Capillary density of skeletal muscle in well-trained and untrained men

of skeletal muscle in well-trained and untrained men. J. Appl. Physiol. 30(6) : 860463. 197 1.-Capillary density in muscle samples obtained by needle biopsies from the lateral portion of muscle quadriceps femoris was measured in 15 young males, 8 untrained (avg maximal oxygen uptake: 50.2 ml/kg x min) and 7 well-trained (avg maximal oxygen uptake: 71.4 ml/kg x min) sub-jects. The number of capillaries per mm2 was found to be 640 =t: 54.5 (mean & SE) in samples taken at rest, and 611 + 28.3 im-mediately after maximal exercise (4-6 min duration) in well-trained subjects. The corresponding values for the untrained sub-jects were 600 & 23.8 and 599 =t 26.6. The difference was not statistically significant (P> 0.1). The average size of the muscle cells was significantly larger (P < 0.01) in the well-trained than in the untrained subjects. Consequently, the number of capillaries per muscle fiber was found to be higher (P < 0.05) in the well-