scholarly journals The effect of intramuscular fat on skeletal muscle mechanics: implications for the elderly and obese

2015 ◽  
Vol 12 (109) ◽  
pp. 20150365 ◽  
Author(s):  
Hadi Rahemi ◽  
Nilima Nigam ◽  
James M. Wakeling
Keyword(s):  
Skeletal Muscle ◽  
Material Properties ◽  
Structural Parameters ◽  
Muscle Mechanics ◽  
Base Material ◽  
Element Model ◽  
Intramuscular Fat ◽  
Muscle Performance ◽  
Muscle Quality ◽  
Tissue Properties

Skeletal muscle accumulates intramuscular fat through age and obesity. Muscle quality, a measure of muscle strength per unit size, decreases in these conditions. It is not clear how fat influences this loss in performance. Changes to structural parameters (e.g. fibre pennation and connective tissue properties) affect the muscle quality. This study investigated the mechanisms that lead to deterioration in muscle performance due to changes in intramuscular fat, pennation and aponeurosis stiffness. A finite-element model of the human gastrocnemius was developed as a fibre-reinforced composite biomaterial containing contractile fibres within the base material. The base-material properties were modified to include intramuscular fat in five different ways. All these models with fat generated lower fibre stress and muscle quality than their lean counterparts. This effect is due to the higher stiffness of the tissue in the fatty models. The fibre deformations influence their interactions with the aponeuroses, and these change with fatty inclusions. Muscles with more compliant aponeuroses generated lower forces. The muscle quality was further reduced for muscles with lower pennation. This study shows that whole-muscle force is dependent on its base-material properties and changes to the base material due to fatty inclusions result in reductions to force and muscle quality.

scholarly journals Maize stalk stiffness and strength are primarily determined by morphological factors

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Christopher J. Stubbs ◽  
Ryan Larson ◽  
Douglas D. Cook
Keyword(s):  
Material Properties ◽  
Structural Strength ◽  
Biological Activities ◽  
Structural Parameters ◽  
Sensitivity Analyses ◽  
Bioenergy Crops ◽  
Tissue Properties ◽  
Three Point Bending ◽  
X Ray Computed ◽  
The Right

AbstractThe maize (Zea mays) stem is a biological structure that must balance both biotic and structural load bearing duties. These competing requirements are particularly relevant in the design of new bioenergy crops. Although increased stem digestibility is typically associated with a lower structural strength and higher propensity for lodging, with the right balance between structural and biological activities it may be possible to design crops that are high-yielding and have digestible biomass. This study investigates the hypothesis that geometric factors are much more influential in determining structural strength than tissue properties. To study these influences, both physical and in silico experiments were used. First, maize stems were tested in three-point bending. Specimen-specific finite element models were created based on x-ray computed tomography scans. Models were validated by comparison with experimental data. Sensitivity analyses were used to assess the influence of structural parameters such as geometric and material properties. As hypothesized, geometry was found to have a much stronger influence on structural stability than material properties. This information reinforces the notion that deficiencies in tissue strength could be offset by manipulation of stalk morphology, thus allowing the creation of stalks which are both resilient and digestible.

scholarly journals The effect of obesity on the contractile performance of isolated mouse soleus, EDL, and diaphragm muscles

2017 ◽  
Vol 122 (1) ◽  
pp. 170-181 ◽  
Author(s):  
Jason Tallis ◽  
Cameron Hill ◽  
Rob S. James ◽  
Val M. Cox ◽  
Frank Seebacher
Keyword(s):  
Skeletal Muscle ◽  
Muscle Function ◽  
Isometric Force ◽  
Muscle Performance ◽  
Muscle Quality ◽  
Control Group ◽  
Protein Kinase Activity ◽  
Negative Cycle ◽  
Contractile Performance

