Respiratory motor output during an inspiratory capacity maneuver is preserved despite submaximal exercise.

It is unknown whether respiratory motor output is constrained during exhaustive exercise in healthy adults. We hypothesised that neural inhibition did occur; to test this hypothesis we measured diaphragm EMG from a maximal inspiratory capacity maneuver (EMG(di)-IC) at rest and during exercise. EMG(di)-IC was measured before and after the amplitude of the diaphragm EMG entered a plateau phase in eleven healthy adults undertaking exercise at 60% and 80% of maximal workload achieved from incremental exercise. The mean EMG(di)-IC at rest was 65 ± 16% of the maximum that could be obtained from a battery of inspiratory tasks. Before and after the plateau phase of diaphragm EMG, EMG(di)-IC was 68 ± 13% and 72 ± 12% (p > 0.05) during 60% of the maximum workload, and was 70 ± 13% and 78 ± 13% (p > 0.05) during 80% of the maximum workload achieved on an incremental test. A further sub-study in which 5 participants exercised at 90% of the maximum workload also showed that EMG(di)-IC was not diminished during exercise. Our data show that exercise condition does not reduce the magnitude of EMG(di)-IC. This argues against neural inhibition as feature of submaximal exercise in healthy adults.
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