Female-related skeletal muscle phenotype in patients with moderate chronicheart failure before and after dynamic exercise training

This study hypothesized that female patients with chronic heart failure (CH F), similarly as previously reported for male patients, have a decreased pr oportion of type I (slow twitch) muscle fibers combined with fiber atrophy, and respond to exercise training with an increased muscular fiber area and performance, and with an unaltered fiber type distribution. Methods: Sixte en women [age 62+/-10 years (mean+/-SD)] with stable, moderate CHF (left ve ntricular ejection fraction 28+/-8%) underwent percutaneous needle biopsies of the lateral vastus muscle, and assessments of isokinetic muscle strengt h and exercise tests with respiratory gas and blood lactate analyses, befor e and after 8 weeks of intensive knee extensor endurance training. Results: When compared to healthy age-matched women, the women with CHF unexpectedl y had a normal proportion of type I fibers (51+/-15%), but a decreased cros s-sectional area in both type I and II fibers. Exercise training increased the cross-sectional area of muscle fibers up to the reference range (21%, p <0.04), while the relative number of type I fibers decreased (12%, p<0.03). Training also increased muscle strength (16%, p<0.0001) and peak oxygen up take (20%, p<0.0001). The increase in peak oxygen uptake was directly relat ed to the training-induced increase in fiber areas (r=0.63; p<0.03), and de crease in lactate accumulation was inversely related to the training-induce d decrease in the relative number of type I fibers (r= -0.62; p<0.02). Conc lusions: As for men with CHF, a skeletal muscle atrophy was found in women, but contrary to the hypothesis, the proportion of type I muscle fibers was normal. Exercise training counteracted the atrophy suggesting skeletal mus cle trainability in female CHF patients. (C) 1999 Elsevier Science B.V. All rights reserved.