scholarly journals Series elasticity facilitates safe plantar flexor muscle–tendon shock absorption during perturbed human hopping

2021 ◽  
Vol 288 (1947) ◽  
Author(s):  
Taylor J. M. Dick ◽  
Christofer J. Clemente ◽  
Laksh K. Punith ◽  
Gregory S. Sawicki
Keyword(s):  
Steady State ◽  
Neuromuscular Control ◽  
Ground Contact ◽  
Plantar Flexor ◽  
Plantar Flexors ◽  
Flexor Muscle ◽  
Unpredictable Environments ◽  
Co Activation ◽  
Length Changes

In our everyday lives, we negotiate complex and unpredictable environments. Yet, much of our knowledge regarding locomotion has come from studies conducted under steady-state conditions. We have previously shown that humans rely on the ankle joint to absorb energy and recover from perturbations; however, the muscle–tendon unit (MTU) behaviour and motor control strategies that accompany these joint-level responses are not yet understood. In this study, we determined how neuromuscular control and plantar flexor MTU dynamics are modulated to maintain stability during unexpected vertical perturbations. Participants performed steady-state hopping and, at an unknown time, we elicited an unexpected perturbation via rapid removal of a platform. In addition to kinematics and kinetics, we measured gastrocnemius and soleus muscle activations using electromyography and in vivo fascicle dynamics using B-mode ultrasound. Here, we show that an unexpected drop in ground height introduces an automatic phase shift in the timing of plantar flexor muscle activity relative to MTU length changes. This altered timing initiates a cascade of responses including increased MTU and fascicle length changes and increased muscle forces which, when taken together, enables the plantar flexors to effectively dissipate energy. Our results also show another mechanism, whereby increased co-activation of the plantar- and dorsiflexors enables shortening of the plantar flexor fascicles prior to ground contact. This co-activation improves the capacity of the plantar flexors to rapidly absorb energy upon ground contact, and may also aid in the avoidance of potentially damaging muscle strains. Our study provides novel insight into how humans alter their neural control to modulate in vivo muscle–tendon interaction dynamics in response to unexpected perturbations. These data provide essential insight to help guide design of lower-limb assistive devices that can perform within varied and unpredictable environments.

In vivo physiological cross-sectional area and specific force are reduced in the gastrocnemius of elderly men

2005 ◽  
Vol 99 (3) ◽  
pp. 1050-1055 ◽  
Author(s):  
Christopher I. Morse ◽  
Jeanette M. Thom ◽  
Neil D. Reeves ◽  
Karen M. Birch ◽  
Marco V. Narici
Keyword(s):  
Achilles Tendon ◽  
Voluntary Contraction ◽  
Pennation Angle ◽  
Specific Force ◽  
Plantar Flexor ◽  
Moment Arm ◽  
Plantar Flexors ◽  
Elderly Men ◽  
Cross Sectional

Sarcopenia and muscle weakness are well-known consequences of aging. The aim of the present study was to ascertain whether a decrease in fascicle force (Ff) could be accounted for entirely by muscle atrophy. In vivo physiological cross-sectional area (PCSA) and specific force (Ff/PCSA) of the lateral head of the gastrocnemius (GL) muscle were assessed in a group of elderly men [EM, aged 73.8 yr (SD 3.5), height 173.4 cm (SD 4.4), weight 78.4 kg (SD 8.3); means (SD)] and for comparison in a group of young men [YM, aged 25.3 yr (SD 4.4), height 176.4 cm (SD 7.7), weight 79.1 kg (SD 11.9)]. GL muscle volume (Vol) and Achilles tendon moment arm length were evaluated using magnetic resonance imaging. Pennation angle and fiber fascicle length (Lf) were measured using B-mode ultrasonography during isometric maximum voluntary contraction of the plantar flexors. PCSA was estimated as Vol/Lf. GL Ff was calculated by dividing Achilles tendon force by the cosine of θ, during the interpolation of a supramaximal doublet, and accounting for antagonist activation level (assessed using EMG), Achilles tendon moment arm length, and the relative PCSA of the GL within the plantar flexor group. Voluntary activation of the plantar flexors was lower in the EM than in the YM (86 vs. 98%, respectively, P < 0.05). Compared with the YM, plantar flexor maximal voluntary contraction torque and Ff of the EM were lower by 47 and 40%, respectively ( P < 0.01). Both Vol and PCSA were smaller in the EM by 28% ( P < 0.01) and 16% ( P < 0.05), respectively. Also, pennation angle was 12% smaller in the EM, whereas there was no significant difference in Lf between the YM and EM. After accounting for differences in agonists and antagonists activation, the Ff/PCSA of the EM was 30% lower than that of the YM ( P < 0.01). These findings demonstrate that the loss of muscle strength with aging may be explained not only by a reduction in voluntary drive to the muscle, but mostly by a decrease in intrinsic muscle force. This phenomenon may possibly be due to a reduction in single-fiber specific tension.

