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EFFECT OF SALTSTICK ELECTROLYTE FASTCHEWS ON HEAT STRESS MARKERS DURING EXERCISE IN HOT CONDITIONS

Abstract

PURPOSE: The purpose of this research was to determine the effect of electrolyte chews on heat stress in temperate and hot conditions. METHODS: 14 subjects (F 14%, Age= 23 ± 4, Height= 172.7 ± 9.3 cm, Weight= 73.9 ± 12.7 kg, VO2 Peak= 41.4 ± 6.1 ml/kg/min) performed four cycling trials: temperate control (TC 18-20◦C), temperate electrolyte chew (TE, 18-20◦C), hot control (HC 36-39◦C), and hot electrolyte chew (HE, 36-39◦C), in random order over 5-weeks. For each trial, subjects cycled at 60-80% HRR for 60 minutes and were given 0.4-0.8 L*hr-1 of distilled water, based on their recorded nude body mass. In TE and HE, subjects chewed two electrolyte chews (100mg sodium (Na+), 30mg potassium (K+), 6mg magnesium, 10mg calcium) for 45 seconds, before exercise and every 15 minutes during exercise. Subjects’ saliva and sweat were collected to analyze Na+ and K+ concentrations. Researchers also obtained sweat rate (SR) over 60 minutes and heart rate (HR), core temperature (CT), rate of perceived exertion (RPE), and thermal comfort (TC) every 5 minutes during exercise. RESULTS: Results indicate that SR was higher in HC and HE than in TC and TE, (M_hot = 0.950, M_temp = 0.607, p< 0.001). The difference in chest Na+ concentration between TE and HE was significantly different (M_diff = 658.422, p= 0.005). The difference in chest Na+ concentration between TC and HC was non-significant (M_diff = 334.938, p= 0.145). There was a significantly higher chest sweat K+ concentration in TE and HE than in TC and HC (M_with electrolytes = 251.151, M_without electrolytes = 288.809, p= 0.026). The difference in chest K+ concentration between TC and TE was significant (M_diff = 65.381, p= 0.021), but not between HC and HE (M_diff = 9.936, p= 0.733). The increase in HR was significantly higher in HC and HE than in TC and HC (M_hot = 13.714, M_temp = 8.786, p= 0.013) and the rise in HR between HE and TE differed significantly (M_diff = 5.929, p= 0.030) but was not significantly different in HC and TC (M_diff = 3.929, p= 0.089). There were no significant differences in thigh NA+/K+ concentrations, CT, or TP between trials. CONCLUSION: In summary these findings suggest that electrolytes may increase SR and Na+/K+ concentrations to increase evaporative heat loss. In contrast, there were no differences in the rise in HR, CT, RPE, or TP between the electrolyte conditions. These findings suggest that the intake of 100mg Na+ and 30mg K+ every 15 minutes for 60 minutes during moderate intensity exercise in temperate or hot conditions was not sufficient in reducing heat stress markers. THE EFFECTS OF LIVE-HIGH, TRAIN-LOW HYPEROXIC TRAINING ON RUNNING AND RECOVERY HEART RATES IN NCAA DISTANCE RUNNERS: A Pilot Study B. Nimmo, M. Torres, E. C. Johnson FACSM. University of Wyoming, Laramie, WY The live-high, train-low (LHTL) altitude training model has been widely studied for its hematological and endurance benefits; however, few studies have examined real-time running and recovery heart rate responses within a hyperoxic chamber. PURPOSE: This pilot study investigated changes in running heart rate and recovery heart rate across two high-intensity aerobic interval training protocols performed in a hyperoxic environment in acclimatized NCAA Division I distance runners. METHODS: Five NCAA Division I cross-country athletes (3 males, 2 females; age: 22.4 ± 4.98 years) residing at ~2200m completed twelve supervised training sessions over four weeks inside a hyperoxic chamber simulating ~366m. Athletes performed two high-intensity interval training protocols: Protocol 1 (P1) consisted of four-minute intervals at 90–95% HRmax with three-minute active recovery at 50–60% HRmax. Protocol 2 (P2) included 47 repetitions of 15-second intervals at 90–95% HRmax, with 15-second active recovery at 50–60% HRmax. Heart rate (HR) was recorded every minute, with recovery HR assessed before each interval. RESULTS: In P1, recovery HR significantly decreased across sessions (p = 0.017). Running HR remained stable (p = 0.25). In P2, no significant changes were observed in recovery HR (p = 0.66) or running HR (p = 0.09). CONCLUSIONS: This study provides preliminary data on running and recovery HR responses within a hyperoxic chamber during LHTL training in acclimatized athletes. While running HR remained stable, improvements in recovery HR in P1 suggest enhanced between-interval cardiac efficiency. The lack of significant changes in P2 recovery HR may indicate a different physiological adaptation pattern or a need for a longer training duration to elicit measurable effects. These findings have practical implications for endurance athletes seeking to optimize training at moderate altitude using LHTL. Future studies should expand sample size and explore the long-term effects of hyperoxic training on physiological adaptation and endurance performance.

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