Isokinetic Muscle Strength Predicts Maximum Exercise Tolerance in Renal Patients on Chronic Hemodialysis

Patients with end-stage renal disease receiving chronic hemodialysis have impaired exercise tolerance. To distinguish between a central card iorespiratory and a peripheral skeletal muscular origin for this fatigue, we measured exercise performance and peak oxygen consumption during a maximum exercise test in 10 patients receiving chronic hemodialysis. Skeletal muscle function was measured with an isokinetic cycle ergometer and a Cybex II isokinetic dynamometer. Peak rates of oxygen consumption (17.7 ± 3.6 [mean ± SD] mL O2/kg/min), blood lactate concentrations (3.4 ± 0.9 mmol/L), peak heart rates (168 ± 12 beats/min), and rates of ventilation (37.3 ± 14.6 L/min) were low, but respiratory exchange ratios (1.1 ± 0.1) were compatible with maximal effort. There was a significant correlation between isokinetic muscle strength and peak, exercise duration, peak ventilation, and peak blood lactate concentrations (P < 0.05 to < 0.001), but not between hemoglobin concentration, total blood hemoglobin content, or hematocrit and these variables. Therefore, in renal dialysis patients, isokinetic muscle strength is a better predictor of exercise capacity than are variables determining blood oxygen carrying capacity. This suggests that altered skeletal muscle function explains the impaired exercise tolerance of anemic patients with end-stage renal disease receiving chronic hemodialysis. © 1990, National Kidney Foundation Inc.. All rights reserved.