Neuromuscular Control and Active Trunk Stiffness during Isometric Flexion and Extension

Pushing and pulling tasks account for 20% of low-back injury claims. Torso flexion necessary for pushing exertions requires different muscle recruitment than for extension exertions typical of lifting tasks. These differences in recruitment and control may influence spinal stability and associated risk of injury. Active muscle stiffness is considered the primary stabilizing mechanism for spinal stability. Therefore, active trunk stiffness was recorded while subjects generated upright isometric trunk flexion and extension exertions against an isotonic preload. Small pseudo-random force disturbances were superimposed on the preloads causing small amplitude trunk movements. Trunk stiffness was computed from systems identification of the measured force and trunk motion data. Results demonstrated significantly greater stiffness during flexion exertions as compared to extension exertions. EMG data suggest this difference was due to increased co-contraction during the flexion exertions. These behaviours were attributed to the need to augment neuromuscular control of spinal stability during pushing tasks. Keywords: Spine; Co-contraction; Push; Manual Materials Handling; Biomechanics

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Co-Contraction Recruitment and Spinal Load during Isometric Pushing Tasks

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/154193120504901414 ◽

2005 ◽

Vol 49 (14) ◽

pp. 1330-1333 ◽

Cited By ~ 1

Author(s):

Kevin Granata ◽

Patrick Lee ◽

Tim Franklin

Keyword(s):

Biomechanical Model ◽

Neuromuscular Control ◽

Surface Emg ◽

Trunk Flexion ◽

Materials Handling ◽

Manual Materials Handling ◽

Muscle Groups ◽

Spinal Load ◽

Theoretical Analyses ◽

Flexion And Extension

Pushing and pulling tasks account for 20% of occupational low-back injury claims but few studies have investigated the neuromuscular control of the spine during these tasks. Primary torso muscle groups recruited during pushing tasks include the rectus abdominis and external obliques. However, theoretical analyses suggest that co-contraction of the paraspinal muscles is necessary to stabilize the spine during flexion exertions. A biomechanical model was implemented to estimate co-contraction and spinal load from measured surface EMG and trunk moment data recorded during trunk flexion and extension exertions. Results demonstrate that co-contraction during flexion exertions was approximately twice the value of co-contraction during extension. Co-contraction accounted for up to 47% of the total spinal load during flexion exertions and spinal load attributed to co-contraction was nearly 50% greater during flexion than during extension exertions despite similar levels of trunk moment. Results underscore the need to consider neuromuscular recruitment when evaluating biomechanical risks. Keywords: Spine; Co-contraction; Push; Manual Materials Handling; Biomechanics

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The effect of task asymmetry, age and gender on dynamic trunk motion characteristics during repetitive trunk flexion and extension in a large normal population

IEEE Transactions on Rehabilitation Engineering ◽

10.1109/86.331563 ◽

1994 ◽

Vol 2 (3) ◽

pp. 137-146 ◽

Cited By ~ 14

Author(s):

W.S. Marras ◽

M. Parnianpour ◽

J.-Y.Y. Kim ◽

S.A. Ferguson ◽

R.R. Crowell ◽

...

Keyword(s):

Normal Population ◽

Trunk Flexion ◽

Age And Gender ◽

Trunk Motion ◽

And Gender ◽

Motion Characteristics ◽

Flexion And Extension

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The Changes of Trunk Motion Rhythm and Spinal Loading During Trunk Flexion and Extension Motions Caused by Lumbar Muscle Fatigue

Annals of Biomedical Engineering ◽

10.1007/s10439-015-1248-0 ◽

2015 ◽

Vol 43 (9) ◽

pp. 2112-2119 ◽

Cited By ~ 12

Author(s):

Boyi Hu ◽

Xiaopeng Ning

Keyword(s):

Muscle Fatigue ◽

Trunk Flexion ◽

Spinal Loading ◽

Trunk Motion ◽

Lumbar Muscle ◽

Flexion And Extension

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Evaluation of Strength and Irradiated Movement Pattern Resulting from Trunk Motions of the Proprioceptive Neuromuscular Facilitation

Rehabilitation Research and Practice ◽

10.1155/2012/281937 ◽

2012 ◽

Vol 2012 ◽

pp. 1-6 ◽

Cited By ~ 3

Author(s):

Luciana Bahia Gontijo ◽

Polianna Delfino Pereira ◽

Camila Danielle Cunha Neves ◽

Ana Paula Santos ◽

Dionis de Castro Dutra Machado ◽

...

