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EFFECT OF EXOGENOUS ICE SLURRY ON PHYSIOLOGICAL STRAIN INDEX DURING EXERCISE IN THE HEAT

Abstract

EFFECT OF EXOGENOUS ICE SLURRY ON PHYSIOLOGICAL STRAIN INDEX DURING EXERCISE IN THE HEAT

F. von Sydow, T.J. Hampton, J.S. Cuddy, B.C. Ruby, FACSM, and C.L. Dumke, FACSM.

The University of Montana, Missoula, MT

Ice slurry solution (IS) ingested during exercise in the heat may alleviate physiological strain index (PSI) by lessening the rise of core temperature (Tc), and heart rate (HR.) PURPOSE: To investigate IS influence on PSI during submaximal running in the heat. METHODS: Six recreationally trained subjects (60+3 ml/kg/min) participated in two running trials on an outdoor track (30+1.5˚C, 25%RH). The two trials were run at the same absolute intensity (187.6 m/s), and given either an ambient carbohydrate drink (25˚C) or IS (-1˚C) in random order. Subsequently, three recreationally aerobic trained subjects (59+3 ml/kg/min) participated in two running trials inside a climate chamber (34˚C, 40%RH). Subjects acclimatized in the chamber for 15 minutes then ran for 1hr with increasing speed every 20 minutes followed by an incremental time trial (TT) test to exhaustion. RESULTS: Using 2x3 ANOVA, outside runners had a significantly lower PSI (5.4+1.6 vs. 7.1+1.3; P=0.01), however HR (P=0.63), Tc (P=0.56), Tsk (P=0.55), and sweat rate (P=0.06) did not reach significance (P>0.05). Chamber runners reported significantly lower RPE during the IS trials (15+0.8 vs. 16+0.9; P<0.03). Although chamber runners did not achieve significantly lower PSI (P=0.35), HR (P=0.51), Tc (P=0.51), Tsk (P=0.43), or sweat rate (P=0.21) when given IS. Nevertheless, chamber runners had a significantly increased TT performance when given IS compared to ambient drink (8.2+2.1 vs 6.4+1.8; P=0.01). CONCLUSIONS: These findings indicate that IS may have a significant impact on PSI. The IS also significantly lowered RPE and significantly increased TT performance. These data show the potential for increased running performance while maintaining a lower RPE when IS is given during moderate exercise in the heat.

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