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Thermoregulatory strategies during short‐term exercise at different intensities
Author(s) -
SCOTT CAROLINE M.,
MARLIN D. J.,
SCHROTER R. C.
Publication year - 1999
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1999.tb05248.x
Subject(s) - intensity (physics) , exercise intensity , heart rate , medicine , horse , degree (music) , thermoregulation , zoology , cardiology , physical therapy , blood pressure , biology , paleontology , physics , quantum mechanics , acoustics
Summary Previously we have observed a decline in sweating rate (SR) during high intensity exercise in an incremental test protocol. In man, the sweating sensitivity (SR/°C) has been shown to vary with exercise intensity. The aim of the present study was to determine if thermoregulatory responses in the horse, a prolific sweater with a high rate of metabolic heat production, were modified by exercise intensity. The effect of 3 separate exercise intensities (50 (S), 70 (M) and 90% (F) V̇ o 2Peak on neck (SR N ) and gluteal sweating rate (SR G ), pulmonary artery (T PA ), rectal (T REC ) and skin temperatures on the neck (T SK‐N ) and gluteal region (T SK‐G ) were investigated. Horses were exercised for ˜2 min at each exercise intensity in a randomised order. The rate of increase in T PA increased with exercise intensity (P<.05) (0.27 ± 0.05, 0.43 ± 0.04 and 0.77 ± 0.05°C/min during S, M and F, respectively. The T PA and T SK temperatures at the onset of sweating were not different between exercise intensities (P>0.05). Despite the increased rate of heat production with increasing exercise intensity, sweating sensitivity decreased on both the neck [(P<.05) (18.2 ± 3.4 (S), 12.0 ± 3.5 (M) and 2.9 ± 0.7 (g/m 2 /min)/°C (F)] and gluteal region [(P<.05) (8.9 ± 2.0 (S), 5.1 ± 1.7 (M) and 0.8 ± 0.3 (g/m 2 /min)/°C (F)]. During exercise at 90% V̇ o 2peak sweating sensitivity and the rate of increase in skin temperature were markedly reduced compared to at 70% V̇ o 2peak . The present investigation demonstrates that the drive to thermoregulate is overridden during short‐term, high‐intensity exercise, resulting in greater heat storage (T PA ) as a result of a lower SR sensitivity.