Women in Steady Exercise Research (WISER): study design and methods

Abstract

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.

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.

Figure 1

Flowchart of recruitment numbers The WISER study screened 1684 women over three and a half years, among which 1260 were eligible and 683 were consented. A total of 391 were randomized to the exercise or control group and 72 of these women dropped out of the study. Among the women who completed the study, 166 were in the exercise group and 153 in the control group.

Figure 2

Flow Diagram of Participation. Orientation: Participants are asked to attend a 2-hour orientation session to learn details about the study and to sign the consent forms. Upon signing of the consent form, they are given an ovulation kit to test at home. Ovulation: Participants are provided with ovulation kits to use during five months of participation in the study. CV: clinic visit. CV1 and CV6: These clinic visits occur during the luteal phase eight days after participants receive a positive ovulation test during menstrual cycles 1 and 5, respectively. CV2 and CV7: These clinic visits occur during the follicular phase on day eight of menstrual cycles 2 and 6, respectively. CV3 and CV8: Participants fill out food records and collect their urine on days 7, 8, and 9 of cycles 2 and 6. Clinic visits 3 and 8 refer to urine processing at the clinic. Mentorship contact: The 9 filled circles shown in the diagram represent a point of contact between participants and staff with the purpose of monitoring participant progression in the study. Group assignment: Randomization into groups occurs after all baseline measurements are taken during a baseline fitness assessment with trainers around day 11 of cycle 2. The follow-up fitness assessment occurs around day 11 of cycle 6. Exercise group: Participants randomized into the exercise group are asked to exercise 5 times per week for about 16 weeks. The intensity of the activity increases every 4 weeks by 5% of the age predicted maximum heart rate. Final report: Upon completing of the study, participants receive a packet in the mail with study results.