Repeated increases in blood flow, independent of exercise, enhance conduit artery vasodilator function in humans

This study aimed to determine the importance of repeated increases in blood flow to conduit artery adaptation, using an exercise-independent repeated episodic stimulus. Recent studies suggest that exercise training improves vasodilator function of conduit arteries via shear stress-mediated mechanisms. However, exercise is a complex stimulus that may induce shear-independent adaptations. Nine healthy men immersed their forearms in water at 42°C for three 30-min sessions/wk across 8 wk. During each session, a pneumatic pressure cuff was inflated around one forearm to unilaterally modulate heating-induced increases in shear. Forearm heating was associated with an increase in brachial artery blood flow ( P < 0.001) and shear rate ( P < 0.001) in the uncuffed forearm; this response was attenuated in the cuffed limb ( P < 0.005). Repeated episodic exposure to bilateral heating induced an increase in endothelium-dependent vasodilation in response to 5-min ischemic ( P < 0.05) and ischemic handgrip exercise ( P < 0.005) stimuli in the uncuffed forearm, whereas the 8-wk heating intervention did not influence dilation to either stimulus in the cuffed limb. Endothelium-independent glyceryl trinitrate responses were not altered in either limb. Repeated heating increases blood flow to levels that enhance endothelium-mediated vasodilator function in humans. These findings reinforce the importance of the direct impacts of shear stress on the vascular endothelium in humans.

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Measuring peripheral resistance and conduit arterial structure in humans using Doppler ultrasound

Journal of Applied Physiology ◽

10.1152/japplphysiol.01047.2004 ◽

2005 ◽

Vol 98 (6) ◽

pp. 2311-2315 ◽

Cited By ~ 66

Author(s):

Louise H. Naylor ◽

Cara J. Weisbrod ◽

Gerry O'Driscoll ◽

Daniel J. Green

Keyword(s):

Blood Flow ◽

Brachial Artery ◽

Peripheral Resistance ◽

Artery Blood Flow ◽

Brachial Artery Diameter ◽

Resistance Vessel ◽

Conduit Artery ◽

Significant Difference ◽

Vessel Structure

The purpose of this study was to establish valid indexes of conduit and resistance vessel structure in humans by using edge detection and wall tracking of high-resolution B-mode arterial ultrasound images, combined with synchronized Doppler waveform envelope analysis, to calculate conduit artery blood flow and diameter continuously across the cardiac cycle. Nine subjects aged 36.7 (9.2) yr underwent, on separate days, assessment of brachial artery blood flow and diameter response to 5-, 10-, and 15-min periods of forearm ischemia in the presence and absence of combined sublingual glyceryl trinitrate (GTN) administration. Two further sessions examined responses to ischemic exercise, one in combination with GTN. The peak brachial artery diameter was observed in response to the combination of ischemic exercise and GTN; a significant difference existed between resting brachial artery diameter and peak brachial artery diameter, indicating that resting diameter may be a poor measure of conduit vessel structure in vivo. Peak brachial artery flow was also observed in response to a combination of forearm ischemia exercise and GTN administration, the response being greater than that induced by periods of ischemia, GTN, or ischemic exercise alone. These data indicate that noninvasive indexes of conduit and resistance vessel structure can be simultaneously determined in vivo in response to a single, brief, stimulus and that caution should be applied in using resting arterial diameter as a surrogate measure of conduit artery structure in vivo.

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Effects of Chemotherapy and Radiation Exposure on Brachial Artery Blood Flow during Dynamic Handgrip Exercise

The FASEB Journal ◽

10.1096/fasebj.29.1_supplement.675.24 ◽

2015 ◽

Vol 29 (S1) ◽

Author(s):

Kaylin Didier ◽

Landon Reiter ◽

Austin Ederer ◽

Jacob Caldwell ◽

Carl Ade

Keyword(s):

Blood Flow ◽

Radiation Exposure ◽

Brachial Artery ◽

Artery Blood Flow ◽

Handgrip Exercise

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Exercise-induced brachial artery blood flow and vascular function is impaired in systemic sclerosis

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00547.2016 ◽

2016 ◽

Vol 311 (6) ◽

pp. H1375-H1381 ◽

Cited By ~ 1

Author(s):

Daniel R. Machin ◽

Heather L. Clifton ◽

Ryan S. Garten ◽

Jayson R. Gifford ◽

Russell S. Richardson ◽

...

