INTRODUCTION

Muscles facilitate joint movement in the body and help maintain posture. Muscle strength can change due to different reasons, which include sitting or standing, repetitive motion, injury, lack of exercise and deconditioning causing a muscle imbalance in the body. According to Vladimir Janda(1), muscle imbalances develop between muscles that have a tendency to develop tightness and other muscles which are prone to inhibition. Janda classified muscles into two groups “postural and phasic”. Postural muscles have a tendency to become overactive, hypertonic, weak and shortened in length. An example of a postural muscle is the psoas muscle, a hip flexor. On the other hand, phasic muscles have a tendency to become weak and inhibited. An example of a phasic muscle is the gluteus maximus muscle, a hip extensor. The tendency for a specific muscle to become overactive and another muscle to become inhibited occurs over time creating a muscle imbalance and an altered movement pattern.

The physician must be able to recognize the muscular imbalance and the altered movement pattern in order to prescribe appropriate relaxation and strengthening exercises to restore the normal movement pattern in the body.

An ” altered movement pattern” is a movement pattern in which a change occurs in the coordination of the muscle firing sequences for a specific group of muscles, facilitating a specific joint movement. The primary muscle responsible for the specific joint movement may become weak and inhibited, causing a synergistic muscle/muscles to become the primary muscle/muscles responsible for that joint movement. As a result, a different sequence of muscular contractions occur called “an altered movement pattern”. The altered movement pattern is a sign of muscle imbalance in the body because of muscular dysfunction. Altered movement patterns do not occur randomly. They can develop because of repetitive motion, injury, pain, illness, muscle deconditioning or sedentary lifestyle.

Changes in posture are often noted with an altered movement pattern in the body. The changes in posture may be observed while the person is sitting, standing or walking. An example of change in posture is one in which the person stands slightly flexed at the waist, unable to stand erect because of hypertonicity of the psoas muscle and weakness of the erector spinae muscle. The hypertonicity of the psoas muscle has a tendency to flex the lumbar spine, causing the lumbar spine to diminish in lordosis especially when a weakness of the erector spinae is present.

The muscles involved in hip extension and abduction can be divided into two groups, postural and phasic (Table 1). Postural muscles have a tendency to become overactive, hypertonic, shortened and weakened because of the physical demands placed upon them. They are composed of red muscle fibers, because they contain significant myoglobin and are innervated by small Alpha a2 motor neurons. Hennemans Size Principle states that the smaller the fiber the easier it activates, the larger the fiber the faster it conducts. This is why postural muscles have abundant red fibers. The neurons are smaller and easier to activate, constantly sending impulses with correction messages to the postural muscles to maintain body position. The red fibers are “slow twitch” fibers and are important in endurance activities or as a base in the activation of a strength effort. This is the reason why red fibers are often referred to as “tonic”, referring to tone or posture. Phasic muscles have a tendency to become weak and inhibited as a result of the action of postural muscles. The phasic muscles are composed of more white fibers and are innervated by Alpha a1 motor neurons. The white fibers receive their name partially from their innervation. It takes more to activate the Alpha a1 neurons but once they are activated, the white fibers are capable of a rapid “fast twitch” reaction. Thus white fibers are referred to as “dynamic”or phasic and are best suited for quick burst activities.

RECOGNIZING ALTERED MOVEMENT PATTERNS AND MUSCULAR IMBALANCES

There is a specific pattern to the sequence of muscle activation involved during joint movement. Two specific patterns to be discussed are Hip Extension and Hip Abduction(1). Hip extension and hip abduction movement patterns involve specific muscles. The muscles involved in the movements are gluteus maximus, gluteus medius, psoas, quadratus lumborum, erector spinae, piriformis, TFL, biceps femoris, adductors and rectus femoris. These muscles are categorized either as the primary mover/agonist, antagonist or synergist according to their function (Table 2). The primary mover/agonist is the muscle responsible for initiating and performing the main function for that specific joint movement. The synergist assists the agonist during the movement. The antagonist acts in opposition to the agonist and moves the joint into the opposite direction of the action of the agonist.

HIP EXTENSION

Hip extension involves the action of three muscles contracting in a coordinated sequence. The three muscles are the gluteus maximus(primary mover/agonist), biceps femoris(synergist) and erector spinae(synergist). Any deviation from the specific muscle activation is considered an altered movement pattern. This will cause hip extension dysfunction, muscle imbalance, pain and contribute to changes in posture. The normal sequence of muscular contractions for hip extension involves the contraction of the gluteus maximus and the ipsilateral biceps femoris, followed immediately by the contraction of the contralateral(opposite side) erector spinae and then the ipsilateral erector spinae.

