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 Reports of the length dependence of fatigue are greatly exaggerated

2006 ◽  
Vol 101 (1) ◽  
pp. 23-29 ◽  
Author(s):  
M. B. MacNaughton ◽  
B. R. MacIntosh
Keyword(s):  
Muscle Length ◽  
Repetitive Stimulation ◽  
Double Pulse ◽  
Medial Gastrocnemius ◽  
Passive Force ◽  
Active Force ◽  
Rightward Shift ◽  
Length Dependence ◽  
Force Depression ◽  
In Series

Relative force depression associated with muscle fatigue is reported to be greater when assessed at short vs. long muscle lengths. This appears to be due to a rightward shift in the force-length relationship. This rightward shift may be caused by stretch of in-series structures, making sarcomere lengths shorter at any given muscle length. Submaximal force-length relationships (twitch, double pulse, 50 Hz) were evaluated before and after repetitive contractions (50 Hz, 300 ms, 1/s) in an in situ preparation of the rat medial gastrocnemius muscle. In some experiments, fascicle lengths were measured with sonomicrometry. Before repetitive stimulation, fascicle lengths were 11.3 ± 0.8, 12.8 ± 0.9, and 14.4 ± 1.2 mm at lengths corresponding to −3.6, 0, and 3.6 mm where 0 is a reference length that corresponds with maximal active force for double-pulse stimulation. After repetitive stimulation, there was no change in fascicle lengths; these lengths were 11.4 ± 0.8, 12.6 ± 0.9, and 14.2 ± 1.2 mm. The length dependence of fatigue was, therefore, not due to a stretch of in-series structures. Interestingly, the rightward shift that was evident when active force was calculated in the traditional way (subtraction of the passive force measured before contraction) was not seen when active force was calculated by subtracting the passive force that was associated with the fascicle length reached at the peak of the contraction. This calculation is based on the assumption that passive force decreases as the fascicles shorten during a fixed-end contraction. This alternative calculation revealed similar postfatigue absolute active force depression at all lengths. In relative terms, a length dependence of fatigue was still evident, but this was greatly diminished compared with that observed when active force was calculated with the traditional method.

scholarly journals The extensive length-force relationship of porcine airway smooth muscle

2007 ◽  
Vol 102 (5) ◽  
pp. 1906-1911 ◽  
Author(s):  
Alexander V. Smolensky ◽  
Lincoln E. Ford
Keyword(s):  
Total Force ◽  
Passive Tension ◽  
Active Force ◽  
Reference Length ◽  
Length Range ◽  
In Series ◽  
Length Changes ◽  
Relationship Of ◽  
Trachealis Muscle ◽  
Force Relationship

The full functional length range of trachealis muscle was measured to identify a precise reference length and to assess the length changes that the myofilament lattice can accommodate. The initial reference length ( L10%) was that where rest tension equaled 10% of total force (passive tension plus active force). Total force at this length served as a force reference (Fref = 219 ± 12 kPa, N = 7). Muscles initially adapted at L10% for 30–60 min had no rest tension when shortened to <0.9 L10%. Passive tension rose steeply and linearly with slope 11.2 Fref/ L10% at lengths >1.04 L10%. Rest tension at 1.1 L10% declined by <10% over 1 h. The steep slope and stability of rest tension at long lengths suggest that a parameter of the slope could serve as a precise, reproducible reference length. Active force was nearly constant at lengths 0.33–1.0 L10% and declined steeply at lengths between 0.1 and 0.2 L10%, extrapolating to zero at 0.076 L10%. Muscles visibly reextended during relaxation at lengths <0.25 L10%. At long lengths, force extrapolated to zero at 1.175 L10%. The >15-fold length range (0.076–1.175 L10%) for force generation and nearly constant force over a greater than threefold length range is likely produced by several structural accommodations, including filament sliding, an increased number of sliding filaments in series, and increased length of passive structures in series with the sliding filaments. Visible reextension during relaxation suggests that the lattice does not undergo plastic adaptations at lengths <25% L10% and that lattice plasticity is limited to a three- to fourfold length range.