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

2006 ◽  
Vol 101 (1) ◽  
pp. 256-263 ◽  
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.

scholarly journals Human ankle plantar flexor muscle–tendon mechanics and energetics during maximum acceleration sprinting

2016 ◽  
Vol 13 (121) ◽  
pp. 20160391 ◽  
Author(s):  
Adrian Lai ◽  
Anthony G. Schache ◽  
Nicholas A. T. Brown ◽  
Marcus G. Pandy
Keyword(s):  
Steady State ◽  
Elastic Strain ◽  
Strain Energy ◽  
Computational Modelling ◽  
Elastic Strain Energy ◽  
Medial Gastrocnemius ◽  
Plantar Flexors ◽  
Flexor Muscle ◽  
Muscle Fascicle ◽  
Human Ankle

Tendon elastic strain energy is the dominant contributor to muscle–tendon work during steady-state running. Does this behaviour also occur for sprint accelerations? We used experimental data and computational modelling to quantify muscle fascicle work and tendon elastic strain energy for the human ankle plantar flexors (specifically soleus and medial gastrocnemius) for multiple foot contacts of a maximal sprint as well as for running at a steady-state speed. Positive work done by the soleus and medial gastrocnemius muscle fascicles decreased incrementally throughout the maximal sprint and both muscles performed more work for the first foot contact of the maximal sprint (FC1) compared with steady-state running at 5 m s −1 (SS5). However, the differences in tendon strain energy for both muscles were negligible throughout the maximal sprint and when comparing FC1 to SS5. Consequently, the contribution of muscle fascicle work to stored tendon elastic strain energy was greater for FC1 compared with subsequent foot contacts of the maximal sprint and compared with SS5. We conclude that tendon elastic strain energy in the ankle plantar flexors is just as vital at the start of a maximal sprint as it is at the end, and as it is for running at a constant speed.

scholarly journals Intra-and Intermuscular Coherence and Body Acceleration Control in Older Adults during Bipedal Stance

Geriatrics ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 114
Author(s):  
Tadayoshi Minamisawa ◽  
Noboru Chiba ◽  
Eizaburo Suzuki
Keyword(s):  
Older Adults ◽  
Center Of Mass ◽  
Plantar Flexor ◽  
Frequency Range ◽  
Plantar Flexors ◽  
Flexor Muscle ◽  
Younger Adults ◽  
Bipedal Stance ◽  
Intermuscular Coherence ◽  
The Relationship

Our aim was to clarify the effect of aging on the coherence of electromyograms of plantar flexor pairs during bipedal stance and to clarify the relationship between coherence and center-of-mass acceleration (COMacc). The subjects were 16 adults and 18 older adults. Intra- and intermuscular coherence and phase analyses were used to analyze the muscle pairs of bilateral and unilateral plantar flexor muscle groups. The relationship between coherence value and anterior–posterior COMacc of the plantar flexor muscle pairs was also examined to determine whether the connectivity of the lower limb muscle pairs is functionally important. The older adults showed higher coherence in the frequency range of 0–4 Hz for muscle pairs than the younger adults. In phase analysis, the older adults showed a phase difference between bilateral heteronymous muscle pairs in the frequency range of 0–6 Hz, which was one of the characteristics not seen in the younger adults. Correlation analysis showed that all the muscle pairs were moderately correlated with COMacc in the older adults. Not only does aging affects the organization of the bilateral and unilateral postural muscle activity of the plantar flexors during bipedal stance, but such organization may also be related to the increased COMacc characteristics of older adults.

