Exercise and small intestinal transit.

The transit of 99Tcm-labelled particles through the small intestine has been monitored in nine healthy subjects undergoing three levels of exercise. The mean +/- 1S.D. small intestine transit times under conditions of minimal, moderate and strenuous activity were 4.5 +/- 1.7 h, 5.4 +/- 2.5 h and 4.1 +/- 1.8 h, respectively. These findings indicate that the bioavailability of drugs from controlled release preparations passing through the small intestine is unlikely to be affected by variations in normal daily activity.