The Physical Activity for Total Health (PATH) Study: rationale and design

Purpose: Physical activity has been associated with a decreased risk for br east cancer. Mechanisms For this association may involve hormonal pathways. The Physical Activity for Total Health study is testing the effect of a 1- yr moderate intensity physical activity intervention on the endogenous sex hormone profile of postmenopausal women in a randomized controlled study. M ethods: Women (N = 168) who are aged 55-75 yr, not using sex hormones, sede ntary, nonsmokers, have no endocrine-related disease or cancer, and with bo dy mass index of 25.0 or greater, are eligible. Women are recruited through mass mailings and media advertising and are randomized to either a 1-yr mo derate intensity aerobic and strength training exercise program (monitored group exercise sessions plus home exercise) or a control program (stretchin g classes). Results: Serum hormones to be assayed at baseline and at the en d of the study include: total estrone, total estradiol, free estradiol, per cent bioavailable estradiol, estrone sulfate sex hormone binding globulin, albumin, testosterone, free testosterone, androstenedione, dehydroepiandros terone, dehydroepiandrosterone sulfate, insulin, glucose, and triglycerides . Other outcome measures include: the ratio of urinary 2-hydroxyestrone:16 alpha-hydroxyestrone lan estrogen metabolite ratio that may be associated w ith risk for breast cancer), weight, body mass index, total fat mass, and b ody fat distribution (waist:hip circumference ratio, DEXA scan, and abdomin al fat measured by computed tomography). Conclusion: This study is the firs t to examine the effect of change in physical activity level on sex hormone s in postmenopausal women. It will provide insight into possible mechanisms through which physical activity might be associated with reduced risk of b reast cancer.