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

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.

scholarly journals EFFECT OF FOOTBALL ON REHABILITATION OF ANKLE INJURY PATIENTS

2022 ◽  
Vol 28 (1) ◽  
pp. 62-64
Author(s):  
Jie Liu
Keyword(s):  
Sports Injuries ◽  
Muscle Tone ◽  
Good Effect ◽  
Plantar Flexor ◽  
Plantar Flexors ◽  
Flexor Muscle ◽  
Level Of Evidence ◽  
Balance Ability ◽  
Speed Training ◽  
The Right

ABSTRACT Introduction: Brief introduction: Ankle tendon and ligament sports injuries are common in football players. Objective: To continue to improve special strength training related to the characteristics of football after rehabilitation of injured ankle tendons and ligaments. Methods: Two master football sportsmen were rehabilitated by multi-point equal-length, short-arc and long-arc equal-speed training combined with balance ability exercises. Results: There were two long muscle L be maintain muscle tone plantar flexors force four times of 96 n/m, n/m 121, 140 n/m, 145 n/m than back flexors force of 63 n/m, 52 n/m, 60 n/m, 74 n/m tall. Plantar flexor fatigue was 57%, 30%, 29%, 12%, 28%, 18%, 20%, 21%. Conclusions: With the passing of time, the relative peak moment value of the right ankle plantar flexor muscle group of the two patients kept rising, the dorsiflexor muscle was basically flat, and the work fatigue index decreased step by step, indicating that the right ankle muscle strength level was significantly improved, the anti-fatigue ability was improved, and the rehabilitation treatment had a good effect. Level of evidence II; Therapeutic studies - investigation of treatment results.

Can passive stretch inhibit motoneuron facilitation in the human plantar flexors?

2014 ◽  
Vol 117 (12) ◽  
pp. 1486-1492 ◽  
Author(s):  
Gabriel S. Trajano ◽  
Laurent B. Seitz ◽  
Kazunori Nosaka ◽  
Anthony J. Blazevich
Keyword(s):  
Inhibitory Effect ◽  
Triceps Surae ◽  
Medial Gastrocnemius ◽  
Plantar Flexor ◽  
Plantar Flexors ◽  
Stimulation Protocol ◽  
Flexor Muscle ◽  
Motor Unit Firing ◽  
Torque Loss ◽  
Passive Stretch

The purpose of the present study was to examine the possible inhibitory effect of passive plantar flexor muscle stretching on the motoneuron facilitatory system. Achilles tendon vibration (70 Hz) and triceps surae electrical stimulation (20 Hz) were imposed simultaneously in 11 subjects to elicit contraction through reflexive pathways in two experiments. In experiment 1, a vibration-stimulation protocol was implemented with the ankle joint plantar flexed (+10°), neutral (0°), and dorsiflexed (−10°). In experiment 2, the vibration-stimulation protocol was performed twice before (control), then immediately, 5, 10, and 15 min after a 5-min intermittent muscle stretch protocol. Plantar flexor torque and medial and lateral gastrocnemius and soleus (EMGSol) EMG amplitudes measured during and after (i.e., self-sustained motor unit firing) the vibration protocol were used as an indicator of this facilitatory pathway. In experiment 1, vibration torque, self-sustained torque and EMGSol were higher with the ankle at −10° compared with 0° and +10°, suggesting that this method is valid to assess motoneuronal facilitation. In experiment 2, torque during vibration was reduced by ∼60% immediately after stretch and remained depressed by ∼35% at 5 min after stretch ( P < 0.05). Self-sustained torque was also reduced by ∼65% immediately after stretch ( P < 0.05) but recovered by 5 min. Similarly, medial gastrocnemius EMG during vibration was reduced by ∼40% immediately after stretch ( P < 0.05), and EMGSol during the self-sustained torque period was reduced by 44% immediately after stretch ( P < 0.05). In conclusion, passive stretch negatively affected the motoneuronal amplification for at least 5 min, suggesting that motoneuron disfacilitation is a possible mechanism influencing the stretch-induced torque loss.

