Impact of inactivity and exercise on the vasculature in humans

The effects of inactivity and exercise training on established and novel cardiovascular risk factors are relatively modest and do not account for the impact of inactivity and exercise on vascular risk. We examine evidence that inactivity and exercise have direct effects on both vasculature function and structure in humans. Physical deconditioning is associated with enhanced vasoconstrictor tone and has profound and rapid effects on arterial remodelling in both large and smaller arteries. Evidence for an effect of deconditioning on vasodilator function is less consistent. Studies of the impact of exercise training suggest that both functional and structural remodelling adaptations occur and that the magnitude and time-course of these changes depends upon training duration and intensity and the vessel beds involved. Inactivity and exercise have direct “vascular deconditioning and conditioning” effects which likely modify cardiovascular risk

Alterations in the blood velocity profile influence the blood flow response during muscle contractions and relaxations

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 (similar to) 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 = 20W during the CDP (ratio: 2.15-2.52) and >= 30W 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

Alterations in the rheological artery during rhythmic thigh flow profile in conduit femoral muscle contractions in humans

The present study examined the rheological blood velocity profile in the conduit femoral artery during rhythmic muscle contractions at different muscle 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 in the common femoral artery were measured during the cardiosystolic phase (CSP) and cardiodiastolic phase (CDP) by the Doppler ultrasound technique. The V-max /V-mean ratio was used as a flow profile index, in which a ratio of similar to 1 indicates a m m "flat velocity flow profile" and a ratio significantly > 1 indicates a "parabolic velocity flow profile ' " At rest, the V-max / V-mean ratio was similar to 1.3 and similar to 1.8 during the CSP and CDP, respectively. The V-max/V-mean ratio was higher (p < 0.01) during the CDP than during the CSP, both at rest and at all work rates. The V-max/V-mean ratio during the CSP was higher Max (p < 0.01) at 30 and 40 W compared to at rest. The V-max/V-mean ratio during the CDP was lower (p < 0.05) at 5 and 10 W compared to at rest. There was a positive linear correlation between blood flow and incremental work rates during both the CSP and CDP, respectively. Thus under resting conditions, the findings indicate a "steeper" parabolic velocity profile during the CDP than during the CSR The velocity profile during the CDP furthermore shifts to being less "steep" during rhythmic muscle contractions at lower intensities, but to being reelevated and normalized as at rest during higher intensities. The "steepness" of the parabolic velocity profile observed during the CSP at rest increased during muscle contraction at higher intensities. In conclusion, the blood velocity in the common femoral artery is parabolic both at rest and during exercise for both the CSP and CDP, indicating the persistence of laminar flow. The occurrence of any temporary slight disturbance or turbulence in the flow at the sight of measurement in the common femoral artery does consequently not induce a persisting "disturbed" and fully flat "plug-like" velocity profile. Instead, the "steepness" of the parabolic velocity profile is only slightly modified, whereby blood flow is not impaired. Thus the blood velocity profile, besides being influenced by the muscle contraction-relaxation induced mechanical "impedance," seems also to be modulated by the cardiac- and blood pressure-phases, consequently influencing the exercise blood flow response