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

Abstract

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 men 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 < .001) during and after both treatments. A faster initial effect was observed from 15 min of CWI (Δ: 4.3°C [1.7°C] 1 cm; 5.5°C [2.1°C] 3 cm; P = .01). However, over time (2 h 15 min), greater effects were observed from prolonged PCM treatment (Δ: 4.2°C [1.9°C] 1 cm; 2.2°C [2.2°C] 3 cm; treatment × time, P = .0001). During the first hour of recovery from both treatments, intramuscular temperature was higher from CWI at 1 cm (P = .013) but not 3 cm. 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. Conclusions: 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.

Don't Lose Your Cool With Cryotherapy: The Application of Phase Change Material for Prolonged Cooling in Athletic Recovery and Beyond

“…As a result, the duration for which muscle temperature is reduced during traditional cryotherapy treatment is likely too short to elicit meaningful reductions in muscle temperature for durations long enough to be clinically relevant (10-15 • C; Sapega et al, 1988). Although the intramuscular temperatures reported from 3 h of 15 • C PCM cooling are nowhere close to those necessary for reducing local muscle metabolism (26.0 ± 2.2 • C at 1 cm and 28.2 ± 2.8 • C at 3 cm of the vastus lateralis), the reduction was safely maintained for a prolonged and continuous duration in individuals at rest (Kwiecien et al, 2019). Furthermore, these temperatures were comparable to those occurring from 15 min of 15 • C CWI even though two PCM packs (864 cm 2 area; 32.4 × 2 × 13.3 cm) were administered locally and fitted directly on the skin over the quadriceps of each leg, while CWI treatment involved whole body immersion up to the umbilicus (Kwiecien et al, 2019).…”

“…A PCM with a melting point <24°C might reduce core temperature more effectively (Gao et al, 2011 ). In rested individuals, local application of 15°C PCM to the quadriceps for 3 h reduced core temperature by 0.28°C compared with a 0.25°C reduction from 15 min of 15°C CWI (Kwiecien et al, 2019 ). Although the difference in the reduction in core temperature from both PCM and CWI was negligible, the CWI reduced core temperature faster than the PCM treatment but the reduction in core temperature was maintained for the 3-h duration of 15°C PCM application (Kwiecien et al, 2019 ).…”

“…Similar to ice, the 15 • C PCM are firm and look like wax when in their frozen solid state and look like vegetable oil once they reach their melted liquid state (Figure 2). A PCM with a latent phase of 15 • C is capable of safely prolonging and maintaining the duration of cooling for 3 h (Kwiecien et al, 2019), while avoiding the need for repeat applications. If there is a need to extend the duration of application beyond 3 h, a fresh set of "frozen" PCM packs can be administered for an additional 3 h. Applying 15 • C PCM packs directly to the skin fitted under a garment might be less time consuming, logistically simpler to implement than other cryotherapy modalities, and is more practical particularly because they can simultaneously deliver a cooling treatment while the individual continues activities of daily living.…”

Prolonging the duration of cooling does not enhance recovery following a marathon

“…During baseline testing, participants were fitted with appropriately sized generic athletic shorts (Eastbay brand), into which four PCM packs (Glacier Tek USDA BioPreferred PureTemp PCM, Plymouth, MN, USA) “frozen” at 15°C were applied directly onto the skin over the quadriceps of both legs, two packs per leg. Based on our previous studies (three‐ 25 and six‐hour duration of PCM application 26,27 ), it was established that the participants would wear the PCM over the quadriceps of both legs for a total of three hours to have a balance between efficacy and practicality of the treatment. Participants receiving three‐hour PCM treatment began the intervention within 1:20 ± 0:34 hours of finishing the marathon.…”

“…A longer duration of cooling can be achieved by utilizing phase change material (PCM) packs that freeze at 15°C. The influence of three hours of PCM cooling on muscle temperature, core temperature, and the cardiovascular response has recently been established and compared with a temperature matched CWI protocol 25 . In the aforementioned study, both PCM and CWI reduced superficial and deep muscle temperature, core temperature, and modulated sympathetic tone to the same magnitude in rested individuals.…”