When a machine moves, stress on the moving components will deteriorate or wear out the machinery. If the alignment of the specific segments or moving parts is not ideal then the machine will eventually break down. In contrast to machinery, stress on the moving segments of the human body is necessary and graded stress can actually improve the strength of the involved tissues-two of the advantageous characteristics of the human body. There are upper and lower limits that determine whether or not it will be beneficial to the health of the tissues. Any loss in the precise movement can begin a process that can induce changes that can cause micro trauma to macro trauma in the involved tissues. I will try to give you examples of common movement impairment syndromes that will create faulty mechanical wear and tear which eventually leads to pain or dysfunction.
Muscles can become weak when they’re maintained in a lengthened position, particularly when the stretch occurs over periods of prolonged rest. For example, the development of elongated dorsiflexor and shortened plantar flexor muscles in the patient confined to supine bed rest with the sheets exerting a downward pull on the feet, causing an additional force into plantar flexion, therefore lengthening the dorsiflexor muscles. Another example is the prolonged stretch of the posterior gluteus medius that occurs while sleeping on your side. A woman with a wide pelvis with her uppermost leg positioned in adduction, flexion and medial rotation will test weak in hip abduction, extension and lateral rotation. The resultant lengthening of the muscle can produce postural hip adduction or an apparent leg length discrepancy in a standing position.
Sleeping in a side-lying position with the lower shoulder pushed forward pushes the scapula into abduction and tilted forward. This position can stretch the lower trapezius and possibly the rhomboids. The top shoulder can also be susceptible to pull the scapula into the abducted, forward position as well, especially if the thorax is large. This sleeping position can cause the humeral head in the glenoid to migrate towards a forward position.
Characteristics of muscles with over-stretched weakness include:
1. Postural alignment controlled by the muscle indicates the muscle is longer than ideal.
2. Muscle tests weak throughout its range of motion and not only in its shortened position.
An over – stretch weakness can also be caused by a strain from trying to lift a heavy object. Remember, strain is a minor form of tear in which the filaments of the muscle have been stretched or stressed beyond their physiological limit resulting in disruption of the Z-lines to which the actin filaments attach. These disruptions alter the alignment of the myofilaments which interferes with the tension-generating ability of the contractile elements. Muscle weakness occurs and in many instances, pain when the muscle is palpated or when resistance is applied during muscle contractions. For example, if the upper trapezius is strained, weight of the shoulder girdle itself might be excessive for the muscle. The shoulder’s pull on the muscle causes it to elongate and the muscle is unable to heal. A strained muscle might actually be under constant tension even when it appears to be at its normal resting length. Typically, a strained muscle is unable to support itself against gravity when positioned at the end of its range. Furthermore, the muscle is unable to maintain its tension at any point of the range when resistance is applied.
When a muscle becomes elongated and weak, then it’s contribution or tension-generating capabilities will change and another muscle will have to take over, creating a compensatory movement pattern. This will eventually become the normal pattern which then causes health problems down the line. Therefore, stretching might not always be optimal to alleviate muscle spasm or pain. Stretching and placing excessive force demands on the muscle is contra-indicated if it is strained. It is the length of the muscle and the presence of pain that act as guides to whether the muscle is merely weak from atrophy or weak form strain.
Traditionally, the emphasis is placed on stretching the muscles that have shortened, but equal emphasis has not been placed on correcting muscles that have lengthened. Lengthened muscles will not automatically shorten when stretching the antagonist. A client who demonstrates Lower-Cross Syndrome might have an exercise program that stretches the hamstrings, however, this does not concurrently shorten the lengthened muscles such as the lumbar back extensors. It would be prudent to shorten the elongated muscle while simultaneously stretching the shortened muscle. This is especially important when the lengthened muscle controls the joint that becomes the site of the compensatory motion as a result of the limited motion caused by the shortened muscles. For example, during forward bending, excessive lumbar flexion can occur as a compensatory motion because of shortened hamstrings. The best intervention would be to stretch the tight hamstring muscles but also shorten the back extensor muscles as well.
Altered Recruitment Patterns
A person with shoulder pain has excessive shoulder elevation during shoulder flexion to 90 degrees as compared to a person without shoulder pain. The elevation is present even after the patient no longer experiences the pain. Runners who tend to keep their weight posterior-closer to the rear than to the front of the foot show they use the hip flexor strategy, which also involves an excessive use of the tibialis anterior muscle, leading to shin splints. In contrast, runners who keep their weight line forward can be observed to use more push off with their ankle plantar flexor muscles.
The upper trapezius muscle, which is the upper component of the force-couple that controls upward rotation of the scapula can be more dominant than the lower trapezius. Muscle testing might show a weakness of the lower trapezius or the serratus anterior. One might notice excessive shoulder elevation when abducting the arm. Muscle strengthening might not necessarily change the pattern of recruitment. Instructing the client in correct performance of shoulder motion using a mirror is as important as the strengthening exercises you might prescribe.
An individual with an exaggerated swayback posture who stands in hip joint extension has diminished contour of the gluteal muscles, suggesting a weakness in these muscles. The hamstrings will usually take up the slack in hip extension. The hamstrings are extremely susceptible to an overuse syndrome when they are dominant because of the inadequate participation of the abdominal, gluteus maximus or even rectus femoris, as well as the lateral rotators of the hip.
The TFL (tensor fascia latae) and rectus femoris muscles are more dominant than the iliopsoas muscle hip flexion. In this situation the client will show excessive hip medial rotation. The person usually has a swayback posture.
The TFL, anterior gluteus medius and gluteus minimus muscles are more dominant than the posterior gluteus muscle in the action of hip abduction. When abducting, the client will substitute with medial rotation and flexion of the hip.
The extensor digitorum longus muscle is more dominant than the anterior tibialis muscle for the action of ankle dorsiflexion. The client will extend the toes as the initial movement of dorsiflexion instead of ankle motion.
The hamstring muscles are more dominant for the action of knee extension. In walking or running, once the foot is fixed on the ground the hip extension action from the hamstrings contributes to extension of the knee. Hip extension to assist in knee extension is commonly used by the person who has weakness of the quadriceps muscles. To reenforce the knee extension action, the person flexes the trunk slightly to use gravity to further contribute to the knee extension movement. A similar pattern is seen in the runner who uses the hamstrings for knee extension control. He or she will bring the knee backward toward the body rather than bring the body up to the knee as when climbing stairs.
When asked to perform finger extension, many individuals will demonstrate a small degree of wrist flexion. This type of compensatory movement pattern occurs most frequently with individuals who perform a lot of repetitive wrist flexion such as typing. As a result of this position of wrist flexion movement, the position of flexed joint and the anterior position of the flexor tendons reduce the carpal tunnel space, which can result in carpal tunnel syndrome.
In summary, the mechanical stress on tissues arising from movement impairment syndromes can cause a wide variety of injuries. The various injuries implicated can be degenerative changes in cartilage and joints, ligament strains, joint inflammation, myofascial strains, myofascial tears, tendinitis, bursitis, neuropathic pain from entrapment and compression and adhesions are a few examples. The better you get at muscle testing and identifying these compensatory movement patterns, the better you’ll be able to keep your clients from injury.