Journal o f Occupational Rehabilitation, Vol. 4, No. 1, 1994
Randomized Study of the Application of Single Motor Unit Biofeedback Training to Chronic Low Back Pain Stuart Donaldson, 1,4 David Romney, 2 Mary Donaldson, 1 and Daniel Skubick 3
The application of single motor unit biofeedback training (SMUBT) techniques was compared to traditional therapies in treating chronic low back pain (CLBP). Thirty-she volunteers (who experienced daily pain for 7 years in the T8 to $1 area) were randomly assigned to one of three treatments; SMUBT, relaxation training, or an educational program. The pain level and electromyographic activity of all subjects were assessed by a person blind to the treatment; before, immediately after, and 90 days after treatment. The SMUBT group reported immediately decreased pain which was maintained at 90 days, the relaxation group showed no changes, while the education group reported decreased pain at 90 days. The EMG results showed decreased amplitude and bilateral differences for the SMUBT and education groups. A 4-year follow-up revealed the SMUBT group remained symptom free. Implications and discussion of the results concludes the paper. KEY WORDS: single motor unit; EMG biofeedback; chronic low back pain.
INTRODUCTION Muscles are innervated by single motor units (SMUs) which arise from the ventral horn of the spinal column (1). Training (increasing and/or decreasing the activity) of the motor unit represents one of the most unequivocal examples of the importance of feedback in the development of specificity of motor control (2). Numerous authors (3-6) have studied acquired control of the SMU with Johnson (7) demonstrating that (a) the ability to develop on-off control, (b) control the rhythm of activity, and (c) maintain isolation from other SMUs, were the best predictors of successful training. 1Behavioral Health Consultants, Calgary, Alberta, Canada. 2Department of Educational Psychology, University of Calgary, Calgary, Alberta. 3Neurologie Group, North Wales, Pennsylvania. 4Correspondence should be directed to Dr. S. Donaldson, Behavioral Health Consultants, 560-10655 Southport Rd. S.W., Calgary, Alberta T2W 4YI Canada. 23 1053-0487/94/0300-0023507.00/0O 1994PlenumPublishingCorporation
Donaldson, Romney, Donaldson, and Skubick
24
The application of the SMU principles to the retraining of muscles is not definitive. A few uncontrolled studies (8-14) and controlled studies (11-13) indicate that electromyographic (EMG) biofeedback is effective in increasing motor activity and decreasing spasticity. Mulder (15-17), in a series of controlled studies, demonstrated that the critical variable in learning motor control was the specificity of the information. Otherwise the application to muscle activity of the SMU techniques [referred to as Single Motor Unit Biofeedback Training (SMUBT) in this paper] has not been studied. Price et al. (18) suggested that chronic low back pain (CLBP) is caused by biomechanical factors (unequal in strength) acting on the vertebrae. Following this theme several authors (19-23) suggested that an imbalance of muscle activity during standing and when moving produces the biomechanical imbalance which may lead to pain and muscle strain. The purpose of this study was to" (1) determine if the principles of S M U B T training [following the criteria of Johnson (7)] could be applied to muscles, (2) determine if application of these principles would impact upon muscle activity, (3) determine if this impact would affect CLBP, and (4) compare the outcome to other standard forms of treatment.
METHODOLOGY
Subjects The subjects (all volunteers) were recruited through advertisement. The acceptance criteria included: (1) CLPB in the area from T8 to S1, (2) pain for at least 1 year, (3) experience daily pain, (4) not be involved in litigation, and (5) be between the ages of 18 and 55. Initially 69 people volunteered, but 18 did not meet the criteria. Fifty-one subjects were screened by a physician (blind to the study) and excluded for any of the following reasons: (1) a history of back surgery, (2) a straight leg raise which produced pain at less than 70 degrees, (3) a loss of reflexes, (4) weakness in the lower limbs, (5) a severe scoliosis, (6) a gait abnormality affecting the biomechanics of the spine, and (7) any significant disease (i.e., lupus). On this basis, a further two subjects were rejected. Following the physician's assessment and before the pre-treatment assessment, another 13 dropped out for various reasons (i.e., illness, receiving other treatment, death in the family, car accident, back surgery) leaving a total of 36 subjects.
