Exploring the Efficacy of a Safe Cryotherapy Alternative: Physiological Temperature Changes From Cold-Water Immersion Versus Prolonged Cooling of Phase-Change Material.

Abstract

To evaluate the effectiveness between cold-water immersion (CWI) and phase-change-material (PCM) cooling on intramuscular, core, and skin-temperature and cardiovascular responses. In a randomized, crossover design, 11 men completed 15min of 15°C CWI to the umbilicus and 2-h recovery or 3h of 15°C PCM covering the quadriceps and 1h of recovery, separated by 24h. Vastus lateralis intramuscular temperature at 1 and 3cm, core and skin temperature, heart-rate variability, and thermal comfort were recorded at baseline and 15-min intervals throughout treatment and recovery. Intramuscular temperature decreased (P < .001) during and after both treatments. A faster initial effect was observed from 15min of CWI (Δ: 4.3°C [1.7°C] 1cm; 5.5°C [2.1°C] 3cm; P = .01). However, over time (2h 15min), greater effects were observed from prolonged PCM treatment (Δ: 4.2°C [1.9°C] 1cm; 2.2°C [2.2°C] 3cm; treatment × time, P = .0001). During the first hour of recovery from both treatments, intramuscular temperature was higher from CWI at 1cm (P = .013) but not 3cm. Core temperature deceased 0.25° (0.32°) from CWI (P = .001) and 0.28°C (0.27°C) from PCM (P = .0001), whereas heart-rate variability increased during both treatments (P = .001), with no differences between treatments. The magnitude of temperature reduction from CWI was comparable with PCM, but intramuscular temperature was decreased for longer during PCM. PCM cooling packs offer an alternative for delivering prolonged cooling whenever application of CWI is impractical while also exerting a central effect on core temperature and heart rate.