Exercise intolerance and skeletal muscle (SM) abnormalities in patients with chronic obstructive airways disease (COAD)

Abstract

South African Journal of Sports Medicine Volume 4, No. 1:7, 1997(Abstract issue) Abstract: Patients with COAD commonly experience fatigue and exercise Intolerance, which is though to be due to pulmonary factors. However, few studies describe both the structural and functional status of SM in patients with COAD. This study examines 10 patients with moderate to severe COAD and 6 sedentary, healthy control subjects (C) underwent i) graded exercise test to exhaustion for determination of peak oxygen consumption(˙VO2peak), peak work load (WLpeak) and peak ventilation(˙VEpeak); ii) isokinetic tests of SM strength and endurance and iii) SM biopsy for determination of skeletal muscle structure.˙VO2peak (18.0 ± 1.59 vs 25.40 ± 1.15 mL·O-[sup]1[inf]2/kg·min-[sup]1; P < 0.05), WLpeak (88.56 ± 21.57 vs 214.17 ± 30.47 W;P < 0.001), ˙VEpeak (43.95 ± 5.40 vs 74.44± 8.22 L; P < 0.001) and total work performed by the quadriceps muscle (TWQ) in a 60 s isokinetic test (2113.08 ± 376.48 vs 3785.86 ± 364.19 J; P < 0.005) were all lower in patients with COAD. Furthermore, ˙VEpeak and peak blood lactate (5.29± 1.25 vs 10.71 ± 0.35 P < 0.001) were lower in patients with COAD when compared with C. Peak torque achieved during a 30 s isometric test was not different between groups (169.92 ± 31.82 vs 217.75 ± 24.17 Nm; P = NS) before or after correction for lean thigh volume (LTV) however, when TWQ was corrected for LTV values tended to be different between groups (766.73 ± 101.24 vs 978.80 ± 114.78 J/L; P = NS). Profound histological and ultrastructural abnormalities were found in all SM biopsies from patients with COAD. Abnormalities included: Type II fiber atrophy, Type II fiber predominance, Type I fiber hypertrophy, necrotic fibers and diffuse mitochondrial abnormalities. These data support the hypothesis that (i) severe SM structural abnormalities are present in patients with COAD (ii) functional abnormalities are present in tests of SM endurance in patients with COAD and (iii) these SM structural and functional abnormalities may play a role in exercise intolerance in patients with COAD.