Impact of 8 Weeks of Moderate- Versus High-Intensity Interval Training on Sleep Quality

Sleep is a fundamental aspect of physiological and psychological functioning, and the beneficial effect of exercise on sleep quality and quantity, depending on training modality, remains underexplored. This study compared the effects of high-intensity interval training (HIIT) versus a moderate-intensity continuous training (MICT) regime on sleep quality. Twenty-five participants (sixteen men, nine women) were randomly assigned to 8-week HIIT or MICT programs. Anthropometric data, blood pressure, and maximal exercise tests (VO_2max, lactate, heart rate) were conducted one week before and after training. Sleep quality was evaluated daily through self-reported perception and duration and via the Pittsburgh Sleep Quality Index (PSQI) at baseline, one week, and two weeks post-intervention. Data were analyzed in SPSS version 29 using repeated-measures ANOVA. PSQI scores improved significantly over time (<i>p</i> = 0.013), regardless of modality, with no significant group or interaction effects. Cardiorespiratory fitness improved for all participants, with significant gains in VO_2max (<i>p</i> = 0.009), maximal aerobic speed (<i>p</i> < 0.001), and reduced maximal heart rate (HIIT: <i>p</i> = 0.003; MICT: <i>p</i> = 0.021). Sleep perception showed no significant change during training (<i>p</i> = 0.063), with a slight improvement trend. In conclusion, exercise training improves sleep quality regardless of modality. Running three sessions per week for eight weeks enhances both aerobic and cardiorespiratory fitness, along with sleep quality. Physical activity is therefore an effective non-pharmacological strategy to improve sleep.