Purpose: To prescribe different physical activity (PA) intensities using activity trackers to increase PA, reduce sedentary time, and improve health outcomes among breast cancer survivors. The maintenance effect of the interventions on study outcomes was also assessed.
Methods: The Breast Cancer and Physical Activity Level pilot trial randomized 45 breast cancer survivors to a home-based, 12-wk lower (300 min·wk at 40%-59% of HR reserve) or higher-intensity PA (150 min·wk at 60%-80% of HR reserve), or no PA intervention/control. Both intervention groups received Polar A360® activity trackers. Study outcomes assessed at baseline, 12 and 24 wk included PA and sedentary time (ActiGraph GT3X+), health-related fitness (e.g., body composition, cardiopulmonary fitness/V˙O2max), and patient-reported outcomes (e.g., quality of life). Intention-to-treat analyses were conducted using linear mixed models and adjusted for baseline outcomes.
Results: Increases in moderate-vigorous intensity PA (least squares adjusted group difference [LSAGD], 0.6; 95% confidence interval [CI], 0.1-1.0) and decreases in sedentary time (LSAGD, -1.2; 95% CI, -2.2 to -0.2) were significantly greater in the lower-intensity PA group versus control at 12 wk. Increases in V˙O2max at 12 wk in both interventions groups were significantly greater than changes in the control group (lower-intensity PA group LSAGD, 4.2; 95% CI, 0.5-8.0 mL·kg·min; higher-intensity PA group LSAGD, 5.4; 95% CI, 1.7-9.1 mL·kg·min). Changes in PA and V˙O2max remained at 24 wk, but differences between the intervention and control groups were no longer statistically significant.
Conclusions: Increases in PA time and cardiopulmonary fitness/V˙O2max can be achieved with both lower- and higher-intensity PA interventions in breast cancer survivors. Reductions in sedentary time were also noted in the lower-intensity PA group.
Trial registration: ClinicalTrials.gov NCT03564899.