scholarly journals Additional in‐series compliance does not affect the length dependence of activation in rat medial gastrocnemius

2020 ◽  
Vol 105 (11) ◽  
pp. 1907-1917 ◽  
Author(s):  
Keenan B. MacDougall ◽  
Anders M. Kristensen ◽  
Brian R. MacIntosh
Keyword(s):  
Medial Gastrocnemius ◽  
Length Dependence ◽  
In Series ◽  
Series Compliance

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 Stiffening the human foot with a biomimetic exotendon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryan C. Riddick ◽  
Dominic J. Farris ◽  
Nicholas A. T. Brown ◽  
Luke A. Kelly
Keyword(s):  
Energy Savings ◽  
Metabolic Energy ◽  
Medial Gastrocnemius ◽  
The Novel ◽  
Abductor Hallucis ◽  
Human Foot ◽  
Alternative Approach ◽  
In Series ◽  
Series Compliance ◽  
Footwear Design

AbstractShoes are generally designed protect the feet against repetitive collisions with the ground, often using thick viscoelastic midsoles to add in-series compliance under the human. Recent footwear design developments have shown that this approach may also produce metabolic energy savings. Here we test an alternative approach to modify the foot–ground interface by adding additional stiffness in parallel to the plantar aponeurosis, targeting the windlass mechanism. Stiffening the windlass mechanism by about 9% led to decreases in peak activation of the ankle plantarflexors soleus (~ 5%, p < 0.001) and medial gastrocnemius (~ 4%, p < 0.001), as well as a ~ 6% decrease in positive ankle work (p < 0.001) during fixed-frequency bilateral hopping (2.33 Hz). These results suggest that stiffening the foot may reduce cost in dynamic tasks primarily by reducing the effort required to plantarflex the ankle, since peak activation of the intrinsic foot muscle abductor hallucis was unchanged (p = 0.31). Because the novel exotendon design does not operate via the compression or bending of a bulky midsole, the device is light (55 g) and its profile is low enough that it can be worn within an existing shoe.

Rises in whole muscle passive tension of mammalian muscle after eccentric contractions at different lengths

2003 ◽  
Vol 95 (3) ◽  
pp. 1224-1234 ◽  
Author(s):  
N. P. Whitehead ◽  
D. L. Morgan ◽  
J. E. Gregory ◽  
U. Proske
Keyword(s):  
Isometric Tension ◽  
The Other ◽  
Medial Gastrocnemius ◽  
Eccentric Contractions ◽  
Passive Tension ◽  
Active Length ◽  
Before And After ◽  
Two Factors ◽  
In Series ◽  
Whole Muscle

This is a report of experiments carried out on the medial gastrocnemius muscle of the anesthetized cat, investigating the effects of eccentric contractions carried out at different muscle lengths on the passive and active length-tension relationships. In one series of experiments, the motor supply to the muscle was divided into three approximately equal parts; in the other, whole muscles were used. Fifty eccentric contractions were carried out over different regions of the active length-tension curve for each partial or whole muscle. Active and passive length-tension curves were measured before and after the eccentric contractions. When eccentric contractions were carried out at longer lengths, there was a larger shift of the optimum length for active tension in the direction of longer muscle lengths and a larger fall in peak isometric tension. Passive tension was higher immediately after the eccentric contractions, and if the muscle was left undisturbed for 40 min, it increased further to higher values, particularly after contractions at longer lengths. A series of 20 passive stretches of the same speed and amplitude and covering the same length range as the active stretches, reduced the passive tension which redeveloped over a subsequent 40-min period. It is hypothesized that there are two factors influencing the level of passive tension in a muscle after a series of eccentric contractions. One is injury contractures in damaged muscle fibers tending to raise passive tension; the other is the presence of disrupted sarcomeres in series with still-functioning sarcomeres tending to reduce it.

scholarly journals Modeling age-related changes in muscle-tendon dynamics during cyclical contractions in the rat gastrocnemius

2016 ◽  
Vol 121 (4) ◽  
pp. 1004-1012 ◽  
Author(s):  
Nicole Danos ◽  
Natalie C. Holt ◽  
Gregory S. Sawicki ◽  
Emanuel Azizi
Keyword(s):  
Elastic Energy ◽  
Metabolic Cost ◽  
Medial Gastrocnemius ◽  
Tissue Properties ◽  
Age Related ◽  
In Series ◽  
Force Velocity ◽  
Length Changes ◽  
Metabolic Performance ◽  
Age Related Changes

