title: Alterations in the blood velocity profile influence the blood flow response during muscle contractions and relaxations.
abstract: The present study examined the influences of the muscle contraction (MCP) and relaxation (MRP) phases, as well as systole and diastole, on the blood velocity profile and flow in the conduit artery at different dynamic muscle contraction forces. Eight healthy volunteers performed one-legged dynamic knee-extensor exercise at work rates of 5, 10, 20, 30, and 40 W at 60 contractions per minute. The time- and space-averaged, amplitude-weighted, mean (V(mean)) and maximum (V(max)) blood flow velocities were continuously measured in the common femoral artery during the cardiosystolic (CSP) and cardiodiastolic (CDP) phases during MCP and MRP, respectively. The V(max)/V(mean) ratio was used as a flow profile index where a ratio of approximately (~) 1 indicates a "flat" velocity profile, and a ratio significantly greater than (>>) 1 indicates a "parabolic" velocity profile. At rest, a "steeper" parabolic velocity profile was found during the CDP (ratio: 1.75 +/- 0.06) than during the CSP (ratio: 1.31 +/- 0.02). During the MRP of exercise, the V(max)/V(mean) ratio shifted to be less steep (p < 0.05) than at rest during the CDP (ratio: 1.41-1.54) at 5, 10, 20, 30, and 40 W; whereas it was slightly higher (p < 0.05) at 30 and 40 W than at rest during the CSP (ratio: 1.43-1.46). During the MCP, the parabolic blood velocity profile was enhanced (p < 0.05) at higher contraction forces, 20 W during the CDP (ratio: 2.15-2.52) and 30 W during the CSP (ratio: 1.49-1.77), potentially because of a greater retrograde flow component. A higher blood flow furthermore appeared during the MRP compared to during the MCP, coinciding with a greater uniformity of the red blood cells moving at higher blood velocities during the MRP. Thus part of the difference in the magnitude of blood flow during the MRP vs. MCP may be due to the alterations of the blood velocity flow profile.
authors.affiliation: Department of Sports Medicine for Health Promotion, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan. DENTACMAC@aol.com
authors.forename: Takuya
authors.initials: T
authors.lastname: Osada
authors.forename: Göran
authors.initials: G
authors.lastname: Rådegran
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D015444:Exercise / Q000502:physiology; D005263:Femoral Artery / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D014465:Ultrasonics; D014463:Ultrasonography