Time course of changes in neuromuscular responses during rides to exhaustion above and below critical power.

OBJECTIVES

To examine the time course of changes in electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) responses during cycle ergometry to exhaustion performed above (CP) and below (CP) critical power (CP) to infer motor unit activation strategies used to maintain power output.

METHODS

Participants performed a 3-min all out test to determine CP, and 2 randomly ordered, continuous rides to exhaustion at CP and CP·V̇O, EMG AMP, EMG MPF, MMG AMP, MMG MPF, and time to exhaustion (T) were recorded. Responses at CP and CP were analyzed separately.

RESULTS

At CP, EMG and MMG AMP were significantly greater than the initial 5% timepoint at 100% T. EMG MPF and MMG MPF reflected a downward trend that resulted in no significant difference between timepoints. At CP, EMG AMP was significantly greater than the initial 5% timepoint from 60% to 100% T. MMG AMP was less than the initial 5% timepoint at only 50% T. EMG and MMG MPF were significantly less than the initial 5% timepoint at 20% T and 100% T, respectively.

CONCLUSIONS

The timecourse of changes in EMG and MMG signals were different at CP and CP, but responses observed indicated cycle ergometry to exhaustion relies on similar motor unit activation strategies.