Feasibility of a Noninvasive Core Temperature Sensor and the Effects of Combined Cooling on Thermal Strain and Performance in Beach Volleyball.

PURPOSE: This study evaluated the practical feasibility of the CORE sensor for noninvasive tracking of changes in estimated core body temperature (Est-Tcore) during simulated beach volleyball match-play in the heat and examined the effects of a combined cooling strategy on countermovement jump (CMJ) and T-agility performance. METHODS: Eleven competitive male collegiate players completed 2 simulated match-play trials under hot outdoor conditions using a randomized crossover design. The COOL condition included precooling with an ice vest and ice slurry ingestion, followed by additional ice slurry during breaks. The CON condition replicated fluid intake without cooling. Est-Tcore and heart rate (HR) were continuously monitored, and thermal sensation, thermal comfort, and session-rating of perceived exertion were assessed. CMJ and T-agility performance were measured immediately before and after the matches. RESULTS: COOL attenuated the increase in Est-Tcore during warm-up and improved perceptual responses (lower thermal sensation, P < .05), while HR did not differ significantly between conditions. Postmatch CMJ and T-agility did not differ significantly between the conditions, although small-to-moderate effect sizes suggested a possible preservation of performance. CONCLUSION: The CORE sensor demonstrated practical applicability for tracking relative changes in Est-Tcore during beach volleyball match play. Combined external-internal cooling attenuated thermal strain and improved perceptual responses; however, these effects did not translate into clear benefits for explosive performance outcomes.