Keyword(s):

Plantar Flexion ◽

Movement Pattern ◽

Lower Limbs ◽

Trunk Flexion ◽

Average Force ◽

Proprioceptive Neuromuscular Facilitation ◽

Muscular Activation ◽

Flexion And Extension ◽

Regional Muscle ◽

Dorsal Flexion

Introduction. The proprioceptive neuromuscular facilitation (PNF) is a physiotherapeutic concept based on muscle and joint proprioceptive stimulation. Among its principles, the irradiation is the reaction of the distinct regional muscle contractions to the position of the application of the motions.Objective. To investigate the presence of irradiated dorsiflexion and plantar flexion and the existing strength generated by them during application of PNF trunk motions.Methods. The study was conducted with 30 sedentary and female volunteers, the PNF motions of trunk flexion, and extension with the foot (right and left) positioned in a developed equipment coupled to the load cell, which measured the strength irradiated in Newton.Results. Most of the volunteers irradiated dorsal flexion in the performance of the flexion and plantar flexion during the extension motion, both presenting an average force of 8.942 N and 10.193 N, respectively.Conclusion. The distal irradiation in lower limbs became evident, reinforcing the therapeutic actions to the PNF indirect muscular activation.

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Evaluation of an Arm Support With Trunk Motion Capability

Journal of Medical Devices ◽

10.1115/1.4034298 ◽

2016 ◽

Vol 10 (4) ◽

Cited By ~ 5

Author(s):

A. G. Dunning ◽

M. M. H. P. Janssen ◽

P. N. Kooren ◽

J. L. Herder

Keyword(s):

Range Of Motion ◽

Daily Living ◽

Loss Of Function ◽

Semg Signal ◽

Trunk Motion ◽

Robotic Exoskeleton ◽

Progressive Muscle Weakness ◽

Trunk Movements ◽

Arm Support ◽

Arm Muscles

Due to progressive muscle weakness, the arm function in boys with Duchenne muscular dystrophy (DMD) reduces. An arm support can compensate for this loss of function. Existing arm supports are wheelchair bound, which restricts the ability to perform trunk movements. To evaluate the function of a body-bound arm support, a prototype (based on the Wilmington robotic exoskeleton (WREX) arm support) that allows trunk movements was built. In order to examine the effect of this device and to compare it with an existing wheelchair-bound device, three healthy subjects performed single joint movements (SJMs) and activities of daily living (ADL) with and without the devices. The range of motion (RoM) of the arm and the surface electromyography (sEMG) signal of five different arm muscles were measured. The range of motion increased when compared to the wheelchair-bound device, and the trunk motion was perceived as important to make specific movements easier and more natural, especially the more extreme movements like reaching for a far object and reaching to the top of the head. The sEMG signal was comparable to that of the wheelchair-bound device. This means that an arm support with trunk motion capability can increase the range of motion of the user, while the amount of support to the arm is equal.

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Neuromuscular Control of the Knee during a Resisted Single-Limb Squat Exercise

The American Journal of Sports Medicine ◽

10.1177/0363546504274150 ◽

2005 ◽

Vol 33 (10) ◽

pp. 1520-1526 ◽

Cited By ~ 49

Author(s):

Richard K. Shields ◽

Sangeetha Madhavan ◽

Emy Gregg ◽

Jennifer Leitch ◽

Ben Petersen ◽

...

