The aim of our study was to describe the endurance capacity of the expiratory muscles and to determine if it is altered following exhaustive cycling exercise. Subjects performed repeated maximal expiratory efforts against a closed breathing valve, with and without prior exercise performed at a work-rate that elicited 75% of the maximum ventilation rate. Each expiratory effort lasted 6 seconds, was separated by 10 seconds of rest, and was initiated from the end expiratory lung volume. Endurance performance was assessed by measuring the decline in area under the pressure time curve over 39 contractions. Prior exhaustive exercise attenuated the ability to generate and sustain maximal expiratory pressure (p=0.013), and resulted in significant declines in the integrated electromyogram (EMG) of the rectus abdominis (p=0.005) and external oblique (p=0.036) abdominal muscles. Each subject also performed a handgrip endurance task before and after exhaustive exercise on a separate day. Prior exercise had no effect on handgrip endurance performance suggesting that the decline in expiratory muscle performance after exercise was not the result of reduced motivation. We conclude that the ability to maximally activate the abdominal expiratory muscles and to generate maximum expiratory pressure is impaired following exhaustive exercise. Declines in the surface integrated EMG despite maximal effort is consistent with findings in limb muscles, and is thought to be due to a slowing of motor neuron firing rates or to neuromuscular transmission failure.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology