Pain from Muscular Dysfunction

An introductory view of SEMG methodology in the investigation and rehabilitation of dysfunctional and painful axial skeleton muscles.
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Muscular dysfunction of the cervical and trunk muscles — from an array of etiologies — is associated with pain.1 If the condition underlying is resolved in a timely manner, i.e., within 6-12 weeks, the pain may be limited to the acute phase. However, if the symptoms and the dysfunction last beyond 12 weeks, the pain may become sub-acute and eventually it may become chronic. Furthermore, chronic neck or trunk muscular or myofascial pain may lead, in time, to hyperalgesia and allodynia.1-3

A muscle suffering from pain for a period of 6 or more weeks develops several characteristics. It tends to stay ‘guarded.’ Consequently, the adjoining muscles from the same myotatic unit tend to become less functional as well.

The overall conditioning level of the entire myotatic unit will decrement over time. The suffering muscle may become shortened and the adjoining muscles from the unit may start functioning at a suboptimal length. The affected joint may have to function at a reduced range of motion (ROM).4 The muscles of the proximal and distal homolateral joints may become involved in a protective guarding capacity. The same may happen to the muscles of the contralateral joint.

Over time, the dysfunctional muscle and its primary myotatic unit may lose strength (LOS). Its neuromuscular engram in the brain may change and engrams of adjacent muscles or myotatic units may start structurally encroaching on it.5 Chronic dysfunction is associated with a deleterious (negative, pathologic) neuroplasticity.6

The rehabilitation process of the neck and trunk muscles will need to take into consideration a number of factors. These include, but are not exclusive to the following: diagnosis, concurrent conditions, current treatments, age, overall state of muscular conditioning, motivation to improve the overall muscular function and reduce pain, emotional make-up and emotional state, and concurrent psycho-social and familial change of roles related to the muscular dysfunction and concurrent conditions.7

Physical Examination

The evaluation of the muscular dysfunction and pain of the neck and trunk is done first and foremost within the framework of a comprehensive physical examination.7 Next, it is quite necessary to perform objective assessments such as dynamometry for the measurement of the muscular strength and loss of strength (LOS). The regional ROM is best measured with inclinometry according to established methods.4 Joint/region muscular proprioception needs to be assessed with semiquantitative means and in comparison to the contra-lateral joint/region. The pain intensity may be assessed on a visual analogue scale.

Factors of dysfunction such as (electric potentials) spasm, hypertonus, hypotonus, co-contraction, co-activation, difficulty with control or achievement of the resting tonus, myokimia, fasciculations, loss of mirror image of segmental motions such as bending or rotation (of the cervical or trunk muscles), utilization of increased numbers of contractile elements, fatigue (as evaluated by the use of the spectral analysis, median frequency), etc. can be achieved via the utilization of well documented dynamic protocols of surface electromyography (SEMG).8

Figure 1.

The electrophysiological modality of SEMG has a dual application: (1) the investigation of the muscular dysfunction through motion and rest during the classic cervical or lumbar region ROM, and (2) the muscular re-education of the resting tonus and activity tonus of the dysfunctional muscles. Both applications can be achieved by utilizing well established protocols, within the framework of the clinical presentation.7 This modality is rather unique in terms of the rehabilitation component: it is active and focused in terms of re-establishment of the neuro-motor engram and the positive neuro-plasticity needed for the healing process.

SEMG Protocols

The database of the SEMG for the asymptomatic ROM of over 6,000 muscles completed by the author allows for a more logical utilization of the choice of the sequence of the segments of motion to be tested both for the cervical and the trunk muscles.9,10 In other words, the SEMG dynamic protocols have been construed to accommodate the fatigue factor commonly present in individuals with painful muscles. As such, the sequence of the segments of motion of flexion, extension, bending and rotation is arranged in a “crescendo” fashion, such that the first motion to be tested is the one that requires the least amount of electrical energy expenditure for the muscles tested. The last motion in the series is the one that requires most electrical effort and the motions in between require intermediate energy expenditure or effort. Table 1 illustrates this process.

The clinician may observe that the segment of motion of extension requires the least energy expenditure for the four muscles tested. Therefore, the motion of extension will be the first motion to be tested in terms of the dynamic study of the SEMG of the cervical ROM. The next motion in the series is that of bending of the neck, to the right or to the left. The next one is that of rotation. The final motion in the series is that of flexion. A simple calculation shows that if the extension motion is considered as the “standard of 1,” bending will have the equivalency of energy expenditure of 1.10, rotation will have the equivalency of 1.18, and flexion will have the equivalency of energy expenditure of 1.38 as compared to that required for cervical extension.

Table 1. Figure 2. Table 2.

Table 2 illustrates this process for the lumbo-sacral ROM. Again, the segment of motion of extension requires the least energy expenditure for the nine muscles tested. In this case, the motion of extension of the trunk will be the first motion to be tested in terms of the dynamic study of the SEMG of the lumbo-sacral ROM. The second motion in the series is that of bending of the trunk, to the right or to the left. The third motion tested is that of rotation of the trunk. The final motion in the series is that of flexion.

If the lumbo-sacral extension motion is considered as the “standard of 1,” bending of the trunk will have the relative equivalency of energy expenditure of 1.29, rotation of the trunk will have the relative equivalency of 1.83, and flexion of the trunk will have the relative equivalency of energy expenditure of 2.02.

First published on: May 1, 2005