Fast Forms of Central Fatigue Account for Decreases in Rate of Execution during Fast and Short Repetitive Motor Tasks

Fatigue of the central nervous system (F-CNS) is a focus of interest in pathology, ergonomics and sports. This can be measured within a sustained maximal voluntary isometric contraction (I-MVC) using a TMS evoked silent period (SP) in cortico-spinal excitability. Here we used the SP to measure the F-CNS developed during the execution of a simple repetitive task, finger tapping (FT), performed at different rates and for different durations. FT executed at maximal rate for 10 or 30s led to a significant increase in SP during a brief I-MVC evoked immediately following tapping. Tapping rate also decreased during the task and SP recovered within 10s following tapping. However, 30s tapping at comfort rate had no effect on SP. We conclude that a fast form of F-CNS induces a fast decay in the tapping rate if performed at fast as possible.