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The effect of ambient temperature on gross-efficiency in cycling

Hettinga, FJ and De Koning, JJ and de Vrijer, A and Wüst, RCI and Daanen, HAM and Foster, C (2007) 'The effect of ambient temperature on gross-efficiency in cycling.' European Journal of Applied Physiology, 101 (4). 465 - 471. ISSN 1439-6319

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Abstract

Time-trial performance deteriorates in the heat. This might potentially be the result of a temperature-induced decrease in gross-efficiency (GE). The effect of high ambient temperature on GE during cycling will be studied, with the intent of determining if a heat-induced change in GE could account for the performance decrements in time trial exercise found in literature. Ten well-trained male cyclists performed 20-min cycle ergometer exercise at 60% P VO2max (power output at which VO 2max was attained) in a thermo-neutral climate (N) of 15.6 ± 0.3°C, 20.0 ± 10.3% RH and a hot climate (H) of 35.5 ± 0.5°C, 15.5 ± 3.2% RH. GE was calculated based on VO 2 and RER. Skin temperature (T sk ), rectal temperature (T re ) and muscle temperature (T m ) (only in H) were measured. GE was 0.9% lower in H compared to N (19.6 ± 1.1% vs. 20.5 ± 1.4%) (P < 0.05). T sk (33.4 ± 0.6°C vs. 27.7 ± 0.7°C) and T re (37.4 ± 0.67deg;C vs. 37.0 ± 0.6°C) were significantly higher in H. T m was 38.7 ± 1.1°C in H. GE was lower in heat. T m was not high enough to make mitochondrial leakage a likely explanation for the observed reduced GE. Neither was the increased T re . Increased skin blood flow might have had a stealing effect on muscular blood flow, and thus impacted GE. Cycling model simulations showed, that the decrease in GE could account for half of the performance decrement. GE decreased in heat to a degree that could explain at least part of the well-established performance decrements in the heat. © Springer-Verlag 2007.

Item Type: Article
Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
Depositing User: Jim Jamieson
Date Deposited: 03 Feb 2015 13:58
Last Modified: 17 Aug 2017 17:55
URI: http://repository.essex.ac.uk/id/eprint/8286

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