VO2max, sleep behaviour, and self-perceived fatigue influences in a sample of german active young subjects

Purpose: Sleep is acknowledged as an important factor in influencing physical performance. Indeed, sleep deficiency linked to fatigue could negatively affect endurance performance. The present study aims to shed light on the relationship between VO2max, sleep, and self-perceived fatigue in a sample of active German young subjects. Methods: 96 German university students (males 54.2%; 21.5 ± 2.9 yrs) completed an incremental exercise test on a bicycle ergometer and filled in the Pittsburgh Sleep Quality Index (PSQI) and two visual analogue scales (VAS) to assess sleep behaviour, self-perceived fatigue and motivation, respectively. The male and female samples were analysed separately. VO2max, self-perceived fatigue and motivation were compared between good and bad sleepers (PSQI score\/[5, respectively) and longer and shorter sleepers (sleep duration[/\7.5 h, respectively), while the predictors of VO2max were defined with regression analysis. Results: In the male sample, even without statistical significance, VO2max was higher in good than bad sleepers (53.9 ± 8.4 vs 49.0 ± 14.1 ml.kg-1.min-1; p = 0.1), and in longer than shorter sleepers (54.2 ± 10.9 vs 50.0 ± 8.4 ml.kg-1.min-1; p = 0.4); selfperceived motivation was better in good and longer sleepers (7.1 ± 1.6 vs 6.3 ± 2.1a.u., p = 0.2; 7.2 ± 1.5 vs 6.4 ± 2.1 a.u., p = 0.1). Self-perceived fatigue was significantly lower in good sleepers (2.3 ± 2.1 a.u.) compared to bad sleepers (3.6 ± 1.7 a.u.; p = 0.04). The regression analysis indicated sleep (b = -0.3, p = 0.02) as a significant predictor of VO2max. In the female sample, good vs bad sleepers and longer vs shorter sleepers showed no significant differences. In contrast with the male sample, the regression analysis indicated self-perceived fatigue (b = -0.4, p = 0.03), and not sleep, as a significant predictor of VO2max. Conclusions: Males seemed to be more negatively influenced by sleep behaviour and quality, whereas females by self-perceived fatigue. Indeed, sleep accounted for 20% of the VO2max variance in males, indicating a relevant factor for cardiovascular performance. In females, physical performance seemed more affected by fatigue. Probably, considering the phase of the menstrual cycle might have highlighted a different role of sleep on VO2max in females. References: Watson, AM, Sleep and Athletic Performance. Current Sports Medicine Reports, 2017. 16(2):413–418. Crowley SK., et al., Cardiorespiratory fitness, sleep, and physiological responses to stress in women. European Journal Sport Science 20(10):1368–1377.