Viscoelastic properties of the contracting detrusor. II. Experimental approach

1991 ◽  
Vol 261 (2) ◽  
pp. C364-C375 ◽  
Author(s):  
J. G. Venegas ◽  
J. P. Woll ◽  
S. B. Woolfson ◽  
E. G. Cravalho ◽  
N. Resnick ◽  
...  
Keyword(s):  
Muscle Length ◽  
Companion Paper ◽  
Cross Sectional Area ◽  
Detrusor Muscle ◽  
Sectional Area ◽  
Positive Dependence ◽  
Muscle Properties ◽  
Cross Sectional ◽  
In Series ◽  
Viscous Element

Mechanical properties of detrusor muscle were studied with small-amplitude oscillatory volume perturbations in isometrically contracting bladders of anesthetized dogs. Contractions were studied at oscillatory frequencies (f) of 2 and 4 Hz and at bladder volumes (Vbl) ranging from 30 to 110 ml. The magnitude of bladder hydrodynamic stiffness (magnitude of G) increased linearly with mean detrusor pressure (Pdet) while the phase angle remained relatively constant during contraction. The slope (mG) of magnitude of G-Pdet relations had a positive dependence on f and a negative dependence on Vbl. Analysis of oscillatory data, described in the companion paper, was performed using incremental lumped-parameter models consisting of a spring with incremental constant (S = dF/dL), a viscous element with incremental viscosity (b = dF/du), and a mass (m). Only the model where elastic and viscous elements were placed in series with each other and in parallel with mass was compatible with the experimental data. Both S and b increased linearly with effective force (F), defined as Pdet times the cross-sectional area of the intravesical cavity. Slopes of the S-F and b-F relationships (ms and mb) were independent of Vbl and varied only slightly with f. The importance of this finding stems from recognizing that ms and mb correspond to the exponential coefficients of nonlinear series elastic and internal viscosity elements. These parameters, when normalized by resting muscle length, represent fundamental muscle properties independent of muscle cross-sectional area, stretch, or level of activation and compare well with parameters derived from other muscle systems using techniques such as quick releases and isotonic contractions.

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.

scholarly journals Plasticity in canine airway smooth muscle.

1995 ◽  
Vol 105 (1) ◽  
pp. 73-94 ◽  
Author(s):  
V R Pratusevich ◽  
C Y Seow ◽  
L E Ford
Keyword(s):  
Smooth Muscle ◽  
Isometric Force ◽  
Strong Dependence ◽  
Smooth Muscles ◽  
Muscle Length ◽  
Relative Length ◽  
Length Range ◽  
Steady Level ◽  
In Series ◽  
Length Changes

The large volume changes of some hollow viscera require a greater length range for the smooth muscle of their walls than can be accommodated by a fixed array of sliding filaments. A possible explanation is that smooth muscles adapt to length changes by forming variable numbers of contractile units in series. To test for such plasticity we examined the muscle length dependence of shortening velocity and compliance, both of which will vary directly with the number of thick filaments in series. Dog tracheal smooth muscle was studied because its cells are arrayed in long, straight, parallel bundles that span the length of the preparation. In experiments where muscle length was changed, both compliance and velocity showed a strong dependence on muscle length, varying by 1.7-fold and 2.2-fold, respectively, over a threefold range of length. The variation in isometric force was substantially less, ranging from a 1.2- to 1.3-fold in two series of experiments where length was varied by twofold to an insignificant 4% variation in a third series where a threefold length range was studied. Tetanic force was below its steady level after both stretches and releases, and increased to a steady level with 5-6 tetani at 5 min intervals. These results suggest strongly that the number of contractile units in series varies directly with the adapted muscle length. Temporary force depression after a length change would occur if the change transiently moved the filaments from their optimum overlap. The relative length independence of the adapted force is explained by the reforming of the filament lattice to produce optimum force development, with commensurate changes of velocity and compliance.

Effect of an interval rehabilitation program with home-based, vibration-assisted training on the development of muscle and bone in children with cerebral palsy – an observational study

2020 ◽  
Vol 33 (8) ◽  
pp. 1083-1092 ◽  
Author(s):  
Ibrahim Duran ◽  
Kyriakos Martakis ◽  
Christina Stark ◽  
Leonie Schafmeyer ◽  
Mirko Rehberg ◽  
...  
Keyword(s):  
Cerebral Palsy ◽  
Bone Growth ◽  
Muscle Growth ◽  
Rehabilitation Program ◽  
Whole Body ◽  
Cross Sectional ◽  
Home Based ◽  
Children With Cerebral Palsy ◽  
One Year ◽  
Intensive Rehabilitation

