The effect of exercise on bone mineral density in adult cancer survivors: a systematic review and meta-analysis

The primary mechanical function of bones is to provide rigid levers for muscles to pull against, and to remain as light as possible to allow efficient locomotion. To accomplish this bones must adapt their shape and architecture to make efficient use of material. Bone adaptation during skeletal growth and development continuously adjusts skeletal mass and architecture to changing mechanical environments. There are three fundamental rules that govern bone adaptation: (1) It is driven by dynamic, rather than static, loading. (2) Only a short duration of mechanical loading is necessary to initiate an adaptive response. (3) Bone cells accommodate to a customary mechanical loading environment, making them less responsive to routine loading signals. From these rules, several mathematical equations can be derived that provide simple parametric models for bone adaptation.

Androgen-deprivation therapy is a commonly used treatment for men with prostate cancer; however, the adverse effects can be detrimental to patient health and quality of life. Exercise has been proposed as a strategy for ameliorating a range of these treatment-related adverse effects. We conducted a systematic review of the literature regarding the effects of exercise on treatment-related adverse effects in men receiving androgen-deprivation therapy for prostate cancer. An online electronic search of the Cochrane Library, EMBASE, MEDLINE, CINAHL, SPORTDiscus, and Health Source databases was performed to identify relevant peer-reviewed articles published between January 1980 and June 2013. Eligible study designs included randomized controlled trials as well as uncontrolled trials with pre- and postintervention data. Information was extracted regarding participant and exercise intervention characteristics as well as the effects of exercise on bone health, body composition, physical performance, cardiometabolic risk, fatigue, and quality of life. Ten studies were included, with exercise interventions involving aerobic and/or resistance training. Exercise training demonstrated benefits in muscular strength, cardiorespiratory fitness, functional task performance, lean body mass, and fatigue, with inconsistent effects observed for adiposity. The impact of exercise on bone health, cardiometabolic risk markers, and quality of life are currently unclear. Among patients with prostate cancer treated with androgen-deprivation therapy, appropriately prescribed exercise is safe and may ameliorate a range of treatment-induced adverse effects. Ongoing research of high methodologic quality is required to consolidate and expand on current knowledge and to allow the development of specific evidence-based exercise prescription recommendations.