Procedure Assessment
All assessments were conducted by the same person who was blind to the treatment assignments. Three assessments were conducted on each subject: (a) pre-
Biofeedback and Low B a c k Pain
2s
treatment, (b) post-treatment (within 7 days of completing treatment), and (c) follow-up (90 days after treatment). All assessment were identical in procedure. Demographic data were collected, then the subject was instructed to complete the McGill Pain Questionnaire (MPQ) following standard instructions (24). A measure of the general level of the intensity of the pain was obtained using a Visual Analogue Scale (VAS---General) as outlined by Huskisson (25). An MMPI was then completed following standard directions (26). Finally an E M G assessment was completed in four different positions (lying, sitting, standing, and movement). Subjects located the spot on their backs that presented the greatest amount of pain. The distance form this spot to the top of the sacrum was recorded for future assessments. The skin on either side of the spine over the paraspinals was abraded, then cleaned with rubbing alcohol. Four 10 mm silver/silver chloride electrodes were attached using double sided adhesive collars, two on either side of the spine, 2.5 cms from the spineous processes, 3 cm center to center. Resistance was measured using an ohm meter with any placement showing a reading of greater than 50,000 ohms replaced. A universal reference was located on the spineous processes. Analogue data was transmitted to a BIOCOMP 2001TM (Biocomp Research Institute 216, 3710 South Robertson, Culver City, CA 90232) system through infrared signal (90 Hz) and converted to digital signal at a rate of 15 samples per second using root mean square procedures, with a bandpass filter setting of 80-400 Hz. For the lying assessment, the subject lay supine on a massage table with pillows under the head, lower back, and knees. For the sitting assessment, the subject sat fully supported in a chair, feet flat on the floor, and arms on the arm rest. For standing, the subject was instructed to stand in what they considered a normal, comfortable position, hands at the side staring straight ahead. Each part of the assessment lasted for 6 minutes with the average EMG score for either side recorded. For the movement assessment the subject was instructed to bend forward from the waist as far as was comfortable, pause, and then return to the upright position. The movement required about 7 seconds with the maximum amplitude for either side recorded, as was the corresponding value for the side opposite. At the end of each part of the E M G assessment the subject filled in a VAS indicating the amount of pain involved for that section. These were labeled VAS--lying VAS sitting, V A S standing, and VAS--movement. Treatment
The subjects were randomly assigned (27) to one of three treatment conditions: (a) SMUBT, (b) relaxation training, (c) education. All subjects received ten 35 minute sessions: session 1, orientation to the treatment, sessions 2--9, treatment, and session 10, assessment of learning. No other treatment was received during the study. The SMUBT group was first instructed in the concepts of SMUBT and muscle symmetry. In sessions 2-9, electrodes were placed over the painful site in an manner identical to the assessment. The subject was instructed while standing, to increase the activity of the low side while keeping the high side quiet, by using visualization tech-
26
Donaldson, Romney, Donaldson, and Skubtck
niques and gentle contraction of the low side. Feedback from the computer was utilized to document the correctness of the muscle activity. During the trials, the trainer offered encouragement when the correct muscle activity was demonstrated. A trial consisted of six 1-minute subtrials with the first 10 seconds of the subtrial used to increase the actMty and the last 50 seconds used to rest. The 10/50 timing was utilized as Mulder (15) demonstrated a change in recruitment patterns occurred after 10 seconds of contraction, and the first author's clinical observations that 50 seconds was necessary for the EMG patterns to stabilize after contraction. Each session involved two trials for a total of 12 subtrials. When symmetry was obtained no further training was completed since the continuation of training would reverse the symmetry. All subjects met this criteria after six sessions. At the start of each session subjects were given a VAS and asked to indicate their present level of pain and on a second VAS asked to rate their change in pain from the previous day. These were labeled VAS-Intensity and VAS-Change. During session 10, the two VASs were completed and then all subjects were asked to demonstrate learning by increasing then decreasing the muscle activity upon command following the training protocol and matching Johnson's criteria. The relaxation group was first instructed in the concepts of relaxation and muscle symmetry and a baseline of level of muscle activity was obtained following the cross-body procedures of Johnson and Hockersmith (28). In sessions 2-9, the subject was talked through a modified version of progressive relaxation training in which the subject tensed and relaxed 16 muscle groups following the format of Lehrer and Woolfolk (29). Each muscle received 1 minute of training in the following manner. The subject tensed the muscle for 7 seconds, relaxed it for 10 seconds, tensed it again for 7 seconds, and