Effects of endurance exercise training in muscle microvascular characteristics of muscle fibers in training compared with nontraining patients. (A) Images of serial cross-sections labeled to identify (1) fiber type distribution (MHC-I or MHC-IIa stained in red), (2) extracellular matrix (anti-laminin-α1 stained in green), and (3) capillaries (CD31 antibody stained in black) of a nontraining patient and a training patient before and after the training period. Increases in the number of capillaries per surface area (CD) and around a muscle fiber (CAF) were observed after training (illustrated by CD31 images at high magnification) in the training patient, but not in the nontraining patient. (B) Percentage change in CAF in training and nontraining groups. CAF increased in training patients compared with nontraining patients (all fibers [mean]) and more specifically in type I muscle fibers. (C) Percentage change in LC/PF in training and nontraining groups. LC/PF increased in training patients compared with nontraining patients (all fibers [mean]) and more specifically in type I and type IIa muscle fibers. Statistically different between the 2 groups: *P < .05 and ***P < .001. Scale bars represent 100 μm.