Capillary permeability and maximal blood flow in skeletal muscle in athletes and non-athletes measured by local clearances of 133Xe and 131I-.

The effect of heavy endurance training on capillary diffusion capacity (CDC) and maximal blood flow (MBF) in skeletal muscle was studied in eleven highly-trained athletes and ten sedentary adult volunteers. MBF was estimated from 133Xe clearance and CDCI from 133Xe and 131I- clearances in the anterior tibial muscle after ischaemic exercise. The athletes had a significantly greater MBF, 131I- clearance and CDCI than the control subjects (P less than 0.001). The average increment of MBF was 37% and that of CDCI 48%. Increase in CDC is considered to reflect an increase in capillary surface area due to physical training.