Impact of repeated increases in shear stress via reactive hyperemia and handgrip exercise: no evidence of systematic changes in brachial artery FMD

2011 ◽  
Vol 300 (3) ◽  
pp. H1078-H1089 ◽  
Author(s):  
K. E. Pyke ◽  
F. Jazuli
Keyword(s):  
Shear Stress ◽  
Brachial Artery ◽  
Reactive Hyperemia ◽  
Area Under The Curve ◽  
Blood Velocity ◽  
Handgrip Exercise ◽  
Related Information ◽  
Versus Trial ◽  
The Impact ◽  
The Relationship

Reactive hyperemia (RH) creates an uncontrolled, transient increase in brachial artery (BA) shear stress (SS) for flow-mediated dilation (FMD) assessment. In contrast, handgrip exercise (HGEX) can create similar, sustained SS increases over repeated trials. The purpose of this study was to examine the impact of repeated SS elevation via RH or HGEX and the relationship between RH and HGEX %FMD. BA diameter and blood velocity were assessed with echo and Doppler ultrasound in 20 healthy subjects. Visit A consisted of four 6-min HGEX trials (HGEX trials 1–4) at the intensity required to achieve a shear rate (SR = mean blood velocity/BA diameter; an estimate of SS) of 65 s−1. Visit B consisted of four RH trials (RH trials 1–4). The RH SR area under the curve (AUC) was higher in trial 1 versus trial 3 and trial 4 ( P = 0.019 and 0.047). The HGEX mean SR was similar across trials (mean SR = 66.1 ± 5.8 s−1, P = 0.152). There were no differences in %FMD across trials or tests (RH trial 1: 6.9 ± 3.5%, trial 2: 6.9 ± 2.3%, trial 3: 7.1 ± 3.5%, and trial 4: 7.0 ± 2.8%; HGEX trial 1: 7.3 ± 3.6%, trial 2: 7.0 ± 3.6%, trial 3: 6.5 ± 3.5%, and trial 4: 6.8 ± 2.9%, P = 0.913). No relationship between subject's RH %FMD and HGEX %FMD was detected ( r2 = 0.12, P = 0.137). However, with response normalization, a relationship emerged (RH %FMD/SR AUC vs. HGEX %FMD/mean SR, r2 = 0.44, P = 0.002). In conclusion, with repeat trials, there were no systematic changes in RH or HGEX %FMD. The relationship between normalized RH and HGEX %FMD suggests that endothelial responses to different SS profiles provide related information regarding endothelial function.

The impact of acute mental stress on brachial artery flow-mediated dilation differs when shear stress is elevated by reactive hyperemia versus handgrip exercise

2013 ◽  
Vol 38 (5) ◽  
pp. 498-506 ◽  
Author(s):  
Ingrid C. Szijgyarto ◽  
Trevor J. King ◽  
Jennifer Ku ◽  
Veronica J. Poitras ◽  
Brendon J. Gurd ◽  
...  
Keyword(s):  
Shear Stress ◽  
Brachial Artery ◽  
Mental Stress ◽  
Stress Reactivity ◽  
Reactive Hyperemia ◽  
Blood Velocity ◽  
Flow Mediated Dilation ◽  
Handgrip Exercise ◽  
Stress Task ◽  
The Impact

Acute mental stress can impair brachial artery (BA) flow-mediated dilation (FMD) in response to reactive hyperemia (RH) induced increases in shear stress. Handgrip exercise (HGEX) is emerging as a useful tool to increase shear stress for FMD assessment; however, the impact of acute mental stress on HGEX-FMD is unknown. The purpose of this study was to determine whether acute mental stress attenuates RH- and HGEX-induced BA-FMD to a similar extent. In 2 counterbalanced visits, 16 healthy males (19–27 years of age) performed RH-FMD or HGEX-FMD tests after a counting control task (prestress FMD) and a speech and arithmetic stress task (poststress FMD). BA diameter and mean blood velocity were assessed with echo and Doppler ultrasound, respectively. Shear stress was estimated using shear rate (SR = BA blood velocity/BA diameter). Mean arterial pressure (MAP), heart rate (HR), and salivary cortisol were used to assess stress reactivity. Results are expressed as mean ± SE. The stress task elevated MAP (Δ24.0 ± 2.6 mm Hg) and HR (Δ15.5 ± 1.9 beats·min–1), but not cortisol (prestress vs. poststress: 4.4 ± 0.7 nmol·L–1 vs. 4.7 ± 0.7 nmol·L–1; p = 0.625). There was no difference between the pre- and poststress SR stimulus for RH (p = 0.115) or HGEX (p = 0.664). RH-FMD decreased from 5.2% ± 0.6% prestress to 4.1% ± 0.5% poststress (p = 0.071); however, stress did not attenuate HGEX-FMD (prestress vs. poststress: 4.1% ± 0.6% vs. 5.3% ± 0.6%; p = 0.154). The pre- to poststress change in FMD was significantly different in the RH-FMD vs. the HGEX-FMD test (–1.1% ± 0.6% vs. +1.1% ± 0.8%; p = 0.015). In conclusion, acute mental stress appears to have a disparate impact on FMD stimulated by RH vs. HGEX induced increases in shear stress.