The gluteus maximus is the primary muscle responsible for the motion of hip extension. The ipsilateral biceps femoris assists during gait by flexing the knee. Immediately after the contraction of these two muscles, the contralateral side erector spinae muscle contracts, followed by the contraction of the ipsilateral erector spinae muscle to help stabilize the lumbar spine and pelvis allowing movement of the hip during gait. Any change in this sequence of muscular contractions is considered an “altered movement pattern”. A change often seen in altered hip extension movement is the contraction of the ipsilateral erector spinae muscle before the gluteus maximus muscle contracts, to initiate the movement of hip extension. This can be observed with the patient prone and performing hip extension. When this occurs, the erector spinae becomes the primary muscle initiating hip extension. Weakness of the gluteus maximus prevents itself from functioning as the primary muscle initiating hip extension.

What can cause an altered hip extension movement? Weakness or inhibition of the gluteus maximus can be the result of an injury to the muscle, deconditioning as a result of an illness or injury limiting the activity of walking, overuse due to excessive repetitive motion or overactivity of an antagonistic muscle. The gluteus maximus muscle will display signs of a weakened contraction, flattened shape and triggers points be found in the muscle. The psoas muscle, a hip flexor and an antagonist muscle of gluteus maximus, is often another cause of altered hip extension. Tightness or hypertonicity of the psoas muscle resulting from prolonged sitting in a flexed position can mechanically restrict the motion of hip extension. A tight psoas muscle will restrict hip extension range of motion, which normally is 20 degrees, and will result in a decreased stride. Tightness of the psoas can also cause postural changes in the lumbar spine by decreasing the lumbar lordosis. The rectus femoris muscle also functions as an antagonistic muscle to gluteus maximus since it also assists in hip flexion. Together, the action of the psoas and the rectus femoris, can mechanically inhibit hip extension range of motion. Weakness in the gluteus maximus muscle will cause recruitment of a synergistic muscle, the erector spinae to initiate hip extension. The erector spinae will change its’ function and become the primary muscle responsible for hip extension causing an altered movement pattern. The erector spinae will contract on the ipsilateral side of hip extension before contraction of the gluteus maximus to initiate hip extension and stabilize the pelvis. As a result, the erector spinae muscle acts as the primary muscle, initiating hip extension replacing the gluteus maximus. This will cause an increase in the stress on the lumbar spine. The erector spinae will also become hypertonic, causing an increase in the stress(load) on the lumbar facet. Pain in the lumbar spine increasing while walking will also be a symptom along with decreased passive and active ranges of motion of hip extension. Tightness of the psoas and/or rectus femoris muscles may also be present. Altered hip extension can occur unilaterally or bilaterally.

Along with mechanical inhibition of the gluteus maximus, a neurological inhibition will occur because of the change in sequence in muscle activation. The new neurological sequence or pathway initiating hip extension will be stored in the cerebellum, which will also inhibit activation of the gluteus maximus.

HIP ABDUCTION

Hip abduction is another movement where an altered movement pattern can develop in the hip. The gluteus medius muscle is the primary muscle responsible for hip abduction. The synergist muscles are the psoas, piriformis, TLF, quadratus lumborum and rectus femoris. The hip adductor muscles are the antagonists to the glutues medius.

Hip abduction involves the contraction of the gluteus medius, causing a smooth lateral abduction of the lower extremity away from the body. “An altered hip abduction movement” is any change in this movement. Changes in the movement will occur when the gluteus medius muscle can not initiate and perform hip abduction by itself. Conditions that can weaken or inhibit the gluteus medius muscle include an injury to the muscle, deconditioning due to an illness or injury limiting the activity of walking, overuse due to excessive repetitive motion and overactivity of an antagonist. The causes are the same types of causes associated with causing hip extension dysfunction.

One sign of altered hip abduction is “hip hiking”. Hip hiking is the raising of the pelvis on the side of the body during gait movement caused by the premature contraction of the quadratus lumborum muscle on the side of hip abduction before contraction of the ipsilateral gluteus medius muscle. The contraction of the quadratus lumborum muscle initiates the sequence of hip abduction. This will occur when gluteus medius is not strong enough or is inhibited in intiating the movement of hip abduction. Hip hiking can be observed while the patient is walking. It can also be diagnosed with the patient laying on his side while performing a hip abduction movement. Another sign of an altered hip abduction movement occurs with the hip drifting into flexion during hip abduction. This occurs because of overactivity of any or all of the following muscles: psoas, rectus femoris, TFL. These muscles will cause the hip to move into flexion during abduction because of their hypertonicity, especially when there is weakness of the gluteus medius in performing hip abduction. External rotation of the lower extremity is another sign of altered hip abduction, which occurs during hip abduction because of an overactive piriformis muscle. The last two dysfunctions of hip flexion and external rotation of the lower extremity can best be observed while testing the patient laying on his side and abducting the hip toward the ceiling.

