LAUSR

Low-intensity electrical stimulation of the common peroneal nerve (CPN) evokes a short latency reflex in the heteronymous knee extensor muscles (referred to as CPN-reflex). The CPN-reflex is facilitated at a heel strike during walking, contributing to body weight support. However, the origin of the CPN-reflex increase during walking remains unclear. We speculate that this increase originates from multiple sources due to a body of evidence suggesting the presence of neural coupling between the arms and legs. Therefore, we investigated the extent to which the CPN-reflex is modulated during rhythmic arm cycling. Twenty-eight subjects sat in an armchair and were asked to perform arm cycling at a moderate cadence using a stationary ergometer while performing isometric contraction of the knee extensors, such that the CPN-reflex was evoked. CPN-reflex was evoked by stimulating the CPN (0.9-2.0 × the motor threshold [MT] in the tibialis anterior muscle) at the level of the neck of the fibula. The CPN-reflex amplitude was measured from the vastus lateralis (VL). The biphasic reflex response in the VL was evoked within 27-45 ms following CPN stimulation. The amplitude of the CPN-reflex increased during arm cycling compared with that before cycling. The modulation of the CPN-reflex during arm cycling was detected only for CPN stimulation intensity around 1.2 × MT. Furthermore, CPN-reflex modulation was not observed during the isometric contraction of the arm or passive arm cycling. Our results suggest the presence of neural coupling between the CPN-reflex pathways and neural systems generating locomotive arm movement.