Comparison of arterial wall mechanics using ring and cylindrical segments

1983 ◽  
Vol 244 (2) ◽  
pp. H298-H303 ◽  
Author(s):  
R. H. Cox
Keyword(s):  
Arterial Wall ◽  
Muscle Length ◽  
Stress And Strain ◽  
Active Force ◽  
Cross Sectional ◽  
Iliac Arteries ◽  
Force Development ◽  
Arterial Wall Mechanics ◽  
Length Data ◽  
Passive Mechanics

Thin rings and intact cylindrical segments of canine carotid and iliac arteries were used to determine wall mechanics. Measurements of force and length were obtained from the ring segments, whereas measurements of pressure and diameter were obtained from the cylindrical segments under conditions of active (147 mM K+) and passive smooth muscle (Ca2+ free and 2 mM ethyleneglycolbis (beta-aminoethylether)-N,N'-tetraacetic acid). These measurements were normalized to values of segment stress and strain. Under passive conditions stress-strain relations for the rings appeared to be stiffer than those obtained using cylindrical segments. Pressure-diameter curves computed using force-length data from the rings were shifted to higher values of diameter compared with values from the intact segments at all pressure levels. Passive mechanics derived from measurements on ring segments yielded poor estimates of mechanics derived from intact segments. Despite this finding, values of active force development from the two sample geometries were similar. No statistically significant differences were found in values of maximum force development expressed in terms of sample cross-sectional area. Some differences in values of active force development at low values of muscle length were found. The latter were probably related to the differences in passive mechanics and the procedure used to normalize muscle length. Reasonable values of active force development can be obtained from ring segments.

Arterial wall properties and dietary atherosclerosis in the racing greyhound

1979 ◽  
Vol 236 (6) ◽  
pp. H790-H797 ◽  
Author(s):  
R. H. Cox ◽  
D. K. Detweiler
Keyword(s):  
Smooth Muscle ◽  
Muscle Activation ◽  
Arterial Wall ◽  
Carotid Arteries ◽  
External Diameter ◽  
Iliac Arteries ◽  
Force Development ◽  
Maximum Range ◽  
Arterial Wall Mechanics ◽  
Elastic Elements

The effects of experimental (dietary) atherosclerosis on arteries from racing greyhounds were studied. Measurements of pressure and external diameter were made on islated carotid and iliac arteries under active (norepinephrine, 5 microgram/ml) and passive (zero Ca2+ and 2 mM EGTA) smooth muscle conditions. Iliac arteries from diet-fed animals demonstrated substantial intimal lesions, but the carotid arteries were usually grossly involved. Arteries from atherosclerotic animals were stiffer during passive conditions, with the iliac arteries having the greater changes. In iliac arteries from treated animals, collagen and elastin contents were decreased, and the collagen-to-elastin ratio was increased; in carotid arteries from treated animals, elastin content was increased and the collagen-to-elastin ratio was decreased. The maximum range of control of arterial wall mechanics by smooth muscle was diminished in treated iliacs but unchanged in carotids. Both force development and constriction responses associated with smooth muscle activation were diminished in treated iliacs but unchanged in treated carotids. Mechanical properties of series elastic elements in treated iliacs were stiffer, but treated carotids were unchanged.

Passive Biaxial Mechanical Response of Aged Human Iliac Arteries

2003 ◽  
Vol 125 (3) ◽  
pp. 395-406 ◽  
Author(s):  
Christian A. J. Schulze-Bauer ◽  
Christian Mo¨rth ◽  
Gerhard A. Holzapfel
Keyword(s):  
Experimental Data ◽  
Deformation Behavior ◽  
Arterial Wall ◽  
Constitutive Models ◽  
Intraluminal Pressure ◽  
Clear Correlation ◽  
Outer Diameter ◽  
Iliac Arteries ◽  
Arterial Wall Mechanics