Obesity affects the major metabolic and cellular processes involved in skeletal muscle contractility. Surprisingly, the effect of obesity on isolated skeletal muscle performance remains unresolved. The present study is the first to examine the muscle-specific changes in contractility following dietary-induced obesity using an isolated muscle work-loop (WL) model that more closely represents in vivo muscle performance. Following 16-wk high-calorific feeding, soleus (SOL), extensor digitorum longus (EDL), and diaphragm (DIA) were isolated from female (CD-1) mice, and contractile performance was compared against a lean control group. Obese SOL produced greater isometric force; however, isometric stress (force per unit muscle area), absolute WL power, and normalized WL power (watts per kilogram muscle mass) were unaffected. Maximal isometric force and absolute WL power of the EDL were similar between groups. For both EDL and DIA, isometric stress and normalized WL power were reduced in the obese groups. Obesity caused a significant reduction in fatigue resistance in all cases. Our findings demonstrate a muscle-specific reduction in contractile performance and muscle quality that is likely related to in vivo mechanical role, fiber type, and metabolic profile, which may in part be related to changes in myosin heavy chain expression and AMP-activated protein kinase activity. These results infer that, beyond the additional requirement of moving a larger body mass, functional performance and quality of life may be further limited by poor muscle function in obese individuals. As such, a reduction in muscle performance may be a substantial contributor to the negative cycle of obesity. NEW & NOTEWORTHY The effect of obesity on isolated muscle function is surprisingly underresearched. The present study is the first to examine the effects of obesity on isolated muscle performance using a method that more closely represents real-world muscle function. This work uniquely establishes a muscle-specific profile of mechanical changes in relation to underpinning mechanisms. These findings may be important to understanding the negative cycle of obesity and in designing interventions for improving weight status.

scholarly journals Influence of ageing and essential amino acids on quantitative patterns of troponin T alternative splicing in human skeletal muscle

2015 ◽  
Vol 40 (8) ◽  
pp. 788-796 ◽  
Author(s):  
Joel Coble ◽  
Rudolf J. Schilder ◽  
Arthur Berg ◽  
Micah J. Drummond ◽  
Blake B. Rasmussen ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Alternative Splicing ◽  
Resistance Exercise ◽  
Troponin T ◽  
Vastus Lateralis ◽  
Essential Amino Acids ◽  
Muscle Performance ◽  
Muscle Quality ◽  
Vastus Lateralis Muscle

Ageing is associated with a loss of skeletal muscle performance, a condition referred to as sarcopenia. In part, the age-related reduction in performance is due to a selective loss of muscle fiber mass, but mass-independent effects have also been demonstrated. An important mass-independent determinant of muscle performance is the pattern of expression of isoforms of proteins that participate in muscle contraction (e.g., the troponins). In the present study, we tested the hypothesis that ageing impairs alternative splicing of the pre-mRNA encoding fast skeletal muscle troponin T (TNNT3) in human vastus lateralis muscle. Furthermore, we hypothesized that resistance exercise alone or in combination with consumption of essential amino acids would attenuate age-associated effects on TNNT3 alternative splicing. Our results indicate that ageing negatively affects the pattern of TNNT3 alternative splicing in a manner that correlates quantitatively with age-associated reductions in muscle performance. Interestingly, whereas vastus lateralis TNNT3 alternative splicing was unaffected by a bout of resistance exercise 24 h prior to muscle biopsy, ingestion of a mixture of essential amino acids after resistance exercise resulted in a significant shift in the pattern of TNNT3 splice form expression in both age groups to one predicted to promote greater muscle performance. We conclude that essential amino acid supplementation after resistance exercise may provide a means to reduce impairments in skeletal muscle quality during ageing in humans.

scholarly journals CT fatty muscle fraction as a new parameter for muscle quality assessment predicts outcome in venovenous extracorporeal membrane oxygenation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Anton Faron ◽  
Stefan Kreyer ◽  
Alois M. Sprinkart ◽  
Thomas Muders ◽  
Stefan F. Ehrentraut ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Extracorporeal Membrane Oxygenation ◽  
Adverse Outcomes ◽  
Muscle Quality ◽  
Imaging Biomarker ◽  
Survival Prediction ◽  
Multivariable Logistic Regression Model ◽  
Muscle Area ◽  
Membrane Oxygenation ◽  
The Impact

AbstractImpaired skeletal muscle quality is a major risk factor for adverse outcomes in acute respiratory failure. However, conventional methods for skeletal muscle assessment are inapplicable in the critical care setting. This study aimed to determine the prognostic value of computed tomography (CT) fatty muscle fraction (FMF) as a biomarker of muscle quality in patients undergoing extracorporeal membrane oxygenation (ECMO). To calculate FMF, paraspinal skeletal muscle area was obtained from clinical CT and separated into areas of fatty and lean muscle based on densitometric thresholds. The cohort was binarized according to median FMF. Patients with high FMF displayed significantly increased 1-year mortality (72.7% versus 55.8%, P = 0.036) on Kaplan–Meier analysis. A multivariable logistic regression model was built to test the impact of FMF on outcome. FMF was identified as a significant predictor of 1-year mortality (hazard ratio per percent FMF, 1.017 [95% confidence interval, 1.002–1.033]; P = 0.031), independent of anthropometric characteristics, Charlson Comorbidity Index, Simplified Acute Physiology Score, Respiratory Extracorporeal Membrane Oxygenation Survival Prediction Score, and duration of ECMO support. To conclude, FMF predicted 1-year mortality independently of established clinical prognosticators in ECMO patients and may have the potential to become a new muscle quality imaging biomarker, which is available from clinical CT.

