Correlation and multiple regression analysis were employed to assess for human physical and physiological predictors of esophageal temperature (TES) thresholds for pulmonary ventilation during exercise (VE). It was hypothesized these TES thresholds would be positively associated to peak oxygen consumption (VO2PEAK) and thermolytic responses as well as negatively associated to the chemosensitivity of breathing. The SFU Office of Research Ethics approved the study. Twenty‐three volunteers participated 2 studies. They were 27.8±7.9 years of age (mean ± SD), 71.9±7.2 kg in weight and 1.76±0.06 m in height. They had a Body Surface Area (BSA) of 1.87±0.1 m2 and a Body Mass Index (BMI) of 23.4±2.4 kg/m2. Twenty‐three volunteers performed incremental cycle ergometer exercise from rest to the point of exhaustion. A second group of 9 volunteers performed a hyperoxic‐hypercapnic, modified Read rebreathing test during normothermia and hyperthermia. For correlation and multiple regression analyses the dependent outcome variables were TES thresholds for ventilatory equivalents for oxygen (VE/VO2) and carbon dioxide (VE/VCO2). For the same analyses the independent variables included age, weight, height, BSA, BMI, VO2PEAK, the ventilatory recruitment threshold and slope from Read rebreathing plots and TES thresholds for onsets of eccrine sweating (ESW) and cutaneous blood velocity (CBV). Results indicated significant positive correlations between TES thresholds for VE/VO2 and VE/VCO2 with VO2PEAK (both r=0.42, p<0.05) and each of the TES thresholds for the onset of ESW and CBV (0.72
During incremental exercise from rest to exhaustion, core temperature thresholds are evident at exercise intensities greater than that at the anaerobic threshold or the onset of blood lactate accumulation. The effect of aerobic fitness on these core temperature thresholds remains poorly understood. PURPOSE: To compare oesophageal temperature (TES) thresholds for exercise ventilation (VE) between competitive, trained and untrained males during incremental exercise. HYPOTHESIS: Trained athletes will demonstrate a greater TES threshold for VE than untrained males. Methods: Seven college‐aged competitive male cyclists with a VO2MAX of 63.9 ± 3.7 mL•min‐1•kg‐1 (mean ± SD) and 7 college‐aged untrained males with a VO2MAX of 53.9 ± 3.5 mL•min‐1•kg‐1 volunteered for the study that approved by the SFU Office of Research Ethics. VE and its components were measured with a breath‐by‐breath metabolic cart and volunteers pedaled an electrically braked cycle ergometer at an ambient temperature of ~22oC. Each incremental exercise test started with a load of 60 W on the cycle ergometer that was incremented by 35 W/min until exhaustion. Core temperature thresholds from plots of ventilatory equivalents for oxygen (VE/VO2) and carbon dioxide (VE/VCO2) as a function of TES were 1.3°C greater (P<0.01) in the trained vs. the untrained group. The trained group relative to the untrained cyclists had a higher (P<0.01) anaerobic threshold as determined from plots of VE/VO2 and VE/VO2 as a function of VO2. CONCLUSION: Evidence supports the hypothesis that increased aerobic fitness results in a higher core temperature threshold for VE during incremental exercise. Grant Funding Source: Supported by NSERC and CFI
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