Effect of sleep behavior on VO2MAX capacity in a sample of active young subjects

INTRODUCTION: In addition to being an essential physiological process in humans, sleep is acknowledged as an important factor in influencing physical performance. Sleep deficiency, also linked to higher self-perceived fatigue, could negatively affect physical performance, especially endurance performance [1]. Notwithstanding this background, VO2max has been poorly investigated in relation to sleep quality [2]. The present study aims to shed light on this relationship in a sample of active young subjects. METHODS: Ninety-six university students (males 54.2%; 21.5 ± 2.9 yrs) were assessed for sleep quality, self-perceived fatigue and motivation by the Pittsburgh Sleep Quality Index (PSQI) and two visual analogue scales (VAS), respectively. Subsequently, they completed an incremental exercise test on a bicycle ergometer. Analyses were performed separately for males and females. Based on PSQI categorization, VO2max, self-perceived fatigue and motivation were compared between good and bad (PSQI score 5 respectively) sleepers and longer and shorter sleepers (sleep duration >/<7.5 hours respectively), while regression analysis defined the predictors of VO2max. RESULTS: In the male sample, good sleepers and longer sleepers reported higher VO2max (53.9 ± 8.4 vs 49.0 ± 14.1 ml.kg-1.min-1; 54.2 ± 10.9 vs 50.0 ± 8.4 ml.kg-1.min-1) and self-perceived motivation (7.1 ± 1.6 vs 6.3 ± 2.1 a.u.; 7.2 ± 1.5 vs 6.4 ± 2.1 a.u.), but only 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 showed sleep (β = - 0.3, p = 0.02) as predictors of VO2max. There were no significant differences between good and bad sleepers and different sleep durations in the female sample. Self-perceived fatigue (β = -0.4, p = 0.03), and not sleep, was a significant predictor of VO2max in females. CONCLUSION: Sleep seems to affect differently the VO2max the performance between males and females. Even without statistically significance, good and long sleepers tend to perform better and suffer significantly less from fatigue. Furthermore, sleep accounts for 20% of the variance in males, indicating a relevant factor for cardiovascular performance. In females, physical performance seems more affected by fatigue rather than sleep. Probably, taking into account the phase of the menstrual cycle, a different role of sleep on VO2max could have been highlighted [3].