In adult women, higher levels of recreational physical activity (RPA) are consistently linked to a lower risk of breast cancer, with studies showing roughly a 20 percent reduction in risk among the most active women compared with the least active.

Girls who reported engaging in at least two hours of recreational physical activity in the prior week, compared with none, had lower percent water content in breast tissue—an indicator of lower breast density—and lower concentrations of urinary biomarkers linked to stress.