Exercise and bone health in cancer: enemy or ally?

Simple Summary Patients with cancer may face bone metastases and osteoporosis due to cancer or treatments, leading to a high risk of developing skeletal-related events. Skeletal-related events may negatively affect patients' quality and length of life. Although physical exercise has been recognized as a potential adjunctive strategy in the cancer setting, it is often not recommended to patients with bone health impairments due to safety concerns. In the present review, we explore the effects of exercise on safety profile, bone health, and the impact on functional outcomes in patients with cancer affected by bone metastasis, osteoporosis/osteopenia, or at high risk of losing bone. Moreover, the underlying mechanisms of the beneficial effect of exercise on bone are explored, and considerations about exercise prescription are discussed. Bone health is often threatened in cancer patients. Bone metastasis and osteoporosis frequently occur in patients with cancer and may lead to different skeletal-related events, which may negatively affect patients' quality of life and are associated with high mortality risk. Physical exercise has been recognized as a potential adjunctive strategy in the cancer setting to improve physical function as well as treatment-related side effects. Nevertheless, exercise is often not recommended to patients with bone health impairments due to safety concerns. In the current review, we aimed, through a comprehensive review of the evidence, to explore the impact of exercise in terms of safety profile, bone outcomes, and the effects on other outcomes in patients with cancer affected by bone metastasis or at high risk of losing bone. Additionally, we explored the potential mechanisms by which exercise may act on bone, particularly the impact of mechanical load on bone remodeling. Finally, considerations about exercise prescription and programming in these populations are also discussed.