scholarly journals Eat like an athlete: insights of sports nutrition science to support active aging in healthy older adults

GeroScience ◽  
2021 ◽  
Author(s):  
Sara Y. Oikawa ◽  
Tristin D. Brisbois ◽  
Luc J. C. van Loon ◽  
Ian Rollo
Keyword(s):  
Skeletal Muscle ◽  
Performance Enhancement ◽  
Protein Supplementation ◽  
Muscle Quality ◽  
Active Aging ◽  
Omega 3 ◽  
Healthy Older Adults ◽  
Increased Risk ◽  
Muscle Health ◽  
Nutritional Strategies

AbstractSkeletal muscle mass losses with age are associated with negative health consequences, including an increased risk of developing metabolic disease and the loss of independence. Athletes adopt numerous nutritional strategies to maximize the benefits of exercise training and enhance recovery in pursuit of improving skeletal muscle quality, mass, or function. Importantly, many of the principles applied to enhance skeletal muscle health in athletes may be applicable to support active aging and prevent sarcopenia in the healthy (non-clinical) aging population. Here, we discuss the anabolic properties of protein supplementation in addition to ingredients that may enhance the anabolic effects of protein (e.g. omega 3 s, creatine, inorganic nitrate) in older persons. We conclude that nutritional strategies used in pursuit of performance enhancement in athletes are often applicable to improve skeletal muscle health in the healthy older population when implemented as part of a healthy active lifestyle. Further research is required to elucidate the mechanisms by which these nutrients may induce favourable changes in skeletal muscle and to determine the appropriate dosing and timing of nutrient intakes to support active aging.

Dynamic Characteristics Analysis of Cable-Rib Tension Deployable Antenna

2016 ◽  
Author(s):  
Liu Ruiwei ◽  
Hongwei Guo ◽  
Zhang Qinghua ◽  
Rongqiang Liu ◽  
Tang Dewei
Keyword(s):  
Dynamic Characteristics ◽  
Structural Parameters ◽  
Element Model ◽  
Structure Design ◽  
Antenna Structure ◽  
Characteristics Analysis ◽  
New Type ◽  
Dynamic Characteristics Analysis ◽  
The Finite Element Model ◽  
Weight Dynamic

Balancing stiffness and weight is of substantial importance for antenna structure design. Conventional fold-rib antennas need sufficient weight to meet stiffness requirements. To address this issue, this paper proposes a new type of cable-rib tension deployable antenna that consists of six radial rib deployment mechanisms, numerous tensioned cables, and a mesh reflective surface. The primary innovation of this study is the application of numerous tensioned cables instead of metal materials to enhance the stiffness of the entire antenna while ensuring relatively less weight. Dynamic characteristics were analyzed to optimize the weight and stiffness of the antenna with the finite element model by subspace method. The first six orders of natural frequencies and corresponding vibration modes of the antenna structure are obtained. In addition, the effects of structural parameters on natural frequency are studied, and a method to improve the rigidity of the deployable antenna structure is proposed.

Structural Optimization of the Telescopic Boom of a Certain Type of Truck-Mounted Crane

2014 ◽  
Vol 548-549 ◽  
pp. 383-388
Author(s):  
Zhi Wei Chen ◽  
Zhe Cui ◽  
Yi Jin Fu ◽  
Wen Ping Cui ◽  
Li Juan Dong ◽  
...  
Keyword(s):  
Finite Element ◽  
Static Analysis ◽  
Cross Sections ◽  
Optimization Design ◽  
Structural Parameters ◽  
Vertical Direction ◽  
Element Model ◽  
Shape Parameters ◽  
Conventional Design ◽  
Design Variables

Parametric finite element model for a commonly used telescopic boom structure of a certain type of truck-mounted crane has been established. Static analysis of the conventional design configuration was performed first. And then an optimization process has been carried out to minimize the total weight of the telescopic structures. The design variables include the geometric shape parameters of the cross-sections and the integrated structural parameters of the telescopic boom. The constraints include the maximum allowable equivalent stresses and the flexure displacements at the tip of the assembled boom structure in both the vertical direction and the circumferential direction of the rotating plane. Compared with the conventional design, the optimization design has achieved a significant weight reduction of up to 24.3%.

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