Cardiovascular adaptations associated with exercise in patients on hemodialysis

Patients on hemodialysis are physically inactive. Less than 50% of hemodialysis patients undertake exercise once a week and such patients have increased mortality compared to patients who undertake regular exercise. The reasons for physical inactivity and reduced functional capacity are complex and inter-related, with skeletal muscle catabolism, chronic inflammation, anemia, malnutrition, uremia, the burden of co-morbid diseases, and "enforced" sedentary time during hemodialysis all contributing. Many of these factors drive cardiovascular disease (CVD) processes in this cohort of patients and in the general population, exercise interventions have been shown to modify many of these risk factors. Whilst there is increasing evidence about the beneficial effects of exercise interventions on quality of life, functional capacity, aerobic fitness, and muscular strength, there are few compelling data on the effects of such programs on cardiovascular outcome measures. The reasons for this are manifold and include: limitations in study size; inconsistencies in study design; the heterogeneous nature of exercise interventions; assessment of nonstandardized outcome measures and; a lack of understanding of what changes in certain traditional measures of CVD (such as blood pressure or lipid profile) mean for patients on hemodialysis. This review summarizes the current evidence base for the effects of exercise on traditional and nontraditional cardiovascular risk factors and the effects of exercise interventions on cardiovascular structure and function, including a review of study limitations and future research priorities.