relaxed for 25 seconds, with the remaining time spent in instruction. At the end of the training any muscles that felt tense (as indicated by the subject) were trained again. The 16 muscle groupings included: (1) dominant forearm and hand, (2) dominant upper arm, (3) nondominant forearm and hand, (4) nondominant upper arm, (5) forehead, (6) upper cheeks and nose, (7) lower face, (8) neck, (9) chest, shoulders and upper back, (10) abdomen and lower back, (11) dominant upper leg, (12) dominant calf, (13) dominant foot, (14) nondominant upper leg, (15) nondominant calf, and (16) nondominant foot. During session 10, all subjects received the relaxation training, but were then asked to demonstrate learning by relaxing to the best of their ability while the E M G cross-body activity was monitored in a manner identical to the first session. The VASs were administered in the same manner as they were for the SMUBT group. The education group was first instructed in the theories of pain, the relationship of pain to CLBP, the orientation of the program, the purpose of the research, and the outline of the course. In sessions 2-9, the subjects received instruction on various topics as related to CLBP. These included anatomy, posture, causes of muscle imbalance (i.e., chronic repetitive actions, lifting), exercise, depression, stress, stress management, and 25 tips to a better back. Modeling of various topics by the instructor was also performed. In session 10, a review of the course was completed after the subjects completed a ten-question test of knowledge. The VASs were administered as outlined above.
27
Biofeedback and Low Back Pain
Data For the MPQ the total score (PRI-T) was utilized as it demonstrates good testretest reliability and face validity (31). For all VAS analyses (except change) the lines were measured with the results averaged for each group. For the VAS-change midway on the line was scored as zero (no change), to the left of center scored as decreased functioning (maximum score of -5) and to the right of center scored as improved functioning (maximum score of +5). These scores were averaged as well. For the E M G values, the average scores for the 6-minute sample was averaged for each side for three conditions (lying, sitting, and standing) and then subtracted to obtain the difference. For the movement condition, the maximum score for either side was located, as was the corresponding value. These were labeled movement-high and movement-low, respectively. The low side was then subtracted from the high side producing the bilateral difference. These scores were averaged for each group by time condition. Statistical Analysis The basic statistical analysis employed was a 3 x 3 repeated measures analysis of variance where one factor was group and the other was time. In order to protect against inflated Type I error rates, multivariate analysis of variance was used when the measures appeared to be related (29). When significant results were obtained univariate analyses of the measures were then performed. For those scales which appeared to differ from each other a two-way A N O V A (group by time) was utilized. Long-Term Follow-Up Effort was made to contact the subjects 4 years after completion of the study. Of the 36 subjects 26 were located. They were interviewed by the first author's secretary (who was blind to the treatment) via telephone and asked the following question. Since your involvement in the study, have you experienced any ongoing back pain similar in manner to what you had before the study? They were also asked if they had received any treatment for their back pain since the study? If they indicated that they had received treatment or had experienced back pain similar to what they had prior to the study they were assigned to the negative category. If they indicated that they had not experienced any back pain nor received any other treatment then they were assigned to the positive category. These results were then subjected to Chi-Square analysis to test for significance.
RESULTS Demographics The subjects were on the average 38.0 years old (standard deviation = 7.5) with a range from 25 to 54 years. There were 17 males with most individuals em-
28
Donaldson, Romney, Donaldson, and Skubick
ployed at the same job for an average of 8.8 (6.9) years. All subjects continued to work or go to school throughout the study. Occupations were varied and included such jobs as laborer, secretary, physiotherapist, student, and housewife. The subjects reported being in pain on the average for 83.4 (80.3) months with a range of 72-360 months. The back pain was reported as occurring daily, varying in intensity (mainly with fatigue), and usually involved the neck. Trauma (a motor vehicle accident) was the cause in 21 cases, with lifting involved in nine others. All subjects had previously received several courses of treatment including physiotherapy, chiropractic, medication, and hospitalization. The physician reported muscle spasm in half the cases, with range of motion and Schober's test of skin distraction not significant. All lab tests, neurological findings and X-rays (when available) were within normal limits. The results of the MMPI were within normal T score limits with the first three scales (hypochondriasis, depression, and hysteria) approaching significance. These results correspond to those reported by Swenson (32) indicating individuals with demonstrable physical pathology show this pattern.
