Arterial properties of the carotid and femoral artery in endurance-trained and paraplegic subjects

2000 ◽  
Vol 89 (5) ◽  
pp. 1956-1963 ◽  
Author(s):  
Arno Schmidt-Trucksäss ◽  
Andreas Schmid ◽  
Christian Brunner ◽  
Nicole Scherer ◽  
Guido Zäch ◽  
...  
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
Femoral Artery ◽  
Arterial Wall ◽  
Activity Level ◽  
Functional Adaptation ◽  
Local Blood Flow ◽  
Flow Changes ◽  
The Impact

In humans, the relationships of blood flow changes to structure, function, and shear rate of conducting arteries have not been thoroughly examined. Therefore, the purpose of this study was to investigate these parameters of the elastic-type, common carotid artery (CCA) and the muscular-type, common femoral artery (CFA) in long-term highly active and extremely inactive individuals, assuming that the impact of activity-induced blood flow changes on conduit arteries, if any, should be seen in these subjects. We examined 21 highly endurance-trained athletes (A), 10 paraplegic subjects (P), and 20 sedentary subjects (S) by means of noninvasive ultrasound. As a result, the CFA diameter and compliance were highest in A (9.7 ± 0.81 mm; 1.84 ± 0.54 mm2/kPa) and lowest in P (5.9 ± 0.7 mm; 0.54 ± 0.27 mm2/kPa) compared with S (8.3 ± 1.0 mm; 0.92 ± 0.48 mm2/kPa) with P < 0.01 among the groups. Both parameters correlated with each other ( r = 0.62; P < 0.01). Compared with A (378 ± 84 s−1; 37 ± 15 s−1) and S (356 ± 113 s−1; 36 ± 20 s−1), the peak and mean shear rates of the CFA were almost or more than doubled in P (588 ± 120 s−1; 89 ± 26 s−1). In the CCA, only the compliance and peak shear rate showed significant differences among the groups (A: 1.28 ± 0.47 mm2/kPa, 660 ± 138 s−1; S: 1.04 ± 0.27 mm2/kPa, 588 ± 109 s−1; P: 0.65 ± 0.22 mm2/kPa, 490 ± 149 s−1; P < 0.05). In conclusion, the results suggest a structural and functional adaptation in the CFA and a predominantly functional adaptation of the arterial wall properties to differences in the physical activity level and associated exercise-induced blood flow changes in the CCA. The results for humans confirm those from animal experiments. Similar shear rate values of S and P in the CFA support the hypothesis of constant shear stress regulation due to local blood flow changes in humans. On the other hand, the increased shear rate in the CFA in P indicates an at least partially nonphysiological response of the arterial wall in long-term chronic sympathectomy due to a change in local blood flow.

Dynamics of Arterial Remodeling in Response to a Sustained Step Change in Blood Flow Using a Constituent-Based Model

2007 ◽  
Author(s):  
Alkiviadis Tsamis ◽  
Nikos Stergiopulos
Keyword(s):  
Blood Flow ◽  
Arterial Wall ◽  
Wall Stress ◽  
Step Change ◽  
Local Blood Flow ◽  
Inner Radius ◽  
Flow Changes ◽  
Baseline Levels ◽  
Two Phases

The arterial wall undergoes substantial remodeling whenever the local blood flow changes for more than a few days [1]. An increase in flow causes an increase in inner radius, which occurs in two phases and tends to restore the baseline levels of intimal shear stress [2]. Firstly, an acute dilation of the artery occurs due to relaxation of vascular smooth muscle (VSM) cells [3]. Secondly, a long-term media reconstruction takes place, during which VSM cells migrate and proliferate circumferentially causing an increase in undeformed lumen. Moreover, arterial wall thickens to restore the altered wall stress [4].

scholarly journals Use of Physical Activity Monitoring Devices by Families in Rural Communities: Qualitative Approach (Preprint)

2018 ◽  
Author(s):  
Iryna Sharaievska ◽  
Rebecca A Battista ◽  
Jennifer Zwetsloot
Keyword(s):  
Physical Activity ◽  
Rural Communities ◽  
Family Members ◽  
Activity Level ◽  
Activity Tracking ◽  
Entire Family ◽  
Physical Activity Monitoring ◽  
Tracking Devices ◽  
The Impact

