Half marathon induces changes in central control and peripheral properties of individual motor units in master athletes

Acute changes in central control and peripheral properties of motor units following a half-marathon has never been examined in master athletes. Therefore, the main purpose of this study was to estimate the firing properties and twitch characteristics of motor units after a 21-km race in a group of ten trained older adults. High-density surface EMG decomposition was used to identify motor unit activity during a submaximal contraction of the tibialis anterior muscle before and after the half marathon. The area of the estimated motor unit twitch profile was found smaller after the race (P = 0.039). This reduction in contractile efficiency was compensated by a significant increase in the initial and average discharge rate of the identified motor units (P < 0.001). By estimating the amount of shared and independent synaptic input to tibialis anterior motor neurons, we demonstrated that adaptations in the discharge properties of master athletes' motor units are the likely consequence of an increased net excitatory synaptic drive to the motor neuron pool. These findings suggest a potential role of longdistance running in ameliorating declines in muscle function of older adults by enhancing the neural drive to muscle.