Increased capillary tortuosity and pericapillary basement membrane thinning in skeletal muscle of mice undergoing running wheel training.

To work out which microvascular remodeling processes occur in murine skeletal muscle during endurance exercise, we subjected C57BL/6-mice to voluntary running wheel training for 1 week (1wk-t) or 6 weeks (6wks-t). By means of morphometry, the capillarity as well as the compartmental and sub-compartmental structure of the capillaries were quantitatively described at the light microscopy and at the electron microscopy level, respectively, in the plantaris muscle (PLNT) of the exercising mice in comparison to untrained littermates. In the early phase of the training (1wk-t), angiogenesis (32%-higher capillary-fiber (CF)-ratio; P0.05), further reduction of CBMT (16.5%; P<0.05) and additional shortening of the intraluminal protrusion length (23%; P