Impaired exercise capacity and exercise training in maintenance hemodialysis patients

Patients with advanced chronic renal failure, including those undergoing maintenance hemodialysis (MHD), commonly suffer from sarcopenia and reduced physical exercise capacity. The causes of these disorders include anemia, cardiovascular and pulmonary diseases, other comorbid conditions, altered skeletal muscle metabolism, myopathic changes that are associated with chronic renal failure per se, malnutrition, and physical deconditioning. Exercise training has been shown to increase exercise capacity and, in some studies, to increase muscle mass. In our experience, cardiopulmonary fitness training of sedentary MHD patients for an average of 8.6 weeks using a stationary ergometer increased endurance capacity, physical performance, and physical strength in the lower extremities, and in particular, quadriceps strength, power, and fatigability. This surprising finding of increased lower-extremity strength with cardiovascular fitness training may reflect the possibility that the MHD patients were so deconditioned that the small amount of resistance encountered with pedaling a stationary ergometer increased their physical strength. By the end of the endurance exercise training program, the MHD patients also showed changes in the right vastus lateralis muscle for the mRNA levels of a number of proteins involved with skeletal muscle protein synthesis and hypertrophy. The mRNA levels changed in a direction that would be expected to promote protein accrual and hypertrophy of skeletal muscle. These findings indicate that in sedentary MHD patients endurance exercise training for a few weeks can result in improved exercise capacity and a pattern of transcriptional factors that may promote an increase in skeletal muscle mass.