scholarly journals Added mass in rat plantaris muscle causes a reduction in mechanical work

2020 ◽  
Vol 223 (19) ◽  
pp. jeb224410
Author(s):  
Stephanie A. Ross ◽  
Barbora Rimkus ◽  
Nicolai Konow ◽  
Andrew A. Biewener ◽  
James M. Wakeling
Keyword(s):  
Muscle Mass ◽  
Maximum Velocity ◽  
Length Change ◽  
Added Mass ◽  
Mechanical Work ◽  
Type Model ◽  
Plantaris Muscle ◽  
Tissue Mass ◽  
Cyclic Contractions ◽  
Modelling Studies

ABSTRACTMost of what we know about whole muscle behaviour comes from experiments on single fibres or small muscles that are scaled up in size without considering the effects of the additional muscle mass. Previous modelling studies have shown that tissue inertia acts to slow the rate of force development and maximum velocity of muscle during shortening contractions and decreases the work and power per cycle during cyclic contractions; however, these results have not yet been confirmed by experiments on living tissue. Therefore, in this study we conducted in situ work-loop experiments on rat plantaris muscle to determine the effects of increasing the mass of muscle on mechanical work during cyclic contractions. We additionally simulated these experimental contractions using a mass-enhanced Hill-type model to validate our previous modelling work. We found that greater added mass resulted in lower mechanical work per cycle relative to the unloaded trials in which no mass was added to the muscle (P=0.041 for both 85 and 123% increases in muscle mass). We additionally found that greater strain resulted in lower work per cycle relative to unloaded trials at the same strain to control for length change and velocity effects on the work output, possibly due to greater accelerations of the muscle mass at higher strains. These results confirm that tissue mass reduces muscle mechanical work at larger muscle sizes, and that this effect is likely amplified for lower activations.

The energy of muscle contraction. IV. Greater mass of larger muscles decreases contraction efficiency

2021 ◽  
Vol 18 (182) ◽  
Author(s):  
Stephanie A. Ross ◽  
James M. Wakeling
Keyword(s):  
Muscle Contraction ◽  
Muscle Mass ◽  
Important Determinant ◽  
Metabolic Cost ◽  
Mechanical Work ◽  
Specific Work ◽  
Cost Models ◽  
Cyclic Contractions ◽  
In Series ◽  
Whole Muscle

While skeletal muscle mass has been shown to decrease mass-specific mechanical work per cycle, it is not yet known how muscle mass alters contraction efficiency. In this study, we examined the effect of muscle mass on mass-specific metabolic cost and efficiency during cyclic contractions in simulated muscles of different sizes. We additionally explored how tendon and its stiffness alters the effects of muscle mass on mass-specific work, mass-specific metabolic cost and efficiency across different muscle sizes. To examine contraction efficiency, we estimated the metabolic cost of the cycles using established cost models. We found that for motor contractions in which the muscle was primarily active during shortening, greater muscle mass resulted in lower contraction efficiency, primarily due to lower mass-specific mechanical work per cycle. The addition of a tendon in series with the mass-enhanced muscle model improved the mass-specific work and efficiency per cycle with greater mass for motor contractions, particularly with a shorter excitation duty cycle, despite higher predicted metabolic cost. The results of this study indicate that muscle mass is an important determinant of whole muscle contraction efficiency.

Supplementation with beta-hydroxy-beta-methylbutyrate impacts glucose homeostasis and increases liver size in trained mice

2020 ◽  
Vol 90 (1-2) ◽  
pp. 113-123
Author(s):  
Ines Schadock ◽  
Barbara G. Freitas ◽  
Irae L. Moreira ◽  
Joao A. Rincon ◽  
Marcio Nunes Correa ◽  
...  
Keyword(s):  
Strength Training ◽  
Muscle Mass ◽  
Glucose Homeostasis ◽  
Fasting Blood Glucose ◽  
Hepatic Metabolism ◽  
Mass Gain ◽  
Trained Group ◽  
Tissue Mass ◽  
Liver Size ◽  
Intensive Training