Keyword(s):

Oxidative Stress ◽

Blood Flow ◽

Systemic Sclerosis ◽

Brachial Artery ◽

Vascular Function ◽

Vascular Dysfunction ◽

Artery Blood Flow ◽

Handgrip Exercise ◽

Brachial Artery Diameter ◽

Exercise Induced

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by debilitating fibrosis and vascular dysfunction; however, little is known about the circulatory response to exercise in this population. Therefore, we examined the peripheral hemodynamic and vasodilatory responses to handgrip exercise in 10 patients with SSc (61 ± 4 yr) and 15 age-matched healthy controls (56 ± 5 yr). Brachial artery diameter, blood flow, and mean arterial pressure (MAP) were determined at rest and during progressive static-intermittent handgrip exercise. Patients with SSc and controls were similar in body stature, handgrip strength, and MAP; however, brachial artery blood flow at rest was nearly twofold lower in patients with SSc compared with controls (22 ± 4 vs. 42 ± 5 ml/min, respectively; P < 0.05). Additionally, SSc patients had an ∼18% smaller brachial artery lumen diameter with an ∼28% thicker arterial wall at rest ( P < 0.05). Although, during handgrip exercise, there were no differences in MAP between the groups, exercise-induced hyperemia and therefore vascular conductance were ∼35% lower at all exercise workloads in patients with SSc ( P < 0.05). Brachial artery vasodilation, as assessed by the relationship between Δbrachial artery diameter and Δshear rate, was significantly attenuated in the patients with SSc ( P < 0.05). Finally, vascular dysfunction in the patients with SSc was accompanied by elevated blood markers of oxidative stress and attenuated endogenous antioxidant activity ( P < 0.05). Together, these findings reveal attenuated exercise-induced brachial artery blood flow and conduit arterial vasodilatory dysfunction during handgrip exercise in SSc and suggest that elevated oxidative stress may play a role.

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Seven days of aerobic exercise training improves conduit artery blood flow following glucose ingestion in patients with type 2 diabetes

Journal of Applied Physiology ◽

10.1152/japplphysiol.00489.2011 ◽

2011 ◽

Vol 111 (3) ◽

pp. 657-664 ◽

Cited By ~ 24

Author(s):

Catherine R. Mikus ◽

Seth T. Fairfax ◽

Jessica L. Libla ◽

Leryn J. Boyle ◽

Lauro C. Vianna ◽

...

Keyword(s):

Type 2 Diabetes ◽

Blood Flow ◽

Insulin Sensitivity ◽

Exercise Training ◽

Aerobic Exercise ◽

Aerobic Exercise Training ◽

Artery Blood Flow ◽

Conduit Artery ◽

Glucose Ingestion

The vasodilatory effects of insulin account for up to 40% of insulin-mediated glucose disposal; however, insulin-stimulated vasodilation is impaired in individuals with type 2 diabetes, limiting perfusion and delivery of glucose and insulin to target tissues. To determine whether exercise training improves conduit artery blood flow following glucose ingestion, a stimulus for increasing circulating insulin, we assessed femoral blood flow (FBF; Doppler ultrasound) during an oral glucose tolerance test (OGTT; 75 g glucose) in 11 overweight or obese (body mass index, 34 ± 1 kg/m2), sedentary (peak oxygen consumption, 23 ± 1 ml·kg−1·min−1) individuals (53 ± 2 yr) with non-insulin-dependent type 2 diabetes (HbA1c, 6.63 ± 0.18%) before and after 7 days of supervised treadmill and cycling exercise (60 min/day, 60–75% heart rate reserve). Fasting glucose, insulin, and FBF were not significantly different after 7 days of exercise, nor were glucose or insulin responses to the OGTT. However, estimates of whole body insulin sensitivity (Matsuda insulin sensitivity index) increased ( P < 0.05). Before exercise training, FBF did not change significantly during the OGTT (1 ± 7, −7 ± 5, 0 ± 6, and 0 ± 5% of fasting FBF at 75, 90, 105, and 120 min, respectively). In contrast, after exercise training, FBF increased by 33 ± 9, 39 ± 14, 34 ± 7, and 48 ± 18% above fasting levels at 75, 90, 105, and 120 min, respectively ( P < 0.05 vs. corresponding preexercise time points). Additionally, postprandial glucose responses to a standardized breakfast meal consumed under “free-living” conditions decreased during the final 3 days of exercise ( P < 0.05). In conclusion, 7 days of aerobic exercise training improves conduit artery blood flow during an OGTT in individuals with type 2 diabetes.