Impact of controlling shear rate on flow-mediated dilation responses in the brachial artery of humans

2004 ◽  
Vol 97 (2) ◽  
pp. 499-508 ◽  
Author(s):  
Kyra E. Pyke ◽  
Erin M. Dwyer ◽  
Michael E. Tschakovsky
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Brachial Artery ◽  
Reactive Hyperemia ◽  
Flow Mediated Dilation ◽  
Response Peak ◽  
Dependent Flow ◽  
Flow Mediated Vasodilation ◽  
The Impact ◽  
Forearm Occlusion

The reactive hyperemia test (RHtest) evokes a transient increase in shear stress as a stimulus for endothelial-dependent flow-mediated vasodilation (EDFMD). We developed a noninvasive method to create controlled elevations in brachial artery (BA) shear rate (SR, estimate of shear stress), controlled hyperemia test (CHtest), and assessed the impact of this vs. the RHtest approach on EDFMD. Eight healthy subjects participated in two trials of each test on 3 separate days. For the CHtest, SR was step increased from 8 to 50 s−1, created by controlled release of BA compression during forearm heating. For the RHtest, transient increases in SR were achieved after 5 min of forearm occlusion. BA diameter and blood flow velocity (ultrasound) were measured upstream of compression and occlusion sites. Both tests elicited significant dilation (RHtest: 6.33 ± 3.12%; CHtest: 3.00 ± 1.05%). The CHtest resulted in 1) reduced between-subject SR and EDFMD variability vs. the RHtest [SR coefficient of variation (CV): 4.9% vs. 36.6%; EDFMD CV: 36.16% vs. 51.80%] and 2) virtual elimination of the impact of BA diameter on the peak EDFMD response (peak EDFMD vs. baseline diameter for RHtest, r2 = 0.64, P < 0.01, vs. CHtest, r2 = 0.14, P < 0.01). Normalization of the RHtest EDFMD response to the magnitude of the SR stimulus eliminated test differences in between-subject response variability. Reductions in trial-to-trial and day-to-day SR variability with the CHtest did not reduce EDFMD variability. Between-subject SR variability contributes to EDFMD variability with the RHtest. SR controls with the CHtest or RHtest response normalization are essential for examining EDFMD between groups differing in baseline arterial diameter.

scholarly journals Impaired handgrip exercise-induced brachial artery flow-mediated dilation in young obese males

2016 ◽  
Vol 41 (5) ◽  
pp. 528-537 ◽  
Author(s):  
David J. Slattery ◽  
Troy J.R. Stuckless ◽  
Trevor J. King ◽  
Kyra E. Pyke
Keyword(s):  
Shear Stress ◽  
Brachial Artery ◽  
Reactive Hyperemia ◽  
Obese Group ◽  
Stress Profile ◽  
Flow Mediated Dilation ◽  
Handgrip Exercise ◽  
Brachial Artery Diameter ◽  
Shear Stress Profile ◽  
Forearm Occlusion

