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3 Articles in Volume 3, Issue #5
Lumbar Spine Rehabilitation
Objective Musculo-skeletal Measurement Protocols
Osteopathic Medicine in Pain Management

Objective Musculo-skeletal Measurement Protocols

Utilizing surface electromyography (SEMG) and systematic, standardized protocols, clinicians can objectively diagnose and document outcomes in the treatment of musculo-skeletal pain and disorders.

A clinician needs objective documentation of both the diagnostic and treatment results for musculo-skeletal dysfunctions. Muscles can be assessed as either subgroups of myotatic units, as subgroups of neuro-innervation or, in measurement terms, as bilateral homologous contra-lateral data. SEMG allows the development of protocols that corresponds with each of the above. Whether testing is done by myotatic units engaging one or more joints or by neuromuscular innervation that may affect several joints, bilateral testing can be done through the relevant range of motion (ROM) and intervening rest periods. ROM is typically composed of numerous motion segments, each having different muscle action/interactions. For example, the ROM of the wrist joint, which utilizes seven muscles for motion, can be broken down into four segments: wrist extension, flexion, ulnar and radial deviation.

The protocols, developed by the author, basically stipulate a five-time repetition of any given segment of ROM activity for seven seconds interspersed with two seconds of rest intervals. The five repetitions allow for more accurate statistical data gathering and for determination of internal consistency and reproducibility along the muscles simultaneously tested. Since range of motion, primary movers, and neuromuscular innervation are all universally known and accepted, these protocols of SEMG testing are based on clinically accepted data.

These protocols aim for overall standardization of the SEMG procedure, similar to the standardization that occurred in the 1920s for the EKG procedure. The author has published database test results on 6,700 individual muscles, representing about 173 skeletal muscles investigated through 22 protocols. This database allows any clinician or investigator to compare individual findings on a given patient with those of the corresponding normalized database values.

The remaining sections will explore general results and implications of these benchmark protocols utilizing the wrist joint ROM as an example. Appendix A describes the corresponding wrist ROM SEMG testing, statistical data for functional inter-muscular and inter-segmental motion relationships of the myotatic unit under asymptomatic conditions.

Muscular Agonism/Antagonism Revisited

The concept of muscular agonism (synergism) and antagonism has not been questioned throughout the modern era of medicine. One tends to use these words almost indiscriminately to define a functional relationship among various muscles or segments of motion, usually within the same myotatic unit, but sometimes among muscles subtending different joints. The closest anatomical definition may relate to the actual position of a given muscle on a bone and joint. One tends to describe muscles positioned on opposite sides of a bone/ joint as “antagonists" and muscles positioned on the same side of a bone/ joint as “agonists or synergists.” The concept may further imply that one muscle may move the joint in one direction, e.g. wrist flexion, while the other may be “inhibited” during such motion and the corollary may apply to the opposite motion, e.g. wrist extension. Until now, there has been no actual study available to demonstrate this functional relationship. Indeed, the concept applies poorly to segments of motion that are neither flexion nor extension as, for example, in the case of the wrist ulnar and radial deviation.

The advent of the ability to test skeletal muscles with SEMG allowed for statistical analysis of objectively-derived electrical amplitude data through the different segments of motion of a given joint in both asymptomatic or symptomatic conditions. Thus, in the case of the wrist joint, one can simultaneously test the primary wrist joint muscles, i.e. the flexor and extensor carpi radialis and ulnaris, pronator teres and quadratus as well as the supinator through the segmental motions of wrist extension, flexion, ulnar and radial deviation.

In the specific example of wrist ROM, SEMG dynamic test protocols of the activity potentials of the myotatic unit of the wrist have been used to define the muscular relationships of agonism and antagonism. The values of the correlation coefficients of the different muscles, computed through the wrist ROM segments served to establish positive or negative relationships among the wrist muscles. Such testing was conducted for the wrist joint ROM as well as all the other major joints.

The amplitude potentials data of each of these muscles through the wrist joint ROM (in asymptomatic muscles or symptomatic muscles) could then be compared to those of the other muscles of the myotatic unit in terms of statistics of correlation coefficients (r).