Abstract. β-hydroxy-β-methyl butyrate (HMB) is a bioactive metabolite derived from the amino acid leucine, usually applied for muscle mass increase during physical training, as well as for muscle mass maintenance in debilitating chronic diseases. The hypothesis of the present study is that HMB is a safe supplement for muscle mass gain by strength training. Based on this, the objective was to measure changes in body composition, glucose homeostasis and hepatic metabolism of HMB supplemented mice during strength training. Two of four groups of male mice (n = 6/group) underwent an 8-week training period session (climbing stairs) with or without HMB supplementation (190 mg/kgBW per day). We observed lower body mass gain (4.9 ± 0.43% versus 1.2 ± 0.43, p < 0.001) and increased liver mass (40.9 ± 0.9 mg/gBW versus 44.8 ± 1.3, p < 0.001) in the supplemented trained group compared with the non-supplemented groups. The supplemented trained group had an increase in relative adipose tissue mass (12.4 ± 0.63 mg/gBW versus 16.1 ± 0.88, P < 0.01) compared to the non-supplemented untrained group, and an increase in fasting blood glucose (111 ± 4.58 mg/dL versus 122 ± 3.70, P < 0.05) and insulin resistance (3.79 ± 0.19 % glucose decay/min versus 2.45 ± 0.28, P < 0.05) comparing with non-supplemented trained group. Adaptive heart hypertrophy was observed only in the non-supplemented trained group (4.82 ± 0.05 mg/gBW versus 5.12 ± 0.13, P < 0.05). There was a higher hepatic insulin-like growth factor-1 expression (P = 0.002) in supplemented untrained comparing with non-supplemented untrained group. Gene expression of gluconeogenesis regulatory factors was increased by training and reduced by HMB supplementation. These results confirm that HMB supplementation associated with intensive training protocol drives changes in glucose homeostasis and liver metabolism in mice.

scholarly journals A Soluble Activin Receptor Type IIB Prevents the Effects of Androgen Deprivation on Body Composition and Bone Health

Endocrinology ◽  
2010 ◽  
Vol 151 (9) ◽  
pp. 4289-4300 ◽  
Author(s):  
Alan Koncarevic ◽  
Milton Cornwall-Brady ◽  
Abigail Pullen ◽  
Monique Davies ◽  
Dianne Sako ◽  
...  
Keyword(s):  
Body Composition ◽  
Muscle Mass ◽  
Serum Levels ◽  
Androgen Deprivation ◽  
Receptor Type ◽  
Whole Body ◽  
Micro Computed Tomography ◽  
Tissue Mass ◽  
Activin Receptor

Androgen deprivation, a consequence of hypogonadism, certain cancer treatments, or normal aging in men, leads to loss of muscle mass, increased adiposity, and osteoporosis. In the present study, using a soluble chimeric form of activin receptor type IIB (ActRIIB) we sought to offset the adverse effects of androgen deprivation on muscle, adipose tissue, and bone. Castrated (ORX) or sham-operated (SHAM) mice received either TBS [vehicle-treated (VEH)] or systemic administration of ActRIIB-mFc, a soluble fusion protein comprised of a form of the extracellular domain of ActRIIB fused to a murine IgG2aFc subunit. In vivo body composition imaging demonstrated that ActRIIB-mFc treatment results in increased lean tissue mass of 23% in SHAM mice [19.02 ± 0.42 g (VEH) versus 23.43 ± 0.35 g (ActRIIB-mFc), P &lt; 0.00001] and 26% in ORX mice [15.59 ± 0.26 g (VEH) versus 19.78 ± 0.26 g (ActRIIB-mFc), P &lt; 0.00001]. Treatment also caused a decrease in adiposity of 30% in SHAM mice [5.03 ± 0.48 g (VEH) versus 3.53 ± 0.19 g (ActRIIB-mFc), NS] and 36% in ORX mice [7.12 ± 0.53 g (VEH) versus 4.57 ± 0.28 g (ActRIIB-mFc), P &lt; 0.001]. These changes were also accompanied by altered serum levels of leptin, adiponectin, and insulin, as well as by prevention of steatosis (fatty liver) in ActRIIB-mFc-treated ORX mice. Finally, ActRIIB-mFc prevented loss of bone mass in ORX mice as assessed by whole body dual x-ray absorptiometry and micro-computed tomography of proximal tibias. The data demonstrate that treatment with ActRIIB-mFc restored muscle mass, adiposity, and bone quality to normal levels in a mouse model of androgen deprivation, thereby alleviating multiple adverse consequences of such therapy.

scholarly journals The Physical Nature of Velocity

2018 ◽  
Vol 10 (6) ◽  
pp. 15
Author(s):  
Zhonggang Li
Keyword(s):  
Mathematical Model ◽  
Total Mass ◽  
Maximum Velocity ◽  
Physical Nature ◽  
Added Mass ◽  
Basic Unit ◽  
Significant Difference ◽  
Moving Body ◽  
Basic Particle ◽  
The Universe

