Soleus H-reflex modulation during balance recovery after forward falling

Introduction: Our purpose was to examine the Hoffmann reflex (H-reflex) during balance recovery after a simulated forward fall from 2 different inclination angles. Methods: The soleus H-reflex of 15 healthy adults was measured in 2 different leaning positions (exerting a horizontal force at 15% and 30% of body weight, respectively), with no release (Int0) and at 2 different intervals (Int1, Int2) after the release (approximate to 45 and approximate to 65 ms, respectively). Results: During Int2, the H-reflex, which was evoked before the onset of the soleus electromyography, was significantly higher than the H-reflex induced 20 ms earlier (Int1). No significant difference was observed between Int0 and Int1 and between the 2 leaning positions. Conclusions: These findings indicate that Ia afferent input is facilitated before muscle activation during forward falling. This could be important for the timely activation and increased rate of force development required during this task. Muscle Nerve54: 952-958, 2016