Differences in Plantar Flexor Fascicle Length and Pennation Angle between Healthy and Poststroke Individuals and Implications for Poststroke Plantar Flexor Force Contributions

Poststroke plantar flexor muscle weakness has been attributed to muscle atrophy and impaired activation, which cannot collectively explain the limitations in force-generating capability of the entire muscle group. It is of interest whether changes in poststroke plantar flexor muscle fascicle length and pennation angle influence the individual force-generating capability and whether plantar flexor weakness is due to uniform changes in individual muscle force contributions. Fascicle lengths and pennation angles for the soleus, medial, and lateral gastrocnemius were measured using ultrasound and compared between ten hemiparetic poststroke subjects and ten healthy controls. Physiological cross-sectional areas and force contributions to poststroke plantar flexor torque were estimated for each muscle. No statistical differences were observed for any muscle fascicle lengths or for the lateral gastrocnemius and soleus pennation angles between paretic, nonparetic, and healthy limbs. There was a significant decrease (P<0.05) in the paretic medial gastrocnemius pennation angle compared to both nonparetic and healthy limbs. Physiological cross-sectional areas and force contributions were smaller on the paretic side. Additionally, bilateral muscle contributions to plantar flexor torque remained the same. While the architecture of each individual plantar flexor muscle is affected differently after stroke, the relative contribution of each muscle remains the same.

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Plantar Flexor Muscle Architecture Changes as a Result of Eccentric Exercise in Patients With Achilles Tendinosis

Foot & Ankle Specialist ◽

10.1177/1938640014539812 ◽

2014 ◽

Vol 7 (6) ◽

pp. 460-465 ◽

Cited By ~ 1

Author(s):

Matthew T. Crill ◽

Gregory Berlet ◽

Christopher Hyer

Keyword(s):

Case Series ◽

Muscle Architecture ◽

Medial Gastrocnemius ◽

Eccentric Training ◽

Plantar Flexors ◽

Flexor Muscle ◽

Fascicle Length ◽

Achilles Tendinosis ◽

Muscle Fascicle ◽

Maximal Load

Eccentric training for Achilles tendinosis (AT) has been reported to significantly improve patient symptoms. There has been no biomechanical explanation on the mechanism for specific rehabilitation technique. The purpose of this study was to determine changes in muscle architecture that occurred as a result of Achilles tendinosis injury and a subsequent eccentric rehabilitation program. Twenty-five patients (age, 53.3 ± 17.5 years) diagnosed with AT participated in 6 weeks of rehabilitation. Specific exercises for the ankle plantar flexors consisted of maximal load eccentric muscle action using 3 sets of 15 repetitions. Patients also completed a protocol for AT, which consisting of traditional rehabilitation. Medial gastrocnemius (GM) and lateral gastrocnemius (GL) muscle fascicle length and thickness were measured with ultrasound at 2-week intervals from initial treatment day to the end of 6 weeks of rehabilitation. Medial gastrocnemius fascicle length increased (45.1 ± 10.5 mm to 51.4 ± 10.5 mm; P = .22) between the initial day of rehabilitation and after 6 weeks of rehabilitation. But, GM thickness (16.3 ± 3.5 mm to 16.8 ± 2.0 mm), GL fascicle length (47.2 ± 10.0 mm to 47.1 ± 7.4 mm), and GL thickness (14.9 ± 5.2 mm to 14.4 ± 2.7 mm) did not change as a result of rehabilitation. A 6-week eccentric-biased exercise increased the GM muscle fascicle length by 12%, but GM thickness, GL fascicle length, and GL thickness did not change as a result of rehabilitation. Eccentric training for the treatment of AT is well recognized, but the mechanism of action has not been previously reported. A 6-week eccentric training protocol increased the GM muscle fascicle length by 12%, and this correlated with improvement in a validated patient outcome scoring system. Further study is warranted to determine a predictive relationship between improvement of GM fascicle length and outcome scores. Levels of Evidence: Therapeutic, Level IV: Case series

