TYPES OF MUSCLE WORK
There are two main ways in which a muscle may work naturally. It may contract and produce no movement, called isometric contraction, or it may produce movement during contraction, called isotonic contraction.
Both these types of contraction may be used therapeutically, but a third type of muscle action may be applied to muscles to strengthen them. This uses isokinetic or accommodative resistance to achieve.
Isotonic Contraction
When a muscle works isotonically it contracts and the part of the body to which it is attached will move. There are two types of isotonic contraction.
Isotonic Shortening.
When a muscle performs a contraction and its two attachments are approximating to one another, the contraction is known as an isotonic shortening, e.g. when the arm is raised from the side and the abductors of the shoulder contract, the contraction is one of isotonic shortening.
Isotonic Lengthening
When the attachments of a muscle move slowly away from one another and the muscle allows this movement to occur in a controlled manner, the muscle action is one of isotonic lengthening, e.g. when the body is in the upright position and the arm is lowered from abduction to adduction, the abductors of the shoulder will control the movement and these abductors will be acting in isotonic lengthening.
Isotonic shortening can take place under any circumstances, i.e. whenever movement takes place in which the attachments of a muscle approximate, the muscle work will be isotonic shortening. Isotonic lengthening, however, may only be brought about if an outside force is applied to the component which is to be moved and the body part is slowly moved so that the attachments of the muscle are moved away from one another.
Gravity may be the outside force which pulls body components towards the earth as in lowering the arm from the abducted position to the side, or in sitting on the edge of a table lowering the outstretched leg to a right angle at the knee. However, under many other circumstances, in order to work a muscle in isotonic lengthening it is necessary for the therapist to be the outside force. The command given is 'resist slightly whilst I move your leg', or arm as the case may be, to a new position. The patient offers slight resistance, the therapist applies pressure which is greater than the resistance offered by the patient and is on the surface which is on the same aspect as the muscles which are required to be worked in isotonic lengthening. For example, if a patient is in side lying and the quadriceps are to be worked, the leg will be arranged straight at the knee, one hand will be placed as a stabilizing hand on the thigh and to palpate the quadriceps. The other hand will be placed on the anterior aspect of the leg and the command will be given 'resist slightly while I bend your leg'. The patient resists, the therapist bends the leg and the quadriceps will be worked in isotonic lengthening.
Many other examples of isotonic shortening and isotonic lengthening can be found and therapists should attempt to work out the single movements of each of the joints of the body with and without resistance so that they are able to identify isotonic shortening and isotonic lengthening. When therapists can identify these two types of muscle work they should then try to apply the range of muscle work as described below.
Isometric Contraction
When a muscle works isometrically it shortens its muscular length and slightly lengthens its non-contractile components and in doing so no movement occurs at any of the joints over which that muscle passes. It is easiest and in fact usual for an induced isometric contraction to be performed when a muscle is resting at the innermost part of its range, i.e. with the muscle attachments approximated, but with practice the skill can be developed so that it is possible isometrically to contract a muscle or muscle group at any part of the range. Isometric contraction can be taught to a muscle by the application of a manual resistance which is exactly equal to the contraction which the muscle produces. The command which the therapist will give will be 'don't let me push or pull that body component about', e.g. 'don't let me push you forwards' with pressure on the back of the shoulders will initially cause contraction of the extensor muscles.
'Don't let me pull you back' will cause contraction of the flexor muscles. 'Don't let me push your foot up' will cause contraction of the plantarflexors of the foot. 'Don't let me push your foot down' will cause contraction of the dorsiflexors of the foot.
When isometric contractions are done to one group of muscles only, they are usually taught in order that the patient might practice these contractions alone without the therapist. Indeed isometric contractions are the only contractions which are possible when the patient is wearing a support such as a plaster or a fixation splint. This is the type of muscle work which is used when the joint is so inflamed that movement would be both painful and inadvisable. The strength and tone of the muscles working over that joint may be maintained by teaching the patient isometric contractions. When a patient is initially incapable of performing an isometric contraction on a damaged part, the technique may be taught on the opposite limb or may be taught on any part of the patient, and if this is completely impossible the contraction per se may be taught with the use of a faradic type current applied in such a manner that it merely teaches the patient what to do and is immediately followed by patient participation. In other words the current is used for re-education of contraction.
THOSE ABOVE ARE COLLECTED FROM SOME BOOKS AND WEBSITES..
THANK YOU,
Comments