Circadian rhythms in gas exchange kinetics at the onset of moderate bicycle exercise / 体力科学

ABSTRACT

Circadian rhythms (diurnal variations) in many physiological parameters have been reported. However, there are no data on gas exchange kinetics at the onset of exercise. The purpose of this study was to establish whether there are circadian rhythms in gas exchange kinetics at the onset of exercise.<BR>Six male subjects performed 120W exercise on a cycle ergometer for 7 min in the morning (AM; 7 30-8 30) and evening (PM; 16 30-17 30) . Rectal temperature (Tr) and mean skin temperature (T<SUB>sk</SUB>) at rest were significantly higher PM than AM, the differences being 0.9±0.2°C and 0.7±0.2°C, respectively. Respiratory and circulatory parameters at rest and during exercise were not different between AM and PM. The time constants of oxygen uptake (Vo<SUB>2</SUB>), carbon dioxide output (Vco<SUB>2</SUB>), minute ventilation (V<SUB>E</SUB>), heart rate (HR), and oxygen pulse (Vo<SUB>2</SUB>/HR) showed the same results. There was no relationship between temperature parameters (Tr, T<SUB>sk</SUB>) and the time constants.<BR>It is suggested that circadian rhythms reflected by the change in body temperature do not have any effect on gas exchange kinetics at the onset of moderate bicycle exercise.