CARDIOVASCULAR-RESPONSES DURING ONE-LEGGED AND 2-LEGGED EXERCISE IN MIDDLE-AGED MEN

Eight healthy and regularly physically active men, 44-69 years old, pe rformed one- and two-legged dynamic knee extension exercise at increas ing work intensities, including one leading to exhaustion. Leg blood B ow increased linearly in relation to work rate, reaching a peak value of 5.1 +/- 0.4 l min(-1). With a mean weight of quadriceps femoris of 2.2 +/- 0.1 kg, a peak perfusion of 2.3 +/- 0.1 l kg(-1) min(-1) was a ttained. The maximal leg oxygen uptake was 0.72 +/- 0.07 1 min(-1) (0. 33 +/- 0.03 l kg(-1) min(-1)). At submaximal work the elevation in lim b oxygen uptake accounted for between 70 and I00% of the rise in pulmo nary oxygen uptake. Comparing two- with one-legged knee extension the cardiac output was 1.5 l min(-1) higher at each work level, reaching 1 3.7 +/- 0.7 and 12.3 +/- 1.0, respectively at exhaustion, leaving 3.5 and 7.2 l min(-1) of blood how to the remaining body (cardiac output-l eg blood flow). The mean arterial pressure was 119 +/- 5 mmHg at rest and increased to 155 mmHg for both test modes at the maximal work rate . The femoral arterial and venous plasma concentrations of lactate, am monia and noradrenaline were significantly higher for two-legged as co mpared with one-legged exercise at the maximal load performed. However , the rate of release per leg, for both lactate and ammonia, did not d iffer between the two test conditions. It is concluded that physically active middle-aged men, with a well-retained muscle mass, can maintai n a high skeletal muscle perfusion, similar to that of young males. Ho wever, the blood flow is achieved with a higher mean arterial pressure and an elevated sympathetic activity, as reflected by noradrenaline i n plasma and spillover from the exercising limb.