EXERCISE

This randomized dose comparison trial examined if higher exercise volume decreased inflammatory biomarkers, associated with postmenopausal breast cancer risk, more than moderate exercise volume. The Breast Cancer and Exercise Trial in Alberta (BETA) was a two-center, two-armed randomized trial in 400 inactive, healthy, postmenopausal women, aged 50-74 years, with a body mass index of 22-40 kg/m2. Participants were randomized to high (300 minutes/week) or moderate (150 minutes/week) volumes of aerobic exercise while maintaining usual diet. Fasting blood concentrations of C-reactive protein (CRP), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-α), were measured at baseline, six, and 12-months. Intention-to-treat analysis was performed using linear mixed models adjusted for baseline biomarker concentrations. Intention-to-treat analyses of 386 (97%) participants showed no statistically significant group differences for changes in biomarkerlevels at 6 and 12 months. Additionally, we did not observe any modification of this effect by baseline characteristics of participants. In post hoc analyses based on self-selected exercise level (measured in minutes/week) , CRP decreased by 22.45% for participants who exercised>246 minutes/week (highest quintile) and increased by 0.07% for those who exercised<110 minutes/week (lowest quintile, P-trend=0.04), adjusted for baseline covariates. When this analysis was restricted to include exercise time in the target heart rate zone only, statistically significant trends were observed for both CRP (P<0.01) and IL-6 (P=0.04). Prescribing 300 minutes/week of moderate-to-vigorous aerobic exercise did not improve inflammatory markers compared to 150 minutes/week in postmenopausal women. Decreases in CRP were observed with higher self-selected exercise volume.