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Tsukuba, Japan – A new study from the University of Tsukuba has shed light on how chronic exercise training uniquely affects sleep in female athletes. The research, published in the journal iScience, highlights how variations in daily training and reproductive function influence sleep stages and energy expenditure during sleep, with a notable connection to the deep sleep stage, known as slow-wave sleep (SWS).
The study found that menstruation status and menstrual cycle phases contribute to distinct energy expenditure patterns and fluctuations in sleep stages. In particular, female athletes undergoing chronic exercise training exhibited differences in menstrual cycle-related sleep phenomena compared to non-athletes.
Among female runners, the researchers discovered that both the sleeping metabolic rate and SWS were higher in the luteal phase than in the follicular phase. This suggests that energy expenditure during sleep and sleep architecture vary depending on the degree of reproductive function differences and the extent of chronic exercise training.
By focusing on energy metabolism, the research team aimed to understand the complex interplay between chronic exercise training, menstrual cycles, and sex on sleep. Their findings may contribute to future strategies for preventing and addressing amenorrhea—a common condition among female athletes that involves the absence of menstruation.
Lead researcher Akiko Uchizawa and colleagues emphasized the need for further investigation into the mechanisms driving these differences, which could lead to improved health and performance outcomes for female athletes.
For more information, the full study is available: Akiko Uchizawa et al., Energy expenditure and slow-wave sleep in runners: Focusing on reproductive function, chronic training, and sex, iScience (2025). DOI: 10.1016/j.isci.2024.111717
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Readers should consult healthcare professionals for concerns related to exercise, sleep, and reproductive health.
