Chronobiological effects on exercise performance and selected physiological responses

Abstract

Previous studies investigating the impact of circadian rhythms on physiological variables during exercise have yielded conflicting results. The purpose of the present investigation was to examine maximal aerobic exercise performance, as well as the physiological and psychophysiological responses to exercise, at four different intervals (0800 hours, 1200 hours, 1600 hours, and 2000 hours) within the segment of the 24-h day in which strenuous physical activity is typically performed. Ten physically fit, but untrained, male university students served as subjects. The results revealed that exercise performance was unaffected by chronobiological effects. Similarly, oxygen uptake, minute ventilation and heart rate showed no time of day influences under pre-, submaximal, and maximal exercise conditions. Ratings of perceived exertion were unaffected by time of day effects during submaximal and maximal exercise. In contrast, rectal temperature exhibited a significant chronobiological rhythm under all three conditions. Under pre- and submaximal exercise conditions, significant time of day effects were noted for respiratory exchange ratio, while a significant rhythmicity of blood pressure was evident during maximal exercise. However, none of these physiological variables exhibited significant differential responses (percent change from pre-exercise values) to the exercise stimulus at any of the four time points selected for study. Conversely, resting plasma lactate levels and lactate responses to maximal exercise were found to be significantly sensitive to chronobiological influences. Absolute post-exercise plasma norepinephrine values, and norepinephrine responses to exercise (percent change from pre-exercise values), also fluctuated significantly among the time points studied. In summary, these data suggest that aerobic exercise performance does not vary during the time frame within which exercise is normally conducted, despite the fact that some important physiological responses to exercise do fluctuate within that time period.

Evaluation of behavioral states among morning and evening active healthy individuals

“…The relations between physical exercise and chronotype are still controversial, since workout performance is a result of many variables, including day shift (12)(13)(14)(15). A previous study (16) did not find differences in responses to exercise between morning and evening types; however, another investigation demonstrated that evening individuals had a higher energetic arousal in the evening than in the morning (17).…”

Time of day has no effect on maximal aerobic and peak power

“…There are also large discrepancies between studies that focused on circadian maximal oxygen uptake patterns. Some studies concluded that this variable was stable throughout the day, [10][11][12][13] while others 14 demonstrated a 4.2% diurnal variation in this variable. Both day-to-day biological variability 10,11 and technical errors in oxygen uptake measurements could mask possible circadian fluctuations in maximal oxygen uptake, submit your manuscript | www.dovepress.com…”

Effect of alpha-lipoic acid and time-of-day on interleukin-6 response to exhaustive exercise in humans

“…The authors also hypothesized that an elevated muscle temperature increased the ATP turnover rate associated with exercise, and/or changes in the aerobic/anaerobic contribution to ATP resynthesis (Febbraio et al, 1996). Moreover, rectal and muscle temperature have shown lowest values in morning hours, and to progressively increase towards afternoon and evening hours (Deschenes et al, 1998;Reilly and Brooks, 1990). Hence in these studies, the lower early morning muscle peak torque values could be partly explained by muscle temperature at this TOD.…”