Temperature dependency of human muscle velocity recovery cycles

Introduction: Velocity recovery cycles (VRCs) of human muscle action potentials have been proposed as a new technique for studying muscle membrane function. This study was undertaken to determine the temperature dependency of VRC parameters.

Methods: VRCs with 1 conditioning stimulus were recorded repeatedly from brachioradialis muscle during cooling, and intramuscular temperature was recorded. VRCs in 6 normal volunteers were measured at 1°C intervals from 34°C to 28°C. The effects of temperature on relative refractory period and early and late supernormality were quantified.

Results: Muscle VRC curves shift progressively upward and to the right with cooler temperatures. The most sensitive parameter to temperature changes was relative refractory period, whereas early supernormality was rather insensitive. Late supernormality was unaffected by temperature changes.

Conclusions: Knowledge of temperature-induced changes of muscle VRC parameters is essential for future studies. Thus, the results of this study provide a firm basis for clinical studies with this technique.