The comparisons result in correlation data which are either positive or negative, according to the tendency of any muscle to become more or less active through a given segment of motion, especially in comparison with its neighbors from the same myotatic unit. Such data could then be translated in terms of correlational relationships of muscular agonism (synergism) or antagonism. The positive correlation coefficients represent muscular synergism or agonism. Negative correlation coefficients represent muscular antagonism.

Thus, the old concept of agonism and antagonism — never before tested scientificall — could be verified with the new technology. In a number of cases, the old assumptions were found to hold, in a number of other cases they did not. The correlation coefficients among the muscles tested through each major joint ROM have been calculated and published in a number of textbooks and articles.1,2, 3, 4

SEMG studies have shown that symptomatic muscles presenting with loss of strength and pain generally show high levels of amplitude potentials both at rest and during motion.

Diagnosis of Symptomatic Muscle

SEMG studies have shown that symptomatic muscles presenting with loss of strength and pain generally show high levels of amplitude potentials both at rest and during motion. This has been shown to be the case in over 500 different muscles from various parts of the body, including the hand and wrist.1,5 When treated statistically in comparison with non-symptomatic muscles, those dysfunctional muscles show greater than 25% higher amplitude potentials both at rest and during any segment of motion. Physiology dictates that muscles that are overworking and utilizing more energy than normal may fatigue earlier. Fatigue itself can promote both pain and general weakness and secondary deconditioning. Thus, if a clinician finds SEMG-derived amplitude potentials abnormally high at rest and during different segments of a given primary joint ROM, the dysfunctional relationship between that muscle and other muscles in its primary myotatic unit may be objectively measured. The SEMG data would then clearly identify the muscle(s) requiring rehabilitation, including pain management and SEMG/biofeedback. Resulting symptomatic improvement, manifested by the muscle no longer presenting weakness or pain, should coincide with SEMG resting and activity potentials returning to the expected range.1,6 In terms of the wrist joint muscles, normalization of such values would be compatible with lack of symptoms and normal wrist/hand strength.2,7

Muscles may be active as a result of motor stimulation and produce measurable motion or they may be active without producing motion via autonomic nervous system (ANS) stimulation, i.e. states of emotional tension. SEMG can measure a number of muscular electrical activity parameters and by extension, abnormal states of the same parameters.

For example, if it is known that a particular muscle fatigues asymptomatically within a given period of time-measurable as median frequency decrementing over time at a nominal rate-observation of prematurely decrementing median frequency would indicate clinical pathology. The clinician would then have to investigate the specifics of the pathology, be it of neural, muscular, metabolic, nutritional, endocrine, toxic, or other origins.

Clinically Objective Assessments

In terms of the statistical data of the assessment protocols, coefficients of variation (CV) at less than 10 percent is a good determinant of the internal consistency of activity for any given muscle. For example, while assessing eight muscles simultaneously, a CV greater than 10 will stand out as inconsistent. If it is found on a symptomatic muscle while it is not found on the remaining asymptomatic muscles, it may fit within the clinical picture of abnormal. Furthermore, it will give credence to the fact that the patient is not trying to symptom-magnify since it is virtually impossible to be consistent in motion on seven muscles while being inconsistent on one.

The statistical parameter of correlation coefficient (c.c., p) is a good indicator of the reproducibility of any test or study. Thus, results that show good consistency will show also a c.c. greater than 75 percent. The same reasoning of consistency described above applies. If an outlier is found and is clinically consistent with muscular symptomatology, then, SEMG can be shown to provide more objective evidence to the subjective complaints or clinical findings.

SEMG and Muscle Re-education

Musculo-skeletal re-education needs to have objective documentation in the present era of outcome measurement requirements. Fortunately, SEMG biofeedback can provide such documentation if the rehabilitative treatment is done according to specific and standardized protocols. Bilateral assessment before the treatment allows for more specific functional diagnoses. The same assessment during and after the treatment period allows for an objective determination of the course of treatment and results within the clinical context of improvement and healing. Since the SEMG protocols are objectively described and standardized, they can be repeated and reproduced by any other investigator or clinician.

