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EMG recordings, typically obtained in biofeedback training sessions, tend to underestimate actual muscle activity in overweight and female pain patients. If unadjusted, these measures will likely result in erroneous diagnostic conclusions.

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The aim of this study was to assess the effect on EMG amplitude measures of variations in the thickness of underlying tissue between surface electrodes and the active muscle. 20 normal subjects with different amounts of subcutaneous tissue performed comparable constant force contractions for a 45-second period, during which paraspinal EMG recordings were taken. Three measures of subcutaneous tissue thickness were obtained from each subject: Body Mass Index, total body fat as calculated by Durnin's formula, and skinfold thickness at the recording sites. The results show that (i) the greater the thickness of subcutaneous tissue between the surface recording site and the contracting muscles, the lower the recorded electromyographic activity, and that (ii) up to 81.2% of the variance in the EMG measures can be explained by variation in the amount of subcutaneous tissue. These findings support the view that the absolute level of surface-recorded EMG cannot simply be taken at face value. The amplitude of the signal will be affected by, for example, the amount of body fat.

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As a prerequisite to the use of electromyographic power spectral analysis of the paraspinal muscles as a low-back pain treatment outcome measure, the long-term reliability of the technique was assessed. The myoelectric signals of the multifidus and iliocostalis lumborum muscles of healthy sedentary women were analyzed with regard to spectral parameters during a constant-force contraction, before and after a 3-month period. Results indicated that for both muscles, estimates of initial median frequency and amplitude had high test/retest reliability, but that the recovery and left-right difference parameters were not stable. Using a confidence interval method, test/retest variation for the fatigue parameter was found to be within the range of variability of potentially underlying metabolic processes.

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It has been suggested, but not substantiated, that electromyographic (EMG) power spectrum (PS) analysis of the paraspinal muscles could be a useful method of evaluating low back pain treatment outcome. The use of PS analysis to measure paraspinal muscle adaptations was investigated in two studies: Study 1, involving previously sedentary healthy women who participated in a 12-week fitness class program, and Study 2, involving low back pain sufferers who participated in a 10-week back-care exercise program. All subjects underwent assessments of physical fitness (aerobic capacity, back strength, and flexibility) and EMG PS analysis of the multifidus and iliocostalis muscles (during a constant force contraction), before and after the experimental period. The results in both studies indicated that the EMG PS measures were sensitive to adaptive changes, with findings of (a) decreases in multifidus initial median frequency (IMF) and fatigue (FTG) of the fitness class participants and (b) an increase in multifidus IMF and decreases in multifidus and iliocostalis FTG of the back-care participants. The results are discussed with regard to possible links between spectral changes and alterations in muscle fiber characteristics and functioning, and the need for further research to substantiate such links.

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The accuracy with which the fibre direction of the multifidus muscle can be predicted in females is comparable to that for males, and is well within the limits of accuracy obtainable in the placement of surface electrodes in relation to a reference line drawn on the skin, i.e. +/- 5 degrees. In females, the observed deviation of the iliocostalis fibres from the corresponding reference line may, however, add some degree of error to the proper orientation of electrode bars perpendicular to muscle fibres. It may thus be concluded that the surface recording of EMG power spectrum parameters of the iliocostalis in women cannot be carried out as accurately as for the multifidus muscle. Nevertheless, the resulting recording error associated with a possible orientation deviation of, for example, 13 degrees is rather small (3%) and may be acceptable for clinical research purposes.

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Some parameters of the electromyographic power spectrum of the paraspinal muscles were recorded and analyzed with regard to their ability to discriminate between normal controls and patients with back pain classified as "avoiders" or "confronters" by their responses to the Pain Behavior Checklist. In terms of the activity of the multifidus muscle, the avoider group displayed spectral changes towards lower frequencies, reduced variability in the density spectrum, and higher values of estimated initial frequencies. Measures of the activity of the iliocostalis lumborum did not contribute in any significant way to these group differences. Based on these findings, and on the available literature concerning the histology and physiology of paraspinal muscles, it is proposed that the observed characteristics of the avoider group may be due to a reduced ratio of slow twitch to fast twitch muscle fibers in the multifidus.

