Reliability of isokinetic strength and aerobic power testing for patients with chronic heart failure

The objective of this study was to assess the reliability of testing skeletal muscle strength and peak aerobic power in a clinical population of patients with chronic heart failure (CHF).

Thirty-three patients with CHF (New York Heart Association (NYHA) Functional Class 2.3 +/- 0.5; left ventricular ejection fraction 27% +/- 7%; age 65 +/- 9 years; 28:5 male-female ratio) underwent two identical series of tests (T1 and T2), 1 week apart, for strength and endurance of the muscle groups responsible for knee extension/flexion and elbow extension/flexion. The patients also underwent two graded exercise tests on a bicycle ergometer to measure peak oxygen consumption (VO(2peak)). Three months later, 18 of the patients underwent a third test (T3) for each of the measures. Means were compared using MANOVA with repeated measures for strength and endurance, and ANOVA with repeated measures for VO(2peak).

Combining data for all four movement patterns, the expression of strength increased from T1 to T2 by 12% +/- 25% (P <.001; intraclass correlation coefficient [ICC] = 0.89). Correspondingly, endurance increased by 13% +/- 23% (P =.004; ICC = 0.87). Peak oxygen consumption was not significantly different (16.2 +/- 0.8 and 16.1 +/- 0.8 mL.kg(-1).min(-1) for T1 and T2, respectively; P =.686; ICC = 0.91). There were no significant differences between T2 and T3 for strength (2% +/- 17%; P =.736; ICC = 0.92) or muscle endurance (-1% +/- 15%; P =.812; ICC = 0.96), but VO(2peak) decreased from 16.7 +/- 1.2 to 14.9 +/- 0.9 mL.kg(-1).min(-1) (-10% +/- 18%; P =.021; ICC = 0.89).

These data suggest that in a population of patients with CHF, a familiarization trial for skeletal muscle strength testing is necessary. Although familiarization is not required for assessing oxygen consumption as a single measurement, VO(2peak) declined markedly in the 3-month period for which these patients were followed. Internal consistency within patients was high for the second and third strength trials and the first and second tests of VO(2peak).