Flow mediated dilation (FMD) stimulated by different shear stress stimulus profiles may recruit distinct transduction mechanisms, and provide distinct information regarding endothelial function. The purpose of this study was to determine whether obesity influences brachial artery FMD differently depending on the shear stress profile used for FMD assessment. The FMD response to a brief, intermediate, and sustained shear stress profile was assessed in obese (n = 9) and lean (n = 19) young men as follows: brief stimulus, standard reactive hyperemia (RH) following a 5 min forearm occlusion (5 min RH); intermediate stimulus, RH following a 15 min forearm occlusion (15 min RH); sustained stimulus, 10 min of handgrip exercise (HGEX). Brachial artery diameter and mean shear stress were assessed using echo and Doppler ultrasound, respectively, during each FMD test. There was no group difference in HGEX shear stress (p = 0.390); however, the obese group had a lower HGEX-FMD (5.2 ± 3.0% versus 11.5 ± 4.4%, p < 0.001). There was no group difference in 5 min RH-FMD (p = 0.466) or 15 min RH-FMD (p = 0.181); however, the shear stress stimulus was larger in the obese group. After normalization to the stimulus the 15 min RH-FMD (p = 0.002), but not the 5 min RH-FMD (p = 0.118) was lower in the obese group. These data suggest that obesity may have a more pronounced impact on the endothelium’s ability to respond to prolonged increases in shear stress.

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

2015 ◽  
Vol 119 (8) ◽  
pp. 858-864 ◽  
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.

The impact of baseline artery diameter on flow-mediated vasodilation: a comparison of brachial and radial artery responses to matched levels of shear stress

2011 ◽  
Vol 301 (4) ◽  
pp. H1667-H1677 ◽  
Author(s):  
F. Jazuli ◽  
K. E. Pyke
Keyword(s):  
Shear Stress ◽  
Reactive Hyperemia ◽  
Regression Line ◽  
Vessel Diameter ◽  
Blood Velocity ◽  
Diameter Estimate ◽  
Within Subjects ◽  
Flow Mediated Vasodilation ◽  
The Impact ◽  
Male Subjects

An inverse relationship between baseline artery diameter (BAD) and flow-mediated vasodilation (FMD) has been identified using reactive hyperemia (RH) to create a shear stress (SS) stimulus in human conduit arteries. However, RH creates a SS stimulus that is inversely related to BAD. The purpose of this study was to compare FMD in response to matched levels of SS in two differently sized upper limb arteries [brachial (BA) and radial (RA) artery]. With the use of exercise, three distinct, shear rate (SR) stimuli were created (SR = blood velocity/vessel diameter; estimate of SS) in the RA and BA. Artery diameter and mean blood velocity were assessed with echo and Doppler ultrasound in 15 healthy male subjects (19–25 yr). Data are means ± SE. Subjects performed 6 min of adductor pollicis and handgrip exercise to increase SR in the RA and BA, respectively. Exercise intensity was modulated to achieve uniformity in SR between arteries. The three distinct SR levels were as follows: steady-state exercise 39.8 ± 0.6, 57.3 ± 0.7, and 72.4 ± 1.2 s−1 ( P < 0.001). %FMD and AbsFMD (mm) at the end of exercise were greater in the RA vs. the BA at each shear level [at the highest level: RA = 15.7 ± 1.5%, BA = 5.4 ± 0.8% ( P < 0.001)]. The mean slope of the within-subject SR-%FMD regression line was greater in the RA (RA = 0.33 ± 0.04, BA = 0.13 ± 0.02, P < 0.001), and a strong within-subjects relationship between %FMD and SR was observed in both arteries (RA: r2 = 0.92 ± 0.02; BA: r2 = 0.90 ± 0.03). Within the RA, there was a significant relationship between baseline diameter and %FMD; however, this relationship was not present in the BA (RA: r2 = 0.76, P < 0.001; BA: r2 = 0.03, P = 0.541). These findings suggest that the response to SS is not uniform across differently sized vessels, which is in agreement with previous studies.

Acute psychological and physical stress transiently enhances brachial artery flow-mediated dilation stimulated by exercise-induced increases in shear stress

2014 ◽  
Vol 39 (8) ◽  
pp. 927-936 ◽  
Author(s):  
Ingrid C. Szijgyarto ◽  
Veronica J. Poitras ◽  
Brendon J. Gurd ◽  
Kyra E. Pyke
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Brachial Artery ◽  
Stress Responses ◽  
Physical Stress ◽  
Flow Mediated Dilation ◽  
Trial Effect ◽  
Condition Effect ◽  
Exercise Induced ◽  
The Impact

