haemorrhage. After winning a marathon in record time, Derek Clayton was quoted as saying: 'Two hours later, the elation had worn off. I was urinating quite large clots of blood, and I was vomiting black mucus and had black diarrhea. I don't think too many people can understand what I went through for the next 48 hours' (Clayton 1979). Other leading runners have been slowed by refractory iron deficiency anaemia. The symptoms of gastric stasis and diarrhoea similarly limit athletic performance. However, despite several excellent reviews (Brouns
et al. 1987; Keeffe et al. 1984; Riddoch & Trinick 1988; Sullivan 1984; Worobetz & Gerrard 1985) little formal attention has been devoted towards these problems and only now are investigators attempting to unravel the physiology ofthe digestive system during exercise. This article reviews recent published series and personal observations and summarises the more common and more serious conditions encountered by physicians caring for athletes.
1. Early Reports and Surveys Interest in exercise physiology of the digestive tract dates back at least to William Beaumont who observed the permanent gastric fistula of Alexis St. Martin. He differentiated the effects of moderate
Effect of Exercise on the GI Tract
and severe exercise after meals and seemed quite aware that fatiguing exercise retarded digestion (Beaumont 1838). Some years later the effects of exercise upon gastric secretion and digestion were again studied and it was said that exercise which produced no discomfort helped digestion and exercise which produced discomfort delayed it (Campbell et al. (928). However, interest in athletic-associated, primarily running-associated, digestive disorders was renewed by a series of reports in the early part of this decade. A letter describing 'athletes' diarrhoea in distance runners (Scobie 1978) was followed by a report of 2 cases of GI disturbances in runners: a young long distance runner who suffered abdominal pain and loose bowel movements with running, and a young medical student and distance runner with a history of bloody diarrhoea and crampy abdominal pain following hard runs (Fogoros (980). Next, a letter detailing a survey of a recreational runners' club reported heartburn in 10% of runners and common complaints of abdominal cramps, the urge to have a bowel movement, and a decrease in appetite following a race (Sullivan 1981). Later that year another report appeared of 2 runners, one who suffered abdominal pain and bloody diarrhoea and presumed to have ischaemic colitis and a second who also suffered bloody diarrhoea with running in whom no aetiology was found (Cantwell (981). In 1984 a survey of 707 respondents in a marathon run noted frequent GI symptoms. Nearly half had occasional loose stools and 13% had 3 or more bowel movements per day. Nausea and vomiting were more frequent following hard runs. Abdominal cramps occurred during and after running in 14% and nearly 2% had bloody bowel movements. Women suffered GI tract symptoms more frequently than men and some runners thought that conditioning lessened their GI disturbances (Keeffe et al. 1984). Similar findings were noted by Priebe and Priebe (1984) who found that runners could prevent diarrhoea with prophylactic medications and confirmed more recently in a larger series (Riddoch & Trinick 1988). In 1985 a survey of the GI symptoms during an
161
enduro multisport event (an 800m harbour swim, a 25km cycle, a 5km canoe paddle, and a 12km run) found a prevalence of GI symptoms similar to previous studies in runners (Worobetz & Gerard 1985). 81 % of respondents claimed at least an occasional symptom. The most prevalent were lower GI complaints ranging from the urge to have a bowel movement to incapacitating diarrhoea. Also noted was an adaptation phenomena with lower GI symptoms being more prevalent during the first few weeks of training. Upper GI symptoms including nausea, vomiting and heartburn were prevalent, but rarely disabling. Upper abdominal symptoms may be more frequent in triathlon or other multisport endurance athletic events. In a survey of an international distance triathlon we noted dyspeptic symptoms such as the loss of appetite, heartburn, nausea, and bloating occurring in 25 to 35% of participants. Lower GI symptoms such as cramps or diarrhoea were less frequent (see table I). Triathletes in general tend to eat and drink more during their races than runners and the type of meal and fluid replacement may effect the nature of the digestive symptoms. In a military group undergoing prolonged high intensity physical and mental training, those individuals who received water rather than a glucose polymer solution as oral rehydration suffered less dyspeptic and reflux-related symptoms, possibly due to gastric emptying differences (unpublished data, Human Performance Laboratory, Uniformed Services University, Bethesda). Abdominal symptoms such as nausea or vomiting may also be manifestations of dehydration or hyperthermia and, in the appropriate clinical setting, conditions such as these should be suspected. This literature review is summarised in table I and indicates that lower GI symptoms are more common than upper GI symptoms and that the urge to defecate is among the most common reported symptoms. Bowel movements and even diarrhoea are frequent after running and may often interrupt a run. Bloody bowel movements are associated with running. All lower GI symptoms are more common in women and probably more common in younger runners. Upper GI symptoms such
Table I. Incidence of gastrointestinal symptoms associated with exercise Reference
Subjects (no.)
0'\ IV
Symptoms (% of athletes) loss of appetite
oesophageal
508
10
heartburn
gastric chest pain
belching
nausea
vomiting
intestinal abdominal cramps
colon or rectal
25 8
30
19.38
urge to have bowel movement
bowel movement with exercise
diarrhoea rectal bleeding
36
13
10
2.4
67
63
51
30e
12
54
44
26
...-.........-.... Sullivan (1981)
Running club (57)
6
11.68
9.58
Keefe et al. (1984) Marathon (707) Priebe & Priebe (1984)b
Runners (425)
Worobetz & Gerard (1985)
Enduro (70)
41
Riddoch & Trinick (1988)
Marathon (536)
288
Worme et al. (1989)
Triathlon (67)
12
11
8
18
1.88
36
21
4
30
20
4
31 8
42
12
6
2
5
27