Pain Measures
Global Measures
As the MPQ (PRI-T) and VAS-General were thought to measure related concepts these two scales were analyzed using a two-way MANOVA (group by time). Pillai's criterion was selected in view of its robustness with a smaller sample (30). Significant results were revealed for the effect of time [F(4, 30) = 8.62, p < .01], and the interaction of group by time [F(8, 62) = 2.12, p < .05], but not for group. A two-way repeated measures ANOVA was then conducted on each of the pain measures. Results for the MPQ revealed significant results for groups over time [F(2, 105) = 7.30, p < .01] and for groups by time [F(4, 103) = 2.60, p < .05]. A test for simple main effects employing a one-way (between groups) A N O V A showed no significant differences pre-treatment or post-treatment, but showed significant results at follow-up [F(2, 33) = 3.53, p < .04]. Post hoc analysis using the Tukey HSD procedure revealed the SMUBT group mean was significantly (p < .05) lower than the relaxation group, with the education group not significantly different from either group. An identical procedure was followed for the VAS-General scores. Results of the two-way A_NOVA showed no significant differences between groups or for the group by time interaction with a significant difference noted for time [F(2, 105) = 9.32,p < .01]. A one-way repeated measures ANOVA for time showed the SMUBT group significantly IF(2, 33) = 5.50, p < .01] decreased between pre- and posttreatment which was maintained at follow-up, the relaxation group did not significantly change, while the education group decreased between post-treatment and follow-up. Table I highlights these results.
Biofeedback and Low Back Pain
29
Table I. Average Pain Measure Scores by Group over Time
Group Biofeedback
Measure MPQ VAS-G
Relax
MPQ
VAS-G Education
MPQ VAS-G
Pre
Post
Follow-up
28.75 (15.11)
16.08 (14.98)
15.33 (15.66)
2.23 (1.59)
1.26 (1.57)
0.72 (1.32)
31.08 (12.39)
27.67 (12.63)
32.33 (11.31)
2.51
1.90
1.78
(2.17)
(1.27)
(1.31)
34.50 (14.43)
28.58 (16.07)
20.08 (20.28)
3.48 (2.83)
2.47 (1.76)
0.87 (1.26)
Table Ii. Significant Changes for VAS Positions Measures for Different Treatments Pre
Post
Follow-up
Sitting
Position
Education
3.12 (2.03)
1.91 (1.88)
0.95 (1.31)
Standing
Biofeedback
2.08 (1.77)
0.87 (1.05)
0.97 (1.44)
Education
2.78 (2.99)
2.10 (2.01)
1.01 (1.36)
Biofeedback
3.33 (2.43)
1.25 (1.20)
1.05 (1.40)
Education
2.80 (2.40)
2.60 (2.06)
1.10 (1.37)
Movement
Group
VAS Measures by Position For all four positions (lying, sitting, standing, and movement) no significant VAS results were obtained when analyzed using a two-way ANOVA for group or group by time, but time showed significant differences. The results for time were: (a) lying [F(2, 105) = 9.32, p < .01], (b) sitting [F(2, 105) = 6.47, p < .01], (c) standing [F(92, 105) = 6.06, p < .01], and (d) movement IF(2, 105) = 9.82, p < .01]. A one-way repeated measures ANOVA for each treatment was then performed. The results of this analysis showed no significant differences for lying for any of the treatments. Significant decreases in pain levels were obtained for the SMUBT treatment group for standing IF(2, 33) = 3.67, p < .05], and movement [F(2, 33) 8.48,
Donaldson, Romney, Donaldson, and Skublck
30
p < .01]. The education treatment group showed significant decreases for sitting IF(2, 33) = 5.28, p < .02], standing IF(2, 33) = 4.27, p < .05], and movement [F(2, 33) = 3.31, p < .05]. Table II illustrates the means and standard deviations for the significant findings.
