NR4A1 and breast cancer: Given the relatively sparse data on physical activity in premenopausal women by hormone receptor subtype, we provide a comprehensive evaluation of recreational physical activity, overall and of moderate-vigorous intensity, and breast cancer risk by menopausal status and hormone receptor status in 187,278 women, including 12,785 breast cancer diagnoses, from two well-characterized cohorts with up to three decades of follow-up.