Matter and energy are made up of the same basic particles. Why, then, is there a significant difference between matter and energy? This is because their basic particle compositions differ. The basic particle is the basic unit of mass and energy. Mass and energy conservations are essentially basic particle conversions. The basic particle is a vector, moving at the maximum velocity of the universe; however, after a substance tangibly solidifies, this velocity becomes zero. The velocity of a moving object is, thus, the ratio between the basic particles contributing to energy and those contributing to mass, and the direction of its velocity is determined by the basic particle directions. Electrons, photons, neutrons, protons, neutrinos, and other microscopic particles consist of basic particles. The total mass of a moving body increases with increasing velocity. This added mass is composed of basic particles provided by an external system. As relativity is a mathematical model, its equations may satisfy mathematical principles even though some of them may not represent objective physical facts; instead, these may simply be mathematical solutions without physical meanings.

Determinants of work produced by skeletal muscle: potential limitations of activation and relaxation

1997 ◽  
Vol 273 (3) ◽  
pp. C1049-C1056 ◽  
Author(s):  
V. J. Caiozzo ◽  
K. M. Baldwin
Keyword(s):  
Skeletal Muscle ◽  
Length Change ◽  
Small Strain ◽  
Mechanical Work ◽  
Slow Skeletal Muscle ◽  
Loop Technique ◽  
Force Velocity ◽  
The Difference ◽  
Kinetics Of ◽  
Work Loop

The objective of this study was to estimate the limitations imposed by the kinetics of activation and relaxation on the ability of slow skeletal muscle to produce mechanical work. These estimates were made by the following methods: 1) using the work loop technique and measuring the actual mechanical work (WA) produced by rat soleus muscles (n = 6) at four different frequencies (0.5, 1, 2, and 4 Hz) and seven different amplitudes of length change (1, 2, 3, 4, 5, 6, and 7 mm); 2) determining the force-velocity relationships of the soleus muscles and using this data to quantify the theoretical mechanical work (WT) that could be produced under the work loop conditions described above; and 3) subtracting WA from WT. The difference between WT and WA was interpreted to represent limitations imposed by activation and relaxation. Under certain conditions (high frequency, small strain), factors controlling the kinetics of activation and relaxation reduced the mechanical work of the soleus muscle by approximately 60%. Hence, activation and relaxation collectively represent important factors limiting the production of mechanical work by slow skeletal muscle.

scholarly journals Pretreatment with a soluble activin type IIB receptor/Fc fusion protein improves hypoxia-induced muscle dysfunction

2010 ◽  
Vol 298 (1) ◽  
pp. R96-R103 ◽  
Author(s):  
Emidio E. Pistilli ◽  
Sasha Bogdanovich ◽  
Matias Mosqueira ◽  
Jennifer Lachey ◽  
Jasbir Seehra ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Muscle Mass ◽  
Transforming Growth Factor ◽  
Eccentric Contraction ◽  
Transforming Growth Factor Β ◽  
Hypoxic Exposure ◽  
Muscle Dysfunction ◽  
Tissue Mass ◽  
Fc Fusion Protein ◽  
And Function

Hypoxia, or reduced oxygen, occurs in a variety of clinical and environmental situations. Hypoxic exposure is associated with decreased muscle mass and a concomitant reduction in exercise capacity, although the exact mechanisms are not completely understood. The activin type IIB receptor (ActRIIB) is a receptor for transforming growth factor-β (TGFβ) superfamily members that are involved in the negative regulation of lean tissue mass. Given that hypoxia has negative effects on muscle mass and function and that modulation of the ActRIIB has been shown to increase muscle mass, we tested the hypothesis that pharmacological targeting of the ActRIIB for 2 wk would attenuate the loss of muscle mass and function in mice after exposure to normobaric hypoxia. ActRIIB modulation was achieved using a soluble activin receptor/Fc fusion protein (sActRIIB) in mice housed in a hypoxic chamber for 1 or 2 wk. Hypoxia induced a reduction in body weight in PBS- and sActRIIB-treated mice, although sActRIIB-treated mice remained larger throughout the hypoxic exposure. The absolute forces generated by extensor digitorum longus muscles were also significantly greater in sActRIIB- than PBS-treated mice and were more resistant to eccentric contraction-induced force drop after eccentric lengthening contractions. In summary, sActRIIB pretreatment attenuated hypoxia-induced muscle dysfunction. These data suggest that targeting the ActRIIB is an effective strategy to counter hypoxia-induced muscle dysfunction and to preacclimatize to hypoxia in clinical or high-altitude settings.

