scholarly journals The length dependence of muscle active force: considerations for parallel elastic properties

2005 ◽  
Vol 98 (5) ◽  
pp. 1666-1673 ◽  
Author(s):  
Brian R. MacIntosh ◽  
Meredith B. MacNaughton
Keyword(s):  
Muscle Length ◽  
Element Model ◽  
Medial Gastrocnemius ◽  
Elastic Component ◽  
Contractile Element ◽  
Total Force ◽  
Passive Force ◽  
Active Force ◽  
Fascicle Length ◽  
The Relationship

The purpose of this study was to choose between two popular models of skeletal muscle: one with the parallel elastic component in parallel with both the contractile element and the series elastic component ( model A), and the other in which it is in parallel with only the contractile element ( model B). Passive and total forces were obtained at a variety of muscle lengths for the medial gastrocnemius muscle in anesthetized rats. Passive force was measured before the contraction ( passive A) or was estimated for the fascicle length at which peak total force occurred ( passive B). Fascicle length was measured with sonomicrometry. Active force was calculated by subtracting passive ( A or B) force from peak total force at each fascicle or muscle length. Optimal length, that fascicle length at which active force is maximized, was 13.1 ± 1.2 mm when passive A was subtracted and 14.0 ± 1.1 mm with passive B ( P < 0.01). Furthermore, the relationship between double-pulse contraction force and length was broader when calculated with passive B than with passive A. When the muscle was held at a long length, passive force decreased due to stress relaxation. This was accompanied by no change in fascicle length at the peak of the contraction and only a small corresponding decrease in peak total force. There is no explanation for the apparent increase in active force that would be obtained when subtracting passive A from the peak total force. Therefore, to calculate active force, it is appropriate to subtract passive force measured at the fascicle length corresponding to the length at which peak total force occurs, rather than passive force measured at the length at which the contraction begins.

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.

Adjustable passive length-tension curve in rabbit detrusor smooth muscle

2007 ◽  
Vol 102 (5) ◽  
pp. 1746-1755 ◽  
Author(s):  
John E. Speich ◽  
Christopher Dosier ◽  
Lindsey Borgsmiller ◽  
Kevin Quintero ◽  
Harry P. Koo ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Strain Softening ◽  
Muscle Length ◽  
Strain History ◽  
Total Force ◽  
Detrusor Smooth Muscle ◽  
Passive Force ◽  
Passive Stiffness ◽  
Active Force ◽  
Length Changes

Until the 1990s, the passive and active length-tension ( L-T) relationships of smooth muscle were believed to be static, with a single passive force value and a single maximum active force value for each muscle length. However, recent studies have demonstrated that the active L-T relationship in airway smooth muscle is dynamic and adapts to length changes over a period of time. Furthermore, our prior work showed that the passive L-T relationship in rabbit detrusor smooth muscle (DSM) is also dynamic and that in addition to viscoelastic behavior, DSM displays strain-softening behavior characterized by a loss of passive stiffness at shorter lengths following a stretch to a new longer length. This loss of passive stiffness appears to be irreversible when the muscle is not producing active force and during submaximal activation but is reversible on full muscle activation, which indicates that the stiffness component of passive force lost to strain softening is adjustable in DSM. The present study demonstrates that the passive L-T curve for DSM is not static and can shift along the length axis as a function of strain history and activation history. This study also demonstrates that adjustable passive stiffness (APS) can modulate total force (35% increase) for a given muscle length, while active force remains relatively unchanged (4% increase). This finding suggests that the structures responsible for APS act in parallel with the contractile apparatus, and the results are used to further justify the configuration of modeling elements within our previously proposed mechanical model for APS.

scholarly journals Age-related reductions in the number of serial sarcomeres contribute to shorter fascicle lengths but not elevated passive tension

2021 ◽  
Author(s):  
Geoffrey A. Power ◽  
Sean Crooks ◽  
Jared R. Fletcher ◽  
Brian R. Macintosh ◽  
Walter Herzog
Keyword(s):  
Force Production ◽  
Muscle Length ◽  
Medial Gastrocnemius ◽  
Slight Reduction ◽  
Passive Force ◽  
Fascicle Length ◽  
Age Related ◽  
Absolute Length ◽  
Old Rats ◽  
Length Changes