Furthermore, SEMG measurements can be used both in the realm of objective investigation and as an objective outcome treatment measure. The amplitude parameter (microvolt RMS) is a measure of muscular activity electrical effort and to some extent of force. Bilateral measurements of homologous contra-lateral muscles are necessary in order to compare the activity of any given muscle with its counterparts in its myotatic unit. In any given condition, there should be normally a difference of less than 25 percent between contra-lateral muscles. A larger difference may have ergonomic or clinical value.

Implications for Ergonomic Design and Sports Training

Based on the normalized SEMG results of specific muscle groups throughout the human body, there is now objective data on muscle interactions and muscle loading. Utilizing this information, the ergonomic design engineer will aim to construct machinery or work environments that conform to the application of the least effort through musculo-skeletal motions. Using the example of the wrist, one would want to build machinery that would utilize the ECR, ECU, FCR, FCU, pronator teres and quadratus and the supinator preferably in wrist flexion while avoiding ulnar deviation. The object is to involve the muscles in such a way that they react with the least amount of electrical effort through the joint ROM.

Since the SEMG protocols are objectively described and standardized, they can be repeated and reproduced by any other investigator or clinician.

The same rationale holds for sports training. The athletic trainer may utilize standardized SEMG amplitude data for comparisons with the subject’s effort before training in order to reduce that effort as far as possible to within the normalized limits. Utilizing correlation coefficients (Appendix A, Tables 2 and 4), one can also compare the pre-training correlation coefficients data and aim at improving the overall correlational values either among muscles, or among the wrist segments of motion tested, to achieve optimum muscle effort and coordination.


The old concept of muscular and wrist joint motion relationships of agonism and antagonism has been revisited in light of SEMG dynamic protocols. These protocols have been utilized to simultaneously measure the actual electrical amplitude potentials derived from the movements and activity of muscle groups. The data demonstrates a number of positive and negative correlations (r) among the muscles tested through the segments of motion and are easily interpreted in terms of agonism and antagonism among the individual muscles tested.

Most functional or myotatic units are composed generally of four or more muscles. Thus, simultaneous SEMG comparisons of four bilateral muscles may allow for a good and functional comparison. This is very important in rehabilitation medicine when it is relevant to focus on a specific muscle that needs to be re-trained.

Currently, proper implementation of SEMG assessment and treatment protocols require a good background in neuromuscular anatomy, physiology, and kinesiology. The clinician must have a clear knowledge of muscles, muscle activity, states of tension, and the resulting electrophysiological markers. While affordable SEMG equipment is now readily available, software that incorporates these new protocols to make them more “user-friendly” and intuitive is not yet available. It is anticipated that the complete mapping of the human musculo-skeletal system will spur improved software tools to make SEMG techniques more readily available to the wider medical community for both diagnosis and musculo-skeletal retraining. n

Appendix A: Sample Benchmark Measurements — Wrist ROM

An SEMG dynamic protocol of testing of the wrist muscles through the wrist joint ROM has been utilized for the purpose of defining the muscular correlation coefficients described in the present article. The protocol has been previously published.7,8

Participants: a number of asymptomatic individuals underwent the wrist ROM testing with SEMG. The gender division was about equal. The age ranged between 19-69. All the participants were able to perform a full wrist joint ROM, with no joint or myofascial restrictions.7

Equipment: the testing was conducted on Myovision 3000 SEMG equipment with 8 discrete channels of SEMG.8

The specifications of the equipment were as follows.8

  • Input Impedance: 1,000,000 MegOhms
  • Resolution: 10 bit A/D
  • Safety: 5000 volt optical Isolation
  • Power Supply: UL medical transformer
  • Filtering: 25-5000 Hz wideband
  • Range: Scanning at 0.08-200 microvolts
  • Calibration: Lifetime through AutoCal

The testing was conducted after calibrating the equipment according to the manufacturer’s instructions before each examination. The SEMG electrodes were of the Ag/AgCl gel type. The electrode placements on the wrist muscles were done in the standardized positions described in the textbooks.7,8