In gluteus medius weakness, the gait may be diminished along with a slight drop in the pelvis on the swing-leg side(2). Inhibition of the gluteus medius can occur with tightness or hypertonicity of the adductor muscles, which are the antagonists to the gluteus medius muscle limiting the normal range of motion of 45 degrees. Weakness of the gluteus medius will also be noted with difficulty standing on one foot. There will also be preference of the person to shift his body weight to the stronger limb when standing on both feet. The inability to abduct the hip when lying on one side or the inability to isometrically hold the hip in abduction for 30 seconds will also be indications of gluteus medius weakness. Another sign of hip muscular imbalances due to hypertonicity of the quadratus lumborum and adductors will be leg length deficiency on the ipsilateral side. TFL hypertonicity can cause lateral knee pain, creating a lateral shift of the patella associated with a groove noted in the lateral thigh. Sacroiliac joint dysfunction because of gluteus medius weakness will occur. Trigger points in the gluteus medius will also be present. Altered hip abduction usually occurs unilaterally but can occur bilaterally. As mentioned in hip extension, the primary muscle responsible for hip abduction can become inhibited both mechanically and neurologically over time, as part of the altered movement pattern syndrome.

TREATMENT

Treatment protocols for hip extension and abduction dysfunction are the same.

Check for the presence of any altered movement patterns first. If an altered movement pattern is detected, identify the tight, hypertonic, overactive muscle/muscles and the weak, inhibited muscle.

Stretching to relax the overactive muscle/muscles is the next procedure.

Two postisometric stretching procedures are effective in relaxing an overactive muscle and increasing the passive range of motion. They are “Hold-Relax” and “Contract-Relax”(1,3). The main difference between the two is the type of the contraction, depending upon whether pain is present. If pain is present, the Hold-Relax technique is utilized because it relaxes the overactive muscle increasing the range of motion and diminishing pain. The Contract Relax technique is used when pain is not present. It is used to facilitate relaxation and to increase range of motion of the hypertonic muscle. Another procedure, “Contract-Relax-Antagonist-Contract” or “CRAC” may also be utilized.

The Hold-Relax technique involves placing the tight muscle into a stretch position, the doctor instructs the patient to inhale, holding his breath utilized if pain is present, because it relaxes the overactive muscle, increases the range of motion and diminishes the pain. The Hold-Relax technique involves placing the tight muscle into a stretch position. The doctor then instructs the patient to inhale and hold her breath while isometrically contracting the muscle slowly, building up resistance in the tight muscle before pain is elicited, holding the position for 5-8 seconds before relaxing the muscle and exhaling. The procedure is repeated three times.

The Contract-Relax technique is used when pain is no longer present, to facilitate relaxation and increase the range of motion of the muscle. It involves placing the tight muscle into a stretch position, the doctor then instructs the patient to inhale and hold his breath while strongly contracting the involved muscle for 5-8 seconds, then exhaling and relaxing the muscle with an increase in length. The procedure is also repeated three times.

The Contract-Relax-Antagonist-Relax technique is the same as the Contract-Relax technique except that after relaxing the muscle, the antagonist muscle is immediately contracted and relaxed, further facilitating an increase in the range of motion of the tight overactive muscle.

There are two purposes for relaxing a tight, overactive, hypertonic muscle. The first purpose is to increase the range of motion and flexibility of the tight muscle. This eventually will cause an increase in the strength and endurance of that muscle. The second purpose is to cause relaxation of the muscle inhibiting the agonistic muscle, so that the agonist can be exercised without inhibition of its’ overactive antagonist. Relaxing the antagonist and strengthening the agonist muscle facilitates the specific muscle movement desired for the proper sequence of muscle activation, reestablishing the correct muscular movement pattern for hip extension and abduction. The movement pattern becomes an established neurological pattern and is stored in the cerebellum of the CNS.

After performing relaxation procedures to the antagonist, the agonist should be actively exercised to increase strength. Initially, isometric exercises can be used, however they offer limited strength gain after the first month. Isokinetic and isotonic exercises should be used to maximize strength gains.

After strengthening the agonist muscle, strengthening of the antagonist muscle should also be performed since the hypertonic shortened antagonistic muscle is a weak muscle.

The desired result after following this type of a rehab program will be a coordinated muscular movement pattern. Any inhibition, whether neurological or mechanical, should no longer be present, muscle imbalances are absent and normal muscle functions should exist.

CONCLUSION

Hip extension and abduction muscular imbalances are fairly common problems affecting the hip, sacroiliac and lumbar spine encountered in a chiropractic practice. Understanding the actions of the muscles associated with these movements allows the practitioner to recognize any altered movement patterns, overactive antagonistic muscles, and weak inhibited agonistic muscles. Understanding that muscular changes are contributing to the patient’s symptoms, a corrective rehab program for these muscular imbalances can be prescribed. The rehabilitation protocols described for hip extension and abduction are one option available to the practitioner, in addition to manipulation to use in treating a patient with these problems.

Dr. Donald J. Fedoryk DC CCSP DACRB

References

1. Liebenson, C. Rehabilitation of the spine: a practitioner’s manual. Baltimore: Williams & Wilkins 1996

2. DeFrance, G. Pelvic locomotor dysfunction: a clinical approach, Aspen Publishers, Inc. 1996

3. Christensen, KD. Rehabilitation guidelines for chiropractic: first edition. Chiropractic Rehabilitation Association. 1992