We investigated age-related changes to fascicle length (FL), sarcomere length (SL), and serial sarcomere number (SSN), and how this affects passive force. Following mechanical testing to determine passive force, the medial gastrocnemius muscle of young (n=9) and old (n=8) Fisher 344BN hybrid rats was chemically fixed at the optimal muscle length for force production; individual fascicles were dissected for length measurement, and laser diffraction was used to assess SL. Old rats had ∼14% shorter FL than young, which was driven by a ∼10% reduction in SSN, with no difference in SL (∼4%). Passive force was greater in the old compared to young rats at long muscle lengths. Shorter FL and reduced SSN in the old rats could not entirely explain increased passive forces for absolute length changes, owing to a slight reduction in SL in old, resulting in similar SL at long muscle lengths.

Tendon organs of cat medial gastrocnemius: responses to active and passive forces as a function of muscle length

1975 ◽  
Vol 38 (5) ◽  
pp. 1217-1231 ◽  
Author(s):  
J. A. Stephens ◽  
R. M. Reinking ◽  
D. G. Stuart
Keyword(s):  
Firing Rate ◽  
Muscle Length ◽  
Motor Units ◽  
Medial Gastrocnemius ◽  
Passive Force ◽  
Force Development ◽  
Single Motor ◽  
Golgi Tendon Organs ◽  
Single Motor Units ◽  
Tendon Organs

The responses of 13 Golgi tendon organs to graded force development of 29 motor units in medial gastrocnemius of the cat have been studied in five experiments. Of the 13 tendon organs, 11 were responsive to passive stretch within the physiological range of muscle length and 5 were "spontaneously" active at very short lengths where no passive tension could be recorded. The relationship between passive force and the firing rates of the various afferents ranged from a linear one to a power relation (Y = Axb + c) with b, a widely varying exponent. Results support the general conclusion that although many Ib afferents respond to passive force within the physiological range of muscle stretch, this form of stimulus is not a particularly effective one. The statis responses of Golgi tendon organs to active force development produced by single motor units was studied at different muscle lengths. In all cases the apparent sensitivity (change in firing rate per active force developed) decreased as muscle length approached Lo. The static responses of Golgi tendon organs to force developed by single motor units were also studied during fatiguing contractions. The data suggest a sigmoid relationship between force developed at the tendon and the Ib response. The collective response of all 13 tendon organs to active and passive forces at different muscle lengths was also examined. This analysis offered further support for the viewpoint that active motor unit contractions provide themost significant excitatory input to tendon organs and that changes in passive force during muscle stretch have comparatively little effect on the collective tendon organ response. The interaction between active and passive force inputs to the Golgi tendon organs is discussed in relation to the complicated nature of the relationship between forces measured at the tendon and those acting within the receptor capsule. When these complications were taken into account it was possible to explain the differences in responsiveness of a given tendon organ to active contraction of several motor units and to passive force in terms of a single force-firing rate curve for the receptor. It is concluded that changes in the force of contraction of single motor units result in relatively small changes in Ib afferent firing and that during normal muscle contractions, changes in the number of motor units acting on a single receptor must produce far more significant changes in firing rate than changes in the amount of force developed by any single unit. Changes in dynamic Ib sensitivity to single motor unit contractions are also shown to depend on length and in a similar way to the changes in static Ib sensitivity. During fatiguing contractions, a sigmoid relation was found between the dynamic Ib response and the rate of force development by single motor units.

Series elastic and contractile elements in heart muscle: changes in muscle length

1964 ◽  
Vol 207 (6) ◽  
pp. 1330-1338 ◽  
Author(s):  
Edmund H. Sonnenblick
Keyword(s):  
Heart Muscle ◽  
Isometric Force ◽  
Muscle Length ◽  
Elastic Component ◽  
Contractile Element ◽  
Series Elastic Component ◽  
Velocity Of Shortening ◽  
Extension Curve ◽  
Muscle Changes ◽  
Series Elastic

Isometric force generation, the result of the interaction of an actively shortening contractile element (CE) with a passive series elastic component (SE), has been analyzed in heart muscle using the cat papillary muscle. The stiffness of the SE (Δ load/Δ extension or d p/d l) was shown to be a linear function of developed force of contraction or load ( P). The load-extension curve of the SE was thus exponential in form, the SE being stretched an amount equivalent to 8–10% of initial muscle length during the development of maximum isometric force (600 g/cm2). The load-extension curve of the SE was also obtained from the curve relating initial velocity of shortening to time after stimulation. This latter relation and the linear relation of SE stiffness to force were found to be independent of initial muscle length. These results were interpreted to suggest that increases in muscle length bring about an increase in the number of series elastic components as well as contractile elements arranged in parallel. The series elastic component thus cannot be relegated entirely to external attachments of the muscle (e.g., tendon), but must be closely associated with the contractile element system itself.

