Exploring the Efficacy of a Safe Cryotherapy Alternative: Physiological Temperature Changes from Cold Water Immersion vs Prolonged Phase Change Material Cooling

Purpose: To evaluate the effectiveness between cold water immersion (CWI) and phase change material (PCM) cooling on intramuscular, core and skin temperature and cardiovascular responses.

Methods: In a randomized, crossover design, 11 males completed 15 min of 15°C CWI to the umbilicus and 2 h recovery or 3 h of 15°C PCM covering the quadriceps and 1 h of recovery, separated by 24 h. Vastus lateralis intramuscular temperature at 1 and 3 cm, core and skin temperature, heart rate variability and thermal comfort were recorded at baseline, and 15 min intervals throughout treatment and recovery.

Results: Intramuscular temperature decreased (P<0.001) during and after both treatments. A faster initial effect was observed from 15 min of CWI (Δ: 4.3±1.7°C 1 cm; 5.5±2.1°C 3 cm; P=0.01). However, over time (2 h 15 min), greater effects were observed from prolonged PCM treatment (Δ: 4.2±1.9°C 1 cm; 2.2±2.2°C 3 cm; treatment × time P=0.0001). During the first hour of recovery from both treatments, intramuscular temperature was higher from CWI at 1 cm (P=0.013) but not 3 cm. Core temperature deceased 0.25±0.32 from CWI (P=0.001) and 0.28±0.27°C from PCM (P=0.0001) while heart rate variability increased during both treatments (P=0.001), with no differences between treatments.

Conclusions: The magnitude of temperature reduction from CWI was comparable to PCM but intramuscular temperature was decreased for longer during PCM. Utilizing PCM cooling packs offers an alternative for delivering prolonged cooling whenever application of CWI is impractical while also exerting a central effect on core temperature and heart rate.