nausea and vomiting after exercise, or the cause
of disabling cramps during running (Olivares
1988 cited in Moses 1990). It would seem from the
literature that gastric stasis may be avoided by
choosing low-volume, isotonic, liquid meals
which are low in fat, protein and dietary fibre.
In addition, there appear to be a number of
anecdotal references to athletes in whom gastric
clearance has been influenced by the psychologi-
cal stresses of competition (Larson & Fisher
1987). References to the link between psychologi-
cal stress and gastric function were made over
60 years ago. A delay in gastric emptying was
noted by Campbell et al.(1928) and revisited by
Beaumont 10 years later. These influences, which
are often more difficult to quantify but are no less
important to the athlete, represent an area of con-
siderable research potential that can be explored
with the aid of contemporary instruments of
measurement including radio isotope-labelled
meals, gamma cameras and ultrasound.
Intestinal symptoms
Reported lower gastrointestinal tract symptoms
during exercise (particularly running) include
abdominal cramps, urgency of bowel movement,
diarrhoea, rectal bleeding, flatulence and post-
exercise anorexia.
A model for factors associated with gastroin-
testinal tract symptoms during exercise has been
proposed by Peters et al. (1995). There is a strong
recognition of the interrelationship between
several factors:
- Hydration status.
- Mechanical trauma.
- Neuroendocrine alterations.
- Psychological stress.
- Reduced gastrointestinal tract blood supply.
- Altered gut motility.
- Influence of medication.
Gastrointestinal tract bleeding
Exercise-associated gastrointestinal bleeding has
been reported by several authors (Porter 1983;
McMahonet al. 1984; Stewart et al. 1984; Scobie
250 nutrition and exercise
1985; Robertson et al. 1987; Baska et al. 1990;
Moses 1990; Schwartz et al. 1990; Green 1992).
Haemorrhage from the gastrointestinal tract is
always of concern to the athlete. The presentation
may be very dramatic and, irrespective of the
source, it is important to evaluate the frequency
and significance of the blood loss given that
occult blood loss has been frequently reported in
endurance athletes (Green 1992). It has become
more evident through contemporary methods of
endoscopic examination that the intensity of
exercise rather than mechanical influences are
causative in the loss of blood from the gastroin-
testinal tract. A proposed mechanism of direct
trauma to the gut through running was the basis
for the syndrome of ‘caecal slap’ reported by
Porter in 1982. It was postulated that the me-
chanical effect of running was physically insult-
ing on the ileocaecal junction and produced a
localized contusion. However, since then the
study of other athletes, including cyclists (Dobbs
et al. 1988 cited in Green 1992), suggests that any
endurance athletes, and not just runners, may
suffer significant occult gastrointestinal blood
loss and that the mechanism for this is likely to be
the result of endocrine and vascular insults and
factors related to hydration status.
The athlete presenting with frank gastroin-
testinal tract bleeding deserves a full clinical
evaluation. Local anorectal causes such as haem-
orrhoids and fissures are easily ruled out by
physical examination, but inflammatory bowel
disease and more sinister causes of bleeding
including carcinoma will require more extensive
endoscopic investigations. In many cases the
athlete may present with haematological evi-
dence of anaemia which is often nutritional, or
due to the expanded plasma volume of exercise
(an apparent or athletes’ pseudoanaemia), but
might also signal insidious blood loss from an
undetermined site. Endoscopic examinations of
both upper and lower gastrointestinal tract are
mandatory investigations particularly where the
age of the athlete, their medical history and the
concurrent use of NSAIDs are reported.
Although the aetiology of gastrointestinal
bleeding is likely to be multifactorial, the litera-