Inflation and extension tests of arteries are essential for the understanding of arterial wall mechanics. Data for such tests of human arteries are rare. At autopsy we harvested 10 non-diseased external iliac arteries of aged subjects (52–87 yrs). Structural homogeneity was ensured by means of ultrasound imaging, and anamneses of patients were recorded. We measured the axial in situ stretches, load-free geometries and opening angles. Passive biaxial mechanical responses of preconditioned cylindrical specimens were studied in 37°C calcium-free Tyrode solution under quasistatic loading conditions. Specimens were subjected to pressure cycles varying from 0 to 33.3kPa (250mmHg) at nine fixed axial loads, varying from 0 to 9.90N. For the description of the load-deformation behavior we employed five “two-dimensional” orthotropic strain-energy functions frequently used in arterial wall mechanics. The associated constitutive models were compared in regard to their ability of representing the experimental data. Histology showed that the arteries were of the muscular type. In contrast to animal arteries they exhibited intimal layers of considerable thickness. The average ratio of wall thickness to outer diameter was 7.7, which is much less than observed for common animal arteries. We found a clear correlation between age and the axial in situ stretch λis(r=−0.72,P=0.03), and between age and distensibility of specimens, i.e. aged specimens are less distensible. Axial in situ stretches were clearly smaller (1.07±0.09,mean±SD) than in animal arteries. For one specimen λis was even smaller than 1.0, i.e. the vessel elongated axially upon excision. The nonlinear and anisotropic load-deformation behavior showed small hystereses. For the majority of specimens we observed axial stretches smaller than 1.3 and circumferential stretches smaller than 1.1 for the investigated loading range. Data from in situ inflation tests showed a significant increase of the axial stretch with intraluminal pressure. Thus, for this type of artery the axial in situ stretch of a non-pressurized vessel is not representative of the axial in vivo stretch. None of the constitutive models were able to represent the deformation behavior of the entire loading range. For the physiological loading range, however, some of the models achieved good agreement with the experimental data.

Effects of chronic cigarette smoking on canine arteries

1984 ◽  
Vol 246 (1) ◽  
pp. H97-H103 ◽  
Author(s):  
R. H. Cox ◽  
T. Tulenko ◽  
W. P. Santamore
Keyword(s):  
Connective Tissue ◽  
Cigarette Smoking ◽  
Arterial Wall ◽  
Passive Stiffness ◽  
Active Force ◽  
Tissue Composition ◽  
Femoral Arteries ◽  
Arterial Wall Mechanics ◽  
Dose Responses

Segments of carotid and femoral arteries were obtained from beagles subjected to cigarette smoking (12/day for 2 yr) and from unexposed controls. The segments were used for in vitro studies of active and passive mechanics, dose responses to norepinephrine (NE) and K+, connective tissue content, and water and electrolyte content and distribution. No significant differences in passive arterial wall mechanics or geometry at 100 mmHg were found, but a small (significant) increase in passive stiffness was found at wall loads corresponding to higher values of pressure for arteries from smokers. No significant changes in connective tissue composition were found at either site. No significant differences in maximum active force development were found at either site between the two groups. However, values of active force near the middle of the active force-length curve were lower (P less than 0.05) for smoker's arteries when expressed as a fraction of the maximum developed force. No differences in cell volume were found in arteries from the two groups. Mg2+ and K+ content of the femoral and Ca2+ content of both arteries were greater in the smokers. No difference in NE dose-response relations were found for either site. A statistically significant decrease in responsiveness to K+ was found for femoral arteries from smokers, but not for the carotids. The results of these studies demonstrate that some significant changes in arterial wall properties occur in beagle dogs exposed to chronic cigarette smoke.

scholarly journals Iliac Veins Are More Compressible Than Iliac Arteries: A New Method of Testing

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Margaret Brass ◽  
Ghassan S. Kassab
Keyword(s):  
Arterial Wall ◽  
Fluid Transport ◽  
Vascular Wall ◽  
Fluid Loss ◽  
Loading Conditions ◽  
Vein Wall ◽  
Iliac Arteries ◽  
Direct Measurements ◽  
Arterial Wall Mechanics ◽  
Venous Wall