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Adaptations in human neuromuscular function following prolonged unweighting: I. Skeletal muscle contractile properties and applied ischemia efficacy

Journal of Applied Physiology ◽

10.1152/japplphysiol.01402.2005 ◽

2006 ◽

Vol 101 (1) ◽

pp. 256-263 ◽

Cited By ~ 75

Author(s):

Brian C. Clark ◽

Bo Fernhall ◽

Lori L. Ploutz-Snyder

Keyword(s):

Lower Limb ◽

Strength Loss ◽

Contractile Properties ◽

Plantar Flexor ◽

Postactivation Potentiation ◽

Flexor Muscle ◽

Muscle Properties ◽

Cross Sectional ◽

Lateral Gastrocnemius

Strength loss following disuse may result from alterations in muscle and/or neurological properties. In this paper, we report our findings on human plantar flexor muscle properties following 4 wk of limb suspension (unilateral lower limb suspension), along with the effect of applied ischemia (Isc) on these properties. In the companion paper (Part II), we report our findings on the changes in neurological properties. Measurements of voluntary and evoked forces, the compound muscle fiber action potential (CMAP), and muscle cross-sectional area (CSA) were collected before and after 4 wk of unilateral lower limb suspension in adults ( n = 18; 19–28 yr). A subset of subjects ( n = 6) received applications of Isc 3 days/wk (3 sets; 5-min duration). In the subjects not receiving Isc, the loss in CSA and strength was as expected (∼9 and 14%). We observed a 30% slowing in the duration of the CMAP, a 10% decrease in evoked doublet force, a 12% increase in the twitch-to-doublet force ratio, and an altered postactivation potentiation response (11% increase in the postactivation potentiation-to-doublet ratio). We also detected a 10% slowing in the ability of the plantar flexor to develop force during the initial phase of an evoked contraction, along with a 6% reduction in in vivo specific doublet force. In the Isc subjects, no preservation was observed in strength or the evoked muscle properties. However, the Isc group did maintain CSA of the lateral gastrocnemius, as the control subjects’ lateral gastrocnemius atrophied 10.2%, whereas the subjects receiving Isc atrophied 4.7%. Additionally, Isc abolished the unweighting-induced slowing in the CMAP. These findings suggest that unweighting alters the contractile properties involved in the excitation-contraction coupling processes and that Isc impacts the sarcolemma.

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Triceps surae torque-length relationships relevant for walking activity levels with and without an ankle exoskeleton

10.1101/778175 ◽

2019 ◽

Author(s):

Anthony L. Hessel ◽

Brent J. Raiteri ◽

Michael J. Marsh ◽

Daniel Hahn

Keyword(s):

Muscle Activity ◽

Metabolic Cost ◽

Activity Levels ◽

Plantar Flexor ◽

Plantar Flexors ◽

Flexor Muscle ◽

Fascicle Length ◽

Lateral Gastrocnemius ◽

Work Requirements ◽

Ankle Exoskeleton

AbstractAnkle exoskeletons have been developed to assist walking by offloading the plantar flexors work requirements, which reduces muscle activity level. However, reduced muscle activity alters plantar flexor muscle-tendon unit dynamics in a way that is poorly understood. We therefore evaluated torque-fascicle length properties of the soleus and lateral gastrocnemius during voluntary contractions at simulated activity levels typical during late stance with and without an ankle exoskeleton. Soleus activity levels (100, 30, and 22% maximal voluntary activity) were produced by participants via visual electromyography feedback at ankle angles ranging from −10° plantar flexion to 35° dorsiflexion. Using dynamometry and ultrasound imaging, torque-fascicle length data of the soleus and lateral gastrocnemius were produced. The results indicate that muscle activity reductions observed with an exoskeleton shift the torque-angle and torque-fascicle length curves to more dorsiflexed ankle angles and longer fascicle lengths where no descending limb is physiologically possible. This shift is in line with previous simulations that predicted a similar increase in the operating fascicle range when wearing an exoskeleton. These data suggest that a small reduction in muscle activity causes changes to torque-fascicle length properties, which has implications for the design and testing of future ankle exoskeletons for assisted walking.Significance StatementAssistive lower-limb exoskeletons reduce the metabolic cost of walking by reducing the positive work requirements of the plantar flexor muscles. However, if the exoskeleton reduces plantar flexor muscle activity too much, then the metabolic benefit is lost. The biological reasons for this are unclear and hinder further exoskeleton development. This research study is the first to directly evaluate if a reduction in plantar flexor muscle activity similar to that caused by wearing an exoskeleton affects muscle function. We found that reduced muscle activity changes the torque-length properties of two plantar flexors, which could explain why reducing muscle activity too much can increase metabolic cost.

