EMG

-Natalia Amaya-Angie Ferrucho-María Gonzáles-Steban Molina-Andres Alvarez

Electromyography in Science Rehabilitation (EMG)

Changes in amplitude are observed in an electromyographic record when the muscle is at rest and when it is in a muscle contraction.

It allows to build the electromyogram, which corresponds to the temporal and spatial sum of the action potentials of the motor units (PAUMs) during the contraction, allowing accurate and objective quantification muscle bioelectric behavior

electromyographic signal

• It is defined as the discipline related to the detection, analysis and use of the electrical signal that is generated when a muscle contracts.

Definition

2. The low repeatability of the evaluation, since, being intramuscular, the probability of locating the electrode in the same muscle area is low.

1. Needle insertion causes discomfort during contraction, which may affect the evaluated motor gesture.

2. Detects electrical activity in specific muscle areas or fascicles.

1. Evaluate deep and small muscles that are superficially impossible to measure due to interference from signals emitted by adjacent muscles

Disadvantages:

Advantages:

An intramuscular electrode is inserted using needles, a method known as fine wire.

Application:

EMG Techniques:

It manages to record the action potential generated by a particular motor unit.

Objective:

1. Invasive EMG:

3. If the electrodes are wired, the cables may be uncomfortable when performing the motor gesture.

2. Potential signal contamination by adjacent musculature.

1. It has a utility to evaluate motor gestures, does not cause muscle discomfort and the location of the electrodes is easily reproducible.

1. It is not able to pick up the signal from a single motor unit.

Disadvantages:

Advantages:

Use of wired or wireless surface electrodes that are located directly on the skin of the muscle to be evaluated.

Application:

Objective:

It allows to study the bioelectrical activity of the muscle by recording the differences in potential recorded on the surface of the skin.

Surface EMG:

Once a motor neuronone discharges, the action potentials are generated in its neuromuscular joints and then spread along all the muscle fibers.

• They have a lot of muscle fibers per motor unit.

Thick motion or power muscles:

• They are made up of multiple small motor units, i.e. a somatic motor neuron stimulates a few muscle fibers.

Fine and precise movement muscles:

• Each motor unit consists of a motor neuronone and all the muscle fibers it inerts, which can vary in number depending on the specificity of the muscle.

Motor unit

Causes the release of acetylcholine the synaptic slit and motor plate

stimulates the exocytosis of the synaptic vesicles,

To the terminal synaptic bulbs of motorneurone

arrival of the nerve impulse,

the concentration of Na+ is higher on the outside

the concentration of K+ is higher indoors

ION PUMP

approximately -80 to -90 mV when not contracted

forms a resting potential in the muscle fiber membrane

In the internal and outer spaces of a muscle cell.

Ionic balance

• Semipermeable membrane model that describes the electrical properties of sarcolema (plasma membrane of a muscle fiber). It is based on action potentials in the muscle fiber membrane that result from depolarization and repolarization processes.

Origin of electromyographic signal

The level of muscle fatigue can be determined from an electrophysiological point of view.

Time it takes for the muscle to activate or pre-activate (before) in relation to the activation of the primary motor muscle of the evaluated movement or gesture.

Another variable that can be obtained is latency:

maximum isometric voluntary contraction (CVIM), in which the specific signal of each muscle is recorded

RMS is the most widely used method in sports and rehabilitation sciences.

You can determine the level of muscle activation or, specifically, the % activation. This can be calculated by analyzing the mean, peak, area under the curve, mean quadratic signal root (RMS)

Signal frequency

Amplitude

Parameters and uses of electromyographic signal

Example:

Muscle latency during arm lift. The normal activation pattern is represented during a predictable task (e.g. Launch).It is observed that the previous serrate is activated prior to activation of the anterior deltoid (primary motor) and the upper trapeze in order to mobilize the scapula, preparing it for arm movement.

• It has helped to understand the neuromuscular patterns used in the execution of different motor gestures.
• Helps to understand the possible causes and consequences of an injury and/or dysfunction on electrophysiological behavior of the muscle.

EMG in the sciences of rehabilitation

From the various researches with EMG, neuromuscular patterns of movement have been established in both normal and pathologies.

EMG is a fundamental tool in understanding human movement, and allows to estimate the magnitude of a muscle contraction (activation), the time when muscle (latency) is activated and fatigue levels that can occur during a maintained contraction.

Conclusion

Eduardo Guzmán-Muñoz, Guillermo Méndez-Rebolledo. (2018). Electromiografía en las Ciencias de la Rehabilitación. Salud Uninorte. Barranquilla (Col.); 34 (3): 753-765

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