Incompressibility implies that a tissue preserves its volume regardless of the loading conditions. Although this assumption is well-established in arterial wall mechanics, it is assumed to apply for the venous wall without validation. The objective of this study is to test whether the incompressibility assumption holds for the venous wall. To investigate the vascular wall volume under different loading conditions, inflation-extension testing protocol was used in conjunction with intravascular ultrasound (IVUS) in both common iliac arteries (n = 6 swine) and common iliac veins (n = 9 dogs). Use of IVUS allows direct visualizations of lumen dimensions simultaneous with direct measurements of outer dimensions during loading. The arterial tissue was confirmed to preserve volume during various load conditions (p = 0.11) consistent with the literature, while the venous tissue was found to lose volume (about 35%) under loaded conditions (p < 0.05). Using a novel methodology, this study shows the incompressibility assumption does not hold for the venous wall especially at higher pressures, which suggests that there may be fluid loss through the vein wall during loading. This has important implications for coupling of fluid transport across the wall and biomechanics of the wall in healthy and diseased conditions.

scholarly journals Stimuli for Adaptations in Muscle Length and the Length Range of Active Force Exertion—A Narrative Review

2021 ◽  
Vol 12 ◽  
Author(s):  
Annika Kruse ◽  
Cintia Rivares ◽  
Guido Weide ◽  
Markus Tilp ◽  
Richard T. Jaspers
Keyword(s):  
Mechanical Loading ◽  
Longitudinal Muscle ◽  
Current Knowledge ◽  
Muscle Growth ◽  
Muscle Length ◽  
Active Force ◽  
Cross Sectional ◽  
Specific Loading ◽  
Length Range ◽  
In Series

Treatment strategies and training regimens, which induce longitudinal muscle growth and increase the muscles’ length range of active force exertion, are important to improve muscle function and to reduce muscle strain injuries in clinical populations and in athletes with limited muscle extensibility. Animal studies have shown several specific loading strategies resulting in longitudinal muscle fiber growth by addition of sarcomeres in series. Currently, such strategies are also applied to humans in order to induce similar adaptations. However, there is no clear scientific evidence that specific strategies result in longitudinal growth of human muscles. Therefore, the question remains what triggers longitudinal muscle growth in humans. The aim of this review was to identify strategies that induce longitudinal human muscle growth. For this purpose, literature was reviewed and summarized with regard to the following topics: (1) Key determinants of typical muscle length and the length range of active force exertion; (2) Information on typical muscle growth and the effects of mechanical loading on growth and adaptation of muscle and tendinous tissues in healthy animals and humans; (3) The current knowledge and research gaps on the regulation of longitudinal muscle growth; and (4) Potential strategies to induce longitudinal muscle growth. The following potential strategies and important aspects that may positively affect longitudinal muscle growth were deduced: (1) Muscle length at which the loading is performed seems to be decisive, i.e., greater elongations after active or passive mechanical loading at long muscle length are expected; (2) Concentric, isometric and eccentric exercises may induce longitudinal muscle growth by stimulating different muscular adaptations (i.e., increases in fiber cross-sectional area and/or fiber length). Mechanical loading intensity also plays an important role. All three training strategies may increase tendon stiffness, but whether and how these changes may influence muscle growth remains to be elucidated. (3) The approach to combine stretching with activation seems promising (e.g., static stretching and electrical stimulation, loaded inter-set stretching) and warrants further research. Finally, our work shows the need for detailed investigation of the mechanisms of growth of pennate muscles, as those may longitudinally grow by both trophy and addition of sarcomeres in series.

scholarly journals Linking cardiorespiratory fitness classification criteria to early subclinical atherosclerosis in children

