Assessing the efficacy of exercise training in patients with chronic disease

PURPOSE: The purpose of this study was to evaluate the meaningfulness of exercise training responses in patients with end stage renal disease (ESRD). METHODS: Eighteen ESRD patients [(mean +/- SD); 54.3 +/- 17.1 yr] completed a training regime progressing to accumulate 40 min of stationary cycling, three times per week for 6 months. .VO(2peak) determined via incremental cycle ergometer protocol, and .VO(2) kinetics determined from a transition from unloaded pedalling to an exercise intensity corresponding to 90% of VT, were assessed at baseline and at 3 and 6 months of training. RESULTS: Repeated measures analysis of variance revealed significant changes (P < 0.05) on the time factor for .VO(2peak), VO(2)-V(T), and .VO(2) kinetics. Post hoc analysis revealed that .VO(2peak) and .VO(2) kinetics significantly (P < 0.05) improved at 3 months of training with no further improvements thereafter. Analysis of individual subject response data revealed that after 3 months of training, 61% of the patients improved .VO(2peak) by greater than the standard error of measurement (SEM = 0.07 L.min(-1)). At 6 months of training, approximately 89% of the patients improved by more than the SEM .VO(2) kinetics improved by more than the SEM (12.3 s) at 3 months of training in approximately 55% of the patients, with no increase in the number of patients exhibiting faster time constants after 6 months of training. CONCLUSION: Although conventional statistical analyses indicate that exercise training favorably alters .VO(2peak) and oxygen uptake kinetics of patients with ESRD, it is apparent that considerable interindividual variability exists in the response to training. Consideration of the SEM data underscores the heterogeneity of adaptive response in this patient group and may be valuable in assessing the efficacy of therapeutic exercise rehabilitation.