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Effects of iodinated contrast media on common carotid and brachial artery blood flow and wall shear stress

European Radiology ◽

10.1007/s00330-006-0280-8 ◽

2006 ◽

Vol 16 (12) ◽

pp. 2721-2727 ◽

Cited By ~ 3

Author(s):

C. Irace ◽

S. Tamburini ◽

B. Bertucci ◽

M. S. De Franceschi ◽

A. Gnasso

Keyword(s):

Blood Flow ◽

Shear Stress ◽

Wall Shear Stress ◽

Contrast Media ◽

Brachial Artery ◽

Iodinated Contrast Media ◽

Artery Blood Flow ◽

Iodinated Contrast ◽

Wall Shear

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Prolonged sitting-induced leg endothelial dysfunction is prevented by fidgeting

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00297.2016 ◽

2016 ◽

Vol 311 (1) ◽

pp. H177-H182 ◽

Cited By ~ 56

Author(s):

Takuma Morishima ◽

Robert M. Restaino ◽

Lauren K. Walsh ◽

Jill A. Kanaley ◽

Paul J. Fadel ◽

...

Keyword(s):

Blood Flow ◽

Shear Stress ◽

Shear Rate ◽

Endothelial Dysfunction ◽

Endothelial Function ◽

Popliteal Artery ◽

Artery Blood Flow ◽

Pronounced Increase ◽

Prolonged Sitting ◽

Leg Movement

Prolonged sitting impairs endothelial function in the leg vasculature, and this impairment is thought to be largely mediated by a sustained reduction in blood flow-induced shear stress. Indeed, preventing the marked reduction of shear stress during sitting with local heating abolishes the impairment in popliteal artery endothelial function. Herein, we tested the hypothesis that sitting-induced reductions in shear stress and ensuing endothelial dysfunction would be prevented by periodic leg movement, or “fidgeting.” In 11 young, healthy subjects, bilateral measurements of popliteal artery flow-mediated dilation (FMD) were performed before and after a 3-h sitting period during which one leg was subjected to intermittent fidgeting (1 min on/4 min off) while the contralateral leg remained still throughout and served as an internal control. Fidgeting produced a pronounced increase in popliteal artery blood flow and shear rate (prefidgeting, 33.7 ± 2.6 s−1 to immediately postfidgeting, 222.7 ± 28.3 s−1; mean ± SE; P < 0.001) that tapered off during the following 60 s. Fidgeting did not alter popliteal artery blood flow and shear rate of the contralateral leg, which was subjected to a reduction in blood flow and shear rate throughout the sitting period (presit, 71.7 ± 8.0 s−1 to 3-h sit, 20.2 ± 2.9 s−1; P < 0.001). Popliteal artery FMD was impaired after 3 h of sitting in the control leg (presit, 4.5 ± 0.3% to postsit: 1.6 ± 1.1%; P = 0.039) but improved in the fidgeting leg (presit, 3.7 ± 0.6% to postsit, 6.6 ± 1.2%; P = 0.014). Collectively, the present study provides evidence that prolonged sitting-induced leg endothelial dysfunction is preventable with small amounts of leg movement while sitting, likely through the intermittent increases in vascular shear stress.

