Age-associated impairments in contraction-induced rapid onset vasodilatation within the forearm are independent of mechanical factors

New Findings

• What is the central question of this study?

  We examined whether the mechanical contribution to contraction-induced rapid onset vasodilatation (ROV) differed with age, and whether ROV is associated with peripheral artery stiffness. Furthermore, we examined how manipulation of perfusion pressure modulates ROV in young and older adults.

• What is the main finding and its importance?

  The mechanical contribution to ROV is similar in young and older adults. Conversely, peripheral arterial stiffness is not associated with ROV. Enhancing perfusion pressure augments ROV to a similar extent in young and older adults. These results suggest that age-related attenuations in ROV are not due to a mechanical component, and ROV responses are independent of peripheral artery stiffness.

Abstract

Contraction-induced rapid onset vasodilatation (ROV) is modulated by perfusion and transmural pressure in young adults; however, this effect remains unknown in older adults. The present study examined the mechanical contribution to ROV in young versus older adults, the influence of perfusion pressure, and whether these responses are associated with arterial stiffness. Forearm vascular conductance (VC; ml·min⁻¹·100 mmHg⁻¹) was measured in 12 healthy young (24 ± 4 yrs.) and 12 older (67 ± 3 yrs.) adults during: 1) single dynamic contractions at 20% of maximum voluntary contraction; and 2) single external mechanical compression of the forearm (200 mmHg) positioned above, at, and below-heart level. Carotid-radial pulse-wave velocity characterized upper limb arterial stiffness. Total ROV responses to single muscle contractions and single external mechanical compressions were attenuated in older adults at-heart level (P < 0.05), however, the relative mechanical contribution to contraction-induced peak (46 ± 14% vs. 40 ± 18% P = 0.21) and total (37 ± 21% vs. 32 ± 18% P = 0.27) responses were not different between young and older adults. Reducing or enhancing perfusion pressure altered ROV responses similarly between young and older adults (P < 0.05). Upper limb arterial stiffness was not associated with peak (r = 0.02; P = 0.93) or total VC (r = -0.01; P = 0.96) in the group as a whole. Our data suggest 1) age-associated attenuations in ROV are not due to a mechanical component; 2) enhancing perfusion pressure augments ROV to a similar extent between young and older adults; and 3) basal upper limb arterial stiffness is not associated with the vasodilator responses following a single skeletal muscle contraction in young and older adults.

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