The relationship of ankle temperature during cooling and rewarming to the human soleus H reflex

Objective: Correlate skin temperature and motoneuron-pool recruitment durin g cooling and rewarming. Design: Within-subjects, correlational analysis. H reflex was correlated to ankle-skin temperature over time using a Pearson product-moment correlatio n coefficient and a coefficient of determination (R-2). Subjects: Ten healthy, physically active college students. Measurements: Soleus H reflex and ankle-skin interface temperature were mea sured during ice application and rewarming. Electrical stimulation was deli vered to produce 75% of each subject's maximum H reflex. Results: Ankle cooling (r = -.95, P < .05) exhibited a strong inverse relat ionship with soleus H reflex. A positive correlation was observed between r ewarming (r = .74, P < .05) and soleus H reflex. Conclusions: Temperature accounts for nearly 90% (R-2 = .90) of the variabi lity in the soleus H reflex during cooling and 55% (R-2 = .55) during rewar ming, suggesting that more motoneurons are recruited as temperature decreas es. These interactions appear to involve both local and central nervous sys tem functions.