Strength training with partial ischaemia stimulates microvascular remodelling in rat calf muscles.

The effects of strength training with partial tourniquet ischaemia on skeletal muscle capillarity were examined, particularly in terms of the distribution of arteriolar and venular capillaries and their capillary domain area, in male Wistar rats. A tourniquet applied around the knee joint induced partial ischaemia. Repeated isometric contractions of calf muscles, 1 s on/1 s off for 3 min, induced by electrical stimulation (100 Hz), were conducted 2 days/week for 6 weeks as training. Morphologic data were obtained from four groups; non-treatment control (C), ischaemic (IS), non-ischaemic training (NIT) and ischaemic training (IT). In the superficial portion of gastrocnemius (GASs) muscle, the total capillary density of arteriolar capillaries was significantly greater in the IT-leg than in the C-leg (P < 0.05). In the plantaris (PL) muscle, these values were significantly greater in the IT-leg than in both the C- and NIT-legs (P < 0.05). Only in the GASs was the capillary-to-fibre ratio significantly greater in the IT-leg than in the C-leg (P < 0.05). In GASs and PL, the capillary domain area (CDA) was smaller in the IT-leg than in the C- and NIT-legs. In all muscles examined, mean fibre cross-sectional area was not significantly changed by the experimental treatment. These findings suggest that adaptive changes in the microvascular network, identified as an increase in the arteriolar capillary area and a reduction in diffusion distance, occur in the skeletal muscles after strength training with partial ischaemia. These adaptive changes probably improve the supply of oxygen and nutrients to skeletal muscle tissues.