scholarly journals Running Characteristics of Plantar Flexor Forces Based on Different Foot Strike Patterns in Medial Tibial Stress Syndrome

2020 ◽  
Vol 22 (4) ◽  
pp. 48-54
Author(s):  
Byungjoo Noh
Keyword(s):  
Traction Force ◽  
Medial Tibial Stress Syndrome ◽  
Plantar Flexor ◽  
Muscle Forces ◽  
Plantar Flexors ◽  
Flexor Muscle ◽  
Camera System ◽  
Barefoot Running ◽  
Stress Syndrome ◽  
Foot Strike

OBJECTIVES The purpose of this study was to compare plantar flexor force due to different foot strike patterns during running in barefoot and shod condition with and without medial tibial stress syndrome (MTSS).METHODS Fifteen collegiate soccer players who volunteered to participate were divided into MTSS group and controls. Participants’ running at 3.3 m/s with and without shoes were recorded with a 12-camera system at a sampling frequency of 250 Hz. Each subject completed different foot strike patterns of running as the forefoot strike pattern (FFS) and rearfoot strike pattern (RFS) were collected. Plantar flexor forces were investigated by software for interactive musculoskeletal modeling.RESULTS Normalized plantar flexor forces in barefoot running with the FFS pattern had greater soleus and peroneus brevis muscle forces in the MTSS group than in controls during the first half of stance, although there were no statistically significant differences for other plantar flexor muscle forces between groups and shod running. In plantar flexor forces due to foot strike pattern, the FFS pattern showed higher plantar flexor forces than the RFS pattern.CONCLUSIONS The results of musculoskeletal modeling suggest that subjects with MTSS have greater muscle forces of the plantar flexor during running, especially barefoot running with the FFS pattern. It also suggests increased forces in some plantar flexors generated great traction force by repetitively landing on connective tissues in the deep crural fascia causing inflammation at the posteromedial site of the tibia in MTSS.

scholarly journals Mechanics, modulation and modelling: how muscles actuate and control movement

2011 ◽  
Vol 366 (1570) ◽  
pp. 1463-1465 ◽  
Author(s):  
Timothy E. Higham ◽  
Andrew A. Biewener ◽  
Scott L. Delp
Keyword(s):  
Muscle Function ◽  
Animal Movement ◽  
Critical Role ◽  
Muscle Length ◽  
Neuromuscular Control ◽  
Clinical Aspects ◽  
Theme Issue ◽  
Recent Advances ◽  
Length Changes

Animal movement is often complex, unsteady and variable. The critical role of muscles in animal movement has captivated scientists for over 300 years. Despite this, emerging techniques and ideas are still shaping and advancing the field. For example, sonomicrometry and ultrasound techniques have enhanced our ability to quantify muscle length changes under in vivo conditions. Robotics and musculoskeletal models have benefited from improved computational tools and have enhanced our ability to understand muscle function in relation to movement by allowing one to simulate muscle–tendon dynamics under realistic conditions. The past decade, in particular, has seen a rapid advancement in technology and shifts in paradigms related to muscle function. In addition, there has been an increased focus on muscle function in relation to the complex locomotor behaviours, rather than relatively simple (and steady) behaviours. Thus, this Theme Issue will explore integrative aspects of muscle function in relation to diverse locomotor behaviours such as swimming, jumping, hopping, running, flying, moving over obstacles and transitioning between environments. Studies of walking and running have particular relevance to clinical aspects of human movement and sport. This Theme Issue includes contributions from scientists working on diverse taxa, ranging from humans to insects. In addition to contributions addressing locomotion in various taxa, several manuscripts will focus on recent advances in neuromuscular control and modulation during complex behaviours. Finally, some of the contributions address recent advances in biomechanical modelling and powered prostheses. We hope that our comprehensive and integrative Theme Issue will form the foundation for future work in the fields of neuromuscular mechanics and locomotion.

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