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Department of Medicine, University of California, La Jolla, California 92093
We measured leg blood flow (LBF), drew
arterial-venous (A-V) blood samples, and calculated muscle
O2 consumption (
O2)
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 O2 difference changed little with
increasing WR in the old group but was elevated compared with the young
subjects. Muscle maximal
O2 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.
O2 max; vascular conductance; skeletal muscle
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