Number of Synergies Impacts Sensitivity of Gait to Weakness and Contracture

Muscle activity during gait can be described by a small set of synergies, weighted groups of muscles, that are often theorized to reflect underlying neural control. For people with neurologic injuries, like in cerebral palsy or stroke, even fewer (e.g., < 5) synergies are required to explain muscle activity during gait. This reduction in synergies is thought to reflect simplified control strategies and is associated with impairment severity and treatment outcomes. Individuals with neurologic injuries also develop secondary musculoskeletal impairments, like weakness or contracture, that can also impact gait. The combined impacts of simplified control and musculoskeletal impairments on gait remains unclear. In this study, we use a musculoskeletal model constrained to synergies to simulate unimpaired gait. We vary the number of synergies (3-5), while simulating muscle weakness and contracture to examine how altered control impacts sensitivity to muscle weakness and contracture. Our results highlight that reducing the number of synergies increases sensitivity to weakness and contracture. For example, simulations using five-synergy control tolerated 40% and 51% more knee extensor weakness than those using four- and three-synergy control, respectively. Furthermore, the model became increasingly sensitive to contracture and proximal muscle weakness, such as hamstring and hip flexor weakness, when constrained to four- and three-synergy control. However, the models sensitivity to weakness of the plantarflexors and smaller bi-articular muscles was not affected by the number of synergies. These findings provide insight into the interactions between altered control and musculoskeletal impairments, emphasizing the importance of incorporating both in future simulation studies.

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Impact of Lockdown during COVID-19 Pandemic on Central Activation, Muscle Activity, Contractile Function, and Spasticity in People with Multiple Sclerosis

BioMed Research International ◽

10.1155/2021/2624860 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Luis Andreu-Caravaca ◽

Domingo J. Ramos-Campo ◽

Linda H. Chung ◽

Pedro Manonelles ◽

Oriol Abellán-Aynés ◽

...

Keyword(s):

Multiple Sclerosis ◽

Muscle Activity ◽

Neural Control ◽

Contractile Function ◽

Knee Extensor ◽

Knee Extensors ◽

Maximum Voluntary Isometric Contraction ◽

Central Activation ◽

The Impact ◽

Muscle Contractile

Background. People with multiple sclerosis (MS) suffer from symptoms related to neural control, such as reduced central activation, lower muscle activity, and accentuated spasticity. A forced 9-week home confinement related to COVID-19 in Spain may have worsened these symptoms. However, no study has demonstrated the impact of home confinement on neuromuscular mechanisms in the MS population. This study was aimed at analyzing the effects of a 9-week home confinement on central activation, muscle activity, contractile function, and spasticity in MS patients. Methods. Eighteen participants were enrolled in the study. Left and right knee extensor maximum voluntary isometric contraction (MVIC), maximal neural drive via peak surface electromyography (EMG) of the vastus lateralis, central activation ratio (CAR), and muscle contractile function via electrical stimulation of the knee extensor muscles, as well as spasticity using the pendulum test, were measured immediately before and after home confinement. Results. Seventeen participants completed the study. CAR significantly decreased after lockdown ( ES = 1.271 , p < 0.001 ). Regarding spasticity, there was a trend to decrease in the number of oscillations ( ES = 0.511 , p = 0.059 ) and a significant decrease in the duration of oscillations ( ES = 0.568 , p = 0.038 ). Furthermore, in the left leg, there was a significant decrease in the first swing excursion ( ES = 0.612 , p = 0.027 ) and in the relaxation index ( ES = 0.992 , p = 0.001 ). Muscle contractile properties, MVIC, and EMG variables were not modified after confinement. Conclusions. The results suggest that a home confinement period of 9 weeks may lead to an increase in lower limb spasticity and a greater deficit in voluntary activation of the knee extensors.

