The interaction of compliance and activation on the force-length operating range and force generating capacity of skeletal muscle

2019 ◽  
Author(s):  
S.M. Cox ◽  
K.L. Easton ◽  
M. Cromie Lear ◽  
R.L. Marsh ◽  
S.L. Delp ◽  
...  
Keyword(s):  
Force Production ◽  
Muscle Performance ◽  
Operating Range ◽  
Compliance Level ◽  
Generating Capacity ◽  
Low Sensitivity ◽  
Fixed End ◽  
Muscle Models ◽  
No Activation ◽  
Tendon Compliance

AbstractMuscle performance is influenced by where it operates on its force-length curve. Here we explore how activation and tendon compliance interact to influence muscle operating lengths and force-generating capacity. To study this, we built a musculoskeletal model of the lower limb of the guinea fowl and simulated the force-length operating range during fixed-end fixed-posture contractions for 39 actuators under thousands of combinations of activation and posture using three different muscle models: Muscles with non-compliant tendons, muscles with compliant tendons but no activation dependent shift in optimal fiber length (L0), and muscles with both compliant tendons and activation-dependent shifts in L0. We found that activation dependent effects altered muscle fiber lengths up to 40% and increased or decreased force capacity by up to 50% during fixed-end contractions. Typically, activation-compliance effects reduce muscle force and are dominated by the effects of tendon compliance at high activations. At low activation, however, activation-dependent shifts in L0 are equally important and can result in relative force changes for low compliance muscles of up to 60%. There are regions of the force-length curve in which muscles are most sensitive to compliance and there are troughs of influence where these factors have little effect. These regions are hard to predict, though, because the magnitude and location of these areas of high and low sensitivity shift with compliance level. Here we provide a map for when these effects will meaningfully influence force capacity and an example of their contributions to force production during a static task, namely standing.

scholarly journals The Interaction of Compliance and Activation on the Force-Length Operating Range and Force Generating Capacity of Skeletal Muscle: A Computational Study using a Guinea Fowl Musculoskeletal Model

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
S M Cox ◽  
K L Easton ◽  
M Cromie Lear ◽  
R L Marsh ◽  
S L Delp ◽  
...  
Keyword(s):  
Computational Study ◽  
Force Production ◽  
Musculoskeletal Model ◽  
Guinea Fowl ◽  
Operating Range ◽  
Compliance Level ◽  
Generating Capacity ◽  
Low Sensitivity ◽  
Fixed End ◽  
Tendon Compliance

Synopsis A muscle’s performance is influenced by where it operates on its force–length (F–L) curve. Here we explore how activation and tendon compliance interact to influence muscle operating lengths and force-generating capacity. To study this, we built a musculoskeletal model of the lower limb of the guinea fowl and simulated the F–L operating range during fixed-end fixed-posture contractions for 39 actuators under thousands of combinations of activation and posture using three different muscle models: Muscles with non-compliant tendons, muscles with compliant tendons but no activation-dependent shift in optimal fiber length (L0), and muscles with both compliant tendons and activation-dependent shifts in L0. We found that activation-dependent effects altered muscle fiber lengths up to 40% and increased or decreased force capacity by up to 50% during fixed-end contractions. Typically, activation-compliance effects reduce muscle force and are dominated by the effects of tendon compliance at high activations. At low activation, however, activation-dependent shifts in L0 are equally important and can result in relative force changes for low compliance muscles of up to 60%. There are regions of the F–L curve in which muscles are most sensitive to compliance and there are troughs of influence where these factors have little effect. These regions are hard to predict, though, because the magnitude and location of these areas of high and low sensitivity shift with compliance level. In this study we provide a map for when these effects will meaningfully influence force capacity and an example of their contributions to force production during a static task, namely standing.

Effects of hypoxia and hypercapnia on geniohyoid contractility and endurance

1991 ◽  
Vol 71 (2) ◽  
pp. 709-715 ◽  
Author(s):  
R. J. Salmone ◽  
E. Van Lunteren
Keyword(s):  
Force Production ◽  
Upper Airway ◽  
Muscle Performance ◽  
Severe Hypoxia ◽  
Force Frequency ◽  
Force Output ◽  
Frequency Curve ◽  
Dilator Muscle ◽  
Index Ratio ◽  
Mild Hypoxia

