Premovement excitability changes of the corticospinal tract are not dependent on the forthcoming task but due to a general excitation of the motor system

Abstract

Premovement excitability changes of the human corticospinal tract have focused mainly on isometric contractions. Little is known about the corticospinal changes prior to a rhythmic and alternating contraction, such as cycling, and whether the modulation of excitability is different from an isometric contraction. Studies using a decerebrate cat model have shown that excitability of the spinal motoneurone is modulated very differently prior to a rhythmic and alternating movement when compared to an isometric contraction. The current study was designed to assess corticospinal excitability using transcranial magnetic stimulation and spinal motoneurone excitability using transmastoid electrical stimulation, prior to arm cycling and an intensity-matched isometric contraction. Using these techniques we sought to determine whether a difference in corticospinal excitability occurred prior to cycling and an intensity-matched isometric contraction, as well as determine whether the changes were spinal or supraspinal in nature.