Recovery of motor performance deterioration induced by a demanding finger motor task does not follow cortical excitability dynamics.

The performance of a demanding exercise can result in motor performance deterioration and depression of primary motor cortex excitability. In the present work we defined a motor task that requires measurable skilled performance to unveil motor performance changes during the execution of a demanding task and to investigate the dynamics of motor performance and cortical excitability changes in absence of overt peripheral fatigue. Twenty-one normal subjects, divided into three groups were asked to perform a sequence of finger opposition movements (SEQ) paced at 2 Hz for 5 min, quantitatively evaluated by means of a sensor-engineered glove able to perform a spatio-temporal analysis of motor performance. Maximal voluntary contraction (MVC) was evaluated before and after the motor task in group 1 while motor evoked potentials (MEP) were evaluated before and after the motor task in group 2 and 3. Group 1 and 2 performed the 5 min-SEQ while group 3 was asked to perform the 5 min-SEQ twice to assess the dynamics of motor performance and cortical excitability. As a result, we found that the execution of 5 min-SEQ induced motor performance deterioration associated with no change in MVC but a decrease in cortical excitability. We further found that the dynamics of cortical excitability and motor performance were different. In fact, a short rest period (i.e., period necessary to collect MEP) between the execution of two 5 min-SEQs was able to recover the motor performance but not the cortical excitability. Finally, no change in spinal excitability was observed. These findings suggest that although primary motor cortex seems to be mainly involved in motor performance deterioration during the execution of a demanding finger motor task, the recovery of motor performance does not follow cortical excitability dynamics.