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Rostrocaudal Distribution of the C-Fos-Immunopositive Spinal Network Defined by Muscle Activity during Locomotion

Brain Sciences ◽

10.3390/brainsci11010069 ◽

2021 ◽

Vol 11 (1) ◽

pp. 69

Author(s):

Natalia Merkulyeva ◽

Vsevolod Lyakhovetskii ◽

Aleksandr Veshchitskii ◽

Oleg Gorskii ◽

Pavel Musienko

Keyword(s):

Spinal Cord ◽

Locomotor Activity ◽

Control Systems ◽

Muscle Activity ◽

Knee Extensors ◽

Emg Activity ◽

Lumbosacral Spinal Cord ◽

Adductor Muscles ◽

Spinal Network ◽

Hip Flexor

The optimization of multisystem neurorehabilitation protocols including electrical spinal cord stimulation and multi-directional tasks training require understanding of underlying circuits mechanisms and distribution of the neuronal network over the spinal cord. In this study we compared the locomotor activity during forward and backward stepping in eighteen adult decerebrated cats. Interneuronal spinal networks responsible for forward and backward stepping were visualized using the C-Fos technique. A bi-modal rostrocaudal distribution of C-Fos-immunopositive neurons over the lumbosacral spinal cord (peaks in the L4/L5 and L6/S1 segments) was revealed. These patterns were compared with motoneuronal pools using Vanderhorst and Holstege scheme; the location of the first peak was correspondent to the motoneurons of the hip flexors and knee extensors, an inter-peak drop was presumably attributed to the motoneurons controlling the adductor muscles. Both were better expressed in cats stepping forward and in parallel, electromyographic (EMG) activity of the hip flexor and knee extensors was higher, while EMG activity of the adductor was lower, during this locomotor mode. On the basis of the present data, which showed greater activity of the adductor muscles and the attributed interneuronal spinal network during backward stepping and according with data about greater demands on postural control systems during backward locomotion, we suppose that the locomotor networks for movements in opposite directions are at least partially different.

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Mycobacterium tuberculosis adhesins: potential biomarkers as anti-tuberculosis therapeutic and diagnostic targets

Microbiology ◽

10.1099/mic.0.082206-0 ◽

2014 ◽

Vol 160 (9) ◽

pp. 1821-1831 ◽

Cited By ~ 22

Author(s):

Viveshree S. Govender ◽

Saiyur Ramsugit ◽

Manormoney Pillay

Keyword(s):

Immune Response ◽

Mycobacterium Tuberculosis ◽

Control Strategies ◽

Host Cells ◽

Tuberculosis Control ◽

Surface Molecules ◽

Host Pathogen Interaction ◽

Bacterial Aggregation ◽

Insight Into

Adhesion to host cells is a precursor to host colonization and evasion of the host immune response. Conversely, it triggers the induction of the immune response, a process vital to the host’s defence against infection. Adhesins are microbial cell surface molecules or structures that mediate the attachment of the microbe to host cells and thus the host–pathogen interaction. They also play a crucial role in bacterial aggregation and biofilm formation. In this review, we discuss the role of adhesins in the pathogenesis of the aetiological agent of tuberculosis, Mycobacterium tuberculosis. We also provide insight into the structure and characteristics of some of the characterized and putative M. tuberculosis adhesins. Finally, we examine the potential of adhesins as targets for the development of tuberculosis control strategies.

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Oral Air Pressure and Nasal Air Flow Rate on Levator Veli Palatini Muscle Activity in Patients Wearing a Speech Appliance

The Cleft Palate-Craniofacial Journal ◽

10.1597/1545-1569_1995_032_0382_oapana_2.3.co_2 ◽

1995 ◽

Vol 32 (5) ◽

pp. 382-389 ◽

Cited By ~ 9

Author(s):

Takashi Tachimura ◽

Hisanaga Hara ◽

Takeshi Wada

Keyword(s):

