SKELETAL Muscle is Defined as Muscle Which Is

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SKELETAL muscle is defined as muscle which is striated or striped,

indicating and ordered cell structure, of myosin and actin filaments,

and is generally under voluntary control, which has an action on the

skeleton or bones in the body.

In its relaxed form the muscle is at its maximum length and this is generally howthe tissue is found.

Stimulation generally causes contraction and a shortening and thickening of the

tissue.

As it is attached to a minimum of 2 points, the Origin (O) and the insertion (I) -

contraction brings these 2 points closer together. To reverse this, another

muscle must be attached to 2 different points which when they move together

cause a reversal of the position of the 2 or more affected bones.

So for each muscle there is an antagonist (opposing muscle) and inmany situations a synergist (a muscle which enhances the original

movement).

Examination of Skeletal Muscles - major groups

Questions for individual joint examination

1 functional limitation

2 SS -limited to one or more joints

3 onset - acute - related to a specific incident

- chronic - slow progressive increase of pain or reduced ROM

4 description of the causative agent if known e.g. accident

5 any prior MSS history of that joint or others

6 Systemic problems

For participation in sport/training activities MSS : for this examination unless

otherwise indicated the patient standing - facing the clinician in the anatomical

position.

CERVICAL SPINE / NECK - ROM tests the following groups of muscles

Scalenes/Colles/Trapezius upper fibres/Cervicis regions of ES and deep muscles

of the VC/Sternocleidomastoid

patient looks at the roof R extension

patient looks at the floor R flexion

patient looks over each shoulder R horizontal rotation


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head bends towards the shoulder - sideways R (shoulders kept still) lateral

flexion

SHOULDER (SCAPULA) - ROM tests the following groups of muscles

Levator Scapulae/Rhomboids/Serratus Anterior/Spinati muscles/Trapezius/Deltoid

observe symmetry of shoulder particularly the Acromioclavicular jt shrug

shoulders R elevation

drop shoulders depression

straighten shoulders - trying to meet shoulder blades lateral rotation

contract shoulders - withdrawing chest medial rotation

abduct shoulders to 90o (flexed arm) R abduction

SHOULDER + ARM - ROM tests the following groups of muscles

Pectorals/Latisimus Dorsi/Trapezius/Scapular muscles

scratch back with each hand from over and under the shoulder or have hands

meet at the back from over and under the shoulder external rotation +

abduction / internal rotation + adduction

move extended abducted arms as high as possible R vertical adduction

move extended abducted arms into the sagittal plane R horizontal

adduction

move extended abducted arms out of the sagittal plane R horizontal

abduction

with bent arms keep them close to the body against R adduction

UPPER LIMB + HAND - ROM tests the following groups of muscles

Brachii muscles/Brachioradialis/Flexors & Extensors of upper limb, hand &

digits/Supinators/Pronators/Carpi muscles/Intrinsic muscles of the hand

flex/extend elbows R, turn wrist in and out R pronation/supination

bend and straighten wrist R flexion/extension

move extended wrist towards the body R ulnar deviation = medial flexion


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move extended wrist away from the body R radial deviation = lateral

flexion

spread extended fingers R abduction

close extended open fingers Radduction

oppose fingers and thumb opposition

make a fist R flexion

extend hand and fingers R extension

BACK ABDOMEN - ROM tests the following groups of mscles

ES, deep muscles of the back, Latissimus Dorsi, Quadratus Lumborum, Obliques,

Gluteal muscles, Rectus Abdominus

observe posture, shoulder and neck symmetry, spinal curvature observe for

balance on one leg bend from side to side while facing the front lateral flexion

bend back as far as possible hyperextension

twist from the hips to the left & right rotation

supine patient - touch toes and back extension/flexion (back/abdomen)