AbstractObjectivesIn children with cerebral palsy (CP), the most common cause of physical impairment in childhood, less muscle and bone growth has been reported, when compared with typically developing children. The aim of this study was to evaluate the effect of an intensive rehabilitation program including physiotherapy in combination with 6 months of home-based, vibration-assisted training on muscle and bone growth in children with CP.MethodsWe included children with CP, who participated in a rehabilitation program utilizing whole-body vibration (WBV). Muscle mass was quantified by appendicular lean mass index (App-LMI) and bone mass by total-body-less-head bone mineral content (TBLH-BMC) assessed by Dual-energy X-ray absorptiometry (DXA) at the beginning of rehabilitation and one year later. To assess the functional muscle-bone unit, the relation of TBLH-BMC to TBLH lean body mass (TBLH-LBM) was used.ResultsThe study population included 128 children (52 females, mean age 11.9 ± 2.7). App-LMI assessed in kg/m2 increased significantly after rehabilitation. The age-adjusted Z-score for App-LMI showed no significant change. TBLH-BMC assessed in gram increased significantly. The Z-scores for TBLH-BMC decreased lesser than expected by the evaluation of the cross-sectional data at the beginning of rehabilitation. The parameter $\frac{TBLH-BMC}{TBLH-LBM}$ did not change relevantly after 12 months.ConclusionsMuscle growth and to a lesser extent bone growth could be increased in children with CP. The intensive rehabilitation program including WBV seemed to have no direct effect on the bone, but the observed anabolic effect on the bone, may only been mediated through the muscle.

scholarly journals Quality of life of patients with lung cancer: A scoping review

2019 ◽  
Vol 22 (2) ◽  
Author(s):  
Rafael Turano Mota ◽  
Helder Márcio Ferreira Júnior ◽  
Fabiane Silva Pereira ◽  
Maria Aparecida Vieira ◽  
Simone de Melo Costa
Keyword(s):  
Quality Of Life ◽  
Lung Cancer ◽  
Scoping Review ◽  
Prospective Studies ◽  
Current Knowledge ◽  
Care Quality ◽  
Life Questionnaire ◽  
Cross Sectional ◽  
European Organization

Abstract Objective: To characterize scientific publications on the quality of life of people with lung cancer in order to explore current knowledge of the subject, with emphasis on assessment instruments and methodological aspects. Method: A scoping type literature review was performed. Articles were sought in the databases of the Virtual Health Library, in an integrative manner, with the descriptors: Quality of life and Lung Neoplasms, with no date of publication or language restrictions (n=138). The selection of articles was based on inclusion and exclusion criteria defined in the study proposal. Results: We included 18 publications published between 2006 and 2017, the majority (n = 10) of which had a cross-sectional design. Eight different instruments were used to evaluate the quality of life of patients with lung cancer, four of which were specific for people with cancer. There was a prevalence of the use of the European Organization for Research and Treatment of Cancer Care Quality of Life Questionnaire - EORTC QLQ-C30 (n=8). Prospective studies (n=8) assessed quality of life before and after chemotherapy, physical therapy or pulmonary resection. The studies adopted different methodologies and provided conflicting results of quality of life. Cross-sectional studies with comparatively healthy subjects found an inferior quality of life for people with lung cancer. Conclusion: The scoping review contributed to the identification of the multiple evaluated instruments, both generic and specific. It found a lack of homogeneity in the methodological approaches of the studies. Further prospective studies with a specific instrument and methodological standardization to evaluate the quality of life of people with lung cancer are recommended.

scholarly journals A Soft Resistive Sensor with a Semicircular Cross-Sectional Channel for Soft Cardiac Catheter Ablation

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4130
Author(s):  
Eric Rasmussen ◽  
Daniel Guo ◽  
Vybhav Murthy ◽  
Rachit Mishra ◽  
Cameron Riviere ◽  
...  
Keyword(s):  
Catheter Ablation ◽  
Liquid Metal ◽  
Force Feedback ◽  
Applied Force ◽  
Medical Community ◽  
Soft Robotics ◽  
Soft Sensors ◽  
Cross Sectional ◽  
Cardiac Catheter ◽  
Specific Loading

