Effect of different intensities of physical exercise on changes in plasma gastrointestinal hormones in humans

In order to investigate the effect of physical exercise on gastrointestinal exocrine secretion, we examined changes in plasma levels of glucose, insulin, glycerol, gastrin and cholecystokinin (CCK) during and after exercise in 6 healthy men. After overnight fasting for 12 hours, subjects ran on a treadmill at 50%, 75%, and 100% of V̇O₂max for 30 minutes followed by 60 minutes of resting (recovery period). Venous blood was sampled immediately before the exercise, at the end of the exercise, and at 10, 30, and 60 minutes during the recovery period. The plasma levels of glucose and insulin significantly increased at 10 minutes into the recovery period in the 75% and 100% V̇O₂ max trials. The plasma glycerol significantly increased at the end of the exercise in every intensity. The peak value of the plasma glycerol in the 100% V̇O₂max trial was the highest among the three trials. The plasma gastrin significantly increased at 10 minutes into the recovery period in every intensity. The peak value of the plasma gastrin in the 75% V̇O₂max trial was the highest among the three trials. In the 100% V̇O₂max trial, however, the plasma gastrin showed the same level of change as in the 50% V̇O₂max trial. Changes in plasma CCK due to exercise showed no significant change throughout the experimental period in every intensity. These results suggest that low intensity exercise may promote gastric, but not pancreatic, exocrine secretion, however, maximal intensity exercise may suppress this promoted function in humans.