VAS-Daily Scores The daily scores were averaged over 3-day periods producing three time intervals (days 2--4, 5-7, and 8-10). Analysis utilizing a two-way A N O V A (group by time) revealed no significant effects for any of the measures although time approached significance. The S M U B T group showed the greatest decrease in reported pain [2.63 (1.86), 2.26 (1.09), and 1.41 (1.47)], with little reported for the relaxation group [2.33 (1.68), 2.14 (1.16), and 1.89 (1.19)], and none for the education group [2.23 (0.66), 2.39 (1.67), and 2.12 (1.69)].
VAS-Perceived Change Scores Similar procedures as outlined above using a two-way A N O V A (group by time) showed a significant IF(2, 105) = 2.86, p < .01] change for time, but not for group or group by time. Table III shows the S M U B T group reported the greatest change in days 8-10, the relaxation group in days 5-7, while the education group was constant throughout. EMG Results
Amplitude Results of a two-way A N O V A (group by time) showed no significant differences except for sitting for the group by time interaction [F(4,103) = 3.00, p < .05] and for the movement-low condition for time [F(4,103) = 3.04, p < .05]. ExTable IlL VAS Perceived Change Scores for Each Treatment Days Treatment
2-4
5-7
8-10
Biofeedback
0.06a (0.91)
0.48 (0.71)
1.40 (1.05)
Relax
-0.22 (0.65)
0.21 (0.56)
0.28 (0.72)
Education
0.24 (0.98)
0.39 (1.50)
0.71 (1.25)
score indicates no change, a negative score increased pain, a positive score decreased pain (range - 5 to +5).
aA zero
Biofeedback and Low Back Pain
31
amination for simple main effects showed no significant effects for either variable. Inspection of the data revealed the S M U B T group scores decreased for all positions, the relaxation group increased for all conditions, while the education group decreased for all positions except movement. These changes are illustrated in Table IV.
Bilateral Difference Results of a two-way A N O V A (group by time) showed no significant differences although there was a tendency for the S M U B T and education groups' scores to decrease over time. Table V reports these results.
Table IV. E M G Amplitude Scores over Time for Each Condition a Time Condition Lying
Group Blot'. Relax. Educ.
Sitting
Biot'. Relax. Educ.
Standing
Biol. Relax. Educ.
Movement High
Biol. Relax. Educ.
Low
Biol. Relax. Educ.
Pre
Post
Follow-up
M SD M SD M SD
3.14 (2.69) 1.30 (0.53) 2.86 (3.79)
2.04 (0.97) 1.87 (1.13) 2.17 (0.85)
2.37 (2.36) 2.93 (5.49) 1.82 (1.15)
M SD M SD M SD
6.13 (5.71) 3.77 (4.17) 3.73 (2.97)
4.27 (2.97) 4.83 (4.19) 5.60 (4.33)
3.08 (2.27) 6.22 (7.03) 3.45 (3.16)
M SD M SD M SD
8.20 (6.35) 6.04 (4.64) 7.44 (3.68)
7.76 (7.58) 5.86 (ado) 7.02 (3.09)
6.15 (3.63) 6.11 (6.14) 6.55 (4.47)
M SD M SD M 8D
49.01 (30.33) 42.78 (28.01) 47.28 (18.56)
57.61 (31.15) 47.99 (21.91) 49.02 (17.13)
43.00 (20.90) 44.33 (21.97) 48.65 (25.35)
M SD M SD M SD
39.33 (18.34) 35.08 (25.53) 34,95 (10.65)
44.26 (25.98) 41.01 (18.71) 40.65 (14.66)
38.98 (19.88) 37,05 (18.62) 41,37 (22.56)
aUnderlined scores indicate significant differences, pre = pre-treatment, and post = post-treatment.
Donaldson, Romney, Donaldson, and Skubick
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Table V. E M G Bilateral Difference Scores over Time for Each Condition Time Condition Lying
Group Biof. Relax. Educ.
Sitting
Biol. Relax Educ.
Standing
Blot'. Relax. Educ.
