Influence of endurance exercise training on distribution of vascular adaptations in rat skeletal muscle

We hypothesized that an exercise training program consisting of treadmill running at 32 m/min up a 15% incline, 90 min/day, 5 days/wk for 12-14 wk, would elicit vascular adaptation in skeletal muscle of all fiber types in rats. This hypothesis was based on previous reports that this intensity and duration of training caused increases in oxidative capacity in rat skeletal muscle of all fiber types. Skeletal muscle vascular transport capacity was examined with measurements of total and regional (radiolabeled microspheres) flow capacity, capillary filtration coefficient (CFC), and permeability-surface area product (PS) for 51Cr-EDTA in maximally vasodilated (papaverine) hindquarters of control (C; n = 25) and exercise-trained (ET; n = 26) rats. CFC was increased in ET (0.038 +/- 0.001 vs. 0.030 +/- 0.001 ml.min-1 x mmHg-1 x 100 g-1; P < or = 0.001). PS was greater in ET than C (7.80 +/- 0.33 vs. 6.39 +/- 0.37 ml.min-1 x 100 g-1; P < or = 0.01). Citrate synthase activity was increased in the soleus (25%; P < or = 0.05), the medial head (35%; P < or = 0.05), and the red portion of the long head (45%; P < or = 0.005) but not in the white portion of the long head of triceps brachii (P = 0.14) of ET rats. Pressure-flow relationships indicate that total flow was greater (P < or = 0.05) in ET hindquarters at all perfusion pressures. Regional flow data revealed that increases in flow capacity were not evident in muscles composed of all fiber types as predicted.(ABSTRACT TRUNCATED AT 250 WORDS)