 Regular physical activity PA after a diagnosis of breast cancer can have various beneficial effects with respect to overall survival 3 as well as health-related quality of life 4. The Dutch PA guideline Nederlandse Norm Gezond Bewegen NNGB recommends to engage in moderate-intensity exercise e.g. brisk walking for at least 30 minutes a day, on at least 5 days a week 5. For people who are overweight Body Mass Index 25 kgm2 it is recommended to exercise at least 60 minutes at a moderate-intensity level, equal or more than 3 Metabolic Equivalent Task Hours 3 METh, on at least 5 days a week 6,7. However, only 61 of the general population, meets these guidelines 8 and among cancer patients this percentage is even less 9. 