Exercise elevates conduit artery shear stress and stimulates flow-mediated dilation (FMD). However, little is known regarding the impact of acute psychological and physical stress on this response. The purpose of this study was to examine the impact of the Trier Social Stress Test (TSST (speech and arithmetic tasks)) and a cold pressor test (CPT) with and without social evaluation (SE) on exercise-induced brachial artery FMD (EX-FMD). A total of 59 healthy male subjects were randomly assigned to 1 of 3 conditions: TSST, CPT, or CPT with SE. During 6 min of handgrip exercise, brachial artery EX-FMD was assessed before and 15 and 35 min poststress with echo and Doppler ultrasound. Shear stress was estimated as shear rate, calculated as brachial artery mean blood velocity/brachial artery diameter. Results are means ± SD. All conditions elicited significant physiological stress responses. Salivary cortisol increased from 4.6 ± 2.4 nmol/L to 10.0 ± 5.0 nmol/L (p < 0.001; condition effect: p = 0.292). Mean arterial pressure increased from 98.6 ± 12.1 mm Hg to 131.9 ± 18.7 mm Hg (p < 0.001; condition effect: p = 0.664). Exercise shear rate did not differ between conditions (p = 0.592), although it was modestly lower poststress (prestress: 72.3 ± 4.5 s−1; 15 min poststress: 70.8 ± 5.4 s−1; 35 min poststress: 70.6 ± 6.1 s−1; trial effect: p = 0.011). EX-FMD increased from prestress to 15 min poststress in all conditions (prestress: 6.2% ± 2.8%; 15 min poststress: 7.9% ± 3.2%; 35 min poststress: 6.6% ± 2.9%; trial effect: p < 0.001; condition effect: p = 0.611). In conclusion, all conditions elicited similar stress responses that transiently enhanced EX-FMD. This response may help to support muscle perfusion during stress.

scholarly journals Surface Roughness Tuning at Sub-Nanometer Level by Considering the Normal Stress Field in Magnetorheological Finishing

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 997
Author(s):  
Xiaoyuan Li ◽  
Qikai Li ◽  
Zuoyan Ye ◽  
Yunfei Zhang ◽  
Minheng Ye ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Shear Stress ◽  
Stress Field ◽  
Normal Stress ◽  
Fused Silica ◽  
Fine Tuning ◽  
Magnetorheological Finishing ◽  
Optical Surfaces ◽  
The Impact ◽  
The Relationship

Although magnetorheological finishing (MRF) is being widely utilized to achieve ultra-smooth optical surfaces, the mechanisms for obtaining such extremely low roughness after the MRF process are not fully understood, especially the impact of finishing stresses. Herein we carefully investigated the relationship between the stresses and surface roughness. Normal stress shows stronger impacts on the surface roughness of fused silica (FS) when compared with the shear stress. In addition, normal stress in the polishing zone was found to be sensitive to the immersion depth of the magnetorheological (MR) fluid. Based on the above, a fine tuning of surface roughness (RMS: 0.22 nm) was obtained. This work fills gaps in understanding about the stresses that influence surface roughness during MRF.

Salesperson-Sales Manager Social Interaction And Communication Quality: The Impact On Salesperson Cooperation

2014 ◽  
Vol 30 (2) ◽  
pp. 607
Author(s):  
Stacey Schetzsle ◽  
Duleep Delpechitre
Keyword(s):  
Social Interaction ◽  
Sales Manager ◽  
Social Setting ◽  
Sales Managers ◽  
Communication Quality ◽  
Work Related ◽  
Related Information ◽  
The Impact ◽  
The Relationship ◽  
Willingness To Cooperate

To get the highest level of performance out of salespeople, companies are searching internally to identify factors that lead to salesperson cooperation. Sales managers create a normative culture that engages the salesperson, which is demonstrated through communication and social interaction. A salesperson who feels connected to the organization is more likely to exert additional effort, such as cooperating with the manager to meet sales objections. The purpose of this paper is to investigate the impact of the salespersons social interaction and communication quality with their sales manager on their willingness to cooperate with the manager. The results show that when salespeople interact with their manager in a social setting and discuss non-work related information, salespeople become more willing to cooperate with their manager. Sales managers communication quality was not found to have a significant relationship between the salespersons willingness to cooperate with the sales manager. Instead, we find that sales managers communication quality with the salesperson significantly moderates the relationship between salespersons social interaction with the sales manager and salespersons willingness to cooperate with the sales manager.

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