Superficial Moist Heat Lack of Influence on Soleus Function

Context: It is reported that thermotherapy decreases motoneuron-pool recruitment. Any decrease in recruitment might have a significant impact on an athlete’s ability to return to competition. Objective: To determine whether moist heat application influences involuntary motoneuron-pool recruitment or voluntary plantar-flexion peak torque of the soleus muscle immediately or 30 min after application. Design: A 3 x 3 crossover design. Setting: Biomechanics laboratory. Participants: Eighteen healthy subjects with no history of lower extremity surgery or injury 12 months before the study volunteered. Intervention: A series of short-duration, high-intensity stimuli was delivered to the tibial nerve to find the Hmax and Mmax measures. Immediately after the Hmax and Mmax measures, subjects were positioned on an isokinetic dynamometer where they performed 5 submaximal warm-up repetitions. Immediately after the warm-up, 5 maximum-intensity peak plantar-flexion torque repetitions were performed. After the dynamometer measures, subjects returned to the table, where a moist heat pack, no heat pack, or a dry nonheated heat pack was applied. Main Outcome Measures: Hmax, Mmax, peak plantar-flexion torque, surface temperature (°C), and ambient temperature (°C). Results: Moist heat did not influence the H:Mmax ratio or peak plantar-flexion torque. Temperature increased with moist heat pack. Ambient temperature remained constant. Conclusions: Moist heat did not influence involuntary motoneuron-pool recruitment or voluntary peak plantar-flexion torque of the soleus muscle immediately or 30 min after application.