CYCLING PERFORMANCE TIPS
Last updated: 12/06/2009
The Athlete and the GI System
Benefits of Exercise on the Gastrointestinal System
We all know about the positive protective effects of exercise on cardiovascular disease.
There is also convincing scientific evidence that regular exercise has a positive effect
on overall health as well as many other chronic conditions - perhaps by increasing the general
sense of "well being". But having said that, it is important to realize that there may be
a level of activity above which " is less" i.e. more vigorous activity becomes less
beneficial as short term negatives begin to outweigh health benefit positives.
We have been discussing the negative effects (and symptoms) of exercise on the digestive
system. Now let's take a look at the benefits of exercise - disease prevention and
rehabilitation in those with pre existing chronic GI diseases. (For those of you not familiar
with the term relative risk (RR), it indicates your risk of the disease state
compared to someone that does not exercise regularly. For example, if your RR is 0.5, you
have 1/2 the chance of being affected. If it is 0.33, 1/3 - and so on.
I. There is clear proof of:
- protection from colon cancer - 3rd leading cancer in the US
- a protective effect at all exercise levels - recreational on up
- but "exercisers" also smoke less, are thinner (a risk factor), etc.
and in general eat higher fiber diets
- RR of 0.5 in studies controlling for risk factors other than exercise -
it is an independent variable and additive to others.
- it has been speculated (and unproven) this may be due to a decrease
in transit time and thus less contact time for carcinogens with the
- a decrease in cholelithiasis
- 30 minutes of aerobic activity 5 times a week) lowers the relative
risk = 0.66
- independent of other variables such as obesity
- a decreased risk of duodenal ulcer disease
- adjusted for life style (smoking, alcohol, self reported tension),
moderate exercise had a RR of 0.38, while higher was 0.54 (this may be a good
example of more being less)
- a decrease in gross, large volume, rectal bleeding in seniors
- recreational activity significantly decreases the risk of overt
bleeding in seniors (>68 yo - 8000 followed for 3 years)
- a decrease in symptomatic diverticular disease
- 47000 men followed over 4 years
- after controlling for fiber in diet, age, and fat intake
- reduced risk associated with activity - more vigorous, less incidence
- vigorous defined as running a 10 min mile), jogging (<10 min mile), cycling
- RR was 0.53 for vigorous
II. Less proven, but with suggestive evidence are:
- a decrease in constipation
- There is an association with inactivity in older individuals
BUT it is unproven that an Rx for exercise will be helpful.
- a controlled trial in 8 women (<50 y/o) with chronic idiopathic
constipation could demonstrate no benefit of 4 weeks of regular activity
- No clear association of constipation with inactivity in younger,
otherwise healthy patients.
- active people tend to eat higher fiber diets - a confounding variable
- Inflammatory Bowel Disease. Unproven, but not harmful! Need to individualize the program.
- exercise can retard osteopenia and osteoporosis - not the preferred
- over all sense of well being is better (proven)
- symptoms/disease no more active with moderate exercise
- a retrospective study (memory error possible) shoed a RR of 0.5, even with
minimal levels of activity
- Irritable Bowel Syndrome - one study of runners demonstrated a prevalence of IBS
symptoms (constipation, abd pain, gas) in ~25% before running and a significant
decrease in symptoms after they started running
- Liver disease - no negative effect, and increases overall sense of well being and
thus rehabilitation with chronic disease (such as Hepatitis C).
Next section - Strategies to Minimize Gastrointestinal Symptoms with Exercise
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