2015 ◽  
Vol 40 (4) ◽  
pp. 386-392 ◽  
Author(s):  
Xavier Melo ◽  
Helena Santa-Clara ◽  
Diana A. Santos ◽  
Nuno M. Pimenta ◽  
Cláudia S. Minderico ◽  
...  
Keyword(s):  
Cardiorespiratory Fitness ◽  
Arterial Wall ◽  
Operating Characteristic ◽  
Screening Tool ◽  
Subclinical Atherosclerosis ◽  
Intima Media Thickness ◽  
Carotid Intima Media Thickness ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
High Resolution Ultrasonography

It is unclear if cardiorespiratory fitness (CRF) can be used as a screening tool for premature changes in carotid intima-media thickness (cIMT) in paediatric populations. The purpose of this cross-sectional study was 3-fold: (i) to determine if CRF can be used to screen increased cIMT; (ii) to determine an optimal CRF cut-off to predict increased cIMT; and (iii) to evaluate its ability to predict increased cIMT among children in comparison with existent CRF cut-offs. cIMT was assessed with high-resolution ultrasonography and CRF was determined using a maximal cycle test. Receiver operating characteristic analyses were conducted in boys (n = 211) and girls (n = 202) aged 11–12 years to define the optimal sex-specific CRF cut-off to classify increased cIMT (≥75th percentile). Logistic regression was used to examine the association between the CRF cut-offs with the risk of having an increased cIMT. The optimal CRF cut-offs to predict increased cIMT were 45.81 and 34.46 mL·kg−1·min−1 for boys and girls, respectively. The odds-ratios for having increased cIMT among children who were unfit was up to 2.8 times the odds among those who were fit (95% confidence interval: 1.40–5.53). Considering current CRF cut-offs, only those suggested by Adegboye et al. 2011. (Br. J. Sports Med. 45(9): 722–728) and Boddy et al. 2012 (PLoS One, 7(9): e45755) were significant in predicting increased cIMT. In conclusion, CRF cut-offs (boys: ≤ 45.8; girls: ≤ 34.5 mL·kg−1·min−1) are associated with thickening of the arterial wall in 11- to 12-year-old children. Low CRF is an important cardiovascular risk factor in children and our data highlight the importance of obtaining an adequate CRF.

Rostrocaudal pattern of fiber-type changes in an overloaded rat ankle extensor

1991 ◽  
Vol 71 (2) ◽  
pp. 558-564 ◽  
Author(s):  
P. F. Gardiner ◽  
B. J. Jasmin ◽  
P. Corriveau
Keyword(s):  
Fiber Type ◽  
Muscle Length ◽  
Similar Degree ◽  
Complex Nature ◽  
Type I ◽  
Fiber Types ◽  
Type Ii ◽  
Cross Sectional ◽  
Hypertrophic Response ◽  
Type I Fibers

Our aim was to quantify the overload-induced hypertrophy and conversion of fiber types (type II to I) occurring in the medial head of the gastrocnemius muscle (MG). Overload of MG was induced by a bilateral tenotomy/retraction of synergists, followed by 12–18 wk of regular treadmill locomotion (2 h of walking/running per day on 3 of 4 days). We counted all type I fibers and determined type I and II mean fiber areas in eight equidistant sections taken along the length of control and overloaded MG. Increase in muscle weights (31%), as well as in total muscle cross-sectional areas (37%) and fiber areas (type I, 57%; type II, 34%), attested to a significant hypertrophic response in overloaded MG. An increase in type I fiber composition of MG from 7.0 to 11.5% occurred as a result of overload, with the greatest and only statistically significant changes (approximately 70–100%) being found in sections taken from the most rostral 45% of the muscle length. Results of analysis of sections taken from the largest muscle girth showed that it significantly underestimated the extent of fiber conversion that occurred throughout the muscle as a whole. These data obtained on the MG, which possesses a compartmentalization of fiber types, support the notion that all fiber types respond to this model with a similar degree of hypertrophy. Also, they emphasize the complex nature of the adaptive changes that occur in these types of muscles as a result of overload.

scholarly journals Posterior chain flexibility and lower back pain in farm workers