Flow Rate ◽

Muscle Activity ◽

Neural Control ◽

Air Flow ◽

Air Pressure ◽

Electromyographic Activity ◽

Air Flow Rate ◽

Circular Area ◽

Pharyngeal Bulb ◽

Levator Veli Palatini

This study was designed to determine if levator veli palatini muscle activity can be elicited by simultaneous changes in oral air pressure and nasal air flow when a speech appliance is in place. The speech appliances routinely worn by 15 subjects were each modified experimentally by drilling a hole in the vertical center of the pharyngeal bulb. The air flow rate into the nasal cavity through the opening in the bulb was altered by changing the circular area of the opening in the bulb from the occluded condition (Condition I), to circular area of 12.6 mm2 (4 mm in diameter; Condition II), and then to 38.5 mm2 (7 mm in diameter; Condition III). Electromyographic activity was measured from the levator veli palatini muscle with changes in nasal air flow rate and oral air pressure. Levator veli palatini muscle activity was correlated with changes in nasal air flow and oral air pressure. Increases in levator veli palatini muscle activity were associated with increases in nasal air flow rate compared to oral air pressure changes. The results indicated that aerodynamic variables of nasal air flow and oral air pressure might be involved in the neural control of speech production in individuals wearing a speech appliance, even if the subjects exhibit velopharyngeal incompetence without using a speech appliance. Also, the stimulating effect of bulb reduction therapy on velopharyngeal function might be achieved through the change in aerodynamic variables in association with the bulb reduction.

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The influence of knee extensor fatigue on lower extremity muscle activity during chair rise in young and older adults

European Journal of Applied Physiology ◽

10.1007/s00421-018-3999-4 ◽

2018 ◽

Vol 119 (1) ◽

pp. 61-71 ◽

Cited By ~ 1

Author(s):

Megan A. Bryanton ◽

Martin Bilodeau

Keyword(s):

Older Adults ◽

Lower Extremity ◽

Muscle Activity ◽

Knee Extensor ◽

Lower Extremity Muscle ◽

Chair Rise

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Adrenergic supersensitivity and impaired neural control of cardiac electrophysiology following regional cardiac sympathetic nerve loss

Scientific Reports ◽

10.1038/s41598-020-75903-y ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Srinivas Tapa ◽

Lianguo Wang ◽

Samantha D. Francis Stuart ◽

Zhen Wang ◽

Yanyan Jiang ◽

...

Keyword(s):

Sympathetic Nerve ◽

Cardiac Electrophysiology ◽

Neural Control ◽

Left Ventricular ◽

Adrenergic Stimulation ◽

Sympathetic Nerve Stimulation ◽

Post Surgery ◽

Dopamine Beta Hydroxylase ◽

Perfused Hearts ◽

Insight Into

Abstract Myocardial infarction (MI) can result in sympathetic nerve loss in the infarct region. However, the contribution of hypo-innervation to electrophysiological remodeling, independent from MI-induced ischemia and fibrosis, has not been comprehensively investigated. We present a novel mouse model of regional cardiac sympathetic hypo-innervation utilizing a targeted-toxin (dopamine beta-hydroxylase antibody conjugated to saporin, DBH-Sap), and measure resulting electrophysiological and Ca2+ handling dynamics. Five days post-surgery, sympathetic nerve density was reduced in the anterior left ventricular epicardium of DBH-Sap hearts compared to control. In Langendorff-perfused hearts, there were no differences in mean action potential duration (APD80) between groups; however, isoproterenol (ISO) significantly shortened APD80 in DBH-Sap but not control hearts, resulting in a significant increase in APD80 dispersion in the DBH-Sap group. ISO also produced spontaneous diastolic Ca2+ elevation in DBH-Sap but not control hearts. In innervated hearts, sympathetic nerve stimulation (SNS) increased heart rate to a lesser degree in DBH-Sap hearts compared to control. Additionally, SNS produced APD80 prolongation in the apex of control but not DBH-Sap hearts. These results suggest that hypo-innervated hearts have regional super-sensitivity to circulating adrenergic stimulation (ISO), while having blunted responses to SNS, providing important insight into the mechanisms of arrhythmogenesis following sympathetic nerve loss.

