Muscle coactivation

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Muscle coactivation occurs when agonist and antagonist muscles (or synergist muscles) surrounding a joint contract simultaneously to provide joint stability, [1] [2] and is suggested to depend crucially on supraspinal processes involved in the control of movement. [3] It is also known as muscle cocontraction, since two muscle groups are contracting at the same time. It is able to be measured using electromyography (EMG) from the contractions that occur. The general mechanism of it is still widely unknown. It is believed to be important in joint stabilization, as well as general motor control. [1]

Contents

Coactivation of biceps and triceps. The biceps' EMG is on top, while the triceps' EMG is on the bottom. EMGCOACTIVATION.JPG
Coactivation of biceps and triceps. The biceps’ EMG is on top, while the triceps’ EMG is on the bottom.

Function

Muscle coactivation allows muscle groups surrounding a joint to become more stable. This is due to both muscles (or sets of muscles) contracting at the same time, which produces compression on the joint. The joint is able to become stiffer and more stable due to this action. [4] [5] For example, when the biceps and the triceps coactivate, the elbow becomes more stable. This stabilization mechanism is also important for unexpected loads impeded on the joint, allowing the muscles to quickly coactivate and provide stability to the joint. [1] [4] This mechanism is controlled neuromuscularly, which allows the muscle(s) to contract. [1] This occurs through a motor neuron sending a signal (through creating action potentials) to the muscle fiber to contract by releasing acetylcholine. [6] When signals are sent to all muscle fibers in a muscle group, the muscle group will contract as a whole.

In the upper limbs, the stability of muscle coactivation allows for precise low-level physical tasks. [1] An example of this would be picking up a small object. By protecting the muscles at the end of their range of motion, the direction of the fine movements is able to be changed. [4] In the lower limbs, stability is important in upright standing balance. The coactivation of different muscle groups allows for proper balance and the ability to adjust weight and to stay upright on uneven ground. [7] It is also believed to be important for postural control by stabilizing the spine. [1] Muscle coactivation is absolutely necessary for learning a fine motor skill or for any activity involving stability. [7] In order for muscle coactivation to occur, it must inhibit reciprocal innervation, which occurs when a muscle contracts and the synergist muscle relaxes. [5] For muscle coactivation to occur, both the muscle and synergist muscle need to contract.

Testing

Muscle coactivation is measured using a technique called electromyography(EMG). [1] This is performed by using surface EMG that responds to electrical activity of the muscle through the skin. [8] Electrical activity is only present in the muscle when the muscle voluntarily contracts. [9] When the muscle is contracted, the EMG is able to display the force of the contraction or how the nerves can respond to stimulation. [10] An EMG of coactivation would display the agonist and antagonist muscle contracting simultaneously. Although it is believed many muscles are involved in the mechanism of coactivation, methods to measure coactivation are finite to specific instances or two muscle systems. Because of this, little is understood about the role of coactivation in a multiple muscle system. [1]

Related Research Articles

In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.

In biology, a motor unit is made up of a motor neuron and all of the skeletal muscle fibers innervated by the neuron's axon terminals, including the neuromuscular junctions between the neuron and the fibres. Groups of motor units often work together as a motor pool to coordinate the contractions of a single muscle. The concept was proposed by Charles Scott Sherrington.

<span class="mw-page-title-main">Electromyography</span> Electrodiagnostic medicine technique

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement. Needle EMG is an electrodiagnostic medicine technique commonly used by neurologists. Surface EMG is a non-medical procedure used to assess muscle activation by several professionals, including physiotherapists, kinesiologists and biomedical engineers. In computer science, EMG is also used as middleware in gesture recognition towards allowing the input of physical action to a computer as a form of human-computer interaction.

<span class="mw-page-title-main">Muscle contraction</span> Activation of tension-generating sites in muscle

Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state.

<span class="mw-page-title-main">Fasciculation</span> Spontaneous, involuntary muscle twitch

A fasciculation, or muscle twitch, is a spontaneous, involuntary muscle contraction and relaxation, involving fine muscle fibers. They are common, with as many as 70% of people experiencing them. They can be benign, or associated with more serious conditions. When no cause or pathology is identified, they are diagnosed as benign fasciculation syndrome.

Reciprocal inhibition describes the relaxation of muscles on one side of a joint to accommodate contraction on the other side. In some allied health disciplines, this is known as reflexive antagonism. The central nervous system sends a message to the agonist muscle to contract. The tension in the antagonist muscle is activated by impulses from motor neurons, causing it to relax.

<span class="mw-page-title-main">Stiff-person syndrome</span> Human medical condition

Stiff-person syndrome (SPS), also known as stiff-man syndrome, is a rare neurologic disorder of unclear cause characterized by progressive muscular rigidity and stiffness. The stiffness primarily affects the truncal muscles and is superimposed by spasms, resulting in postural deformities. Chronic pain, impaired mobility, and lumbar hyperlordosis are common symptoms.