HIP + THIGH - ROM tests the following muscles

Gluteal muscles/Iliopsoas /Obturators/Quadriceps/Hamstrings/

Adductors/Abductors

observe symmetry of the hips and stance turn leg inwards/outwards

medial/lateral rotation

standing patient - touch toes with straight legs extension/flexion (back) &

hamstring tightness

lift the extended leg forwards/backwards flexion/extension (hip)

lift the extended leg sideways lateral flexion (hip)

with the sitting patient keep legs together against R adduction

LOWER LIMB + KNEE + FOOT - ROM tests the following groups of

muscles


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Gluteal muscles/Iliopsoas/Quadriceps/Hamstrings/Adductors/Abductors/Peroneal

muscles/Soleus/Intrinsic muscles of the foot

observe for knee & ankle symmetry - looking for effusions &/or deformities bend

and straighten legs with erect posture flexion/extension (knee & ankle)

spread toes abduction (toes)

point toes plantar flexion (ankle)

duckwalk with buttocks on heals - this tests all lower limb and hip ROM point feet

outwards/inwards eversion/inversion (foot)

Electromyography

Electromyography 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 electrical potential generated by muscle cells when

these cells are electrically or neurologically activated. The signals can be

analyzed to detect medical abnormalities, activation level, recruitment order or

to analyze the biomechanics of human or animal movement.

There are two kinds of EMG

i. surface EMG

ii. intramuscular (needle and fine-wire) EMG

To perform intramuscular EMG,

i. a needle electrode or a needle containing two fine-wire electrodes is

inserted through the skin into the muscle tissue.

ii. A trained professional (such as a neurologist, physiatrist, or physical

therapist) observes the electrical activity while inserting the electrode.

iii. The insertion activity provides valuable information about the state of the

muscle and its innervating nerve. Normal muscles at rest make certain,

normal electrical signals when the needle is inserted into them.

iv. Then the electrical activity when the muscle is at rest is studied.

(Abnormal spontaneous activity might indicate some nerve and/or muscle

damage. )

v. Then the patient is asked to contract the muscle smoothly.

vi. The shape, size, and frequency of the resulting motor unit potentials arejudged.


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vii. Then the electrode is retracted a few millimetres, and again the activity is

analysed until at least 1020 units have been collected.

* Each electrode track gives only a very local picture of the activity of the whole

muscle. Because skeletal muscles differ in the inner structure, the electrode has

to be placed at various locations to obtain an accurate study.

Intramuscular EMG may be considered too invasive or unnecessary in some

cases.

Instead, a surface electrode may be used to monitor the general picture of

muscle activation. This technique is used in a number of settings; for example, in

the physiotherapy clinic.

Muscle activation is monitored using surface EMG and patients have an auditory

or visual stimulus to help them know when they are activating the muscle

(biofeedback).

A motor unit is defined as one motor neuron and all of the muscle fibres it

innervates.

When a motor unit fires, the impulse (called an action potential) is carried down

the motor neuron to the muscle.

The area where the nerve contacts the muscle is called the neuromuscular

junction.

After the action potential is transmitted across the neuromuscular junction, an

action potential is produced in all of the innervated muscle fibres of that

particular motor unit.

The sum of all this electrical activity is known as a motor unit action

potential (MUAP). This electro physiologic activity from multiple motor units is

the signal typically evaluated during an EMG.

The composition of the motor unit, the number of muscle fibres per motor unit,

the metabolic type of muscle fibres and many other factors affect the shape of

the motor unit potentials in the electromyogram.

Normal results

Muscle tissue at rest is normally electrically inactive. After the electrical

activity caused by the irritation of needle insertion subsides, the

electromyograph should detect no abnormal spontaneous activity. When the

muscle is voluntarily contracted, action potentials begin to appear. As the

strength of the muscle contraction is increased, more and more muscle fibres

produce action potentials. When the muscle is fully contracted, there should

appear a disorderly group of action potentials of varying rates andamplitudes.


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Abnormal results

EMG is used to diagnose diseases that generally may be classified into one of the

following categories: neuropathies, neuromuscular junction diseases and

myopathies.

Neuropathic disease has the following defining EMG characteristics:

An action potential amplitude that is twice normal due to the increased

number of fibres per motor unit because of reinnervation of denervated

fibres

An increase in duration of the action potential

A decrease in the number of motor units in the muscle (as found

using motor unit number estimation techniques)

Myopathic disease has these defining EMG characteristics:

A decrease in duration of the action potential

A reduction in the area to amplitude ratio of the action potential

A decrease in the number of motor units in the muscle (in extremely

severe cases only)

SKELETAL Muscle is Defined as Muscle Which Is

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