CYCLING PERFORMANCE TIPS

The Athlete and the GI Tract

I. Heartburn, Dyspepsia, and Chest Pain

• nausea
• belching - the most common symptom of reflux - more than dyspepsia
• heartburn or dyspepsia (epigastric discomfort with an acid peptic pattern)
• vomiting

These can be a particular problem as you try to decide:

• Is this cardiac chest pain? A big problem with the older, recreational athlete. Think of reflux high on the DDx in young athletes who have minimal risk factors
• What to do with this recurrent and oftentimes bothersome problem in your athlete-patient?
• When should you do an evaluation?

• Frequency
  • up to 90% of runners in one study
  • depends on the type of exercise - using esophageal manometry to identify reflux
    • most common in running
    • weight lifting very close behind in frequency
    • minimal problem in cycling
  • more common if prior symptoms - with 10 minutes of cycling (as the exercise) 25 % of random controls had reflux (measured by manometry) versus 85% of those with pre exercise symptoms.
• Etiologies
  1. LES pressure changes - serves as the primary barrier between the stomach and esophagus
     • decrease in pressure with exercise - documented with manometry in healthy subjects.
     • allows belching
       • most common symptom
       • can be provoked by aerophagia from
         • Increased resp rate
         • Deep inspirations with more negative intrathoracic pressure
     • it as been suggested it is not just the absolute LES pressure itself, but an increase in frequency of transient relaxations (i.e. LES pressure could be normal with manometry and still have symptoms. It would require 24 hour pH monitoring to identify)
     • increases in exercise decreases esophageal body contractions - duration, freq, amplitude.
       • Normally these contractions push refluxed food back into the stomach
       • Dysmotility may cause some of the chest discomfort with exercise - as opposed to angina or reflux
  2. Changes in upper GI motility
     • delays in stomach emptying result in more gastric material present to reflux
       • gastric emptying may be stimulated at low exercise levels but delayed at higher ones - esp. > 70% VO2max.
       • emotional and mental stress can decrease gastric emptying rate
       • pre ride
         • large or fatty meal
       • intake while riding
         • hypertonic solutions
         • large volumes (>1000 cc/hr)
       • air swallowing related to increased respiratory effort can lead to even more gastric distention with resulting belching and regurgitation. Provoked by aerophagia from
         • Increased resp rate
         • Deep inspirations with more negative intrathoracic pressure
       • Dehydration
  3. GI hormones - no causal relationship has been demonstrated
  4. Prior diet
     • large diet before exercise increases reflux
     • certain foods decrease LES pressure - greasy, chocolate, mints, caffeine
  5. Medications
     • nitrates, calcium channel blockers, estrogens - all are smooth muscle relaxers and can decrease LES pressure
  6. Increased intra abdominal pressure
     • tight clothes
     • heavy athlete
     • bent over position while cycling
• Treatment
  • eat right - i.e. avoid large fatty meals esp. just before exercising
  • loose clothing
  • avoid caffeine chocolate
  • consider an OTC PPI or H2 as prophylaxis - by pH monitoring acid exposure is less, but symptoms can remain.

II. Diarrhea and Rectal Urgency - also known as "runner's trots", this is mainly a runner's issue.

• Frequency
  • diarrhea occurs pre race in about 50% of runners
  • more common in runners 19-26 % of marathon runners
  • 50% of marathon runners report fecal urgency during the race or training
• Etiologies
  • this is a combination of a change in motility with a decrease in segmenting contractions (which inhibit propulsion of material through the colon) aided and abbetted by
  • mechanical factors
    • jarring in an upright position which helps move stool into the rectum - thus the urge to defecate progresses with duration of the activity.
    • the fact that endotoxemia is more common in runners than cyclists suggests mechanical trauma may play a role in direct colonic irritation.
      • can assume a break in mucosal barrier as endotoxemia (from colonic bacteria) can be detected in postexertional exercise specimens - levels are equivalent to those with sepsis
      • interestingly 80% of runners with endotoxemia had symptoms of nausea, vomiting, diarrhea versus only 18% of those without endotoxemia.
    • jarring felt to be more important than a decrease in splanchnic blood flow as bleeding and diarrhea can occur with longer events where the %V02max of the exertion remains low throughout.
  • mucosal ischemia
    • intestinal blood flow decreased by up to 80% - exaggerated if the athlete is hypoglycemic, hyperthermic, or dehydrated
    • dehydration may change blood viscosity and thus affect capillary blood flow and gut ischemia
  • Diet
    • lactose intolerance - brought out with exercise
    • high fiber (healthy) diet can exacerbate the problem - esp. an issue in vegetarian diets. Fiber increases the volumes of colonic material thus more CHO for bacteria to ferment as well as more volume to expel.
    • artificial sweeteners - sorbitol with osmotic diarrhea
• Treatment
  • evaluation - definitely
    • if over 40
    • if bleeding
  • decrease intensity of the exercise and/or consider cross training
  • evaluate diet - trial of lactose free, decrease dietary fiber, eliminate diet candies
  • prophylaxis
    • loperimide helped in 20%
      • anticholinergic effect - decreased sweating (heat stroke?)
    • aluminum silicate helped in 3/4 of athletes
    • prescription opioids

III. GI blood loss (and anemia) - again mainly a runner's issue, and long distance runners at that.

• ferritin, haptoglobin, serum iron all lower in runners (as a group, not individually) than controls
• speculation as to etiologies have included erythrocyte destruction in the feet, hematuria, impaired absorption, occult GI blood loss

And the blood loss can be quite rapid and severe. In one case, autopsy results indicated the cause of death was GI hemorrhage from hemorrhagic gastritis.

• Frequency
  • related to the length and severity of the event
    • more positive stools if
      • younger runners with faster times (pushing it)
      • accelerated training
      • competitive runners versus leisure
      • 26% positive in runners after a hard run/race versus 13% after an easy run
      • more frequently during a race than a training period
    • 1983 Boston Marathon: 8 to 22% of marathon runners have occult blood
    • 85% of ultra marathoners (100 miles) and full triathlons have occult blood in stool
    • gross blood in up to 16% of runners
    • less of a problem in cyclists (occult)
      • 35 participants in a 7 day ride across Nebraska, ~70 miles a day, asymptomatic the prior 6 months - 2/163 specimens hemoccult positive (1.2%)
      • 12 cyclists over a season - 8.4% of 310 specimens were +
    • walkers (37 K in 4 days)- no change in occult blood findings
  • more frequent in those with lower GI symptoms
• Etiologies
  • ischemic colitis (less frequent) and hemorrhagic gastritis (more frequent) have been observed when endoscopic procedures are done immediately post race
  • the low rate of hemoccult positivity in non running sports supports idea that it takes mechanical jostling plus other factors to cause mucosal injury.
  • interestingly, recreational activity significantly decreases the risk of overt bleeding in seniors (>68 yo - 8000 followed for 3 years)
• Treatment
  • it has been suggested that it may be diminished by regular fluid intake
  • theoretically could be increased with NSAIDs, oral contraceptives (OCT)
    • OCTs can cause an ischemic colitis - any role in increased symptoms in women?
    • NSAIDs have been reported to cause a spotty colitis
  • no changes in occult blood findings (hemoccult) on tagamet up to marathon level, but there have been benefits in ultramarathon events
  • runners consistently have lower ferritins and hgbs than controls - watch and Rx for fe def anemia