Efficient muscle-tendon performance during cyclical tasks is dependent on both active and passive mechanical tissue properties. Here we examine whether age-related changes in the properties of muscle-tendon units (MTUs) compromise their ability to do work and utilize elastic energy storage. We empirically quantified passive and active properties of the medial gastrocnemius muscle and material properties of the Achilles tendon in young (∼6 mo) and old (∼32 mo) rats. We then used these properties in computer simulations of a Hill-type muscle model operating in series with a Hookean spring. The modeled MTU was driven through sinusoidal length changes and activated at a phase that optimized muscle-tendon tuning to assess the relative contributions of active and passive elements to the force and work in each cycle. In physiologically realistic simulations where young and old MTUs started at similar passive forces and developed similar active forces, the capacity of old MTUs to store elastic energy and produce positive work was compromised. These results suggest that the observed increase in the metabolic cost of locomotion with aging may be in part due to the recruitment of additional muscles to compensate for the reduced work at the primary MTU. Furthermore, the age-related increases in passive stiffness coupled with a reduced active force capacity in the muscle can lead to shifts in the force-length and force-velocity operating range that may significantly impact mechanical and metabolic performance. Our study emphasizes the importance of the interplay between muscle and tendon mechanical properties in shaping MTU performance during cyclical contractions.

scholarly journals Additional in-series compliance reduces muscle force summation and alters the time course of force relaxation during fixed-end contractions

2016 ◽  
Vol 219 (22) ◽  
pp. 3587-3596 ◽  
Author(s):  
Dean L. Mayfield ◽  
Bradley S. Launikonis ◽  
Andrew G. Cresswell ◽  
Glen A. Lichtwark
Keyword(s):  
Time Course ◽  
Muscle Force ◽  
Force Relaxation ◽  
In Series ◽  
Series Compliance ◽  
Fixed End

Low-frequency depression of tension in the cat gastrocnemius muscle after eccentric exercise

2004 ◽  
Vol 97 (4) ◽  
pp. 1195-1202 ◽  
Author(s):  
S. Parikh ◽  
D. L. Morgan ◽  
J. E. Gregory ◽  
U. Proske
Keyword(s):  
Eccentric Exercise ◽  
Muscle Activation ◽  
Low Frequency ◽  
Muscle Length ◽  
Isometric Tension ◽  
Medial Gastrocnemius ◽  
Eccentric Contractions ◽  
Optimum Length ◽  
Length Dependence ◽  
Before And After

Subjecting a muscle to a series of eccentric contractions in which the contracting muscle is lengthened results in a number of changes in its mechanical properties. These include a fall in isometric tension that is particularly pronounced during low-frequency stimulation, a phenomenon known as low-frequency depression (LFD). Reports of LFD have not taken into account the shift in optimum length for active tension generation to longer muscle lengths that takes place after eccentric contractions. Given the length dependence of the stimulation frequency-tension curve, we tested the hypothesis that the change in this relationship after eccentric exercise is due to the shift in optimum length. We measured LFD by recording tension in response to a linearly increasing rate of stimulation of the nerve to medial gastrocnemius of anesthetized cats, over the range 0–100 pulses per second. Tension responses were measured before and after 50 eccentric contractions consisting of 6-mm stretches starting at 3 mm below optimum length and finishing at 3 mm above it. An index of LFD was derived from the tension responses to ramp stimulation. It was found that LFD after the eccentric contractions was partly, but not entirely, due to changes in the muscle's optimum length. An additional factor was the effect of fatigue. These observations led to the conclusion that the muscle length dependence of LFD was reduced by eccentric contractions. All of this means that after eccentric exercise the tension deficit at low rates of muscle activation is likely to be less severe than first thought.

scholarly journals In-series compliance of gastrocnemius muscle in cat step cycle: do spindles signal origin-to-insertion length?

1990 ◽  
Vol 429 (1) ◽  
pp. 237-258 ◽  
Author(s):  
J Elek ◽  
A Prochazka ◽  
M Hulliger ◽  
S Vincent
Keyword(s):  
Gastrocnemius Muscle ◽  
Step Cycle ◽  
In Series ◽  
Series Compliance ◽  
Insertion Length

scholarly journals The effects of triceps surae muscle stimulation on localized achilles subtendon tissue displacements

2021 ◽  
Author(s):  
Nathan L. Lehr ◽  
William H. Clark ◽  
Michael D. Lewek ◽  
Jason R. Franz
Keyword(s):  
Achilles Tendon ◽  
Muscle Activation ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Muscle Stimulation ◽  
Triceps Surae Muscle ◽  
Ankle Angle ◽  
In Series ◽  
Fixed End

