Kinesiology 1 Credit H. 3

KinesiologyM Farrukh ShahzadBSPT, PPDPT

Lesson 12

Muscle Strength

MUSCLE STRENGTH AND MUSCLE ACTIONOverview of muscle structureTypes of Muscles contractionMuscles toneTypes of muscle workRange of muscle workGroup action of musclesTwo joint muscle workActive and passive insufficiency Group movement of jointsMuscular weakness and paralysisPrevention of muscles wasting The initiation of muscular contractionStrengthening methods page

Overview of muscle structure

Contractile tissue:The contractile tissue of each muscle is composed of numerous muscle fibers. Each muscle fiber is a multinucleated, cross-striated cylindrical cell. The length of each muscle fiber is between 1 and 300 mm. It consists of a cell membrane (sarcolemma), which encloses the cytoplasm (sarcoplasm).There are two types of substances embedded in the sarcoplasm.Several nuclei arranged at the periphery beneath the sarcolemma.A number of evenly distributed longitudinal threads called myofibrils.Each myofibril shows alternate light and dark bands. Dark bands are Anisotropic and thus are known as A-bands. The light bands are Isotropic and thus are known as I-bands. The bands of adjacent fibrils are aligned transversely so that the muscle fiber appears cross striated. In the middles of the A band (dark band) there is a light H band. In the middle of the H band there is a dark M line. In the middle of the I band (light band) there is a dark Z disk also known as Krauses membrane. The segment of myofibril between two Z discs is called sarcomere.Supporting tissue:It helps in organization of the muscle. Endomysiumsurrounds each muscle fiber separately. Perimysiumsurrounds bundles (fasciculi or myonemes) of muscle fibers of various sizes. Epimysiumsurrounds the entire muscle. The connective tissue of the muscle becomes continuous with the tendon.

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Supporting tissue:It helps in organization of the muscle. Endomysiumsurrounds each muscle fiber separately. Perimysiumsurrounds bundles (fasciculi or myonemes) of muscle fibers of various sizes. Epimysiumsurrounds the entire muscle. The connective tissue of the muscle becomes continuous with the tendon.

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3 types of muscular contractionISOMETRIC CONTRACTIONTension develops in muscle but there is no change in muscle length. It is a static contraction as no movement occurs at the jointISOTONIC CONTRACTIONTension is produced in the muscles while there is a change in muscle length. It is a dynamic contraction because movement occurs at the jointMUSCULAR CONTRACTIONTension develops in a muscleCONCENTRIC CONTRACTIONTension develops while muscle shortensCauses joint movementECCENTRIC CONTRACTIONTension develops while muscle lengthensControls joint movementISOMETRIC CONTRACTIONStops joint movementRange of muscle work It can be called as excursion of the muscles i-e the amount of shortening or lengthening during contractionORThe range of muscle work is the extent of the muscular contraction which results in joint movement

Full RangeThe joint is moved as the muscle work from the position in which they are fully stretched to the position in which they are fully contracted. This work is done concentrically

Full RangeJoint is moved from the position of full contraction to the position of maximum extension. This work is done eccentricallyUnder ordinary circumstances muscles are rarely required to work in full rangeIn emergencies muscle may have to do full range workMaintain joint mobility Increase circulationEnsure emergency reserve of power and mobility is preserved

Inner RangeThe muscle works either concentrically from the position in which it is partially contracted (approximately half way b/w the limits of full range) to a position of full contraction

Inner RangeVice versa if it works eccentrically

Exercise in inner range are used to gain or to maintain movement of the joint in the direction of the muscle pull

And to train some extensor muscles responsible for stabilising the joints.

Outer RangeThe muscle work concentrically from the position in which they are fully stretched to a position in which they are they are partially (half) contracted

Outer RangeVice versa if the muscles are working eccentrically

Outer range is used in muscle re-education, as contraction is initiated more easily from stretch in most muscles

Middle RangeThe muscle during this range are never either fully stretched or fully contractedThis is the range in which the muscles are most often used during every day lifeMost efficient range of muscle workExercises performed in this range maintain muscular tone and normal power.Full joint movement is never achieved during middle range exercises.

Group action of musclesUnder normal conditions a single muscle never works alone to produce movement or secure stability.Functionally muscles work together in groups although each muscle may have some specific part to play in relation to action of the whole group e.g. by determining the precise direction of the movement

Group action of musclesBy maintaining its progress in a particular part of range

The integrated activity of many muscles groups is required for the production of efficient functional movement

The functions of theses muscle groups are indicated by their names.

Muscle groupsAgonist Antagonist Synergist Fixator

AgonistThese are the group of muscles which contract to provide the force required to produce the movement

EXAMPLEAn example that comes to mind is the quadriceps group during the act of running. They are one of the primary accelerators of the lower body because of their ability to extend the lower leg during the pushing action of running.

AntagonistThese are the group of muscles whose action would oppose that of the agonists,

Their activity is producing inhibition

They relax progressively to control and permit the movement

EXAMPLETo continue with the example above, if the quads are considered an agonist for running, then the hamstrings can be considered antagonists. Their primary role during running is to decelerate the lower leg to control toe placement while running.