The field of soft robotics has attracted the interest of the medical community due to the ability of soft elastic materials to traverse the abnormal environment of the human body. However, sensing in soft robotics has been challenging due to the sensitivity of soft sensors to various loading conditions and the nonlinear signal responses that can arise under extreme loads. Ideally, soft sensors should provide a linear response under a specific loading condition and provide a different response for other loading directions. With these specifications in mind, our team created a soft elastomeric sensor designed to provide force feedback during cardiac catheter ablation surgery. Analytical and computational methods were explored to define a relationship between resistance and applied force for a semicircular, liquid metal filled channel in the soft elastomeric sensor. Pouillet’s Law is utilized to calculate the resistance based on the change in cross-sectional area resulting from various applied pressures. FEA simulations were created to simulate the deformation of the sensor under various loads. To confirm the validity of these simulations, the elastomer was modeled as a neo-Hookean material and the liquid metal was modeled as an incompressible fluid with negligible shear modulus under uniaxial compression. Results show a linearly proportional relationship between the resistance of the sensor and the application of a uniaxial force. Altering the direction of applied force results in a quadratic relationship between total resistance and the magnitude of force.

scholarly journals A Comprehensive Review on Solitary Fibrous Tumor: New Insights for New Horizons

Cancers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2913
Author(s):  
Javier Martin-Broto ◽  
Jose L. Mondaza-Hernandez ◽  
David S. Moura ◽  
Nadia Hindi
Keyword(s):  
Solitary Fibrous Tumor ◽  
Fusion Gene ◽  
Current Knowledge ◽  
Fusion Transcript ◽  
Chemotherapeutic Agents ◽  
Comprehensive Review ◽  
Molecular Events ◽  
In Series ◽  
Prospective Phase ◽  
Fibrous Tumor

Solitary fibrous tumor (SFT) is a rare mesenchymal, ubiquitous tumor, with an incidence of 1 new case/million people/year. In the 2020 WHO classification, risk stratification models were recommended as a better tool to determine prognosis in SFT, to the detriment of “typical” or “malignant” classic terms. The risk for metastasis is up to 35–45%, or even greater, in series with a longer follow-up. Over the last few decades, advances in immunohistochemistry and molecular diagnostics identified STAT6 nuclear protein expression and the NAB2–STAT6 fusion gene as more precise tools for SFT diagnosis. Recent evidence taken from retrospective series and from two prospective phase II clinical trials showed that antiangiogenics are active and their sequential use from first line should be considered, except for dedifferentiated SFT for which chemotherapy is the best option. Since the fusion transcript driver’s first description in 2013, new insights have been brought on key molecular events in SFT. This comprehensive review mainly focuses on the superior efficacy of antiangiogenics over chemotherapeutic agents in SFT, provides the current knowledge of key molecules that could co-drive the SFT behavior, and suggests new target candidates that deserve to be explored in preclinical and clinical research in SFT.

Muscle growth, cell number, type and morphometry in single and twin fetal lambs during mid to late gestation

2000 ◽  
Vol 12 (6) ◽  
pp. 319 ◽  
Author(s):  
S. A. McCoard ◽  
W. C. McNabb ◽  
S. W. Peterson ◽  
S. N. McCutcheon ◽  
P. M. Harris
Keyword(s):  
Muscle Mass ◽  
Litter Size ◽  
Muscle Growth ◽  
Cell Number ◽  
Late Gestation ◽  
Postnatal Life ◽  
Cross Sectional ◽  
Hindlimb Muscles ◽  
Full Complement ◽  
Gastrocnemius Muscles

Muscle growth, myofibre number, type and morphometry were studied in large hindlimb muscles of single and twin fetal lambs during mid to late gestation. Placental insufficiency, evident by lower total placentome weight and number per fetus, resulted in reduced fetal weights from 100 to 140 days gestation in twins compared with singletons (at 140 days: 5016 108 g v. 5750 246 g, respectively; P<0.05). However, competition between littermates did not consistently reduce muscle mass (15–22%) until 140 days gestation. Apparent myofibre number increased with age, indicating that the full complement of myofibres in some large hindlimb muscles may be achieved during early postnatal life. Litter size did not impact on apparent myofibre number in the semitendinosus, plantaris or gastrocnemius muscles. However, a transient effect on myofibre number in the adductor femoris muscle was observed from 80–120 days gestation. The phenotypic maturation of myofibres was unaffected by increasing litter size. Smaller muscle mass in twins was associated with smaller myofibre cross-sectional area in the semitendinosus, adductor femoris and gastrocnemius muscles at 140 days gestation. A similar trend was observed for the plantaris muscle. These results indicate that while competition between littermates for nutrients in late gestation can impact on both fetal and muscle mass, the fetus has the capacity to buffer against the effects of restricted nutrient supply on myofibre hyperplasia and phenotypic maturation, but myofibre hypertrophy is compromised.

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