Maximizing sleep quality and well-being in female athletes: the role of the menstrual cycle and whole-body cryostimulation

The aim of this study was to evaluate the effects of two menstrual cycle (MC) phases - early follicular phase (EFP) and mid-luteal phase (MLP) - on sleep, well-being, and the effects of whole-body cryostimulation (WBC) in young female athletes. Core temperature (CT) and heart rate variability (HRV) were also assessed to explore the physiological mechanisms underlying these effects, both under control conditions and after WBC. Using a randomized, controlled, cross-over design, seventeen naturally menstruating women (24 ± 3.3 years) were evaluated over two consecutive cycles (cycle length 21-35 days, positive urinary ovulation test). The experimental cycle included two three-day WBC sessions (3 min at -110 °C) compared to a control cycle without WBC. Subjective and objective sleep quality (SQ), CT, and HRV were measured during both cycles. The MC phase did not significantly affect subjective SQ, but was associated with decreased objective SQ and increased fatigue during the MLP compared to the EFP. The MLP was also characterized by elevated CT and increased sympathetic activity, suggesting impaired nocturnal thermoregulation during this phase. WBC improved objective SQ and perceived fatigue during the MLP and appeared to help restore thermoregulatory function, although sympathetic activity remained elevated. These findings suggest that WBC may be an effective intervention to counteract MC-related impairments in sleep and fatigue in female athletes.