Sleep apnea and other respiratory diseases produce hypoxemia and hypercapnia, factors that adversely affect skeletal muscle performance. To examine the effects of these chemical alterations on force production by an upper airway dilator muscle, the contractile and endurance characteristics of the geniohyoid muscle were examined in situ during severe hypoxia (arterial PO2 less than 40 Torr), mild hypoxia (PO2 45–65 Torr), and hypercapnia (PCO2 55–80 Torr) and compared with hyperoxic-normocapnic conditions in anesthetized cats. Muscles were studied at optimal length, and contractile force was assessed in response to supramaximal electrical stimulation of the hypoglossal nerve (n = 7 cats) or geniohyoid muscle (n = 2 cats). There were no significant changes in the twitch kinetics or force-frequency curve of the geniohyoid muscle during hypoxia or hypercapnia. However, the endurance of the geniohyoid, as reflected in the fatigue index (ratio of force at 2 min to initial force in response to 40-Hz stimulation at a duty cycle 0.33), was significantly reduced by severe hypoxia but not by hypercapnia or mild hypoxia. In addition, the downward shift in the force-frequency curve after the repetitive stimulation protocol was greater during hypoxia than hyperoxia, especially at higher frequencies. In conclusion, the ability of the geniohyoid muscle to maintain force output during high levels of activation is adversely affected by severe hypoxia but not mild hypoxia or hypercapnia. However, none of these chemical perturbations affected muscle contractility acutely.

Force-length relation of isometric sarcomeres in fixed-end tetani

1993 ◽  
Vol 264 (1) ◽  
pp. C19-C26 ◽  
Author(s):  
A. Horowitz ◽  
G. H. Pollack
Keyword(s):  
Sarcomere Length ◽  
Production Capacity ◽  
Force Production ◽  
Length Change ◽  
Optical Diffraction ◽  
Tetanic Force ◽  
End Conditions ◽  
Linear Force ◽  
Fixed End

The higher force observed in fixed-end tetani relative to sarcomere-isometric tetani is commonly attributed to sarcomere length inhomogeneity; sarcomeres in the end regions of the fiber shorten extensively at the expense of the central sarcomeres. By shortening, these sarcomeres supposedly attain higher force production capacity and can thus account for the extra force. However, the fibers could also contain sarcomeres that stay isometric throughout most of the tetanic force plateau. If such sarcomeres undergo slight shortening before their isometric phase, their force-length relation should be elevated (A. Horowitz, H. P. M Wussling, and G. H. Pollack. Biophys. J. 63: 3-17, 1992). These sarcomeres may therefore account for the higher force in fixed-end tetani. To test this possibility, single frog semitendinosus fibers were tetanized under fixed-end conditions. Sarcomere length change during the tetanus was measured at different locations along the fiber by optical diffraction. Fibers stretched to average sarcomere lengths between 2.2 and 3.2 microns contained sarcomeres that, except for some initial shortening during the early part of the tetanus, remained isometric. These sarcomeres were located between the ends and the central region of the fibers. Their force-length relation was higher than the linear force-length relation based on sarcomere length clamps by an average of 14% between sarcomere lengths of 2.4-3.2 microns. Thus slight (1-5%) shortening may explain the relatively higher fixed-end force-length relation.

The influence of respiratory acid-base changes on muscle performance and excitability of the sarcolemma during strenuous intermittent hand grip exercise

2012 ◽  
Vol 112 (4) ◽  
pp. 571-579 ◽  
Author(s):  
M. Hilbert ◽  
V. Shushakov ◽  
N. Maassen
Keyword(s):  
Force Production ◽  
Respiratory Acidosis ◽  
Respiratory Alkalosis ◽  
Muscle Performance ◽  
Protective Effects ◽  
Acid Base ◽  
M Wave ◽  
Hand Grip

Acidification has been reported to provide protective effects on force production in vitro. Thus, in this study, we tested if respiratory acid-base changes influence muscle function and excitability in vivo. Nine subjects performed strenuous, intermittent hand grip exercises (10 cycles of 15 s of work/45 s of rest) under respiratory acidosis by CO2 rebreathing, alkalosis by hyperventilation, or control. The Pco2, pH, K+ concentration ([K+]), and Na+ concentration were measured in venous and arterialized blood. Compound action potentials (M-wave) were elicited to examine the excitability of the sarcolemma. The surface electromyogram (EMG) was recorded to estimate the central drive to the muscle. The lowest venous pH during the exercise period was 7.24 ± 0.03 in controls, 7.31 ± 0.05 with alkalosis, and 7.17 ± 0.04 with acidosis ( P < 0.001). The venous [K+] rose to similar maximum values in all conditions (6.2 ± 0.8 mmol/l). The acidification reduced the decline in contraction speed ( P < 0.001) but decreased the M-wave area to 73.4 ± 19.8% ( P < 0.001) of the initial value. After the first exercise cycle, the M-wave area was smaller with acidosis than with alkalosis, and, after the second cycle, it was smaller with acidosis than with the control condition ( P < 0.001). The duration of the M-wave was not affected. Acidification diminished the reduction in performance, although the M-wave area during exercise was decreased. Respiratory alkalosis stabilized the M-wave area without influencing performance. Thus, we did not find a direct link between performance and alteration of excitability of the sarcolemma due to changes in pH in vivo.

