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 (BC-PAL) pilot trial randomized 45 breast cancer survivors to a home-based, 12-week lower (300 minutes/week at 40-59% of heart rate reserve) or higher (150 minutes/week at 60-80% of heart rate reserve) intensity PA, or no PA intervention/control. Both intervention groups received Polar A360® activity trackers. Study outcomes assessed at baseline, 12- and 24-weeks included PA and sedentary time (ActiGraph GT3X+), health-related fitness (e.g. body composition, cardiopulmonary fitness/VO2max) 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, -0.2)) were significantly greater in the lower intensity PA group versus control at 12-weeks. Increases in VO2max at 12-weeks 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 VO2max remained at 24-weeks, but differences between the intervention and control groups were no longer statistically significant.

Conclusion 
Increases in PA time and cardiopulmonary fitness/VO2max 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.