The isokinetic assessment of peripheral muscle function in patients with coronary artery disease: correlations with cardiorespiratory capacity

Abstract

Objective We aimed to determine whether diminished cardiorespiratory capacity in patients with coronary artery disease (CAD) is accompanied by impaired skeletal muscle function as measured by isokinetic dynamometry. We also evaluated the correlation between isokinetic strength and aerobic capacity in these patients. Materials and methods Fifteen CAD patients and 15 age-matched healthy subjects (mean age 60 ± 6 vs. 57 ± 3.5 years) underwent maximal laboratory exercise testing, a 6-min walking test and an assessment of peripheral skeletal muscle function by use of an isokinetic apparatus. Quadricep and hamstring function was tested at two angular velocities, 150 and 180°s −1 with simultaneous electrocardiography monitoring. The cardiorespiratory and mechanical parameters (VO 2, ventilatory threshold [VT], heart rate [HR], and power) were measured at VT and at maximal effort. Results Quadricep and hamstring peak torque was impaired in CAD patients, with quadriceps peak torque at 180° being 71.13 ± 14 vs. 91.13 ± 23 Nm ( P < 0.01) and hamstring peak torque 46.50 ± 10 vs. 59.86 ± 12 Nm ( P < 0.01). CAD subjects presented a deficient aerobic capacity as compared with the healthy subjects at maximal effort. At VT, the VO 2, ventilation, and HR were significantly lower in CAD patients, at 13.77 ± 2.33 vs. 17.08±3.59 ml min −1 kg −1 ( P < 0.05), 29.64 ± 664 vs. 37.76 ± 7.2 ml min −1 ( P < 0.05), and 86 ± 14 vs. 111 ± 15 beats min −1 ( P = 0.001), respectively. The 6-min walking distance was significantly shorter for CAD patients than healthy subjects (425.93 ± 52.77 vs. 551.46 ± 57.94 m; P < 0.01). In CAD patients quadriceps and hamstring strength was not correlated with VO 2 at maximal effort and at VT. Total distance walked during the 6-min walk and VO 2max were correlated ( r = 0.869; P < 0.001) but not at VT. Conclusion CAD patients showed impaired cardiorespiratory capacity accompanied by increased muscle fatigability as compared with healthy subjects. An isokinetic muscle assessment in these patients must be achieved systematically and seems to have value in cardiovascular rehabilitation.