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The relative lengthening of the myotendinous structures in the medial gastrocnemius during passive stretching differs among individuals

Journal of Applied Physiology ◽

10.1152/japplphysiol.90577.2008 ◽

2009 ◽

Vol 106 (1) ◽

pp. 169-177 ◽

Cited By ~ 78

Author(s):

Séverine Abellaneda ◽

Nathalie Guissard ◽

Jacques Duchateau

Keyword(s):

Plantar Flexion ◽

Pennation Angle ◽

Medial Gastrocnemius ◽

Electromyographic Activity ◽

Plantar Flexors ◽

Fascicle Length ◽

Relative Contribution ◽

Passive Stretching ◽

Muscle Stretching ◽

Passive Torque

The increase in passive torque during muscle stretching may constrain the range of motion of a joint. As passive torque can vary substantially among individuals, the present study examined whether the relative lengthening of the myotendinous structures of the medial gastrocnemius (MG) during passive stretching differs among individuals. Sixteen subjects performed passive stretching of the plantar flexor muscles from ankle angles ranging from 10° plantar flexion (−10°) to 30° dorsiflexion (+30°). Changes in passive torque, muscle architecture (fascicle length and pennation angle) of the MG and electromyographic activity of MG and soleus were recorded. The results showed that passive torque produced by the plantar flexors increased exponentially ( r2 = 0.99; P < 0.001) with ankle dorsiflexion, whereas MG fascicle length increased linearly from 57.6 ± 9.1 to 80.5 ± 10.3 mm ( P < 0.001), and pennation angle decreased linearly from 21.2 ± 4.2 to 14.4 ± 3.1° ( P < 0.001) when the ankle joint angle was moved from −10° to +30°. The relative contribution of muscle (fascicles and aponeuroses) and tendon elongation to the change in length of the muscle-tendon unit (MTU) at 30° dorsiflexion was 71.8 and 28.2%, respectively. However, the adjustment differed across individuals during MTU lengthening; in subjects (62.5%) with small, passive stiffness, the elongation of the free tendon was less and that of the fascicles larger than for subjects (37.5%) with greater stiffness. In conclusion, the results indicate that the strain of muscle and tendon varies among individuals, and difference in the relative compliance of these structures influences MTU lengthening differently during passive stretching.

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Ultrasound reveals negligible cocontraction during isometric plantar flexion and dorsiflexion despite the presence of antagonist electromyographic activity

Journal of Applied Physiology ◽

10.1152/japplphysiol.00825.2014 ◽

2015 ◽

Vol 118 (10) ◽

pp. 1193-1199 ◽

Cited By ~ 13

Author(s):

Brent J. Raiteri ◽

Andrew G. Cresswell ◽

Glen A. Lichtwark

Keyword(s):