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Standard Value of Lower Extremity Muscle Strength of 8 Years Old Children and Its Correlation with Body Weight and Height

Indonesian Journal of Physical Medicine & Rehabilitation ◽

10.36803/ijpmr.v2i01.226 ◽

1970 ◽

Vol 2 (01) ◽

pp. 45-54

Author(s):

Sarifitri FH Hutagalung ◽

Ferial Hadipoetro Idris, ◽

[email protected]

Keyword(s):

Body Weight ◽

Muscle Strength ◽

Lower Extremity ◽

Body Height ◽

Knee Extensor ◽

Left Knee ◽

Knee Flexor ◽

Lower Extremity Muscle ◽

Left Ankle ◽

Hip Flexor

Objectives: to know the standard value of lower extremity muscle strength of eight year old children and furthermore to explore the correlation of the muscle strength and body height and weight.Methods: The study design is cross sectional. The target is eight year old children in public elementary school in Jakarta Pusat. The subjects’ characteristics are normal nutritional state, and no neurological normusculoskeletal disorders. Sampling was done by cluster randomization to determine the location and simple randomization on site to determine subjects. There were 171 boys and 180 girls in this tudy. Independentvariables are age, sex, body weight, body height and nutritional state that was determine with Z-score of body mass index. Dependent variables are lower extremity muscle strength that classify as torque. This study usedhand-held dynamometer for muscle strength measurement. Statistical analysis was done with descriptive statistic and Pearson and Spearman correlation test.Results: Standard values of eight year old boy’s lower extremity muscle strength are: right hip flexor 21.86 Nm (SD 3.40), left hip flexor 19.64 Nm (SD 3.19), right hip extensor 17.05 Nm (SD 3.66), left hip extensor16.08 Nm (SD 3.56), right knee extensor 18.19 Nm (SD 3.60), left knee extensor 16.09 Nm (SD 3.55), right knee flexor 15.18 Nm (SD 4.23), left knee flexor 14.48 Nm (SD 3.97), right ankle dorsiflexor 6.58 Nm (SD1.53), left ankle dorsiflexor 6.05 Nm (SD 1.42), right ankle plantarflexor 10.08 Nm (SD 1.69), left ankle plantar flexor 9.13 Nm (SD 1.90).Standard values of eight year old girl’s lower extremity muscle strength are: right hip flexor 21.60 Nm (SD 3.62), left hip flexor 19.62 Nm (SD 3.37), right hip extensor 16.66 Nm (SD 4.06), left hip extensor 15.81 Nm(SD 3.94), right knee extensor 17.43 Nm (SD 3.79), left knee extensor 15.20 Nm (SD 3.38), right knee flexor 14.61 Nm (SD 4.28), left knee flexor 13.51 Nm (SD 4.00), right ankle dorsiflexor 6.34 Nm (SD 1.45), leftankle dorsiflexor 5.97 Nm (SD 1.52), right ankle plantarflexor 9.55 Nm (SD 1.98), left ankle plantar flexor 8.69 Nm (SD 1.83). The boy’s lower extremity muscle strength are stronger than the girl’s in left knee extensor,left knee flexor, right ankle plantarflexor and left ankle plantarflexor. The boy’s muscle strength are moderately correlated to body height except for right hip extensor, left hip extensor and right ankle dorsiflexorthat weakly correlated. The boy’s muscle strength are moderately correlated to body weight except for left hip extensor that weakly correlated. The girl’s muscle strength are moderately correlated to body height. Thegirl’s muscle strength are moderately correlated to body weight except for left hip flexor and left hip extensor that weakly correlated.Conclusions: The muscle strength pattern of boys and girls is similar; the strongest are right hip flexor and the weakest are left ankle dorsiflexor.Keywords: Muscle strength, standard values of eight year old children, torque, hand-held dynamometer

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Scratch responses in normal cats: hindlimb kinematics and muscle synergies

Journal of Neurophysiology ◽

10.1152/jn.1990.64.6.1653 ◽

1990 ◽

Vol 64 (6) ◽

pp. 1653-1667 ◽

Cited By ~ 33

Author(s):

P. C. Kuhta ◽

J. L. Smith

Keyword(s):