BACKGROUND Several studies support the impact of information communication technology–based interventions to promote physical activity among youth. However, little is known on how technology can be used by the entire family to encourage healthy behavior. Previous studies showed that children and youth rely and are dependent upon the decisions and values of their caregivers when it comes to having a healthy lifestyle. Thus, the exploration of behavior and attitudes of the entire family is needed. OBJECTIVE The study aimed to explore (1) perceptions of how the use of physical activity tracking devices (Fitbit Zip) by families in rural communities influence their patterns of participation in physical activity, (2) how attitudes toward physical activity change as a result of using physical activity tracking devices as a family, and (3) what factors influence participation in physical activity among families in rural communities. METHODS A total of 11 families with 1 to 3 children of different ages (7-13 years) took part in semistructured group interviews following 2 weeks of using physical activity tracking devices (Fitbit Zip) as a family. The participants were asked to discuss their experience using the Fitbit Zip as a family, the motivation to be physically active, the changes in their pattern of participation in those activities, the level of engagement by different family members, and the factors that affected their participation. All interviews were voice-recorded with the participants’ permission and later transcribed verbatim using pseudonyms. To analyze the data, the principal investigator (IS) used open, axial, and selective coding techniques. RESULTS A total of 3 themes and several subthemes appeared from the data. The families in rural communities reported no or minimal changes in physical activities as a result of using physical activity tracking devices (Fitbit Zip) because of a lack of interest or an already active lifestyle. However, the attitude toward physical activity was altered. The family members reported an increased awareness of their activity level, introduced more conversations about active and healthy lifestyles, and changed their view of physical activity to a more positive one. The participants described the changes they were able to make and the constraining factors that stopped them from making further changes in their lifestyle. CONCLUSIONS Technology might serve as a facilitator to participation in physical activity among families. Technology can motivate the change in attitude toward active recreation. As long-term changes in lifestyle require internal motivation, the change in the attitude might have a more long-lasting impact than the change in the immediate behavior. More longitudinal studies are needed to further explore long-term change in both behavior and attitude toward physical activity. Additional exploration of constraints to participation in physical activity among families is also an important area of exploration.

Empirical Analysis of Relationship-based User Reposting Behavior on Microblog Network

2015 ◽  
Vol 7 (3) ◽  
pp. 1-12
Author(s):  
Su-Meng Diao ◽  
Yun Liu ◽  
Qing-An Zeng
Keyword(s):  
Social Influence ◽  
Empirical Analysis ◽  
Power Law ◽  
Social Service ◽  
Large Scale ◽  
Activity Level ◽  
Information Propagation ◽  
Interval Time ◽  
The Impact

Microblogs have become a significant online social service for information propagation. Compared with other SNS, a microblog makes use of a flexible unidirectional subscription structure to encourage users to get information from others. In this paper, the authors performed relationship-based large-scale statistics and analyzed long-term reposting behavior. The total number of reposts from a certain followee with a bidirectional or unidirectional relationship is power-law, as well as a reposting interval time. Statistics suggest the curve of bidirectional friends decays slower with a smaller slope, which implies the interactions between bidirectional friends are more stable and intensive. Moreover, reposts from bidirectional friends take approximate 55 percentages, although bidirectional relationships comprise only 33 percent of relationships. Furthermore, the authors investigated the impact of following relationships and found that users focus more on social influence and activity level for unidirectional friends; however, for bidirectional friends, interactions and closeness are more crucial.

Sympathetic vasomotor control does not explain the change in femoral artery shear rate pattern during arm-crank exercise

2009 ◽  
Vol 296 (1) ◽  
pp. H180-H185 ◽  
Author(s):  
Dick H. J. Thijssen ◽  
Daniel J. Green ◽  
Sjoerd Steendijk ◽  
Maria T. E. Hopman
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
Flow Pattern ◽  
Femoral Artery ◽  
Peripheral Resistance ◽  
Retrograde Flow ◽  
Artery Blood Flow ◽  
Femoral Artery Blood Flow ◽  
Exercise Induced ◽  
Retrograde Shear

