MRI reveals menstrually-related muscle edema that negatively affects athletic agility in young women

CONTEXT About 10% of Japanese female athletes are afflicted by menstrually-related edema, mainly in the lower limbs, and, with few studies on this problem, the effect on performance remains unclear. OBJECTIVE To quantitatively evaluate fluid retention in the calf in female students over their menstrual cycle using magnetic resonance imaging (MRI) and to determine the relationship of MRI changes and athletic performance. DESIGN The menstrual cycle was divided into 5 phases: menstrual, follicular, ovulatory, early luteal, and late luteal with sampling done in either morning (AM) or afternoon (PM) sessions. At each phase, MRI of the calf (7:00-8:00, 14:00-16:00), body composition and hormones (7:00-8:00), and athletic performance (14:00-16:00) were evaluated. PARTICIPANTS 13 adult healthy Japanese female students with eumenorrhea. RESULTS Estradiol levels decreased significantly in the menstrual phase and the follicular phase compared to the early luteal phase (P = 0.001, P = 0.024 respectively). Menstrual phase estradiol levels were significantly lower compared to the ovulatory phase (P = 0.015), and the late luteal phase (P = 0.003). Progesterone levels decreased significantly in the menstrual phase and the follicular phase compared to the ovulatory phase (P = 0.012, P = 0.009 respectively), the early luteal phase (both P = 0.007), and the late luteal phase (P = 0.028, P = 0.029 respectively), and it along with a significant decrease in the ovulatory phase compared to the early luteal phase (P = 0.010). AM T2 signals were significantly lower in the menstrual phase compared to the ovulatory phase (P = 0.043) but not other phases. PM T2 signals increased significantly in the menstrual phase compared to the follicular phase (P = 0.003), ovulatory phase (P = 0.009), and the late luteal phase (P = 0.032), and the difference between the AM and PM values increased significantly in the menstrual phase compared to the other 4 phases (P<0.01). A negative correlation between fluid retention and agility was observed. CONCLUSION In female students fluid retention during the menstrual phase could be a factor that influences athletic agility.