Unlike young men who had a ~70% greater peak leg blood flow in the upright posture, older men showed no posture-induced increase in hyperemia (412 vs 417 ml/min) despite similar perfusion pressure increases.
Cross-Sectional (n=22)
Does increased femoral perfusion pressure via posture change improve movement-induced hyperemia in older compared to younger healthy men?
Increased femoral perfusion pressure via posture change elicits an increase in movement-induced hyperemia and vasodilation in young but not older healthy men, suggesting limited vasodilatory reserve with age.
To better understand the mechanisms contributing to reduced blood flow with age, this study sought to elucidate the impact of altered femoral perfusion pressure (FPP) on movement-induced hyperemia. Passive leg movement was performed in 10 young (22 ± 1 yr) and 12 old (72 ± 2 yr) healthy men for 2 min, with and without a posture-induced change in FPP (~7 ± 1 ΔmmHg). Second-by-second measurements of central and peripheral hemodynamic responses were acquired noninvasively (finger photoplethysmography and Doppler ultrasound, respectively), with FPP confirmed in a subset of four young and four old subjects with arterial and venous catheters. Central hemodynamic responses (heart rate, stroke volume, cardiac output, mean arterial pressure) were not affected by age or position. The young exhibited a ~70% greater movement-induced peak change in leg blood flow (ΔLBF(peak)) in the upright-seated posture (supine: 596±68 ml/min; upright: 1,026 ± 85 ml/min). However, in the old the posture change did not alter ΔLBF(peak) (supine: 417±42 ml/min; upright: 412±56 ml/min), despite the similar increases in FPP. Similarly, movement-induced peak change in leg vascular conductance was ~80% greater for the young in the upright-seated posture (supine: 7.1 ± 0.8 ml·min(-1)·mmHg(-1); upright: 12.8 ± 1.3 ml·min(-1)·mmHg(-1)), while the old again exhibited no difference between postures (supine: 4.7 ± 0.4 ml·min(-1)·mmHg(-1); upright: 4.8 ± 0.5 ml·min(-1)·mmHg(-1)). Thus this study reveals that, unlike the young, increased FPP does not elicit an increase in movement-induced hyperemia or vasodilation in the old. In light of recent evidence that the majority of the first minute of passive movement-induced hyperemia is predominantly nitric oxide (NO) dependent in the young, these findings in the elderly may be largely due to decreased NO bioavailability, but this remains to be definitively determined.
Groot et al. (Sat,) conducted a cross-sectional in Healthy aging (n=22). Upright-seated posture (increased femoral perfusion pressure) vs. Supine posture was evaluated on Movement-induced peak change in leg blood flow (ΔLBF(peak)). Unlike young men who had a ~70% greater peak leg blood flow in the upright posture, older men showed no posture-induced increase in hyperemia (412 vs 417 ml/min) despite similar perfusion pressure increases.