Effects of an intra-dyalitic aerobic training program on oxygen uptake kinetics in patients with end-stage renal disease

Background: End-stage renal disease (ESRD) is associated with several hemodynamic and peripheral muscle abnormalities that could slow the rate of change in oxygen uptake (VO2) at the onset and at the end of dynamic exercise. We therefore investigated the effects of supervised aerobic training during hemodialysis on the VO2 on- and off-kinetics in ESRD patients. Methods: Twelve patients and 12 age- and gender-matched, non-trained patients underwent an incremental and constant work rate cardiopulmonary exercise tests on a cycle ergometer at baseline and after 12 wks of exercise training or a similar control period. Exercise training was performed during the first two hours of hemodialysis sessions by using a stationary cycle, three times a week. Results: Training significantly accelerated VO2 kinetics (τ decreased from 62.5±19.6 s to 45±12.6 s) and reduced O2 deficit at the onset of a sub-anaerobic threshold (AT) exercise test (p<0.05). At a supra-AT test, τ decreased from 52.9±17.4 s to 40.4±13.8 s (p<0.05) and time to exercise intolerance increased significantly (311.9±223.4 s vs. 589.2±358.1 s). Similar positive effects of training were observed at the off-exercise transient in both sub- and supra-AT tests (τ=75.1±16.4 s vs. 66.2±20.8 s and 73.4±20.4 s vs. 59.9±12.8 s, p<0.05, respectively). In contrast, VO2 on- and off-kinetics were significantly slower at the final evaluation in the non-trained patients (p<0.05). Conclusions: A 12-week supervised aerobic training program was highly effective in accelerating on- and off-exercise VO2 kinetics at both moderate and severe exercise intensity domains in ESRD patients undergoing hemodialysis.