title: Differential effects of aging on limb blood flow in humans.
abstract: Aging appears to attenuate leg blood flow during exercise; in contrast, such data are scant and do not support this contention in the arm. Therefore, to determine whether aging has differing effects on blood flow in the arm and leg, eight young (22 +/- 6 yr) and six old (71 +/- 15 yr) subjects separately performed dynamic knee extensor [0, 3, 6, 9 W; 20, 40, 60% maximal work rate (WRmax)] and handgrip exercise (3, 6, 9 kg at 0.5 Hz; 20, 40, 60% WRmax). Arterial diameter, blood velocity (Doppler ultrasound), and arterial blood pressure (radial tonometry) were measured simultaneously at each of the submaximal workloads. Quadriceps muscle mass was smaller in the old (1.6 +/- 0.1 kg) than the young (2.1 +/- 0.2 kg). When normalized for this difference in muscle mass, resting seated blood flow was similar in young and old subjects (young, 115 +/- 28; old, 114 +/- 39 ml x g(-1) x min(-1)). During exercise, blood flow and vascular conductance were attenuated in the old whether expressed in absolute terms for a given absolute workload or more appropriately expressed as blood flow per unit muscle mass at a given relative exercise intensity (young, 1,523 +/- 329; old, 1,340 +/- 157 ml x kg(-1) x min(-1) at 40% WRmax). In contrast, aging did not affect forearm muscle mass or attenuate rest or exercise blood flow or vascular conductance in the arm. In conclusion, aging induces limb-specific alterations in exercise blood flow regulation. These alterations result in reductions in leg blood flow during exercise but do not impact forearm blood flow.
authors.affiliation: Dept. of Medicine, Physiology Division, 9500 Gilman Drive, Univ. of California, San Diego, La Jolla, CA 92093-0623, USA.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Donato
authors.forename: Abhimanyu
authors.initials: A
authors.lastname: Uberoi
authors.forename: D Walter
authors.initials: DW
authors.lastname: Wray
authors.forename: Steven
authors.initials: S
authors.lastname: Nishiyama
authors.forename: Lesley
authors.initials: L
authors.lastname: Lawrenson
authors.forename: Russell S
authors.initials: RS
authors.lastname: Richardson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001916:Brachial Artery / Q000000981:diagnostic imaging; D015444:Exercise / Q000502:physiology*; D005263:Femoral Artery / Q000000981:diagnostic imaging; D005542:Forearm / Q000098:blood supply*; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology*; D018608:Ultrasonography, Doppler; D014655:Vascular Resistance / Q000502:physiology