Keyword(s):

Body Weight ◽

Knee Joint ◽

Knee Flexion ◽

Neuromuscular Control ◽

Biceps Femoris ◽

Medial Gastrocnemius ◽

Isometric Contractions ◽

Low Resistance ◽

Squat Exercise ◽

Flexion And Extension

Background Closed kinetic chain exercises such as single-limb squats are preferred for knee rehabilitation. A complete understanding of the neuromuscular control of the knee during the single-limb squat is essential to increase the efficiency of rehabilitation programs. Hypothesis Performing a controlled single-limb squat with resistance to knee flexion and extension will increase the coactivation of the hamstring muscle group, thus reducing the quadriceps/hamstrings ratio. Study Design Descriptive laboratory study. Methods A total of 15 healthy human subjects (7 women, 8 men) performed controlled single-limb squats in a custom mechanical device that provided resistance to both flexion and extension. Subjects performed the task at 3 levels of resistance, set as a percentage of body weight. Surface electromyographic recordings from 7 muscles (gluteus medius, rectus femoris, vastus medialis oblique, vastus lateralis, biceps femoris, semitendinosus, and medial gastrocnemius) were collected during the task. Results Biceps femoris activity during knee flexion increased from approximately 12% maximum voluntary isometric contractions during low resistance (0% body weight) to approximately 27% maximum voluntary isometric contractions during high resistance (8% body weight). Although the quadriceps had greater activity than the hamstrings at all levels of resistance, the quadriceps/hamstrings ratio declined significantly with resistance (F2,27 = 29.05; P=. 012) from 3.0 at low resistance to 2.32 at the highest resistance. Conclusions Performing controlled resisted single-limb squats may help to simultaneously strengthen the quadriceps and facilitate coactivation of the hamstrings, thus reducing anterior tibial shear forces. The coactivation may also increase the dynamic control of the knee joint. Clinical Relevance The typical single-limb squat exercise performed in the clinic does not usually control for bidirectional resistance and knee joint excursion. As seen in this study, controlled single-limb squats at increased levels of resistance help to increase the coactivation of the hamstring muscles, which is essential to optimize neuromuscular control of the knee.

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Human Finger Independence: Limitations due to Passive Mechanical Coupling Versus Active Neuromuscular Control

Journal of Neurophysiology ◽

10.1152/jn.00480.2004 ◽

2004 ◽

Vol 92 (5) ◽

pp. 2802-2810 ◽

Cited By ~ 114

Author(s):

Catherine E. Lang ◽

Marc H. Schieber

Keyword(s):

Neuromuscular Control ◽

The Other ◽

Passive Condition ◽

Mechanical Coupling ◽

Complete Independence ◽

Active Condition ◽

Middle Ring ◽

Human Finger ◽

Passive Movements ◽

Flexion And Extension

We studied the extent to which mechanical coupling and neuromuscular control limit finger independence by studying passive and active individuated finger movements in healthy adults. For passive movements, subjects relaxed while each finger was rotated into flexion and extension by a custom-built device. For active movements, subjects moved each finger into flexion and extension while attempting to keep the other, noninstructed fingers still. Active movements were performed through approximately the same joint excursions and at approximately the same speeds as the passive movements. We quantified how mechanical coupling limited finger independence from the passive movements, and quantified how neuromuscular control limited finger independence using an analysis that subtracted the indices obtained in the passive condition from those obtained in the active condition. Finger independence was generally similar during passive and active movements, but showed a trend toward less independence in the middle, ring, and little fingers during active, large-arc movements. Mechanical coupling limited the independence of the index, middle, and ring fingers to the greatest degree, followed by the little finger, and placed only negligible limitations on the independence of the thumb. In contrast, neuromuscular control primarily limited the independence of the ring, and little fingers during large-arc movements, and had minimal effects on the other fingers, especially during small-arc movements. For the movement conditions tested here, mechanical coupling between the fingers appears to be a major factor limiting the complete independence of finger movement.

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