Muscle Activity ◽

Knee Flexion ◽

Knee Extensor ◽

Head Movements ◽

Medial Gastrocnemius ◽

Emg Activity ◽

Circular Path ◽

Contact Phase ◽

Ankle Joints ◽

Flexor Muscles

1. Scratch responses evoked by a tactile stimulus applied to the outer ear canal were characterized in nine adult cats. Chronic electromyographic (EMG) electrodes were surgically implanted in selected flexor and extensor muscles of the hip, knee, and ankle joints to determine patterns of muscle activity during scratching. In some trials EMG records were synchronized with kinematic data obtained by digitizing high-speed cine film, and in one cat, medial gastrocnemius (MG) tendon forces were recorded along with EMG. For analysis the response was divided into three components: the approach, cyclic, and return periods. Usually scratch responses were initiated with the cat in a sitting position, but in some trials the animal initiated the response from a standing or lying posture. 2. During the approach period the hindlimb ipsilateral to the stimulated ear was lifted diagonally toward the head by a combination of hip and ankle flexion with knee extension. Hindlimb motions during the approach period were associated with sustained EMG activity in hip-flexor, knee-extensor (occasionally), and ankle-flexor muscles. Initial hindlimb motions were typically preceded by head movements toward the hindpaw, and at the end of the approach period, the head was tilted downward with the stimulated pinna lower than the contralateral ear. During the return period movements were basically the reverse of the approach period, with the hindpaw returning to the ground and the head moving away from the hindlimb. 3. During the cyclic period the number of cycles per response varied widely from 1 to 60 cycles with an average of 13 cycles, and cycle frequency ranged from 4 to 8 cycles/s, with a mean of 5.6 cycles/s. During each cycle the paw trajectory followed a fairly circular path, and the cycle was defined by three phases: precontact, contact, and postcontact. On average the contact phase occupied approximately 50% of the cycle and was characterized by extensor muscle activity and extension at the hip, knee, and ankle joints. The hindpaw contacted the pinna or neck at the base of the pinna throughout the contact phase, and paw contact typically resulted in a rostral motion of the head as the hindlimb extended. 4. The postcontact phase constituted approximately 24% of scratch cycle and was usually initiated by the onset of knee flexion. Ankle and then hip flexion followed knee flexion, and flexor muscles were active during the postcontact phase as the paw was withdrawn from the head. The precontact phase constituted approximately 26% of scratch cycle and was initiated by knee joint extension and knee-extensor activity.(ABSTRACT TRUNCATED AT 400 WORDS)

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Spatiotemporal distribution of location and object effects in the electromyographic activity of upper extremity muscles during reach-to-grasp

Journal of Neurophysiology ◽

10.1152/jn.00008.2016 ◽

2016 ◽

Vol 115 (6) ◽

pp. 3238-3248 ◽

Cited By ~ 3

Author(s):

Adam G. Rouse ◽

Marc H. Schieber

Keyword(s):

Upper Extremity ◽

Muscle Activity ◽

Neural Control ◽

Emg Activity ◽

Electromyographic Activity ◽

Proximal Muscle ◽

Reach To Grasp ◽

Distal Muscle ◽

The Subject ◽

Later Phase

In reaching to grasp an object, proximal muscles that act on the shoulder and elbow classically have been viewed as transporting the hand to the intended location, while distal muscles that act on the fingers simultaneously shape the hand to grasp the object. Prior studies of electromyographic (EMG) activity in upper extremity muscles therefore have focused, by and large, either on proximal muscle activity during reaching to different locations or on distal muscle activity as the subject grasps various objects. Here, we examined the EMG activity of muscles from the shoulder to the hand, as monkeys reached and grasped in a task that dissociated location and object. We quantified the extent to which variation in the EMG activity of each muscle depended on location, on object, and on their interaction—all as a function of time. Although EMG variation depended on both location and object beginning early in the movement, an early phase of substantial location effects in muscles from proximal to distal was followed by a later phase in which object effects predominated throughout the extremity. Interaction effects remained relatively small. Our findings indicate that neural control of reach-to-grasp may occur largely in two sequential phases: the first, serving to project the entire upper extremity toward the intended location, and the second, acting predominantly to shape the entire extremity for grasping the object.

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