Effects of Moderate and High-intensity Exercise During Chemotherapy on Muscle Cells in Women With Breast Cancer

(Neo-)adjuvant chemotherapy for breast cancer has deleterious effects on muscle tissue resulting in reduced skeletal muscle mass, muscle function, and cardiorespiratory fitness. Various exercise regimens during cancer treatment have been shown to counteract some of these side effects. However, no study has compared the effect of high intensity training vs. low-to moderate intensity training on muscle tissue cellular outcomes and function in breast cancer patients during chemotherapy. The present study aims to compare the effects of high vs. low-to moderate intensity training on its ability to counteract deleterious effects of chemotherapy on skeletal muscle in women diagnosed with breast cancer. Eighty newly diagnosed women with breast cancer planned to start (neo-)adjuvant chemotherapy will be randomized to either a group performing a combination of strength and endurance training with high intensity or a group performing training with low to moderate intensity. Muscle biopsies from m. vastus lateralis for assessment of muscular cellular outcomes will be collected and muscle function and cardiorespiratory fitness will be measured before the first cycle of chemotherapy (or, when not possible, one week after) (T0), halfway through chemotherapy (T1), and after completion of chemotherapy (T2). It is estimated that approximately 50% will be willing to take muscle biopsies. The study will give important information about the effects of different training intensities for breast cancer patients during treatment and will contribute with knowledge about how to refine exercise programs that are effective and compatible with multidisciplinary management of breast cancer.