Facilitating Cutaneous Afferent Feedback with Texture on Mechanically Induced Stretch Reflex Excitability During Gait Termination.

Abstract

Cutaneous feedback plays a large role in the reflexive activation of muscle activity (Ia stretch reflex) generating postural responses during planned gait termination. As the mechanisms to induce a cutaneous afferent volley have been limited to electrical stimulation, it remains unknown if mechanical stimuli can modulate stretch reflex (SR) excitability. The purpose of this study was to examine the effect of adding cutaneous inputs on modulating the SR during perturbed gait termination. Thirty young adults completed walking trials when a platform unexpectedly tilted 10 degrees anteriorly or posteriorly, inducing a tibialis anterior (TA) or medial gastrocnemius (MG) short-latency reflex. The SR latency, the peak SR amplitude, and the total SR amplitude of the agonist burst, were compared between the stretched muscle and cutaneous facilitation. Statistically significant interactions were observed between the stretched muscle and cutaneous facilitation on the SR peak and SR burst. More notably, texture resulted in a consistent expression on the TA SR magnitude, without a similar effect in MG. Despite confirming the ability of cutaneous afferent facilitation on modulating spinal interneuronal circuitry, participant variability in response to texture highlights the importance of focusing on individual participant results when studying the effects of cutaneous facilitation on modulating spinal motorneuron excitability.