The relationship between intramuscular temperature, skin temperature, and adipose thickness during cryotherapy and rewarming

Objective: To describe the relationships among muscle temperature, skin temperature, room temperature, body core temperature, time, and subcutaneous adipose thickness during cryotherapy and rewarming. Design: A multiple linear regression with 5 independent variables (skin temperature, body core temperature, subcutaneous adipose thickness, room temperature, time) predicting intramuscular (IM) temperature. Setting: A sports injury research laboratory. Participants: Fifteen volunteers with thigh skinfold measurements smaller than 40mm. Interventions: Thirty-minute cryotherapy treatment (ice bag) followed by a 120-minute rewarming period. Main Outcome Measures: The relationship between skin and IM temperature was described, and an equation predicting IM temperature by using room temperature, skin temperature, body core temperature, time, and adipose thickness was developed. Results: Pearson's correlations between each predictor variable of IM temperature during cryotherapy were skin temperature, r = .46; skinfold, r = .37; rime, r = -.59; core temperature, r = .21; and room temperature, r = -.47. During rewarming, the correlations were skin temperature, r = .71; skinfold, r = .27; rime, r = .76; core temperature, r = -.05; and room temperature, r = -.21. A multiple regression equation (R² = .76) was developed to predict IM temperature during cryotherapy. A separate equation (R² = .81) was developed to predict muscle temperatures during rewarming. Conclusions: During and after ice application, no single predictor adequately explained the change in IM temperature. Skin surface temperature was a weak predictor of IM temperature during cryotherapy and should not be used as the sole dependent measure in cryotherapy efficacy studies.