Impaired abdominal muscle contractility after high-intensity exhaustive exercise assessed by magnetic stimulation

High-intensity exercise can induce diaphragm fatigue which can, in turn, limit exercise performance. We investigated whether expiratory muscles fatigue similarly during exhaustive exercise. Eleven healthy male volunteers cycled to exhaustion at 85% maximal power. Before, immediately after exercise, and after 30 and 60 min of recovery, the nerve roots supplying the abdominal muscles were stimulated magnetically at the T10 level in the prone position after full potentiation. Twitch gastric pressure (P-ga,P-tw) was simultaneously recorded. After cycling, P-ga,P-tw was significantly reduced compared to before exercise (40.2 +/- 6.6 vs. 45.3 +/- 7.5 cmH(2)O; P < 0.001), whereas after 30 and 60 min of recovery differences were no longer significant. The reduction in P-ga,P-tw directly after exercise correlated neither with the fitness level nor with abdominal muscle work, respiratory sensations, or blood lactate concentration during exercise. These results indicate that the ventilatory requirements during intensive exercise can impair abdominal muscle contractility similar to diaphragmatic contractility. Thus, abdominal muscle fatigue may also contribute to exercise limitation, especially when expiratory resistance is increased as in patients with chronic obstructive pulmonary disease.