Procedure: Seven muscles were utilized for wrist ROM testing: the extensor carpi ulnaris (N=61), extensor carpi radialis (N=61), flexor carpi radialis (N=61), flexor carpi ulnaris (N=61), supinator (N=61), pronator quadratus (N=15), and pronator teres (N=61). The utilization through the testing was bilateral. The testing protocol was such that each segment of motion was measured through five repetitions of wrist segmental activity and rest, each motion being tested through 7 seconds of activity at the minimal effort of contraction (eccentric or concentric minimal voluntary effort) and a 2 second period of ‘return to resting state.’ The testing was performed at the effort level of minimal voluntary contraction.

The testing was done with the subjects in the standing position and the resting period was performed with the wrist/ upper limb in the neutral position, the arm hanging freely by the body. The positioning was according to the instructions given in standardized texts.7,8

All persons tested agreed with the examination and were informed about its purpose and lack of invasiveness. The participants were instructed beforehand how to proceed with the testing. No participant had any wrist joint restrictions, myofascial or neuromuscular symptoms or restrictions.

Data Collection: the data described and discussed below are a compilation of the statistics gathered from the testing of 381 muscles tested through 4 segments of wrist ROM, each segment measured through 5 repetitions of full motion. Thus, the data derive from a total of (381 x 4 x 5) =7620 measurements. The data consists of activity and resting potentials calculated by the software in terms of microvolt RMS (µV RMS) SEMG values of amplitude domain.

The data obtained from the testing were utilized for the compilation of statistics for the purpose of establishing the correlation coefficients (r) necessary for the understanding of the inter-muscular and inter-segmental relationships of agonism and antagonism.

The following statistics were compiled from the data:

  1. Similar statistics compiled for each muscle tested, (N).
  2. Average activity potential amplitude values (µV RMS) of each wrist segmental motion for each muscle, mean value for the 5 repetitions of each motion, mean value for the number of muscles (N).
  3. Standard deviation (S.D.) and lower and upper 95% confidence intervals ( <95% and >95% C.I.) values for the average value of muscular wrist segmental motion, for each muscle tested.
  4. Statistics of correlation coefficients (c.c., r) among the seven wrist joint muscles and segments of motion tested.

Results: The results are tabulated in the tables below followed by a brief discussion explaining the results.

Table 1. Activity potentials (µV RMS) data of seven wrist joint muscles tested through four wrist ROM segments of motion with SEMG.

Table 1 shows the statistics of the activity potentials of wrist muscular activity in the four segmental motions tested. The data show that the ECU muscle is the most active of the group at the minimum effort of motion level. The ranking in terms of overall amplitude of activity is the following: ECU, ECR, FCR, FCU, supinator, pronator quadratus and pronator teres.

There is an obvious range of average segmental activity for each muscle tested. Of all values of the seven muscles, ulnar deviation of the ECU shows the highest amplitude activity (57.9 µV RMS) while extension of the pronator quadratus shows the lowest amplitude (8.8 µV RMS).

The average amplitude of electrical activity potentials for the 7 muscle group moving through the wrist joint ROM was 19.7 µV RMS. In general, the lower and upper 95% confidence intervals (C.I.) were 23% and 19% lower and higher respectively than the average amplitude values for the group. The average activity/ rest ratio for the group as a whole was 11.5.

This represents the statistics of the ratio of the overall segmental activity of the wrist ROM for the 7 muscles above to the overall minimal resting potentials for the muscles tested. The average minimal resting potential for the group was 1.7 µV RMS, an expected value for the resting potentials of skeletal muscles tested as a whole.1,4,9

Thus, the 7 wrist joint muscles tested show an almost 12-fold (11.5) activity pattern as compared to minimal resting values through the wrist ROM. An examination of the probability (probability > F) value for each muscle tested showed a significant difference for the four segments of motion as a whole. The average probability > F value for the 7 muscles tested was 0.064, indicating a non-significant difference for each wrist joint muscle tested.

An examination of the inter-segmental variance for each muscle showed that there were some significant and some non-significant differences in the inter-segmental variance. A total of 5 inter-segmental non-significant variance were found and only one (1) significant variance difference was found. Thus, most inter-segmental differences were not significant in terms of the wrist ROM segments.

