Quantitative morphometric analyses of the exercised extensor digitorum longus muscle of the mouse

The metric properties of several important components of muscle, the capillaries, the myonuclei and also the cross-sectional areas of type I and type II fibres in the extensor digitorum longus muscle of the mouse have been studied using techniques appropriate for anisotropic tissues. Myonuclear volume density (Nv) was found to be increased by 70% whilst capillary length density (Lv) was increased by 50%. The results were analysed using multivariate statistical analysis (MANOVA) which is necessary for the multiple comparisons which inevitably occur in any morphometric investigation. The mitochondrial distribution within type I fibres was analysed using two-way ANOVA to study the effect of exercise on the mitochondrial contents of the inner, intermediate and outer zones of the muscle fibre. Significant differences in the mitochondrial content in the various zones were found. Exercise was found to increase mitochondrial contents in all three zones.