scholarly journals Plantarflexor Torque and Work is Positively Correlated with Medial Gastrocnemius Fascicle Length in Healthy Young Adults

2019 ◽  
Author(s):  
John F Drazan ◽  
Todd J Hullfish ◽  
Josh R Baxter
Keyword(s):  
Young Adults ◽  
Healthy Adult ◽  
Peak Torque ◽  
The Elderly ◽  
Medial Gastrocnemius ◽  
Total Work ◽  
Fascicle Length ◽  
Muscle Structure ◽  
The Relationship ◽  
Maximal Effort

ABSTRACTAnkle kinetics are critical for ambulatory function in elite athletes, the elderly, and many patient populations. Despite the robust findings linking plantarflexor muscle structure to gross function with these populations, the link between plantarflexor fascicle length and ankle kinetics has not been established in the literature. In this study, we determined the relationship between muscle structure and peak torque and total work produced by the plantarflexors during maximal effort contractions. We measured resting fascicle length and pennation angle of the medial gastrocnemius using ultrasound in healthy adult subjects (n=12). Subjects performed contractions on a dynamometer during isokinetic and isometric conditions. Longer fascicles were positively correlated with higher peak torque and total work (R2 > 0.41, p < 0.013) across all isokinetic velocities. Higher pennation angles were negatively correlated with peak torque and total work (R2 > 0.296, p < 0.067). None of these correlations were significant in isometric conditions. This provides experimental evidence demonstrating the link between plantarflexor muscle structure and ankle kinetics in healthy young adults which has hitherto not been experimentally demonstrated in existing literature.

In vivo determination of fascicle curvature in contracting human skeletal muscles

2002 ◽  
Vol 92 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Tadashi Muramatsu ◽  
Tetsuro Muraoka ◽  
Yasuo Kawakami ◽  
Akira Shibayama ◽  
Tetsuo Fukunaga
Keyword(s):  
Maximum Voluntary Contraction ◽  
Muscle Length ◽  
Muscle Thickness ◽  
Voluntary Contraction ◽  
Pennation Angle ◽  
Medial Gastrocnemius ◽  
Fascicle Length ◽  
Fascicle Curvature

Fascicle curvature of human medial gastrocnemius muscle (MG) was determined in vivo by ultrasonography during isometric contractions at three (distal, central, and proximal) locations ( n = 7) and at three ankle angles ( n = 7). The curvature significantly ( P < 0.05) increased from rest to maximum voluntary contraction (MVC) (0.4–5.2 m−1). In addition, the curvature at MVC became larger in the order dorsiflexed, neutral, plantar flexed ( P < 0.05). Thus both contraction levels and muscle length affected the curvature. Intramuscular differences in neither the curvature nor the fascicle length were found. The direction of curving was consistent along the muscle: fascicles were concave in the proximal side. Fascicle length estimated from the pennation angle and muscle thickness, under the assumption that the fascicle was straight, was underestimated by ∼6%. In addition, the curvature was significantly correlated to pennation angle and muscle thickness. These findings are particularly important for understanding the mechanical functions of human skeletal muscle in vivo.

Contractile force of canine tracheal smooth muscle during continuous stretch

1982 ◽  
Vol 52 (3) ◽  
pp. 655-663 ◽  
Author(s):  
S. J. Gunst ◽  
J. A. Russell
Keyword(s):  
Smooth Muscle ◽  
Isometric Contraction ◽  
Muscle Force ◽  
Muscle Length ◽  
Force Transducer ◽  
Contractile Force ◽  
Tracheal Smooth Muscle ◽  
Contractile Element ◽  
Active Force ◽  
Force Curve

