Whole-body Heat Shock Accelerates Recovery from a Single Blunt Trauma Contusionin Mice

Abstract

Contusions are a common sports injury, often resulting in acute skeletal muscle contractile dysfunction. Whole-body heat shock is reported to attenuate skeletal muscle atrophy in animal models. PURPOSE: The purpose of this study was to test the hypothesis that whole-body heat shock attenuates contusion induced-skeletal muscle contractile dysfunction. METHODS: Male mice (14.4 ± 1.4 mo) were randomized to either the heat shock contusion group (HSC n=5), the normal body temperature contusion group (NTC n=4), or sham (n=3). Under anesthesia, the in vivo torque-frequency relationship (1hz-300hz) of the anterior crural muscle group was measured in all mice. Body temperature was then raised to 41°C (HSC) or maintained at 37°C (NTC and sham) for 30 min and then all mice were allowed to recover consciousness. Twenty-four hours later all mice were anesthetized again and a single contusion (HSC and NTC) was delivered via the instrumented mass-drop technique (14.1 g steel ball was dropped through a tube from 115 cm onto an impactor directly striking the tibialis anterior) or no contusion (sham); all mice were then allowed to recover. Following 5 days of normal cage activity (5-d recovery), in vivo torque-frequency relationships were measured in all mice. Data were analyzed using a factorial ANOVA with an a priori level of significance of 0.05. Fisher’s LSD pair-wise comparisons were made post hoc. RESULTS: There was a significant group-time-frequency interaction (F=1.791, p=0.034). Within group pairwise comparison pre to 5-d recovery revealed sham did not differ (p=0.529), HSC fully recovered (p=0.899), and NTC did not recover (p=0.001) muscle contractile function. Within group comparison pre to 5-d at 40hz (submaximal stimulation) and 250hz (maximal stimulation) found sham did not differ (p=0.765; p=0.912, respectively), HSC recovered (p=0.786; p=0.602, respectively), and NTC did not recover at either frequency (p=0.001; p=0.006, respectively). CONCLUSION: Whole body heat shock treatment prior to a single blunt trauma contusion accelerates the rate of recovery of in-vivo skeletal muscle contractile function within the 5-d recovery period. Funding: This work was partially supported by an Appalachian State University GRAM award.