engleski

Peak body core temperature in graded exercise testing

Introduction Severe increase in body core temperature (BCT) can limit duration and/or intensity of a physical activity. It is well documented that individuals with higher aerobic capacity already show thermoregulatory features that are otherwise characteristic for heat acclimatization (Gleeson, 1998 ; Nielsen, 1998). The aims of this study were twofold: a) to analyze peak BCT (BCTpeak) during a graded treadmill exercise test ; b) to determine the relationship between BCTpeak and some indicators of aerobic capacity (maximal oxygen uptake (VO2max), maximum speed (vmax), ventilatory anaerobic threshold (vAT), heart rate at vAT (HRAT)). Methods Thirty-two physically active males (age (mean±SD) 26.5±6.6 years ; height 179.2±5.0 cm ; body mass 76.8±8.1 kg) participated in the study. Graded treadmill exercise test with speed increments of 0.5 km/h each 30 seconds was performed until volitional exhaustion. The test was performed in controlled thermoneutral conditions. Ventilatory parameters, heart rate, and rectal temperature (at 8 cm from anal sphincter) were registered throughout the test. Pearson product-moment correlation coefficients were used to determine the relationship between BCTpeak and indicators of aerobic capacity (VO2max, vmax, vAT, HRAT). Results BCTpeak measured during the test was (mean±SD ; range) 37.96±0.37°C ; 37.11–38.84°C, while the values for VO2max, vmax, vAT, HRAT were, respectively, (mean±SD) 60.4±6.6 mlO2/kg/min, 17.8±2.2 km/h, 13.1±2.1 km/h, 170.1±9.8 bpm. Moderate correlations were found between BCTpeak and vmax (r=0.36, p=0.043) and between BCTpeak and HRAT (r=0.48, p=0.006). No significant correlation was found between BCTpeak and VO2max (r=0.13, p=0.490) and between BCTpeak and vAT (r=0.29, p=0.106). Discussion No participant reached BCTpeak levels that would indicate hyperthermia, so increase in BCT was not a limiting factor in test performance. The positive correlations between BCTpeak and parameters of aerobic capacity could be the combined result of: a) participants with higher aerobic capacity being able to accommodate more heat (Mora- Rodriguez et al., 2010), b) longer test duration in these participants. The relationship between the rate of temperature increase and indicators of aerobic capacity should be investigated. References Gleeson M (1998). Int J Sports Med, 19:S96-9. Nielsen B (1998). Int J Sports Med ; 19:S154-6. Mora-Rodriguez R, Del Coso J, Hamouti N, Estevez E, Ortega JF (2010). Eur J Appl Physiol ; 109:973-81.

hyperthermia ; rectal temperature ; running ; treadmill test ; ramp test

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