The Efficacy of Cooling with Phase Change Material for the Treatment of Exercise-Induced Muscle Damage

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PURPOSE: The limited efficacy of cold-water immersion in diminishing muscle damage may be due to inadequate treatment duration. Phase Change Material (PCM) can provide prolonged cooling. The purpose of this study was to examine the efficacy of post-exercise PCM cooling on strength loss and pain after eccentric exercise. METHODS: Four men and 2 women (39±13 yo) performed isometric quadriceps strength tests at 30°, 50° and 70° knee flexion, then performed 120 eccentric quadriceps contractions (Biodex System 2, Shirley NY) at 90% MVC. The protocol was repeated on the contralateral leg. PCM packs were then placed inside compression shorts over the quadriceps. PCM at 15°C were applied to the first leg, and PCM at room temperature were applied to the second leg. The 15°C packs were replaced after 3 hr (6 hr total). Quadriceps skin temperature was recorded continually. Strength and pain (VAS 0-10 scale) were assessed for 4 days. The protocol was repeated 5 mo later (room temperature PCM on both legs). Since cooling one leg might have a systemic effect on the contralateral leg, the effect of cooling was assessed by Treatment by Time ANOVA with treatments defined as Direct Cooling (leg with 15°C packs), Systemic Cooling (leg with room temperature packs contralateral to the 15°C packs), and Control (legs tested 5 mo later). RESULTS: Skin temperature averaged 21±1° C for Direct Cooling versus 31±2°C for Systemic Cooling and Control (P<0.01). Strength (% of baseline) across 4 days post-exercise was 101±9% for Direct Cooling, 94±16% for Systemic Cooling, and 91±7% for Control (Linear Treatment effect P<0.05). Peak strength loss occurred 1 day post exercise: Direct Cooling, 93±13%, Systemic Cooling, 92±16%, Control 83±10% (Linear Treatment effect P<0.01). Pain across 4 days post exercise was 0.9±1.0 for Direct Cooling, 1.6±1.4 for Systemic Cooling, and 2.5±2.4 for Control (Linear Treatment effect P<0.05). Peak pain occurred 2 days post exercise: Direct Cooling, 1.7±1.9, Systemic Cooling, 2.7±2.3, Control 4.0±0.7 (Linear Treatment effect P<0.05). CONCLUSIONS: Prolonged post-exercise muscle cooling using PCM resulted in minimal strength loss and pain compared to control (with a possible systemic effect also evident). This study demonstrates the potential utility of a cooling garment for accelerating recovery from damaging exercise.