Isokinetic strength testing in patients with chronic heart failure--a reliability study.

Measurement of skeletal muscle strength gains increasing importance as outcome parameter in patients with chronic heart failure. This study aimed at establishing short-term reliability of isokinetic strength measurements of knee extensor and flexor muscles in 38 patients with chronic heart failure. Strength tests were performed on the Cybex 6000 dynamometer. Trunk fixation was restricted to pelvic fixation. Two bouts of strength testing were performed on day 1 and one on day 5. Each isokinetic bout consisted of 3 reciprocal knee extension and flexion movements with an angular speed of 60 degrees per second. Isometric strength was measured at 30 degree knee angulation. Intraclass correlations ranged between 0.96 and 0.99 for isokinetic and isometric peak torque of knee extensor muscles and 0.82-0.96 for flexor muscles. Analysis of repeated measurements showed significant differences among the values of flexor peak torque in the isokinetic mode and between all measurements in the isometric mode (p < 0.05). Pearson's correlation coefficients for isokinetic and isometric extensor peak torques ranged between 0.95 and 0.99, for flexor peak torques between 0.81 and 0.85 (all p < 0.0001). Measurement of isokinetic knee extensor and flexor peak torque is a reliable method to assess muscle strength in patients with chronic heart failure even with altered trunk fixation.

Improvement of thigh muscles by neuromuscular electrical stimulation in patients with refractory heart failure: a single-blind, randomized, controlled trial.

OBJECTIVE: To determine the impact of an 8-wk neuromuscular stimulation program of thigh muscles on strength and cross-sectional area in patients with refractory heart failure listed for transplantation. DESIGN: Forty-two patients with a stable disease course were assigned randomly to a stimulation group (SG) or a control group (CG). The stimulation protocol consisted of biphasic symmetric impulses with a frequency of 50 Hz and an on/off regime of 2/6 sec. RESULTS: Primary outcome measures were isometric and isokinetic thigh muscle strength and muscle cross-sectional area. Our results showed an increase of muscle strength by mean 22.7 for knee extensor and by 35.4 for knee flexor muscles. The CG remained unchanged or decreased by -8.4 in extensor strength. Cross-sectional area increased in the SG by 15.5 and in the CG by 1.7. CONCLUSIONS: Activities of daily living as well as quality of life increased in the SG but not in the CG. Subscales of the SF-36 increased significantly in the SG, especially concerning physical functioning by +7.5 (1.3-30.0), emotional role by +33.3 (0-66.6), and social functioning by +18.8 (0-46.9), all P < 0.05. Neither a change nor a decrease was observed in the CG. Neuromuscular electrical stimulation of thigh muscles in patients with refractory heart failure is effective in increasing muscle strength and bulk and positively affects the perception of quality of life and activities of daily living.

Strength improvement of knee extensor muscles in patients with chronic heart failure by neuromuscular electrical stimulation.

Patients with severe chronic heart failure (CHF) suffer from marked weakness of skeletal muscles. Neuromuscular electrical stimulation (NMES) proved to be an alternative to active strength training. The objective of this study was to test the feasibility and effectiveness of NMES in patients with chronic heart failure. Seven patients (56.0 +/- 5.0 years, CHF for 20 +/- 4 months, left ventricular ejection fraction 20.1 +/- 10.0%) finished an 8 week course of NMES of the knee extensor muscles. The stimulator delivered biphasic, symmetric, constant voltage impulses of 0.7 ms pulse width with a frequency of 50 Hz, 2 s on and 6 s off. No adverse effects occurred. After the stimulation period, the isokinetic peak torque of the knee extensor muscles increased by 13% from 101.0 +/- 8.7 Nm to 113.5 +/- 7.2 Nm (p = 0.004). The maximal isometric strength increased by 20% from 294.3 +/- 19.6 N to 354.14 +/- 15.7 N (p = 0.04). This increased muscle strength could be maintained in a 20 min fatigue test indicating decreased muscle fatigue. These results demonstrate that NMES of skeletal muscles in patients with severe chronic heart failure is a promising method for strength training in this group of patients.