Increased tetanic force and reduced myoplasmic [P(i)] following a brief series of tetani in mouse soleus muscle

1997 ◽  
Vol 272 (3) ◽  
pp. C870-C874 ◽  
Author(s):  
J. D. Bruton ◽  
C. Wretman ◽  
A. Katz ◽  
H. Westerblad
Keyword(s):  
Soleus Muscle ◽  
Inorganic Phosphate ◽  
Force Production ◽  
Muscle Performance ◽  
Tetanic Force ◽  
Warm Up ◽  
Improved Performance

Muscle performance is improved after a brief period of exercise (warm-up). One factor that is known to strongly affect force production is the myoplasmic concentration of inorganic phosphate ([P(i)]). Improved performance after warm-up may therefore be due to a reduction of [P(i)]. Herein, we show that after a warm-up protocol (15 tetani at 2-s intervals), tetanic force is increased by approximately 6% (P < 0.05) and [P(i)] is almost halved (P < 0.05) in isolated mouse soleus muscle. A warm-up protocol with longer intervals (15 tetani at 5-s intervals) reduced tetanic force and did not alter [P(i)]. We conclude that a reduction of [P(i)] contributes to the force-potentiating effect of warm-up.

scholarly journals Can Mental Practice Increase Ankle Dorsiflexor Torque?

2005 ◽  
Vol 85 (10) ◽  
pp. 1053-1060 ◽  
Author(s):  
Ben Sidaway ◽  
Amy (Robinson) Trzaska
Keyword(s):  
Treatment Options ◽  
Force Production ◽  
Mental Practice ◽  
Control Group ◽  
Physical Practice ◽  
Practice Group ◽  
Generating Capacity ◽  
Abductor Digiti Minimi ◽  
Group A ◽  
Ankle Dorsiflexor

Abstract Background and Purpose. Mental practice has been shown to be effective in increasing the force production of the abductor digiti minimi muscle in the hand. The aim of this study was to determine whether mental practice could produce strength gains in the larger ankle dorsiflexor muscles, which are important during walking. Subjects. Twenty-four subjects were randomly assigned to a physical practice group, a mental practice group, or a control group (8 subjects per group). Methods. In the practice groups, subjects either physically or mentally practiced producing maximal isometric contractions for 3 sets of 10 repetitions, 3 times per week for 4 weeks. Changes in mean peak isometric torque normalized to body weight and the resulting percentage of improvement were analyzed across the 3 groups. Results. Differences in raw torque production after training in the 2 practice groups resulted in significant percentages of improvement for the physical practice group (25.28%) and the mental practice group (17.13%), but not for the control group (−1.77%). The 2 practice groups were not statistically different in their maximal torque-generating capacity after training. Discussion and Conclusion. These findings show that mental practice in people without impairments can lead to an increase in torque production similar to that produced by physical practice. Such a technique may prove to be a useful adjunct to traditional treatment options aimed at increasing muscle strength.

scholarly journals Desmin is a modifier of dystrophic muscle features in Mdx mice

2019 ◽  
Author(s):  
Arnaud Ferry ◽  
Julien Messéant ◽  
Ara Parlakian ◽  
Mégane Lemaitre ◽  
Pauline Roy ◽  
...  
Keyword(s):  
Neuromuscular Disease ◽  
Muscle Hypertrophy ◽  
Force Production ◽  
Muscle Performance ◽  
Mdx Mice ◽  
Force Transmission ◽  
Dystrophic Muscle ◽  
Adeno Associated Virus ◽  
Dystrophin Deficiency ◽  
Insight Into

AbstractDuchenne muscular dystrophy (DMD) is a severe neuromuscular disease, caused by dystrophin deficiency. Desmin is like dystrophin associated to costameric structures bridging sarcomeres to extracellular matrix that are involved in force transmission and skeletal muscle integrity. In the present study, we wanted to gain further insight into the roles of desmin which expression is increased in the muscle from the mouse Mdx DMD model. We show that a deletion of the desmin gene (Des) in Mdx mice (DKO, Mdx:desmin-/-) induces a marked worsening of the weakness (reduced maximal force production) as compared to Mdx mice. Fragility (higher susceptibility to contraction-induced injury) was also aggravated and fatigue resistance was reduced in DKO mice. Moreover, in contrast to Mdx mice, the DKO mice did not undergo a muscle hypertrophy because of smaller and less numerous fibers, with reduced percentage of centronucleated fibres. Interestingly, Desmin cDNA transfer with adeno-associated virus in 1-month-old DKO mice and newborn Mdx mice improved muscle weakness. Overall, desmin plays important and beneficial roles on muscle performance, fragility and remodelling in dystrophic Mdx mice.