Cross Talk ◽

Muscle Activity ◽

Plantar Flexion ◽

Medial Gastrocnemius ◽

Electromyographic Activity ◽

Plantar Flexors ◽

Fascicle Length ◽

Lateral Gastrocnemius ◽

Muscle Fascicle

Because of the approximate linear relationship between muscle force and muscle activity, muscle forces are often estimated during maximal voluntary isometric contractions (MVICs) from torque and surface electromyography (sEMG) measurements. However, sEMG recordings from a target muscle may contain cross-talk originating from nearby muscles, which could lead to erroneous force estimates. Here we used ultrasound imaging to measure in vivo muscle fascicle length ( Lf) changes and sEMG to measure muscle activity of the tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and soleus muscles during ramp MVICs in plantar and dorsiflexion directions ( n = 8). After correcting longitudinal Lfchanges for ankle rotation, the antagonist Lfat peak antagonist root-mean-square (RMS) amplitude were significantly longer than the agonist Lfat this sEMG-matched level. On average, Lfshortened from resting length by 1.29 to 2.90 mm when muscles acted as agonists and lengthened from resting length by 0.43 to 1.16 mm when muscles acted as antagonists (depending on the muscle of interest). The lack of fascicle shortening when muscles acted as antagonists indicates that cocontraction was likely to be negligible, despite cocontraction as determined by sEMG of between 7 and 23% MVIC across all muscles. Different interelectrode distances (IEDs) over the plantar flexors revealed significantly higher antagonist RMS amplitudes for the 4-cm IEDs compared with the 2-cm IEDs, which further indicates that cross-talk was present. Consequently, investigators should be wary about performing agonist torque corrections for isometric plantar flexion and dorsiflexion based on the antagonist sEMG trace and predicted antagonist moment.

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Musculotendon Parameters and Musculoskeletal Pathways Within the Human Foot

Journal of Applied Biomechanics ◽

10.1123/jab.23.1.20 ◽

2007 ◽

Vol 23 (1) ◽

pp. 20-41 ◽

Cited By ~ 3

Author(s):

Melissa R. Lachowitzer ◽

Anne Ranes ◽

Gary T. Yamaguchi

Keyword(s):

Three Dimensional ◽

Pennation Angle ◽

Fascicle Length ◽

Cross Sectional ◽

Large Variability ◽

Human Foot ◽

Volume Weight ◽

Bony Landmarks ◽

Muscle Fascicle ◽

Musculoskeletal Models

In order to create a flexible model of the foot for dynamic musculoskeletal models, anthropometric data combined with geometric information describing the intrinsic musculature are needed. In this study, the left feet of two male and two female cadavers were dissected to expose the intrinsic musculotendon pathways. Three-dimensional coordinates of bony landmarks, tendon origins, insertions, and via points were digitized to submillimeter accuracy. Muscle architectural parameters were also measured, including volume, weight, and pennation angle and sarcomere, fascicle, and free tendon lengths. Optimal muscle fascicle lengths, pennation angles at optimal length, physiological cross-sectional areas (PCSA), and tendon slack lengths were calculated from the directly measured values. Fascicle length and pennation angle varied greatly within each subject. Average fascicle lengths normalized by optimal fascicle length varied between 0.73 and 1.25, with 75% of the formalin-preserved muscles being found in a shortened state. The muscle volume and PCSA also had a large variability within subjects but less variation between subjects. The ratio of tendon slack length to optimal fascicle length was found to vary between 1.05 and 9.56. Using this data, a deformable model of the foot can now be created. It is envisioned that deformable feet will significantly improve

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An automatic fascicle tracking algorithm quantifying gastrocnemius architecture during maximal effort contractions

PeerJ ◽

10.7717/peerj.7120 ◽

2019 ◽

Vol 7 ◽

pp. e7120 ◽

Cited By ~ 6

Author(s):

John F. Drazan ◽

Todd J. Hullfish ◽

Josh R. Baxter

Keyword(s):