scholarly journals NFκB Regulates Muscle Development and Mitochondrial Function

2018 ◽  
Vol 75 (4) ◽  
pp. 647-653 ◽  
Author(s):  
Joseph M Valentine ◽  
Mengyao E Li ◽  
Steven E Shoelson ◽  
Ning Zhang ◽  
Robert L Reddick ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Life Span ◽  
Muscle Mass ◽  
Mitochondrial Function ◽  
Muscle Development ◽  
Tissue Mass ◽  
Lower Oxygen ◽  
Consumption Rates ◽  
Nfκb Pathway ◽  
Gastrocnemius Muscles

Abstract Nuclear factor (NF)κB is a transcription factor that controls immune and inflammatory signaling pathways. In skeletal muscle, NFκB has been implicated in the regulation of metabolic processes and tissue mass, yet its affects on mitochondrial function in this tissue are unclear. To investigate the role of NFκB on mitochondrial function and its relationship with muscle mass across the life span, we study a mouse model with muscle-specific NFκB suppression (muscle-specific IκBα super-repressor [MISR] mice). In wild-type mice, there was a natural decline in muscle mass with aging that was accompanied by decreased mitochondrial function and mRNA expression of electron transport chain subunits. NFκB inactivation downregulated expression of PPARGC1A, and upregulated TFEB and PPARGC1B. NFκB inactivation also decreased gastrocnemius (but not soleus) muscle mass in early life (1–6 months old). Lower oxygen consumption rates occurred in gastrocnemius and soleus muscles from young MISR mice, whereas soleus (but not gastrocnemius) muscles from old MISR mice displayed increased oxygen consumption compared to age-matched controls. We conclude that the NFκB pathway plays an important role in muscle development and growth. The extent to which NFκB suppression alters mitochondrial function is age dependent and muscle specific. Finally, mitochondrial function and muscle mass are tightly associated in both genotypes and across the life span.

Comparison of Estimates of Resting Energy Expenditure Equations in Haemodialysis Patients

2017 ◽  
Vol 40 (3) ◽  
pp. 96-101 ◽  
Author(s):  
Rachel Hung ◽  
Sivakumar Sridharan ◽  
Ken Farrington ◽  
Andrew Davenport
Keyword(s):  
Body Composition ◽  
Energy Expenditure ◽  
Muscle Mass ◽  
Strong Association ◽  
Resting Energy Expenditure ◽  
Tissue Mass ◽  
Waste Products ◽  
Co Morbidity ◽  
Patient Reported ◽  
Resting Energy

Purpose Waste products of metabolism accumulate in patients with chronic kidney disease, and require clearance by haemodialysis (HD). We wished to determine whether there was an association between resting energy expenditure (REE) and total energy expenditure (TEE) in HD patients and body composition. Subjects/Methods We determined REE by recently validated equations (CKD equation) and compared REE with that estimated by standard equations for REE, and TEE calculated from patient reported physical activity, in HD patients with corresponding body composition measured by dual energy X-ray absorptiometry (DEXA) scanning. Results We studied 107 patients, 69 male (64.5%), mean age 62.7 ± 15.1 years. The CKD equation REE was 72.5 ± 13.3 watts (W) and TEE 83.2 ± 9.7 W There was a strong association between REE with body surface area (BSA) (r2 = 0.80), total soft lean and fat lean tissue mass (r2 = 0.69), body mass index (BMI) (r2 = 0.34), all p<0.001. REE estimated using the modified Harris Benedict, Mifflin St. Jeor, Katch McArdle, Bernstein and Robertson equations underestimated REE compared to the CKD equation. TEE was more strongly associated with BSA (r2 = 0.51), appendicular muscle mass (r2 = 0.42), than BMI (r2 = 0.15) all p<0.001. TEE was greater for those employed (104.9 ± 10.7 vs. 83.1 ± 12.3 W, p<0.001), and with no co-morbidity (88.7 ± 14.8 vs. 82.7 ± 12.3 W, P<0.05). Conclusions Standard equations underestimate REE in HD patients compared to the CKD equation. TEE was greater in those with more skeletal muscle mass, in those who were employed and in those with the least comorbidity. More metabolically active patients may well require greater dialytic clearances.

scholarly journals Effects of Resveratrol on the Recovery of Muscle Mass Following Disuse in the Plantaris Muscle of Aged Rats

PLoS ONE ◽  
2013 ◽  
Vol 8 (12) ◽  
pp. e83518 ◽  
Author(s):  
Brian T. Bennett ◽  
Junaith S. Mohamed ◽  
Stephen E. Alway
Keyword(s):  
Muscle Mass ◽  
Aged Rats ◽  
Plantaris Muscle
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