In physiology, motor coordination is the orchestrated movement of multiple body parts as required to accomplish intended actions, like walking. This coordination is achieved by adjusting kinematic and kinetic parameters associated with each body part involved in the intended movement. The modifications of these parameters typically relies on sensory feedback from one or more sensory modalities, such as proprioception and vision.

Preflexes are the latent capacities in the musculoskeletal system that auto-stabilize movements through the use of the nonlinear visco-elastic properties of muscles when they contract. The term "preflex" for such a zero-delay, intrinsic feedback loop was coined by Loeb. Unlike stabilization methods using neurons, such as reflexes and higher brain control, a preflex happens with minimal time delay; however, it only stabilizes the main movements of the musculoskeletal system.

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Ballistic movement can be defined as muscle contractions that exhibit maximum velocities and accelerations over a very short period of time. They exhibit high firing rates, high force production, and very brief contraction times.

<span class="mw-page-title-main">Neuromechanics</span> Interdisciplinary field

Neuromechanics is an interdisciplinary field that combines biomechanics and neuroscience to understand how the nervous system interacts with the skeletal and muscular systems to enable animals to move. In a motor task, like reaching for an object, neural commands are sent to motor neurons to activate a set of muscles, called muscle synergies. Given which muscles are activated and how they are connected to the skeleton, there will be a corresponding and specific movement of the body. In addition to participating in reflexes, neuromechanical process may also be shaped through motor adaptation and learning.

As humans move through their environment, they must change the stiffness of their joints in order to effectively interact with their surroundings. Stiffness is the degree to a which an object resists deformation when subjected to a known force. This idea is also referred to as impedance, however, sometimes the idea of deformation under a given load is discussed under the term "compliance" which is the opposite of stiffness . In order to effectively interact with their environment, humans must adjust the stiffness of their limbs. This is accomplished via the co-contraction of antagonistic muscle groups.

<span class="mw-page-title-main">Spinal interneuron</span> Interneuron relaying signals between sensory and motor neurons in the spinal cord

A spinal interneuron, found in the spinal cord, relays signals between (afferent) sensory neurons, and (efferent) motor neurons. Different classes of spinal interneurons are involved in the process of sensory-motor integration. Most interneurons are found in the grey column, a region of grey matter in the spinal cord.

<span class="mw-page-title-main">Anatomical terms of muscle</span> Muscles terminology

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<span class="mw-page-title-main">Proportional myoelectric control</span>

Proportional myoelectric control can be used to activate robotic lower limb exoskeletons. A proportional myoelectric control system utilizes a microcontroller or computer that inputs electromyography (EMG) signals from sensors on the leg muscle(s) and then activates the corresponding joint actuator(s) proportionally to the EMG signal.

Intermuscular Coherence is a measure to quantify correlations between the activity of two muscles, which is often assessed using electromyography. The correlations in muscle activity are quantified in frequency domain, and therefore referred to as intermuscular coherence.

Robotic prosthesis control is a method for controlling a prosthesis in such a way that the controlled robotic prosthesis restores a biologically accurate gait to a person with a loss of limb. This is a special branch of control that has an emphasis on the interaction between humans and robotics.

<span class="mw-page-title-main">Interlimb coordination</span> Coordination of the left and right limbs

Interlimb coordination is the coordination of the left and right limbs. It could be classified into two types of action: bimanual coordination and hands or feet coordination. Such coordination involves various parts of the nervous system and requires a sensory feedback mechanism for the neural control of the limbs. A model can be used to visualize the basic features, the control centre of locomotor movements, and the neural control of interlimb coordination. This coordination mechanism can be altered and adapted for better performance during locomotion in adults and for the development of motor skills in infants. The adaptive feature of interlimb coordination can also be applied to the treatment for CNS damage from stroke and the Parkinson's disease in the future.

References

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  2. "cocontraction". The Free Dictionary. Retrieved 27 April 2017.
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  8. Dotan, Raffy; Mitchell, Cameron; Cohen, Rotem; Klentrou, Panagiota; Gabriel, David; Falk, Bareket (2017-04-27). "Child—Adult Differences in Muscle Activation — A Review". Pediatric Exercise Science. 24 (1): 2–21. doi:10.1123/pes.24.1.2. ISSN   0899-8493. PMC   3804466 . PMID   22433260.
  9. Klass, Malgorzata; Baudry, Stéphane; Duchateau, Jacques (2007-07-01). "Voluntary activation during maximal contraction with advancing age: a brief review". European Journal of Applied Physiology. 100 (5): 543–551. doi:10.1007/s00421-006-0205-x. PMID   16763836. S2CID   21581969.
  10. "Before, During and After Your EMG Test". www.hopkinsmedicine.org. Retrieved 2017-04-10.