WHOLE-BODY TL-201 SCINTIGRAPHY DURING ONE-LEG EXERCISE AND AT REST INNORMAL SUBJECTS - ESTIMATION OF REGIONAL BLOOD-FLOW CHANGES

To determine the effect of exercise intensity on regional blood flow i n exercising and resting leg muscles and organs, we assessed relative changes in the regional distribution of Tl-201 during one-leg ergomete r exercise and at rest by whole-body scintigraphy as an estimate of re gional blood flow changes in 10 healthy males. The regional Tl-201 act ivity was expressed as a percentage of the whole-body activity, and re lative changes in each region were compared to those at the anaerobic threshold (AT) and at peak exercise. In the legs, the distribution of Tl-201 in the exercising thigh and calf increased significantly at the AT to 390.7 and 219.2% respectively of resting levels (both P<0.01), but remained unchanged in the resting thigh from rest to peak exercise . Conversely, its distribution in the resting calf decreased significa ntly at the AT to 60.0% of the resting level, (P<0.01). However, there were no significant differences between AT and peak exercise. In the organs, the distribution of Tl-201 in the lung, liver, spleen and kidn eys decreased significantly at the AT to 88.4 +/- 10.4%, 67.0 +/- 11.5 %, 62.4 +/- 11.8% and 67.0 +/- 8.6% respectively of resting levels (al l P<0.01). Redistribution of blood flow to the exercising leg occurs p redominantly during mild to moderate exercise. Therefore, blood flow i n the leg during strenuous exercise depends primarily upon an increase in cardiac output. The splanchnic organs are the major sources of red istribution.