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This report addresses some of the statistical problems that are encountered when the test/retest recording reliability of fatigue-related parameters of the EMG power spectrum is evaluated. It can be shown that some classical methods for reliability assessment such as correlational procedures are unsuitable for this purpose. Because the EMG power spectrum fatigue parameter depends on metabolic changes in muscle tissue, it is suggested that methods similar to those used in the evaluation of bioequivalence studies may be more appropriate in the assessment of such test/retest results.

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The technique of monitoring the frequency shift of the electromyographic signal through a single parameter, the median frequency (MF), was investigated with regard to its reliability characteristics as tested on two back muscle groups: the multifidus and iliocostalis lumborum. The proportion of variance in the MF parameters accounted for by the test/retest reliability as well as by the left versus right side analysis is satisfactory for the multifidus, it is, however, consistently lower for the iliocostalis. For the purpose of measuring muscular function, the MF recording technique appears to be well suited for clinical research, its application in the assessment of muscular dysfunction of back muscles is nevertheless far from simple.

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Electromyographic biofeedback and behavioral control techniques were used to treat two patients who suffered from Bell's palsy. Both patients (one case with a long history of Bell's Palsy which included extensive surgery to her face, the other of more recent onset) appeared to have benefited from these procedures and also perceived themselves as having done so. It is recommended that the noninvasive techniques outlined should be tried at an early stage in this condition in order to: (1) prevent the acquisition of inappropriate behavior; (2) accelerate progress toward normal facial functioning; and (3) reduce the need for any surgical intervention.

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Epidemiological studies have shown correlations between muscular deficiencies (low endurance capacity) and low back pain. With the emergence of new electromyographic surface recording methodologies (power spectrum investigations), a renewed interest in the electromyographic signal during sustained muscular contractions can be observed. A technique is described which is acceptable to chronic low back pain patients and which creates comparable constant force contractions in normal controls and pain patients. This method has advantages over those procedures requiring maximum voluntary contractions by the patients.

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Considerable inter-individual variations in the fibre direction angles of the iliocostalis lumborum, longissimus and multifidus were observed, thus bringing the applicability of a two dimensional fixed angle grid system for fibre direction determination into question. However, the angulation of the fibres of the multifidus and iliocostalis lumborum were found to be easily identifiable by the use of three surface anatomical landmarks: the caudal tip of the superior iliac spine, the lateral border of the iliocostalis at the twelfth rib and the L1-L2 interspinous space. No reliable index was found for the longissimus. Suggested electrode placement sites for the electromyographic study of the iliocostalis lumborum and the multifidus are at the levels of the L2-L3 and the L4-L5 interspinous spaces respectively.

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Treatment responses to relaxation-oriented EMG biofeedback (EMGBF) in patients categorized in terms of the Back Pain Classification Scale (BPCS) were examined. It was demonstrated that the previously observed effectiveness of EMGBF training became even more pronounced when the patients were divided into "organic" and "functional" subtypes according to the BPCS. The "organic" group showed the greatest degree of improvement. The mechanism of treatment effectiveness is discussed with reference to physiological changes, i.e., restoration of appropriate back muscle strength and back muscle functioning.

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A 63-year old depressed woman with a 2-year history of chronic pain on the right side of her face in the area of the zygomatic arch and temporomandibular joint received acupuncture before and after the medical treatment of her depression. During her unmedicated state electroacupuncture provided pain relief, while after prolonged intake of doxepin the treatment no longer produced analgesia. The literature fails to provide a mechanism explaining the differential responses to acupuncture with regard to antidepressant medication. Suggestions on further endorphin related research are made with particular emphasis on gonadotropin activity.

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Substantial numbers of patients suffer from chronic back pain without demonstrating identifiable organic pathology of the spine. Since standardized methods of assessing psychological disturbances (e.g. MMPI) in such patients often provoke hostility and resentment, a questionnaire (BPCS) was developed which employs verbal descriptors of pain in the evaluation of emotional problems. Although the initial findings were very promising our investigations question the psychometric properties of the BPCS.

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The underlying assumption in comparing muscle activity levels in back pain research is the reliability of the documented biological record. Surface-recorded EMG data are often used as "objective" indicators in treatment outcome studies. The present paper questions the reliability of this somatic measure. Three sources of error variance that interfere with the reliability of the recorded biological signal are discussed: movement of the body, replacement of electrodes, and electronic equipment instability. It is argued that surface-recorded EMG activities of the back are unreliable and unsuited for comparing the efficacy of a back pain treatment program.

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