2017 ◽  
Vol 30 (2) ◽  
pp. 219-226
Author(s):  
Marcia Regina da Silva ◽  
Lucimare Ferraz ◽  
Fátima Ferretti ◽  
Cristiane Sfredo
Keyword(s):  
Back Pain ◽  
Lower Back Pain ◽  
Muscle Length ◽  
Cross Sectional Study ◽  
Farm Workers ◽  
Cross Sectional ◽  
Chain Flexibility ◽  
Lower Back ◽  
Significant Difference ◽  
Post Hoc

Abstract Introduction: Flexibility is an essential component of physical aptitude that reduces the incidence of muscle distention and improves movement efficiency and posture. Objective: To analyze posterior chain flexibility and lower back pain (LBP) in farm workers from a city in western Santa Catarina state, Brazil. Methods: Quantitative and cross-sectional study conducted with 185 rural workers, average age of 44.24 (±10.83) years. The Rural Worker Health Questionnaire, containing individual issues related to work; sit and reach box, goniometer, visual analog scale (VAS) and Oswestry and Roland-Morris questionnaires were used to evaluate posterior chain flexibility, hamstring muscle length, pain and lumbar spine dysfunction, respectively. Flexibility was compared with the degree of dysfunction using one-way ANOVA followed by the Bonferroni post hoc test. Results: 181 (97.8%) workers reported LBP symptoms: 100% of the women and 95.2% of the men. The average Oswestry score was 7.09 (±8.25), Roland-Morris 1.22 (±1.63), and VAS 5.81 (±2.5). Average flexibility by the sit and reach test (SRT) was 23.91cm (±18.81); straight leg raise (SLR), 66° (±11.77) and popliteal angle 123.21° (±12.45). There was a significant difference in the popliteal angle (p = 0.003) and SLR (0.001) when compared with the degree of dysfunction. Women showed significant differences in all tests; however, the post hoc test showed a significant difference only in the SRT (p = 0.013), and women with minimal dysfunction had greater flexibility in relation to those with severe dysfunction. Conclusion: Self-reported LBP was severe and women with higher levels of dysfunction exhibited less posterior chain flexibility.

Dynamics of cardiac muscle: analysis of isotonic, isometric, and isochronal curves

1987 ◽  
Vol 253 (3) ◽  
pp. H645-H653
Author(s):  
O. N. Nwasokwa
Keyword(s):  
Muscle Force ◽  
Isometric Force ◽  
Impedance Matching ◽  
Time Intervals ◽  
Cross Sectional ◽  
Contraction Coupling ◽  
Force Development ◽  
Pentobarbital Sodium Anesthesia ◽  
Matching Transformer ◽  
Isotonic Shortening

Canine papillary muscle force-length-time relation (F-L-t) was investigated under pentobarbital sodium anesthesia. The time intervals taken from end diastole to any point (P) on the force-length plane was determined for isometric (t1) and isotonic (t2) systole and corrected for excitation contraction coupling duration. The ratio t1/t2, designated km, was approximately constant for widely scattered positions of P chosen systematically. The km in the 10 dogs ranged from 0.36 to 0.94 with means +/- SD of 0.66 +/- 0.16; km correlated negatively with muscle average cross-sectional area (r = -0.82; P less than 0.005). Assuming constancy of km, a general relationship was derived between (delta F/delta t)t1L, the rate of isometric force development at P; (delta L/delta t)t2F, the velocity of isotonic shortening at P; (delta F/delta L)(t1,t2)t, the stiffness; and (delta L/delta F)(t1,t2)t, the compliance of the myocardium (all taken at P) as follows (delta F/delta L)t1,t2t = -km(delta F/delta t)t1L/(delta L/delta t)t2F and (delta L/delta F)t1,t2t = -km-1(delta L/delta t)t2F/(delta F/delta t)t1t. The ratio of (delta F/delta t)t1L to (delta L/delta t)t2F defines functional proclivity and measures the differential propensity to force development relative to shortening. Thus myocardial stiffness or compliance determines functional proclivity by acting as an impedance-matching transformer that steps up or steps down force development of shortening as warranted by the loading conditions.

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