Age and sex influence the balance between maximal cardiac output and peripheral vascular reserve

Abstract

We evaluated the influence of age and sex on the relationship between central and peripheral vasodilatory capacity. Healthy men (19 younger, 12 older) and women (17 younger, 17 older) performed treadmill and knee extensor exercise to fatigue on separate days while maximal cardiac output (Q, acetylene uptake) and peak femoral blood flow (FBF, Doppler ultrasound) were measured, respectively. Maximal Q was reduced with age similarly in men (Y: 23.6 +/- 2.7 vs. O: 17.4 +/- 3.5 l/min; P < 0.05) and women (Y: 17.7 +/- 1.9 vs. O: 12.3 +/- 1.6 l/min; P < 0.05). Peak FBF was similar between younger (Y) and older (O) men (Y: 2.1 +/- 0.5 vs. O: 2.2 +/- 0.7 l/min) but was lower in older women compared with younger women (Y: 1.9 +/- 0.4 vs. O: 1.4 +/- 0.4 l/min; P < 0.05). Maximal Q was positively correlated with peak FBF in men (Y: r = 0.55, O: r = 0.74; P < 0.05) but not in women (Y: r = 0.34, O: r = 0.10). Normalization of cardiac output to appendicular muscle mass and peak FBF to quadriceps mass reduced the correlation between these variables in younger men (r = 0.30), but the significant association remained in older men (r = 0.68; P < 0.05), with no change in women. These data suggest that 1) aerobic capacity is associated with peripheral vascular reserve in men but not women, and 2) aging is accompanied by a more pronounced sex difference in this relationship.

Fig. 1.

Peak cardiac output during treadmill exercise vs. peak quadriceps blood flow during knee extensor exercise: ▴, younger men (n = 19); ▵, older men (n = 12) (A); ●, younger women (n = 17); ○, older women (n = 17) (B). Peak cardiac output during treadmill exercise vs. femoral artery conductance during peak knee extensor exercise: ▴, younger men; ▵, older men (C); ●, younger women; ○, older women (D).

Fig. 2.

Peak cardiac output during treadmill exercise normalized to appendicular muscle mass vs. femoral blood flow during peak knee extensor exercise normalized to quadriceps muscle mass: ▴, younger men (n = 19); ▵, older men (n = 12) (A); ●, younger women (n = 17); ○, older women (n = 17) (B).

Fig. 3.

Subset analysis of the minimum vascular resistance attained during peak treadmill exercise (∼90% maximal oxygen uptake) vs. femoral blood flow during peak knee extensor exercise: ▴, younger men (n = 9); ▵, older men (n = 7) (A); ●, younger women (n = 8); ○, older women (n = 9) (B). SVR, systemic vascular resistance.