Capillary supply of the quadriceps femoris muscle of man: adaptive response to exercise

TLDR

Five subjects trained 8 weeks on a bicycle ergometer at 80 % VO₂max, with quadriceps biopsies taken before and during training, stained for fibre types and capillaries, and assayed for succinate dehydrogenase and cytochrome oxidase activities. The training increased VO₂max by 16 %, capillary density by 20 %, mean fibre area by 20 %, and succinate dehydrogenase and cytochrome oxidase activities by ~40 %, with equal capillary supply increases across fibre types, demonstrating capillary proliferation as a powerful stimulus. The study is referenced as 1 and reports VO₂max measurements.

Abstract

1. Five subjects trained for 8 weeks on a bicycle ergometer for an average of 40 min/day, four times a week at a work load requiring 80% of the maximal oxygen uptake (V(O2 max.)). V(O2 max.) determinations were performed, and muscle biopsies from the quadriceps femoris muscle (vastus lateralis) were taken before, as well as repeatedly during, the training period. The muscle biopsies were histochemically stained for fibre-types (myofibrillar ATPase) and capillaries (amylase-PAS method), and analysed biochemically for succinate dehydrogenase and cytochrome oxidase activities.2. The training programme resulted in a 16% increase in V(O2 max.), a 20% increase in capillary density, a 20% increase in mean fibre area, and an approximately 40% increase in the activities of succinate dehydrogenase and cytochrome oxidase.3. The capillary supply to type I, IIA and IIB fibres, expressed as the mean number of capillaries in contact with each fibre-type, relative to fibre-type area, increased equally.4. The present study shows that endurance training constitutes a powerful stimulus for capillary proliferation in human skeletal muscle.