Abstract
To determine if the increases in rectal temperature (T REC) during exercise in the heat at a given percent of \( \dot{V}\hbox{O}_{{2\,{\text{peak}}}} \) depend on a subject’s aerobic fitness level. On three occasions, 10 endurance-trained (Tr) and 10 untrained (UTr) subjects (\( \dot{V}\hbox{O}_{2\,{\rm peak}} \): 60 ± 6 vs. 44 ± 3 mL kg−1 min−1, P < 0.05) cycled in a hot-dry environment (36 ± 1°C; 25 ± 2% humidity, airflow 2.5 m s−1) at three workloads (40, 60, and 80% \( \dot{V}\hbox{O}_{2\,{\rm peak}} \)). At the same percent of \( \dot{V}\hbox{O}_{2\,{\rm peak}} \), on average, Tr had 28 ± 5% higher heat production but also higher skin blood flow (29 ± 3%) and sweat rate (20 ± 7%; P = 0.07) and lower skin temperature (0.5°C; P < 0.05). Pre-exercise T REC was lower in the Tr subjects (37.4 ± 0.2 vs. 37.6 ± 0.2; P < 0.05) but similar to the UTr at the end of 40 and 60% \( \dot{V}\hbox{O}_{2\,{\rm peak}} \) trials. Thus, exercise T REC increased more in the Tr group than in the UTr group (0.6 ± 0.1 vs. 0.3 ± 0.1°C at 40% \( \dot{V}\hbox{O}_{2\,{\rm peak}} \) and 1.0 ± 0.1 vs. 0.6 ± 0.3°C at 60% \( \dot{V}\hbox{O}_{2\,{\rm peak}} \); P < 0.05). At 80% \( \dot{V}\hbox{O}_{2\,{\rm peak}} \) not only the increase in T REC (1.7 ± 0.1 vs. 1.3 ± 0.3°C) but also the final T REC was larger in Tr than in UTr subjects (39.15 ± 0.1 vs. 38.85 ± 0.1°C; P < 0.05). During exercise in the heat at the same relative intensity, aerobically trained individuals have a larger rise in T REC than do the untrained ones which renders them more hyperthermic after high-intensity exercise.
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Acknowledgments
The study was partially supported by a grant from the Spanish Ministry of Education DEP2006-56076-C06-02. Juan Del Coso and Nassim Hamouti were supported by a pre-doctoral fellowship from the Castilla-La Mancha government in Spain. Juan F. Ortega was supported by a Latin-American grant from the Gatorade Sports Science Institute. The authors of this study declare that the experiments comply with the current laws of the country in which they were performed. The study was approved by the local Hospital Research Ethics Committee and conducted in accordance with the guidelines of the revised Declaration of Helsinki.
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The authors of this study declare that they have no financial, professional or other personal interest of any nature in any product, service and/or company that could be construed as influencing the position presented in this manuscript.
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Communicated by George Havenith.
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Mora-Rodriguez, R., Coso, J.D., Hamouti, N. et al. Aerobically trained individuals have greater increases in rectal temperature than untrained ones during exercise in the heat at similar relative intensities. Eur J Appl Physiol 109, 973–981 (2010). https://doi.org/10.1007/s00421-010-1436-4
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DOI: https://doi.org/10.1007/s00421-010-1436-4