Pennation Angle ◽

Tracking Algorithm ◽

Medial Gastrocnemius ◽

Fascicle Length ◽

Automatic Tracking ◽

Individual Muscle ◽

Muscle Fascicle ◽

Muscle Fascicles ◽

Maximal Effort ◽

Strong Agreement

Background Ultrasound has become a commonly used imaging modality for making dynamic measurements of muscle structure during functional movements in biomechanical studies. Manual measurements of fascicle length and pennation angle are time intensive which limits the clinical utility of this approach while also limiting sample sizes in research. The purpose of this study was to develop an automatic fascicle tracking program to quantify the length and pennation angle of a muscle fascicle during maximal effort voluntary contractions and to evaluate its repeatability between days and reproducibility between different examiners. Methods Five healthy adults performed maximal effort isometric and isokinetic contractions at 30, 120, 210, and 500 degrees per second about their ankle on an isokinetic dynamometer while their medial gastrocnemius muscle was observed using ultrasound. Individual muscle fascicles and the two aponeuroses were identified by the user in the first frame and automatically tracked by the algorithm by three observers on three separate days. Users also made manual measurements of the candidate fascicle for validation. Repeatability within examiners across days and reproducibility across examiners and days were evaluated using intra-class correlation coefficients (ICC). Agreement between manual and automatic tracking was evaluated using the coefficient of multiple correlations (CMC) and root-mean-square error. Supervised automatic tracking, where the program could be reinitialized if poor tracking was observed, was performed on all videos by one examiner to evaluate the performance of automatic tracking in a typical use case. We also compared the performance our program to a preexisting automatic tracking program. Results We found both manual and automatic measurements of fascicle length and pennation angle to be strongly repeatable within examiners and strongly reproducible across examiners and days (ICCs > 0.74). There was greater agreement between manual and automatic measurements of fascicle length than pennation angle, however the mean CMC value was found to be strong in both cases (CMC > 0.8). Supervision of automatic tracking showed very strong agreement between manual and automatic measurements of fascicle length and pennation angle (CMC > 0.94). It also had considerably less error relative to the preexisting automatic tracking program. Conclusions We have developed a novel automatic fascicle tracking algorithm that quantifies fascicle length and pennation angle of individual muscle fascicles during dynamic contractions during isometric and across a range of isokinetic velocities. We demonstrated that this fascicle tracking algorithm is strongly repeatable and reproducible across different examiners and different days and showed strong agreement with manual measurements, especially when tracking is supervised by the user so that tracking can be reinitialized if poor tracking quality is observed.

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Architecture of the Triceps Surae Muscles Complex in Patients with Spastic Hemiplegia: Implication for the Limited Utility of the Silfverskiöld Test

Journal of Clinical Medicine ◽

10.3390/jcm8122096 ◽

2019 ◽

Vol 8 (12) ◽

pp. 2096 ◽

Cited By ~ 2

Author(s):

Kun-Bo Park ◽

Sun Young Joo ◽

Hoon Park ◽

Isaac Rhee ◽

Jong-Kwan Shin ◽

...

Keyword(s):

Mixed Model ◽

Operative Procedure ◽

Pennation Angle ◽

Triceps Surae ◽

Medial Gastrocnemius ◽

Fascicle Length ◽

Lateral Gastrocnemius ◽

Group I ◽

Equinus Deformity ◽

Triceps Surae Muscles

The Silfverskiöld test has long been used as an important tool for determining the affected muscles of the triceps surae in patients with equinus deformity. However, the test may not reflect the altered interactions between the muscles of the triceps which are affected by spasticity. The purpose of this study was to compare the architectural properties of the triceps surae muscles complex using ultrasonography, between hemiplegic patients and typically-developing children. Specifically, we wished to examine any differences in the architecture of the three muscles with various angle configurations of the knee and ankle joints. Ultrasound images of the medial gastrocnemius, lateral gastrocnemius, and soleus were acquired from paretic (group I) and non-paretic (group II) legs of ten patients and the legs (group III) of 10 age-matched normal children. A mixed model was used to evaluate the differences in the measurements of muscle architecture among the groups and the effects of various joint configurations on the measurements within the muscles. Compared to the results of measurements in groups II and III, the fascicle length was not different in the medial gastrocnemius of a paretic leg but it was longer in the lateral gastrocnemius and shorter in the soleus; the pennation angle was smaller in both medial and lateral gastrocnemii and was not different in the soleus; and the muscle thickness was found to be reduced in the three muscles of the paretic leg. Contrary to the observations in both the medial and lateral gastrocnemii, the fascicle length was increased and the pennation angle was decreased in the soleus with an increase of knee flexion. Through the current simulation study of the Silfverskiöld test using ultrasonography, we found that the changes detected in the architectural properties of the three muscles induced by systematic variations of the position at the ankle and the knee joints were variable. We believe that the limited utility of the Silfverskiöld test should be considered in determining an appropriate operative procedure to correct the equinus deformity in patients with altered architecture of the muscles in conditions such as cerebral palsy, as the differing muscle architectures of the triceps surae complex may affect the behavior of the muscles during the Silfverskiöld test.

