Mixed

Breast cancer patients undergoing chemotherapy exhibit significantly impaired muscle strength (5-25% lower in lower extremities, 12-16% in upper extremities) and increased muscular fatigue compared to healthy controls, regardless of whether treatment is ongoing or completed.

Breast cancer patients, especially those undergoing chemotherapy, experience significant and measurable muscle strength loss (up to 25% in legs, 16% in shoulders) and faster fatigue compared to healthy peers. This loss is driven by both the direct toxic effects of chemotherapy on muscle fibers and reduced physical activity. To counteract this, patients should engage in resistance training as early as possible, as it is safe during treatment and helps preserve muscle function, which is critical for survival and quality of life.