Intra-dialytic training accelerates oxygen uptake kinetics in hemodialysis patients

Abstract

Background: End-stage renal disease is associated with several hemodynamic and peripheral muscle abnormalities that could slow the rate of change in oxygen uptake (V02) at the onset and at the end of exercise. This study was performed to determine whether an intra-dialytic aerobic training program would speed V02 kinetics at the transition to and from moderate and high-intensity exercise. Design: This study was a randomized controlled trial. Methods: Twenty-four patients with end-stage renal disease (14 females; 47.0 ± 11.9 years) were randomly assigned to either 12-week cycle ergometer-based training at moderate exertion or a similar control period. At initial and final evaluations, patients underwent 6min moderate and high-intensity tests to exercise intolerance (Tlim). Results: Training improved Tlim by ∼90% (median (inter-quartile range) = 232 (59) s to 445 (451) s, ρ <0.05); in contrast, Tlim decreased by -30% in controls (291 (134) s to 202 (131) s). V02 kinetics at the onset of moderate-intensity exercise were significantly accelerated with training leading to lower oxygen (02) deficit (mean ± standard deviation (SD) = 3.2 ± 1.3 I vs 2.3 ± 1.21). Similar positive effects were found at the high-intensity test either at the onset of, or recovery from, exercise (p < 0.05). "Excess" V02 at the high-intensity test was also lessened with training. Changes in Tlim correlated with faster V02 kinetics and lower "excess" V02 (Spearman's ρ = -0.56 and -0.75, respectively; p<0.0l). Conclusions: A symptom-targeted intra-dialytic training program improved sub-maximal aerobic metabolism and endurance exercise capacity. V02 kinetics are valuable in providing relatively effort-independent information on the efficacy of exercise interventions in this patient population.