Intermittent claudication and muscle fiber fine structure: correlation between clinical and morphological data

Bilaterally obtained muscle biopsies (anterior tibial muscle) from 22 patients with unilateral peripheral arterial insufficiency (intermittent claudication) were qualitatively and quantitatively analyzed by means of enzyme histochemistry and electron microscopy. In a majority of the biopsies from the symptomatic legs, two different patterns of morphological deviations were seen in the abnormal muscles: one suggested primary muscle fiber damage and the other indicated denervation. Biopsies from the asymptomatic legs were often only slightly changed or normal. Significant correlations were found in both legs between the relative number of type 1 (slow twitch, highly oxidative) fibers and the age of the subjects. In symptomatic legs, furthermore, a relation could be demonstrated between the relative number of type 1 fibers and (1) the initial walking tolerance (walking distance covered before pain occurred), (2) duration of symptoms, and (3) occlusion or stenosis at high level (i.e., above the deep femoral artery). Finally, the diameters of both type 1 and type 2 fibers in the symptomatic leg were correlated to the initial walking tolerance. The importance of circulatory disturbances as differential diagnostic points (arteriovasculo-occlusive myopathy) in the diagnosis of neuromuscular diseases is stressed.

Physical training in man. Skeletal muscle metabolism in relation to muscle morphology and running ability

The metabolic and morphologic adaptation to physical training in skeletal muscle tissue of eleven middle-aged, physically untrained men was studied. Muscle biopsies were taken from the vastus lateralis before, after 8 weeks and after 6 months of physical training for analysis of metabolic and morphologic variables. Glucose tolerance test indicated increased insulin sensitivity after 6 months of physical training. The activities of glycogen phosphorylase, hexokinase and glucose-6-P-dehydrogenase were increased but other enzymes involved in glycogen turnover and glycolysis were unchanged after 6 months of physical traning. The activities of citrate synthase and cytochrome-c-oxidase, representing the oxidative capacity were significantly increased already after 8 weeks of physical training. The incorporation rate of palmitate-carbon into CO2 and triglycerides increased, and the incorporation rate of leucine-carbon into CO2 decreased with 6 months of physical training. The fiber diameter of both Type 1- and Type 2-fibers increased, while the mitochondrial volume increased predominantly in Type 2-fibers. Significant correlations were found between metabolic, physiologic and morphologic variables before and after physical training. The results indicate an increased oxidative capacity, mainly located to Type 2-fibers, and an increased utilization of fatty acids in response to this type of physical training.