SynergistIts the Greek prefix syn- means with.Its name indicate that these muscles work with the agonist to provide a suitable back ground for activity and to facilitate the movementSynergist may be required to modify the direction of the pull of an agonistSometimes to control joints not involved in the movements it happens in case of muscles passes over two or more joints

EXAMPLEA good example of a pair ofsynergistmusclescan be found in the elbow, where the brachioradialisand biceps work together to extend or flex the arm by moving the elbow joint.

EXAMPLEA perfect example of this relationship is the Hamstring group. The hamstrings are designed to assist with hip extension, but the primary mover for hip extension are the Glutes.

FixatorThese muscles works to stabilise bones of origin of the agonists to increase their efficiency for the production of the movement

Fixator secure the stability of the body as a whole

EXAMPLEWhen you look at the shoulder, it is impossible to have good shoulder function, if the rhomboids and low to mid traps aren't functioning well to stabilize the scapula.

Two joint muscle work ( Group Movement of joints)

Active insufficiencyThe inability of a muscle, which spans two or more joints, to exert enough tension and shorten sufficiently to cause a full range of movement in all joints at the same time

Active insufficiency Its mean Poor Lengthening of the agonist muscle - Example (i):When bend the wrist ( flexion the wrist ) and bend the elbow ( flexion the elbow ), its hard to make a fist of the hand. It is because the length of the agonist muscle ( flexor ) is not sufficient.

Passive insufficiency The inability of a muscle that spans two or more joints to be stretched sufficiently to produce a full range of motion in all the joints simultaneously.

Passive insufficiency Passive insufficiency : - Its mean Poor Lengthening of the antagonist muscle- Example (i):Make a fist of the hand first, and then bend the wrist and elbow. The fist will be weak. Its is because of pulling back of antagonist muscle for fist.

TopicsMuscular weakness and paralysis

Muscular weakness and paralysis Paralysisis complete loss ofmusclefunction for one or more muscles. Paralysis can be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage as well as motor. Paresis: partial loss of function of muscle is called paresis.Muscular weakness and paralysis results in loss of movement, stability, it develops the state of muscular imbalance which will lead to uncoordinated movements.Weak muscles should be protected and encouraged by early re-education until they become normal and strong enough.

Causes ofmuscular weakness and paralysiscontraction is the only mean by which muscle power can be maintained or increased

Causes of muscular weakness could be any lesion effecting the tissue or inclination not to move

Causes ofmuscular weakness and paralysisLesion affecting AHCs(Anterior horn cells)Lesion affecting the motor pathwaysLesion affecting the muscular tissueDisuse of normal muscle and nerve tissueConstitutional diseases:Functional

Prevention of muscle wastingMuscles tend to waste when they are:ImmobilizedInjuredDe nervatedLack contraction/activity

Prevention of muscle wastingMuscle wasting can be prevented by:ExercisesIsometric, concentric, eccentric, ROMModalitiesElectrical stimulation, heat therapyMassageGood nutritionAerobic exercises

Muscle wastingMuscle wasting causes:A decrease in size and volume of muscleA decrease in the number of motor unitsA decrease in the ability to generate tension and contract

Prevention of muscular weakness In flaccid paralysis In flaccid paralysis there is lower motor neuron lesion Muscles are hypotonic and unable to contract.Rapid wasting of muscles took place.This wasting can not be prevented but can be arrested.

Principles of treatment during flaccid paralysis 1.Protection of the effected muscle or muscle groups.Example foot drop/wrist drop discussion?2. Maintenance of Circulation 3. Range of movement in joints immobilisedConsideration of two joint muscles4. Remembrance of pattern of movement 5. Strength and use of normal muscles

Prevention of muscular weaknessIn spastic paralysisupper motor neuron lesionMuscles are hypertonicIncapable of performing voluntary movements (contraction, relaxation)In spastic paralysis muscle wasting is not marked.

Principles of treatment during spastic paralysisIn spastic paralysis the affected area or the limb is locked in spasm

Circulation is impeded, muscle and joint contractures may developed if remained untreated over a period of time

Principles of treatment during spastic paralysisAim of treatment Position of the limb Maintain normal joint range of motion Maintain muscle extensibility Improve circulation Reflex movement initiation by means of PNF techniques (proprioceptive neuromuscular facilitation)

Treatment in primary lesion of the muscle tissueLoss of power can not be arrested as the contractile tissue muscle itself got injured

Improvement can be gained with light exercises this improvement is the result of making the best use of the fibres which are still in tact

Prevention of muscular weakness in disuse atrophy If there is no constitutional disease it can be prevented or controlled byStrong and frequent contraction against resistance Exercise should be carried out within the limit of disability Exercise with manual resistance in early stages of recovery Patient understanding about the need to exercise Five minutes in every hour for exercises Suitable games, sports under supervision

In constitutional diseaserheumatoid arthritisIsometric exercises in pain free area helps to prevent the atrophy

It will also lead to increased pain free movement to achieve functional movements

Initiation of Muscular Contraction(Early Re-Education)Measures used to obtain initiation of contraction

Strengthening MethodsTreatment to increase muscular strength and function