Canine tracheal smooth muscle strips were mounted horizontally in a tissue bath between a force transducer and a motor-driven movable steel rod, which was used to change muscle length. Muscle length and force were continuously measured during stretch and simultaneously plotted on an X-Y recorder. Active force during stretch was investigated as follows: an initial length was set with the muscle relaxed, where it was contracted isometrically with acetylcholine. After active force reached a steady state, muscle length was decreased until the total tension was equal to zero. The muscle was then stretched slowly to obtain a continuous length-force curve. Results show that force during stretch increases as the length at which the initial isometric contraction is elicited, is decreased. A possible interpretation is that during tonic muscle contraction, the contractile element is able to shorten very slowly relative to the rate at which the muscle was retracted. Thus, the contractile element length established during isometric contraction would affect the muscle force obtained during subsequent stretch of the muscle.

scholarly journals Age-related reductions in the number of serial sarcomeres contribute to shorter fascicle lengths but not elevated passive tension

2020 ◽  
Author(s):  
Geoffrey A. Power ◽  
Sean Crooks ◽  
Jared R. Fletcher ◽  
Brian R. Macintosh ◽  
Walter Herzog
Keyword(s):  
Muscle Length ◽  
Medial Gastrocnemius ◽  
Slight Reduction ◽  
Passive Tension ◽  
Passive Force ◽  
Older Individuals ◽  
Age Related ◽  
Old Rats ◽  
Length Changes ◽  
Age Related Changes

AbstractWe investigated age-related changes to fascicle length (FL), sarcomere length (SL), and serial sarcomere number (SSN), and how this affects passive force. Following mechanical testing to determine passive force, the medial gastrocnemius muscle of young (n=9) and old (n=8) Fisher 344BN hybrid rats was chemically fixed at the optimal muscle length for force production; individual fascicles were dissected for length measurement, and laser diffraction was used to assess SL. Old rats had ∼14% shorter FL than young, which was driven by a ∼10% reduction in SSN, with no difference in SL (∼4%). Passive force was greater in the old compared to young rats at long muscle lengths. Shorter FL and reduced SSN in the old rats could not entirely explain increased passive forces for absolute length changes, owing to a slight reduction in SL in old, resulting in similar SL at long muscle lengths.Summary StatementThis study sought to explain the increased passive tension observed for muscles of older individuals owing to age-related changes to muscle architecture.

scholarly journals How does passive lengthening change the architecture of the human medial gastrocnemius muscle?

2017 ◽  
Vol 122 (4) ◽  
pp. 727-738 ◽  
Author(s):  
Bart Bolsterlee ◽  
Arkiev D’Souza ◽  
Simon C. Gandevia ◽  
Robert D. Herbert
Keyword(s):  
Diffusion Tensor ◽  
Muscle Fibers ◽  
Three Dimensional ◽  
Muscle Length ◽  
Muscle Architecture ◽  
Medial Gastrocnemius ◽  
Fascicle Length ◽  
Muscle Belly ◽  
Whole Muscle

There are few comprehensive investigations of the changes in muscle architecture that accompany muscle contraction or change in muscle length in vivo. For this study, we measured changes in the three-dimensional architecture of the human medial gastrocnemius at the whole muscle level, the fascicle level and the fiber level using anatomical MRI and diffusion tensor imaging (DTI). Data were obtained from eight subjects under relaxed conditions at three muscle lengths. At the whole muscle level, a 5.1% increase in muscle belly length resulted in a reduction in both muscle width (mean change −2.5%) and depth (−4.8%). At the fascicle level, muscle architecture measurements obtained at 3,000 locations per muscle showed that for every millimeter increase in muscle-tendon length above the slack length, average fascicle length increased by 0.46 mm, pennation angle decreased by 0.27° (0.17° in the superficial part and 0.37° in the deep part), and fascicle curvature decreased by 0.18 m−1. There was no evidence of systematic variation in architecture along the muscle’s long axis at any muscle length. At the fiber level, analysis of the diffusion signal showed that passive lengthening of the muscle increased diffusion along fibers and decreased diffusion across fibers. Using these measurements across scales, we show that the complex shape changes that muscle fibers, whole muscles, and aponeuroses of the medial gastrocnemius undergo in vivo cannot be captured by simple geometrical models. This justifies the need for more complex models that link microstructural changes in muscle fibers to macroscopic changes in architecture. NEW & NOTEWORTHY Novel MRI and DTI techniques revealed changes in three-dimensional architecture of the human medial gastrocnemius during passive lengthening. Whole muscle belly width and depth decreased when the muscle lengthened. Fascicle length, pennation, and curvature changed uniformly or near uniformly along the muscle during passive lengthening. Diffusion of water molecules in muscle changes in the same direction as fascicle strains.

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