muscle energy techniques Course
MUSCLE ENERGY TECHNIQUES – POST ISOMETRIC RELAXATION – HOW IT AFFECTS MUSCLE LENGTH & TONE
Muscle energy techniques are used in manual medicine to affect the length and tone of a hypertonic muscle, in order to therapeutically reduce pain or improve posture.
Muscle energy techniques post isometric relaxation is best used when the muscle is considered to be tight or have too much tone. There is a lengthening and strengthening aspect to muscle energy techniques which can be very beneficial in a therapeutic setting.
In order to use MET PIR the range of movement (ROM) is assessed both in active and passive movement. The joint is then taken to the first barrier and pain scale is checked. The therapist then asks the client to perform an isometric contraction for 10 seconds at 10 percent of effort. This increases the tension being applied to the tendon and the golgi tendon organ (GTO). This causes the GTO to register the tension in the muscle via the afferent nerve. The muscle isometric contraction then stops, but the GTO has an inhibitory effect on the muscle, causing a powerful relaxation. The joint is then taken to the new barrier over 10 seconds and the muscle spindles, which would normally be triggered are inhibited by the effect of the GTO. This must be done slowly to avoid stretch reflex stimulation. This effectively resets the muscle spindles at the new length.
The lengthening of the muscle while the muscle spindles are inhibited enables the tone in the whole muscle to be reduced. It does not produce a full inhibition, but it does enough to inhibit the efferent nerve to the agonist. The muscle can be taken to the next barrier increasing the ROM. The CNS recognizes this new position as normal, after a few turns of this technique the final barrier is held for 20 seconds making sure that the muscle spindles are not firing. The technique is then completed by passively, but gently taking the joint through its new ROM to ensure that there are no problems. Active and passive ROM can be reexamined at this point.
MUSCLE ENERGY TECHNIQUES – PIR & RI – PHYSIOLOGICAL PRINCIPLES
The term muscle energy technique comes from the way we get the client to use their own energy (via muscle contraction) to enable a physiological chain of events to occur (NLSSM, 2014).
There are two different forms of muscle energy technique, which can be used to improve the range of movement around a joint by lengthening the muscle.
Muscle energy techniques can be used to reduce muscle hypertonicity, improve circulation, re- align muscle fibres, lengthen a short tightened muscle, strengthen physiologically weakened muscle and restore proprioception (NLSSM, 2014).
The first muscle energy technique is called post isometric relaxation (PIR). Post isometric relaxation means that after a static muscle contraction, relaxation of the target muscle occurs. The process of the techniques goes as follows; the patient’s active and passive ROM are assessed. The therapist checks for the existence of pain during the movement. MET should not be used on acute injuries or if pain is present. If there is no pain then the process begins by the therapist taking the muscle to the first barrier. A ten second contraction of ten percent effort against the therapist’s resistance is then performed. This stretches the muscle causing impulses from the muscle spindles to travel to the posterior horn cell of the spinal cord. The anterior horn cell then transmits an increase in motor impulses to the muscle fibres, creating a protective tension to resist the stretch. After a few seconds the GTO’s are stimulated and transmit an impulse to the posterior horn cell. The GTOs are located in the tendon and measure load / tension on the muscle. These impulses create an inhibitory effect on the anterior horn cell and the muscle spindles and thus allow the muscle to relax (Gibbons, 2011). The GTO reflex is a protective measure to avoid injury and it can be used in METs in a mild form to increase ROM.
The client then performs a respiratory cycle and relaxes for ten seconds. The lengthening & re setting of the muscle spindles during the phase of inhibition allows a reduction in the tone and an increase in ROM.
The therapist then moves to the new barrier over ten seconds and repeats the process. After the last repetition the new ROM is held for twenty seconds. PIR can be used to increase the ROM of a joint, reduce hypertonicity of muscle tissue and increase proprioception. Due to the inhibitory nature of PIR on the agonist it results in increases of strength in the antagonist, because they are no longer being constantly inhibited by the hypertonic agonist.
The second muscle energy technique is called reciprocal inhibition (RI). The therapist performs the same basic assessments of active and passive ROM. The same principles with regards to pain still apply. The target muscle is still the area we are trying to stretch, but we are reducing it’s stimulation by activating its antagonist.
RI involves contracting the antagonist in order to decrease the tone and increase the length of the target muscle. The client’s limb is taken to the barrier in the same way as described in the PIR method. The client is asked to contract the antagonist at ten percent of effort with resistance from the therapist. The isometric contraction stimulates the muscle spindles and they send information to the spinal cord. This results in a reciprocal inhibition of the alpha motor neuron to the target muscle. This relaxes the target muscle. The contraction is held for ten seconds and a respiratory cycle, after which the target muscle is stretched to the next barrier straight away. RI produces the same result as PIR, but uses a different mechanism to achieve it. The basic principle is that agonist and antagonist cannot create movement and both contract at the same time. Therefore, they are hard wired to turn each other off.
The process can be repeated a number of times, each for ten seconds, a respiratory cycle of six seconds to relax after the new barrier is engaged and then the final position is held for twenty seconds.
RI can be used in sub-acute stages of injury provided that pain does not exist. This is because the damaged tissue is not being contracted. Caution needs to be used with RI to avoid cramping. This is done by not using the technique in an extremely shortened position.
It is important to consider tissue condition and case history when deciding which method to use. PIR techniques are used in favour of RI techniques in chronic situation, when the therapist is trying to increase the ROM by a substantial distance. This is because RI causes cramping when the antagonist is in an extremely shortened position. At this stage the tissues are healed but need stretching and re- alignment of the fibres. On the other hand RI can be used in the sub-acute phases of injury because it is not contracting the damaged tissue. However, you must continually check the pain scale to make sure it is safe. This means that you can increase pain free ROM earlier in the treatment process than if you were using PIR alone. Furthermore, RI is very good at strengthening weakened muscles. In many situation the therapist may want to use both techniques to help strengthen weakened muscles and inhibited tight muscles. If the muscle is very short, RI may have more effect than PIR in reducing tone and increasing length.
Muscle energy techniques are contraindicated if the client cannot follow the instruction for the techniques, or if the client has a tendency for cramping (in particular RI), as well as in the acute phases of treatment and if the client is already hypermobile in that area.