Primary Outcome Measures:
- Serum concentrations of endogenous estrogens: estradiol (total, free), estrone, estrone sulfate
- Serum concentrations of endogenous androgens: testosterone, androstenedione
- Serum concentrations of sex hormone binding globulin
- Serum concentrations of fasting insulin
- Insulin sensitivity
Secondary Outcome Measures:
- Amount of total body fat and intra-abdominal fat
- Weight
- Body Mass Index (BMI)
- Body fat distribution
- Waist to hip ratio
- Physical Fitness
- Blood pressure
- Lifestyle parameters (covariates)
- Exercise behaviour (habitual physical activity, past week activity, physical activity in the past)
- Diet (daily caloric intake; percent daily calories from fat, carbohydrates and proteins)
- Alcohol consumption
- Medication use
- Reproductive factors
- Medical history
Physical activity has been associated with a decreased risk for breast cancer. The biological mechanism(s) underlying the association between physical activity and breast cancer is not clear. Most prominent hypothesis is that physical activity may protect against breast cancer through reduced lifetime exposure to endogenous hormones. Another hypothesis is that physical activity prevents overweight and abdominal adiposity.
In this intervention study, 189 sedentary postmenopausal women who are aged 50-69 years are randomly allocated to an intervention or a control group. The intervention consists of an 1-year moderate-to-vigorous intensity aerobic and strength training exercise programme. Participants allocated to the control group are requested to retain their habitual exercise pattern. Primary study parameters measured at baseline, at four months and at 12 months are: serum concentrations of endogenous estrogens, endogenous androgens, sex hormone binding globulin and insulin. Other study parameters include: amount of total and abdominal fat, weight, BMI, body fat distribution, physical fitness, blood pressure and lifestyle factors.
This study will contribute to the body of evidence relating physical activity and breast cancer risk and will provide insight into possible mechanisms through which physical activity might be associated with reduced risk of breast cancer in postmenopausal women.
Purpose
