Effect of a hot environment on performance of prolonged, intermittent, high-intensity shuttle running
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CONTRIBUTORS:
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JOURNAL:
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YEAR:
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1998
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PUB TYPE:
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Journal Article
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SUBJECT(S):
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RUNNING; MAN; BODY-TEMPERATURE-REGULATION; HEAT; PHYSIOLOGY; YOUNG-ADULT
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DISCIPLINE:
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No discipline assigned
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HTTP:
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LANGUAGE:
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English
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PUB ID:
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103-366-612
(Last edited on
2002/02/27 18:44:59 US/Mountain)
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SPONSOR(S):
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ABSTRACT:
In this study we examined the performance during, and the physiological and metabolic responses to, prolonged, intermittent, high-intensity shuttle running in hot (approximately 30 degrees C, dry bulb temperature) and moderate (approximately 20 degrees C) environmental conditions. Twelve male students, whose mean (plus/minus S mean) age, body mass and maximal oxygen uptake (VO2max) were 22 plus/minus 1 years, 69.8 plus/minus 1.8 kg and 56.9 plus/minus 1.1 ml.kg-1.min-1 respectively, performed intermittent high- and low-speed running involving five sets of approximately 15 min of repeated cycles of walking and variable speed running followed by 60 s run/rest exercise until fatigue. The total distance completed in the hot and moderate trials was 8842 plus/minus 790 m and 11,280 plus/minus 214 m respectively (P is less than 0.01). This decrement in performance occurred even though no differences existed in the level of dehydration, rating of perceived exertion, blood glucose and lactate, plasma free fatty acid and ammonia concentrations between the two trials. However, water consumption was almost twice as great in the hot trial (hot vs moderate: 1.18 plus/minus 0.12 vs 0.63 plus/minus 0.07 1.h-1, P is less than 0.01). Rectal temperature (hot vs moderate: 39.4 plus/minus 0.1 vs 38.0 plus/minus 0.1 degrees C, P is less than 0.01) and heart rate (hot vs moderate: 186 plus/minus 2 vs 179 plus/minus 2 beats.min-1, P is less than 0.05) were higher at the end of the hot condition than at the same point in time in the moderate condition. The correlation between the rate of rise in rectal temperature and the distance completed during the hot condition was -0.94 (P is less than 0.01); for the moderate condition it was -0.65. The reduced performance in the hot condition was associated with high body temperature; the precise mechanisms by which the performance decrement was brought about are, however, unclear.
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