Motor unit discharge rate is not associated with muscle relaxation time in sustained submaximal contractions in humans.

The muscle wisdom hypothesis suggests that motor unit discharge rates decrease in parallel with the slowing of muscle contractile properties during fatigue. In this study, the discharge rates of single motor units and the muscle contractile properties were measured during a sustained submaximal contraction. The majority of motor units that were active from the beginning of the task demonstrated a decline in discharge rate in the absence of any slowing of muscle relaxation time. These findings suggest that the muscle wisdom hypothesis may not apply to sustained submaximal contractions.