Abstract 5404: Perturbation of Tropomyosin Amino Acid Residues Binding to Actin at the “Off” State of Tropomyosin Increase Cardiac Muscle Dynamics

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Mariappan Muthuchamy ◽  
Rochelle Dowdie ◽  
Xin Wu ◽  
Scott Zawieja ◽  
Kuppan Gokulan ◽  
...  
Keyword(s):  
Cardiac Muscle ◽  
Force Production ◽  
Site Directed Mutagenesis ◽  
Muscle Performance ◽  
Amino Acid Residues ◽  
Surface Charges ◽  
Data Analyses ◽  
Muscle Dynamics ◽  
C Terminus ◽  
Charged Residues

Tropomyosin (TM), an essential thin filament protein, binds along F-actin in association with troponin and plays a central role in regulating cardiac muscle dynamics. Previous structural studies have shown that TM molecule consists of 14 negatively charged, alternating α- and β-bands along its length, responsible for binding to actin. The 7 α-bands of TM are implicated in the binding to actin at the “off” state where actomyosin crossbridging is blocked. The 7 β-bands of TM bind to actin at the “on” state that permits actomyosin interaction and results in force production. In this study, we hypothesize that if the α-bands are perturbed by changing the charged residues at that region, it will cause TM molecule “slipping” at the “off” state that will allow TM to be in an extended “on” state leading to enhanced cardiac muscle dynamics. To test this hypothesis we have generated TG mouse lines expressing α-TM with mutations in the α-bands located in the carboxy terminus (α-TM CTM). More specifically, codons encoding negatively charged amino acids (aspartate or glutamate) at positions 212, 219, 223, 255 and 259 were changed to lysine by site-directed mutagenesis. Molecular analyses revealed one of the TG lines α-TM CTM-6 expressed 100% of mutant protein. Echocardiogram data analyses showed that α-TM CTM-6 hearts exhibited significant decrease in heart rate (10%; p<0.05, n=6)) in the absence or presence of dobutamine. Furthermore, the percentage fractional shortening and ejection fraction were significantly increased (13% and 15%, respectively, p<0.05, n=6) in TG hearts when compared to non-transgenic (NTG) controls. To investigate the mechanisms for the increase in cardiac muscle dynamics in the TG hearts, we measured force and calcium levels in the papillary muscle fiber. Force- [Ca2+]i data analyses showed that the α-TM CTM TG hearts produced more force per given [Ca2+]i when compared to NTG hearts, indicating that α-TM CTM myofilaments exhibit an increase in Ca2+ sensitivity. Protein modeling analyses show surface charges of α-TM CTM molecule is altered. We propose that the changes in charged residues in the α-bands located in the C-terminus of TM molecule perturb the “off” state, which augment the crossbridge kinetics and lead to enhanced cardiac muscle performance.

Doublet potentiation in the triceps surae is limited by series compliance and dynamic fascicle behavior

2015 ◽  
Vol 119 (7) ◽  
pp. 807-816 ◽  
Author(s):  
Dean L. Mayfield ◽  
Glen A. Lichtwark ◽  
Neil J. Cronin ◽  
Janne Avela ◽  
Andrew G. Cresswell
Keyword(s):  
Force Production ◽  
Muscle Length ◽  
Triceps Surae ◽  
Ultrasound Images ◽  
Lateral Gastrocnemius ◽  
Nonlinear Force ◽  
Series Compliance ◽  
Fixed End ◽  
High Series ◽  
Stimulation Of

Activation of skeletal muscle twice in quick succession results in nonlinear force summation (i.e., doublet potentiation). The force contributed by a second activation is typically of augmented amplitude, longer in duration, and generated at a greater rate. The purpose of this study was to examine force summation in a muscle attached to a compliant tendon, where considerable internal shortening occurs during a fixed-end contraction. The triceps surae of 21 ( Experiment 1) and 9 ( Experiment 2) young adults were maximally activated with doublet stimulation of different interstimulus intervals (ISIs) (5-100 ms) at several muscle lengths. Ultrasound images acquired from lateral gastrocnemius and soleus muscles allowed quantification of dynamic fascicle behavior. Force summation was muscle length dependent. Force augmentation was limited to a short muscle length. Lateral gastrocnemius and soleus fascicles underwent large amounts of active shortening and achieved high velocities in response to doublet stimulation, dynamics unfavorable for force production. Summation amplitude and the sensitivity of summation to ISI were dramatically depressed in the triceps surae after comparison to muscles with less fixed-end compliance. We propose that the internal shortening permitted by high series compliance limited force augmentation by offsetting and/or interfering with activation and cross-bridge processes driving augmentation. High series compliance may also reduce the sensitivity of the summated response to ISI, an assertion supported by predictions from a Hill-type muscle model. These muscles may exhibit greater force augmentation during more accustomed stretch-shorten tasks (i.e., hopping), where the compliance of the Achilles tendon actually enables near-isometric fascicle behavior.

Sign in / Sign up

Export Citation Format

Share Document