Muscle ECU FCR FCU Pronator Quadratus Pronator Teres Supinator
ECR 0.47 0.27 0.14 -0.17 0.52 0.40
ECU   -0.01 0.02 -0.10 0.18 0.15
FCR     0.14 0.10 0.22 0.26
FCU       -0.16 0.36 0.016
Pronator Quadratus         -0.24 0.09
Pronator Teres           0.28

Table 2 shows the positive and negative correlation coefficients calculated from the comparison of 7 muscles through the four segments of wrist ROM tested with SEMG.

It may be of note that each muscle showed a different pattern in terms of correlation coefficient, i.e. agonism or antagonism with the other muscles in the wrist myotatic unit.

ECR showed the highest synergism (agonism) with pronator teres and the least with FCU. It showed only one antagonistic relationship, with pronator quadratus.

ECU showed generally low correlations with the other muscles with the highest being a synergistic relationship with pronator teres and the lowest correlation was an antagonistic one with FCR. However, ECU’s relationships with FCR and FCU should be considered as a stabilizer in myofascial terms.

FCR showed the highest synergistic relationship with supinator and the lowest with pronator quadratus. It had a minimal negative relationship (antagonism) with ECU.

FCU had the highest synergistic relationship with pronator teres and the lowest synergistic relationship with supinator. It had an antagonist relationship with pronator quadratus.

Pronator quadratus had an antagonistic relationship with pronator teres and a weakly synergistic relationship with supinator. Pronator teres had the highest synergistic relationship with ECR and the lowest with ECU. It did not show any antagonistic relationship with the other muscles of the wrist joint.

Muscle Ulnar Deviation Extension Radial Deviation Flexion Avg
ECU 57.9 36.6 26.3 25.1 36.5
ECR 22.4 31.8 23.7 21.2 24.8
FCR 15.9 21.8 26.6 17.9 20.6
FCU 19.3 17.2 17.03 24.1 19.4
Supinator 12.02 16 12.4 11.6 13.0
Pronator Quadratus 13.3 8.8 12.6 16.8 12.9
Pronator Teres 10 12.8 10.7 10.13 10.9
Average 21.5 20.7 18.5 18.1  

Table 3 shows the average values of the SEMG amplitude potentials of the 7 muscles tested through the wrist ROM. The ulnar deviation segment has the total highest amplitude potential.

The flexion motion showed the lowest amplitude potential in this study performed at the minimal voluntary contraction level of effort.

Within each segment of motion one can find different patterns of effort for each muscle tested. Ulnar deviation showed the highest range of effort, i.e. between 57.9-10 mV RMS. The segment of flexion shows the least overall difference, ranging between 25.1-10.1 mV RMS.

Thus, it may be expected both in ergonomic and in rehabilitative terms that movements requiring ulnar deviation should be more fatiguing for the forearm muscles affecting the wrist than the wrist flexion movement.

ROM Segment Extension Radial Deviation Ulnar Deviation
Flexion 0.16 0.57 0.47
Extension   0.36 0.59
Radial Deviation     0.76

Table 4 shows the correlation coefficient among the four wrist joint segments of motion as derived from the testing of the ECU, ECR, FCU, FCR, pronator quadratus and teres and the supinator muscles with the SEMG dynamic protocol. The data show only positive correlations coefficients (r). The highest positive correlation between two motions was found between radial and ulnar deviation. The lowest was found between flexion and extension of the wrist.

The relationship between flexion and pronation was very low, compatible with the definition of stabilizer relationship.1


The seven muscles tested with SEMG represent the wrist myotatic unit in terms of primary distal insertion and vector of action as well as direct inter-connecting fascia. The data show not only the relationships among the seven muscles of the wrist joint myotatic unit but also among the four segments of motion tested.

Table 2 shows four antagonist relationships among the muscles tested and eleven agonist relationships among the same muscles as well as three stabilizer relationships. Thus, the wrist joint ROM is imbalanced in terms of agonist and antagonist relationships among the muscles tested.