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Rapid vasodilation within contracted skeletal muscle in humans: new insight from concurrent use of diffuse correlation spectroscopy and Doppler ultrasound

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00761.2020 ◽

2020 ◽

Author(s):

Masashi Ichinose ◽

Mikie Nakabayashi ◽

Yumie Ono

Keyword(s):

Skeletal Muscle ◽

Blood Flow ◽

Doppler Ultrasound ◽

Muscle Contractions ◽

Correlation Spectroscopy ◽

Flow Index ◽

Single Muscle ◽

Artery Blood Flow ◽

Diffuse Correlation Spectroscopy ◽

Conduit Artery

Previous studies showed that conduit artery blood flow rapidly increases after even a brief contraction of muscles within the dependent limb. Whether this rapid hyperemia occurs within contracted skeletal muscle in humans has yet to be confirmed, however. We therefore used diffuse correlation spectroscopy (DCS) to characterize the rapid hyperemia and vasodilatory responses within the muscle microvasculature induced by single muscle contractions in humans. Twenty-five healthy male volunteers performed single 1-s isometric handgrips at 20%, 40%, 60% and 80% of maximum voluntary contraction (MVC). DCS probes were placed on the flexor digitorum superficialis muscle, and a skeletal muscle blood flow index (SMBFI) was derived continuously. At the same time, brachial artery blood flow (BABF) responses were measured using Doppler ultrasound. Single muscle contractions evoked rapid, monophasic increases in both SMBFI and BABF that occurred within 3 s after release of contraction. The initial and peak responses increased with increases in contraction intensity and were greater for BABF than for SMBFI at all intensities. BABF reached its peak within 5 to 8 s after the end of contraction. The SMBFI continued to increase after the BABF passed its peak and was decreasing toward the resting level and peaked about 10 to 15 s after completion of the contraction. We conclude that single muscle contractions induce rapid, intensity-dependent hyperemia within the contracted skeletal muscle microvasculature. Moreover, the characteristics of the rapid hyperemia and vasodilatory responses of skeletal muscle microvessels differ from that simultaneously evaluated in the upstream conduit artery.

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Opposing effects of shear-mediated dilation and myogenic constriction on artery diameter in response to handgrip exercise in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.01086.2014 ◽

2015 ◽

Vol 119 (8) ◽

pp. 858-864 ◽

Cited By ~ 12

Author(s):

Ceri L. Atkinson ◽

Howard H. Carter ◽

Louise H. Naylor ◽

Ellen A. Dawson ◽

Petra Marusic ◽

...

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Shear Stress ◽

Shear Rate ◽

Arterial Pressure ◽

Brachial Artery ◽

Muscle Sympathetic Nerve Activity ◽

Handgrip Exercise ◽

Brachial Artery Diameter ◽

The Impact

While the impact of changes in blood flow and shear stress on artery function are well documented, the acute effects of increases in arterial pressure are less well described in humans. The aim of this study was to assess the effect of 30 min of elevated blood pressure, in the absence of changes in shear stress or sympathetic nervous system (SNS) activation, on conduit artery diameter. Ten healthy male subjects undertook three sessions of 30 min unilateral handgrip exercise at 5, 10, and 15% of maximal voluntary contractile (MVC) strength. Brachial artery shear rate and blood flow profiles were measured simultaneously during exercise in the active and contralateral resting arms. Bilateral brachial artery diameter was simultaneously assessed before and immediately postexercise. In a second experiment, six subjects repeated the 15% MVC condition while continuous vascular measurements were collected during muscle sympathetic nerve activity (MSNA) assessment using peroneal microneurography. We found that unilateral handgrip exercise at 5, 10, and 15% MVC strength induced stepwise elevations in blood pressure ( P < 0.01, Δmean arterial pressure: 7.06 ± 2.44, 8.50 ± 2.80, and 18.35 ± 3.52 mmHg, P < 0.01). Whereas stepwise increases were evident in shear rate in the exercising arm ( P < 0.001), no changes were apparent in the nonexercising limb ( P = 0.42). Brachial artery diameter increased in the exercising arm ( P = 0.02), but significantly decreased in the nonexercising arm ( P = 0.03). At 15% MVC, changes in diameter were significantly different between arms (interaction effect: P = 0.01), whereas this level of exertion produced no significant changes in MSNA. We conclude that acute increases in transmural pressure, independent of shear rate and changes in SNS activation, reduce arterial caliber in normotensive humans in vivo. These changes in diameter were mitigated by exercise-induced elevations in shear rate in the active limb.

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