Menstrual cycle changes and predictors of movement-related breast pain during treadmill running

Movement-related breast pain is a common barrier to women's participation in sport and exercise, yet little is known about how menstrual cycle fluctuations influence this condition.

This repeated-measures study investigated associations between breast pain, breast volume, breast kinematics, and sex hormone concentrations across one menstrual cycle.

Fifteen women (bra sizes 34C-36B) attended six laboratory appointments aligned with key menstrual phases and confirmed by hormonal testing. Movement-related breast pain and breast kinematics were recorded during bare-breasted treadmill running (10 km/h). Breast volume was measured using 3D scanning, and salivary oestradiol and progesterone were sampled at and between each appointment.Linear mixed-effects and cumulative link mixed models were applied to understand menstrual cycle-related changes and predictors of movement-related breast pain.

Movement-related breast pain was more frequently rated higher at three days before menses and on the second day of the subsequent cycle (5/10) compared to the second day of the first cycle (4.5/10). Breast volume was 7.3% greater at three days before menses than ovulation but did not significantly predict movement-related breast pain. Hormone concentrations were not significant predictors. Accordingly, regardless of the menstrual cycle phase, superoinferior and mediolateral breast accelerations were the strongest kinematic predictors of pain severity, with mediolateral kinematics significantly different across the menstrual cycle compared to three days before menses.

These findings suggest that mechanical rather than hormonal factors primarily influence movement-related breast pain. Small cycle-related changes in pain, volume, and kinematics were observed, but they were not practically meaningful and were not consistently associated.