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Gastrocnemius Fascicle Length Changes with Two-Joint Passive Movements

Journal of Applied Biomechanics ◽

10.1123/jab.24.3.252 ◽

2008 ◽

Vol 24 (3) ◽

pp. 252-261 ◽

Cited By ~ 3

Author(s):

Timothy J. Brindle ◽

Jeri L. Miller ◽

Maria K. Lebiedowska ◽

Steven J. Stanhope

Keyword(s):

Kinematic Model ◽

Medial Gastrocnemius ◽

Ultrasound Images ◽

Fascicle Length ◽

Knee Motion ◽

Lateral Gastrocnemius ◽

Ankle Motion ◽

Muscle Fascicle ◽

Length Changes ◽

Passive Movements

Predicting muscle fascicle length changes during passive movements may lead to a better understanding of muscle function. The purpose of this study was to experimentally compare fascicle length changes in the gastrocnemius during two-joint passive movements with a previously derived kinematic model based on anatomical measures from a cadaver. The ratio of passive ankle to knee motion was manipulated to generate medial gastrocnemius fascicle elongation and lateral gastrocnemius fascicle shortening. Ultrasound images from both heads of the gastrocnemius fascicles were acquired at 10° knee flexion increments and compared with this kinematic model. Our results suggest that the two-joint kinematic model from which we originally based our knee and ankle movements did not adequately reflect fascicle length changes during any of the movement conditions in this study. From our data, we propose that for every degree of ankle motion the medial and lateral gastrocnemius changes 0.42 mm and 0.96 mm, respectively, whereas changes of 0.14 mm and 0.22 mm are observed for the medial and lateral gastrocnemius, respectively, during knee movements.

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Disentangling age-dependent DNA methylation: deterministic, stochastic, and nonlinear

10.1101/2020.10.07.329987 ◽

2020 ◽

Author(s):

O. Vershinina ◽

M. Ivanchenko ◽

M.G. Bacalini ◽

A. Zaikin ◽

C. Franceschi

Keyword(s):

Dna Methylation ◽

Environmental Factors ◽

Methylation Level ◽

Signal To Noise Ratio ◽

Cross Sectional ◽

Ample Evidence ◽

Systematic Assessment ◽

Relative Contribution ◽

Age Dependent ◽

The Individual

ABSTRACTDNA methylation variability arises due to concurrent genetic and environmental influences. Each of them is a mixture of regular and noisy sources, whose relative contribution has not been satisfactorily understood yet. We conduct a systematic assessment of the age-dependent methylation by the signal-to-noise ratio and identify a wealth of “deterministic” CpG probes (about 90%), whose methylation variability likely originates due to genetic and general environmental factors. The remaining 10% of “stochastic” CpG probes are arguably governed by the biological noise or incidental environmental factors. Investigating the mathematical functional relationship between methylation levels and variability, we find that in about 90% of the age-associated differentially methylated positions, the variability changes as the square of the methylation level, whereas in the most of the remaining cases the dependence is linear. Furthermore, we demonstrate that the methylation level itself in more than 15% cases varies nonlinearly with age (according to the power law), in contrast to the previously assumed linear changes. Our findings present ample evidence of the ubiquity of strong DNA methylation regulation, resulting in the individual age-dependent and nonlinear methylation trajectories, whose divergence explains the cross-sectional variability. It may also serve a basis for constructing novel nonlinear epigenetic clocks.

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