During lower limb exercise, blood flow through the resting upper limbs exhibits a change characterized by increased anterograde flow during systole, but also large increases in retrograde diastolic flow. One explanation for the retrograde flow is that increased sympathetic nervous system (SNS) tone and concomitant increased peripheral resistance generate a rebound during diastole. To examine whether the SNS contributes to retrograde flow patterns, we measured femoral artery blood flow during arm-crank exercise in 10 healthy men (31 ± 4 yr) and 10 spinal cord-injured (SCI) subjects who lack sympathetic innervation in the legs (33 ± 5 yr). Before, and every 5 min during 25-min arm-crank exercise at 50% maximal capacity, femoral artery blood flow and peak anterograde and retrograde shear rate were assessed using echo Doppler sonography. Femoral artery baseline blood flow was significantly lower in SCI compared with controls. Exercise increased femoral artery blood flow in both groups (ANOVA, P < 0.05), whereas leg vascular conductance did not change during exercise in either group. Mean shear rate was lower in SCI than in controls ( P < 0.05). Peak anterograde shear rate was higher in SCI than in controls ( P < 0.05), whereas peak retrograde shear rate did not differ between groups. Arm-crank exercise induced an increase in peak anterograde and retrograde shear rate in the femoral artery in controls and SCI subjects ( P < 0.05). This suggests that the SNS is not obligatory to change the flow pattern in inactive regions during exercise. Local mechanisms may play a role in the arm-crank exercise-induced changes in flow pattern in the femoral artery.

scholarly journals Solar rotational cycle in lightning activity in Japan during the 18–19th centuries

2018 ◽  
Vol 36 (2) ◽  
pp. 633-640 ◽  
Author(s):  
Hiroko Miyahara ◽  
Ryuho Kataoka ◽  
Takehiko Mikami ◽  
Masumi Zaiki ◽  
Junpei Hirano ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Rotation ◽  
Galactic Cosmic Rays ◽  
Activity Level ◽  
Lightning Activity ◽  
Activity Levels ◽  
Rotational Period ◽  
Solar Activity Level ◽  
The Impact

Abstract. Thunderstorm and cloud activities sometimes show a 27-day period, and this has long been studied to uncover a possible important link to solar rotation. Because the 27-day variations in the solar forcing parameters such as solar ultraviolet and galactic cosmic rays become more prominent when the solar activity is high, it is expected that the signal of the 27-day period in meteorological phenomena may wax and wane according to the changes in the solar activity level. In this study, we examine in detail the intensity variations in the signal of the 27-day solar rotational period in thunder and lightning activity from the 18th to the 19th centuries based on 150-year-long records found in old diaries kept in Japan and discuss their relation with the solar activity levels. Such long records enable us to examine the signals of solar rotation at both high and low solar activity levels. We found that the signal of the solar rotational period in the thunder and lightning activity increases as the solar activity increases. In this study, we also discuss the possibility of the impact of the long-term climatological conditions on the signals of the 27-day period in thunder/lightning activities. Keywords. Meteorology and atmospheric dynamics (lightning)

The Effect of Flow on Lysis of Plasma Clots in a Plasma Environment

2000 ◽  
Vol 83 (03) ◽  
pp. 469-474 ◽  
Author(s):  
Dingeman Rijken ◽  
Dmitry Sakharov
Keyword(s):  
Blood Flow ◽  
Shear Rate ◽  
High Concentration ◽  
Specific Lysis ◽  
Plasma Environment ◽  
Thrombolytic Agents ◽  
Flow Through ◽  
The Impact

SummaryFibrinolysis initially generates channels in an occluding thombus which results in blood flow through the thrombus. Since the impact of flow along the surface of a thrombus on thrombolysis has not been investigated in detail, we studied in vitro how such a flow affects lysis. Compacted and noncompacted plasma clots were used as model thrombi. With compacted clots, fibrin-specific lysis induced by alteplase in the outer plasma was accelerated about 2-fold by strong flow (arterial shear rate). Non-fibrin-specific lysis induced either by a high concentration of alteplase or by streptokinase was slow, was accompanied by rapid depletion of plasminogen in the outer plasma, and was only slightly accelerated by flow. With noncompacted clots, similar acceleration factors were documented, when mild flow (venous shear rate) was applied. Strong flow further accelerated fibrin-specific lysis, up to 10-fold as compared to lysis without flow, but paradoxically retarded non-fibrin-specific lysis. The data suggest that flow accelerates lysis by enhancing transport of plasminogen from the outer plasma to the surface of the clot. Both opposite effects of the strong flow were mediated by forceful intrusion of the outer plasma into the noncompacted clot due to flow irregularities. In the case of non-fibrin-specific lysis this resulted in the replacement of the plasminogen-containing milieu by plasminogen-depleted outer plasma in certain areas of the clot turning them into virtually unlysable fragments. This flow-enforced “plasminogen steal” may contribute to the relatively high percentage of incomplete thrombolysis (TIMI-2 grade flow) documented in a number of trials for non-fibrin-specific thrombolytic agents. In the case of fibrin-specific lysis, the effect of flow on the speed of fibrinolysis is always beneficial.

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