Discussion
WISER consented 683 women among which 391 enrolled and 319 successfully completed the study. The overall dropout rate was 18.4% (n=72) with a higher number of participants dropping from the exercise group (n=46). No differences were found between dropouts and completers with respect to age, body weight, BMI, and demographic characteristics with the exception of degree of education. Findings from this trial will be useful in understanding the physiologic mechanisms by which exercise possibly contributes to decreased breast cancer risk.
Purpose
Observational studies have shown that physical activity is inversely associated with breast cancer etiology. WISER is a randomized controlled trial examining the effects of exercise training on oxidative stress, and hormonal and metabolic factors associated with breast cancer risk. Method: Subjects were recruited via emails, flyers, and mass media advertising. Inclusion criteria included: sedentary, age 18-30 years, non-smokers, BMI 18-40 kg/m2, not using any hormonal contraceptives. After completion of all baseline measures subjects were randomized into a control group or an exercise intervention for 4 menstrual cycles. The exercise group was asked to complete five 45 min exercise sessions per week. Exercise intensity was set at 65-70% of maximum age- predicted heart rate (max HR) and increased every four weeks. All women provided blood samples four times during the study for measurement of blood F2-isoprostanes, hormones and IGF-axis proteins. In addition, 24-hour urine samples were collected at baseline and follow-up for measurement of estrogen metabolites, as well as 24-hour food records to monitor participants' diets.