The aim of this study was to compare the maximal lactate steady state (MLSS) and ventilatory threshold (VT) under different environments (TEMP: 22°C; and HOT: 40°C; 50% RH). 8 male subjects (age 23.9±2.4 years, body mass 75.9±7.3 kg and VO2(max) 47.8±4.9 mL·kg(-1)·min(-1)) performed a series of tests to determine the peak workload (W(peak)), VT and MLSS on a cycle ergometer. W(peak) was higher in the TEMP as compared to the HOT condition (225±9 W vs. 195±8 W, respectively; p<0.05). The workload at MLSS was higher at 22°C (180±11 W) than 40°C (148±11 W; p<0.05), as well as VT at 22°C (156±9 W) was higher than 40°C (128±6 W). Likewise, the blood lactate concentration at MLSS was higher at 22°C (5.60±0.26 mM) than 40°C (4.22±0.48 mM; p<0.05). The mean of heart rate (HR) was not statistically different between TEMP (168±3 bpm) and HOT (173±3 bpm) at MLSS, despite being different at trials between the 25(th) and the 30(th) min of exercise. The HR at VT was significantly higher in HOT (153±4 bpm) as compared to the TEMP (145±2 bpm). Our results suggest that environmental conditions may influence the determination of MLSS and VT. Moreover, VT was appropriate for estimation of the workload at MLSS in the HOT.
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