Exercise in patients on chronic hemodialysis: current evidence, knowledge gaps and future perspectives

Purpose of review Physical inactivity is common in hemodialysis patients, and is associated with disability and poor outcomes. We summarize the effects of aerobic, resistance or mixed exercise training on aerobic capacity, muscle mass and strength, dialysis efficiency, quality of life and cardiovascular adaptation according to clinical studies on this population, also focusing on knowledge gaps as topics for future research. Finally, we put evidence into clinical context deriving practical indications for exercise implementation in these patients. Recent findings In hemodialysis patients, aerobic or mixed exercise training increases predominantly aerobic capacity, whereas resistance training seems more effective in increasing muscle strength. Data concerning dialysis efficiency are equivocal, although phosphate and potassium clearances seem to be improved. There is also inconclusive evidence concerning changes in cardiovascular risk factors. All types of exercise improve patients' quality of life. However, there is a need for protocol standardization and selection of easily measurable endpoints. In clinical practice, it is advised that exercise implementation be performed gradually, and goals be tailored to individual pretraining fitness levels to maximize patient adherence and clinical benefits. The overall evidence suggests that exercise training is beneficial and well tolerated in hemodialysis patients, although heterogeneity across studies hinders generalization of results. In any case, a gradual and individualized approach should be used to implement exercise in these patients.