Article Title



Cody R. Smith, Cory L. Butts, J.D. Adams, Jeffrey A. Bonacci, Matthew S. Ganio, Nicole E. Moyen, Matthew A. Tucker & Brendon P. McDermott

University of Arkansas, Fayetteville, Arkansas

Exercising in a hot environment increases thermal discomfort, raises gastrointestinal temperature (TGI), and potentially leads to heat illness. Limited evidence exists regarding the effect of external phase change cooling modalities on these variables. PURPOSE: Examine the effect of the phase change (10°C) Heat Emergency Kit (HEK) on thermoregulatory and perceptual response, and subsequent performance following exercise in the heat. METHODS: Twenty-six (13 male, 13 female) individuals (20-27y) participated in two trials (ambient temperature 31.5±1.8°C, 59.0±5.6% RH). Trials consisted of 30 minutes of volitional games (soccer or Frisbee), treatment (T1) for 15 minutes in random order with HEK (covers chest, back, thighs, neck, and head) or lying in shade (control), an agility test (5-10-5 pro) and a distance run (1500m), and treatment (T2) with same modality as T1. Cooling rates were calculated using TGI (ingestible thermistor) measures over time. Mean skin temperature (TSK) was calculated via thermocouples and heart rate (HR) was recorded via cardiotachometer. TGI, TSK, HR, and perceptual measures of thermal and thirst sensation were assessed twice during games and every 5 minutes during T1 and T2. Perceived muscle pain was measured before and after games and performance. RESULTS: Maximum TGI following games and performance was not significantly different between trials (p>.05). Overall cooling rates were significantly greater in T1 control (0.053±0.026°C/min) versus HEK (0.043±0.020°C/min, p=0.048), with no differences in T2 (p=0.63). There was a significant decrease in TSK when using HEKafter 10 (control: 35.3±0.9°C, HEK: 34.0±0.9°C, p=.012) and 15 minutes (control: 35.1±0.9°C, HEK: 33.7± 0.9°C, p=.001) of T1. Muscle pain was significantly lower for HEK (0.6±0.8) versus control (1.1±1.3, p=0.026) after T2. Thirst was significantly decreased following T2 for control (4.1±1.7) compared to HEK (4.4±1.8; p=.021). Agility (control: 5.74±0.44s, HEK: 5.68±0.47s) and distance (control: 7:49.3±1:43.6min, HEK: 7:44.6±1:48.3min) performances were not significantly different (p>.05). CONCLUSION: The HEK did not reduce TGI more effectively than lying supine in the shade and therefore cannot be suggested as an effective modality to treat exercise-induced hyperthermia. Perceptual benefits identified that HEK improves comfort following exercise in the heat and that future testing should be done to solidify performance responses.

Supported by PreventaMed, Inc.

This document is currently not available here.