Pre
Post
Follow-up
M SD M SD M SD
1.96 (2.05) 0.70 (0.55) 1.50 (0.99)
1.70 (1.94) 1.09 (1.00) 1.53 (0.91)
0.96 (1.09) 2.02 (5.18) 0.82 (0.95)
M SD M SO M SD
2.29 (1.98) 1.80 (2.34) 1.58 (1.28)
1.94 (1.51) 2.04 (2.65) 2.19 (1.36)
0.90 (0.61) 3.35 (5.82) 0.75 (0.59)
M SD M SD M SD
2.13 (1.86) 2.34 (1.95) 3.16 (2.96)
3.46 (4.35) 1.95 (1.96) 2.47 (1.94)
1.61 (1.76) 2.87 (5.62) 1.80 (1.86)
M SD M SD M SD
9.73 (21.82) 8.50 (7.70) 12.33 (12.34)
13.27 (13.40) 6.98 (5,43) 8.12 (8.56)
4.03 (5.04) 7.23 (7.31) 7.31 (8.86)
Movement Biot'. Relax. Educ.
Summary In view of the amount and complexity of the data a summary of the group by time changes between pre-treatment and follow-up is contained in Table VI. This table shows the S M U B T and education groups decreased the amplitude and bilateral differences, while the relaxation group did not.
Learning Learning of the S M U B T principles was deemed to have occurred if the subject was able to upon command increase and decrease the E M G activity 6 times consecutively as per Johnson's criteria (7). Of the 12 subjects, 11 performed to this level on the first attempt, while the other did on the second attempt. Thus all were considered to have learned the task. For the relaxation group, the criteria as developed by Johnson and Hockersmith (28) was employed. On this basis, 11 of the 12 subjects were deemed to have learned relaxation. The knowledge acquired by
33
Biofeedback and Low B a c k Pain Table VI. E M G Score Changes over Time for Each Group and Condition a
Group Biofeedback Condition
Relaxation
Education
Amp.
Bil. dif.
Amp.
Bil. dif.
Amp.
Bil. dif.
Lying Sitting Standing
-0.8 -3.0 -2.0
-1.0 -1.4 -0.5
+ 1.6 +2.5 + 0.1
+ 1.4 + 1.6 + 0.6
-1.2 -0.3 -0.9
-0.7 -0.8 -1.4
Movement High Low
-6.0 -0.4
-5.7 NA
+ 1.6 +2.0
-1.3 NA
+ 1.4 +6.42
-5.0 NA
aLegend: - decrease in activity, + increase in activity, 0 no change, NA not applicable.
Table VII. Long-Term Follow-Up Group Biofeedback Relaxation Education
Number
Positive
Negative
11/12 8/12 7/12
9 4 4
2 4 3
the education group was measured by paper and pencil test. When compared to naive subjects all participants demonstrated a higher score indicating knowledge acquisition. Long-Term Follow-Up A long-term 4-year follow-up was conducted. Of the 36 subjects, 26 were located: 11 from the SMUBT group, eight from the relaxation group, and seven from the education group. Of the 11 in the SMUBT group, nine reported that they were virtually symptom free with the other two reporting that their symptoms had returned within a few months of the end of the study. The relaxation group indicated that four of the eight were still symptom free. The four who experienced a return in symptoms reported they all were receiving ongoing treatments since the study. The education group reported that four of the seven were improved while three reported that the long-term benefits were minimal. Differences in the expressed reactions of the different groups was reported, with the SMUBT group really clear in their responses (i.e., I've had no pain since the study), while the other two groups required more probing and clarification to their responses (i.e., some days I feel good but that's usually after a treatment). Chi-Squared analysis of the entire sample showed a score of 4.68 (dr = 2) which approached but was not significant. The results of the long-term follow-up are highlighted in Table VII.
