Effects of Exercise Intensities on Alterations of Surface and Core Temperature, and Physiological Metabolic Variables

PURPOSE: The relationship between core and surface body temperatures should be elucidated under various exercise conditions. This study investigated whether body temperature patterns were differentially regulated between body surface area (Tbs) and gastrointestinal core area (Tgi) during two different exercise intensities.METHODS: Ten healthy young men undertook treadmill running for 40 min at two different intensities of target heart rate (THR) set at 35% or 65% of heart rate reserve. The participants took an e-Celsius capsule with water for the core temperature measurements. Heart rate (HR) was continuously monitored using a wireless HR sensor upon exercise, and blood samples (70 μl) were collected at four different time points (30 min before exercise [PreE-30], 20 min after initiate exercise [Exe-20], 40 min after initiate exercise [Exe-40], and 30 min after recovery [Rec-30]) for subsequent biochemical analyses. The statistical significance level was set at α=.05.RESULTS: Energy expenditure, oxygen consumption, and metabolic equivalents were higher during the 65% THR than the 35% THR exercise (p<.001). Regardless of exercise intensity, Tbs decreased but Tgi increased as exercise progressed (p<.001). At Exe-20, the blood glucose level was significantly lower, but the lactic acid level was significantly higher after the 65% THR exercise than after the 35% THR exercise. Compared to PreE-30, creatinine levels increased during exercise (p<.05). PO₂ remained higher than Rec-30; however, PCO₂ decreased during the exercise (p<.05). Potassium ions showed an increase during exercise regardless of exercise intensities (p<.05).CONCLUSIONS: Neither Tgi nor Tbs was influenced by exercise intensities while an increase in Tgi and decrease in Tbs was observed as exercise was progressed. This may provide crucial information for understanding of temperature control upon exercise.