Vascular and metabolic response to cycle exercise in sedentary humans: effect of age

We measured leg blood flow (LBF), drew arterial-venous (A-V) blood samples, and calculated muscle O-2 consumption ((V) over dot O-2) during incremental cycle ergometry exercise [15, 30, and 99 W and maximal effort (maximal work rate, WRmax)] in nine sedentary young (20 +/- 1 yr) and nine sedentary old (70 +/- 2 yr) males. LBF was preserved in the old subjects at 15 and 30 W. However, at 99 W and at WRmax, leg vascular conductance was attenuated because of a reduced LBF (young: 4.1 +/- 0.2 l/min and old: 3.1 +/- 0.3 l/min) and an elevated mean arterial blood pressure (young: 112 +/- 3 mmHg and old: 132 +/- 3 mmHg) in the old subjects. Leg A-V 02 difference changed little with increasing WR in the old group but was elevated compared with the young subjects. Muscle maximal (V) over dot O-2 and cycle WRmax were significantly lower in the old subjects (young: 0.8 +/- 0.05 l/min and 193 +/- 7 W; old: 0.5 +/- 0.03 l/min and 117 +/- 10 W). The submaximally unchanged and maximally reduced cardiac output associated with aging coupled with its potential maldistiribution are candidates for the limited LBF during moderate to heavy exercise in older sedentary subjects.