The triceps surae muscle tendon unit is comprised of the lateral and medial gastrocnemius (MG) and soleus (SOL) muscles and three in series elastic “subtendons” that form the Achilles tendon. Comparative literature and our own in vivo evidence suggests that sliding between adjacent subtendons may facilitate independent muscle actuation. We aim to more clearly define the relation between individual muscle activation and subtendon tissue displacements. Here, during fixed-end contractions, electrical muscle stimulation controlled the magnitude of force transmitted via individual triceps surae muscles while ultrasound imaging recorded resultant subtendon tissue displacements. We hypothesized that MG and SOL stimulation would elicit larger displacements in their associated subtendon. 10 young adults completed 4 experimental activations at 3 ankle angles (-20°, 0°, 20°) with knee flexed to approximately 20°: MG stimulation (STIMMG), SOL stimulation (STIMSOL), combined stimulation, and volitional contraction. At 20° plantarflexion, STIMSOL elicited 49% larger tendon non-uniformity (SOL – MG subtendon tissue displacement) than that of STIMMG (p=0.004). For STIMSOL, a one-way post-hoc ANOVA revealed a significant main effect of ankle angle (p=0.009) on Achilles tendon non-uniformity. However, peak tendon non-uniformity decreased by an average of 61% from plantarflexion to dorsiflexion, likely due to an increase in passive tension. Our results suggest that localized tissue displacements within the Achilles tendon respond in anatomically consistent ways to differential patterns of triceps surae muscle activation, but these relations are highly susceptible to ankle angle. This in vivo evidence points to at least some mechanical independence in actuation between the human triceps surae muscle-subtendon units.

scholarly journals Repeated contractions alter the geometry of human skeletal muscle

2002 ◽  
Vol 93 (6) ◽  
pp. 2089-2094 ◽  
Author(s):  
Constantinos N. Maganaris ◽  
Vasilios Baltzopoulos ◽  
Anthony J. Sargeant
Keyword(s):  
Skeletal Muscle ◽  
Maximal Voluntary Contraction ◽  
Human Skeletal Muscle ◽  
Voluntary Contraction ◽  
Pennation Angle ◽  
Medial Gastrocnemius ◽  
Myotendinous Junction ◽  
Rest Interval ◽  
In Series ◽  
The Moment

The aim of this study was to investigate the effect of repeated contractions on the geometry of human skeletal muscle. Six men performed two sets ( sets Aand B) of 10 repeated isometric plantarflexion contractions at 80% of the moment generated during plantarflexion maximal voluntary contraction (MVC), with a rest interval of 15 min between sets. By use of ultrasound, the geometry of the medial gastrocnemius (MG) muscle was measured in the contractions of set A and the displacement of the MG tendon origin in the myotendinous junction was measured in the contractions of set B. In the transition from the 1st to the 10th contractions, the fascicular length at 80% of MVC decreased from 34 ± 4 (means ± SD) to 30 ± 3 mm ( P < 0.001), the pennation angle increased from 35 ± 3 to 42 ± 3° ( P < 0.001), the myotendinous junction displacement increased from 5 ± 3 to 10 ± 3 mm ( P < 0.001), and the average fascicular curvature remained constant ( P > 0.05) at ∼4.3 m−1. No changes ( P > 0.05) were found in fascicular length, pennation angle, and myotendinous junction displacement after the fifth contraction. Electrogoniometry showed that the ankle rotated by ∼6.5° during contraction, but no differences ( P > 0.05) were obtained between contractions. The present results show that repeated contractions induce tendon creep, which substantially affects the geometry of the in-series contracting muscles, thus altering their potential for force and joint moment generation.

Active muscle stiffness in the human medial gastrocnemius muscle in vivo

2014 ◽  
Vol 117 (9) ◽  
pp. 1020-1026 ◽  
Author(s):  
Keitaro Kubo
Keyword(s):  
Gastrocnemius Muscle ◽  
Muscle Stiffness ◽  
Medial Gastrocnemius ◽  
Plantar Flexors ◽  
Active Muscle ◽  
Tendon Stiffness ◽  
Series Elastic Component ◽  
In Series ◽  
Medial Gastrocnemius Muscle

The aims of this study were to 1) directly assess active muscle stiffness according to actual length changes in muscle fibers (fascicles) during short range stretching; and 2) compare actual measured active muscle and tendon stiffness using ultrasonography with the stiffness of active (i.e., muscle) and passive (i.e., tendon) parts in series elastic component of plantar flexors using the alpha method. Twenty-four healthy men volunteered for this study. Active muscle stiffness in the medial gastrocnemius muscle was calculated according to changes in estimated muscle force and fascicle length during fast stretching after submaximal isometric contractions [10, 30, 50, 70, and 90% maximal voluntary contractions (MVC)]. Using the variables measured during this fast stretch experiment, the stiffness of active (i.e., muscle) and passive (i.e., tendon) parts in plantar flexors was assessed using alpha method. Tendon stiffness was determined during isometric plantar flexion by ultrasonography. Active muscle stiffness increased with the exerted torque levels. At 30, 50, 70, and 90% MVC, there were no significant correlations between muscle stiffness using ultrasonography and stiffness of active part (i.e., muscle) by alpha method, although this relationship at 10% MVC was significant ( r = 0.552, P = 0.005). In addition, no correlation was noted in tendon stiffness between the two different methods ( r = 0.226, P = 0.209). The present study demonstrated that ultrasonography could quantified active muscle stiffness in vivo. Furthermore, active muscle stiffness and tendon stiffness using ultrasonography were not related to active (i.e., muscle) or passive (i.e., tendon) stiffness in series elastic component of plantar flexors by alpha method.

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