Duration-dependant response of mixed-method pre-cooling for intermittent-sprint exercise in the heat

Minett, Geoffrey M., Duffield, Rob, Marino, Frank E., & Portus, Marc (2012) Duration-dependant response of mixed-method pre-cooling for intermittent-sprint exercise in the heat. European Journal of Applied Physiology, 112(10), pp. 3655-3666.

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Abstract

This study examined the effects of pre-cooling duration on performance and neuromuscular function for self-paced intermittent-sprint shuttle running in the heat. Eight male, team-sport athletes completed two 35-min bouts of intermittent-sprint shuttle running separated by a 15-min recovery on three separate occasions (33°C, 34% relative humidity). Mixed-method pre-cooling was completed for 20 min (COOL20), 10-min (COOL10) or no cooling (CONT) and reapplied for 5-min mid-exercise. Performance was assessed via sprint times, percentage decline and shuttle-running distance covered. Maximal voluntary contractions (MVC), voluntary activation (VA) and evoked twitch properties were recorded pre- and post-intervention and mid- and post-exercise. Core temperature (T c), skin temperature, heart rate, capillary blood metabolites, sweat losses, perceptual exertion and thermal stress were monitored throughout. Venous blood draws pre- and post-exercise were analyzed for muscle damage and inflammation markers. Shuttle-running distances covered were increased 5.2 ± 3.3% following COOL20 (P < 0.05), with no differences observed between COOL10 and CONT (P > 0.05). COOL20 aided in the maintenance of mid- and post-exercise MVC (P < 0.05; d > 0.80), despite no conditional differences in VA (P > 0.05). Pre-exercise T c was reduced by 0.15 ± 0.13°C with COOL20 (P < 0.05; d > 1.10), and remained lower throughout both COOL20 and COOL10 compared to CONT (P < 0.05; d > 0.80). Pre-cooling reduced sweat losses by 0.4 ± 0.3 kg (P < 0.02; d > 1.15), with COOL20 0.2 ± 0.4 kg less than COOL10 (P = 0.19; d = 1.01). Increased pre-cooling duration lowered physiological demands during exercise heat stress and facilitated the maintenance of self-paced intermittent-sprint performance in the heat. Importantly, the dose-response interaction of pre-cooling and sustained neuromuscular responses may explain the improved exercise performance in hot conditions.

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ID Code: 55356
Item Type: Journal Article
Refereed: Yes
Keywords: precooling, thermoregulation, team-sports, heat stress, fatigue
DOI: 10.1007/s00421-012-2348-2
ISSN: 1439-6319
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000)
Divisions: Current > QUT Faculties and Divisions > Faculty of Health
Current > Schools > School of Exercise & Nutrition Sciences
Copyright Owner: Copyright 2012 Springer
Copyright Statement: The original publication is available at SpringerLink
http://www.springerlink.com
Deposited On: 10 Dec 2012 22:21
Last Modified: 12 Dec 2012 17:42

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