Corticospinal excitability and interconnectivity of the limbs during arm cycling

Abstract

There is evidence of neural interlimb communication between the fore and hind limbs in quadrupeds and the arms and legs in humans. Appropriate coordination between upper and lower limbs is an important characteristic of quadrupedal and human locomotion and part of this coordination involves cortical and spinal control. This communication between the cortex and spinal cord suggests that neural coupling between the upper and lower limbs occurs during rhythmic movement. Most studies aimed at assessing interlimb coordination during locomotor output have utilized H- reflexes and/or surface EMG. However, the effects of rhythmic locomotor output (arm and/or leg cycling) on corticospinal excitability of stationary limbs (arm and/or leg) has yet to be clearly examined. In addition, it seems interlimb pathways probably modulate cortical and spinal pathways during locomotor tasks as a function of movement intensity. The current study demonstrated an intensity-dependent enhancement in corticospinal excitability to the resting biceps brachii and vastus lateralis during leg and arm cycling, respectively. Assessing of interlimb coordination between upper and lower limbs may improve knowledge translation to neurological rehabilitation programs.