engleski

Rectal temperature dynamics during graded exercise testing

Introduction Different physiological variables show distinct trends of increase during incremental exercise. The increase trend reflects the underlying changes in skeletal muscle metabolism related to increasing exercise intensity, and is often used to describe different intensity zones. The aim of this study was to determine the pattern of increase in body core temperature during incremental treadmill exercise test. Methods The sample consisted of 32 physically active males (age (mean±SD) 26.5±6.6 years ; height 179.2±5.0 cm ; body mass 76.8±8.1 kg). They performed a graded treadmill exercise test until volitional exhaustion (speed increments of 0.5 km/h each 30 seconds) in controlled thermoneutral conditions. Rectal temperature (measured at 8 cm from the anal sphincter) was registered throughout the test. Three independent evaluators performed computer- assisted fitting of temperature curves. Results Three models of temperature increase during graded exercise test were identified. Each was described by three distinct segments of temperature rise (an additional fourth segment was identifiable in several cases), delimited by threshold-like changes in trend of increase. The first model was described by three segments of progressive linear increase. The second model was described by an initial segment of linear increase, followed by a curvilinear increase (best fitted by a 2nd-degree polynomial model), and a third segment of linear increase. The third identified model consisted of an initial curvilinear increase (2nd-degree polynomial model), followed by two segments of linear increase. The slope of temperature rise increased between subsequent zones in all models. Discussion The rectal temperature, as a measure of body core temperature, showed three distinct patterns of increase during graded treadmill exercise test. A phasic increase identified in all models, characterized by distinct segments of increasing slope of temperature rise, arguably reflects thermodynamic changes imposed by metabolic effects of increasing intensity of exercise. References González-Alonso (2012). Exp Physiol ; 97(3):340-6. Noakes et al. (1991). Med Sci Sports Exerc ; 23(4):443-9.

body core temperature ; exercise intensity ; curve fitting

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