It is clear that the ECU is the muscle that shows the largest amount of overall activity and pronator teres shows the least. The motions of ulnar deviation and wrist extension require the largest amount of activity potentials from the ECU. The ECU ulnar deviation movement requires almost six times the effort of motion at the minimal voluntary effort level than the pronator quadratus extension motion. The neuromuscular rehabilitation specialist or ergonomist may utilize the data in terms of instituting re-education or muscular rehabilitation programs for wrist dysfunction or wrist muscular optimization.

The data shown in tables 1 through 4 aim at redefining the old concepts of muscular agonism (synergism) and antagonism.2 It is clear that the anatomic position of a given muscle does not reflect necessarily on its activity through the range of motion (ROM) of the primary joint of action as was assumed in the concept of muscle agonism/antagonism. A study of the data in Table 1 shows that all seven of the wrist joint muscles are active through the four classic segments of wrist ROM. Thus, the old idea that a muscle such as the ECU is primarily a muscle of extension of the wrist can be brought into question since this muscle is more active in ulnar deviation.

With the exception of the knee, all other major joints have a larger number of classic segments of motion.1,2,9 Until the advent of SEMG dynamic studies and protocols, it was rather difficult to identify and measure the activity pattern of discrete muscles within a myotatic unit and within a given joint ROM. This technique allows for the simultaneous bilateral measurement of the electrical potentials of amplitude values of different muscles through a given set of segments of joint motions. Thus, one can identify the pattern of electrical amplitude of potentials for any segment of joint motion tested for a group of muscles such as a myotatic unit. This may apply equally well to asymptomatic muscles whose activity and resting potentials (µV RMS) have been described in the tables above and to symptomatic and dysfunctional muscles described elsewhere.2, 5

Table 3 presents the data in terms of both the average amplitude of activity potentials (µV RMS) for each muscle tested as well as for each wrist joint segment of motion. It is noticeable that the ranking of the muscles through the wrist joint ROM is (from high to low) ECU, ECR, FCR, FCU, supinator and pronator quadratus and teres when the motions are performed at the minimal effort level of contraction in the standing position.

The ranking pattern from high to low in terms of the segments of motion is that of ulnar deviations, extension, radial deviation and flexion. These data have relevance both in terms of ergonomic planning and in terms of muscular rehabilitation or optimization for a variety of activities.

It is relevant to note that there is a difference of 34% in the activity amplitude pattern between the highest and lowest ranking muscle, whereas there is only a difference of 19% in terms of the highest and lowest segments of motion ranking. Thus, a clinician involved in wrist joint muscles rehabilitation, may consider appropriately those findings in terms of neuromuscular rehabilitation.5, 10,11,12

Table 4 represents the correlation coefficients (r) calculated from the segmental data of the 7 muscles tested through the wrist joint ROM with SEMG. The data clearly shows that all the muscles of a primary myotatic unit are active through any primary joint segment of ROM, whether they act in a concentric or eccentric contraction. The data rebuke the old concept that the “agonist is active" and the “antagonist is inhibited" through the concentric contraction of the agonist. In this specific case of wrist ROM, all seven muscles act through the four segments of wrist joint motion, either in concentric, eccentric or in a rotational (twisting) contraction. While the ECU is contracting concentrically through wrist extension (avg 36.6 µV RMS), the FCU is contracting eccentrically simultaneously (avg 17.2 µV RMS). By the same token while the FCU is contracting concentrically through flexion (avg 24.1 µV RMS), the ECU is simultaneously contracting eccentrically (avg 25.1 µV RMS). As seen from those values, the theory that a concentrically contracting muscle expends more energy than an eccentrically contracting muscle holds true for ECU and FCU in extension, i.e. 36.6 vs. 17.2 µV RMS, the same theory does not hold true when the two muscles contract in flexion, i.e. 24.1 vs. 25.1 µV RMS. These results demonstrate that scientific verification of energy expenditure of muscles in motion with SEMG testing should be done to understand the true meaning of muscular agonism and antagonism within the framework of concentric versus eccentric contraction.

Last updated on: December 20, 2011
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