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Donaldson, Romney, Donaldson, and Skubick
DISCUSSION The primary purpose of this study was to examine the application of single motor unit biofeedback training (SMUBT) principles to muscle activity and investigate the impact on same. The results indicate that the ability to increase and decrease the level of muscle activity as per the picket fence criteria developed by Johnson (7) can be easily understood and quickly learned by naive subjects. The application of this principle appears to impact upon muscle activity by changing the amplitude and bilateral imbalance in CLBP subjects. Concurrently with the EMG changes the CLBP subjects reported a decrease in their pain. This decrease was immediate (within six treatments), affected most body positions (sitting, standing, and movement), and was maintained over the length of the study. Follow up (telephone contact) indicated that these changes were permanent. What is particularly striking about this study is the rapid decrease in reported pain for the SMUBT and education groups. The sample had on the average been in pain almost 7 years, which was significantly decreased within six appointments for the SMUBT groups, and within 90 days for the education group. While it is possible to attribute the decreased pain to placebo, the power of the computer or some other nonspecific factor, the length of time in pain, the number of previous treatments and the 4-year follow-up results makes this doubtful. The SMUBT and education groups both appear to have achieved the return to symmetry. Mulder (17) indicated that the specificity of the information was the critical variable in the learning of motor control. For the SMUBT group, the EMG information allowed the therapist and subject to clearly identify the muscle imbalance and target specifically on this. The immediate feedback from the computer allowed for immediate adjustments in the training protocol facilitating learning. Daily monitoring documented the accuracy of the training as well. The education group was trained in specific muscle activity and how specific movements affected same. It is believed that this increased awareness of the muscles and the need to maintain symmetry resulted in a change in work habits and how to function at the worksite. The SMUBT and education training significantly impacted upon the pain in most positions except lying. The SMUBT training was completed in the standing position only, suggesting the technique generalized to the other positions. The education program was not taught in any specific position, but emphasized knowledge of activity in various positions. Lying appears not to be significant as the EMG values were low to begin with, not allowing room for much change. It is interesting to speculate about the physical reason(s) for the decreased pain. The change(s) in degrees of asymmetry (bilateral difference) and in the high side EMG readings (amplitude) would suggest an association between these findings and the reported pain, although this needs further research. While EMG readings reflect the electrical activity occurring in the muscle, they also reflect the neurological and joint activity affecting the muscle. In this case it is thought that the EMG readings reflect neurological or joint involvement, rather than muscular, as muscle strengthening (of the low side) would take longer. In personal communications with
Biofeedback and Low Back Pain
35
S. Wolf (University of Calgary, April 21, 1990) it was suggested that the rapidity of the changes would lend support to the idea of a change in a joint position. An alternative explanation is the EMG imbalances reflect a disturbance in the engram (35) which is altered in the dysfunction and restored by the treatment programs. However, these ideas should be considered only as speculative at the present time. The SMUBT and education groups appeared to have impacted upon the reported pain in a manner different from the relaxation training. Both the SMUBT and education groups were designed to return the muscle activity to symmetry and indirectly reduce the muscle activity, whereas relaxation training is reported to improve the subject's ability to cope and decrease muscle spasm (33). If the return to symmetry is responsible for the decreased pain, it would lend support to the biomechanical theory of chronic pain first suggested by Price et al. (18). The similar decreases in EMG data for the education and SMUBT groups appear to have negated the obtaining of significant statistical results at the 90-day interval. Although the trends in the data are quite clear, the point at which sampling of the data occurred would have produced differing results. The SMUBT group appeared to respond to treatment within the treatment time period (14 days), while the education group took longer to respond (90 days). Sampling at different time intervals would have produced different results. A larger sample and/or differing treatment techniques (those which do not stress muscle symmetry) might clarify the issue of time vs. treatment. This study is unique in that it carefully controlled for learning. As Shellenberger and Green (34) indicated, the active component of treatment in EMG biofeedback (SMLIBT) is learning. Careful control for this variable demonstrated that it had occurred and could be related to the change in pain. Research in the area of EMG biofeedback needs to carefully control for and emphasize this variable. This study needs to be viewed as exploratory in nature. A larger sample size would reduce the susceptibility to Type II error. There are several different issues which were introduced which need further investigation. The relationship of symmetry to CLPB and its impact upon the worksite needs to be studied. Can the worksite be modified, can SMUBT be taught to high risk injury situations, or can workers be taught the concepts of symmetry thus altering their function? These questions need further investigation. Will all of these changes or one more effectively than the others impact upon the time lost injury rate and the related costs? Which procedure is the most economical remains to be determined? The striking feature of this study however is the rapid decrease in the level of reported pain in the SMUBT group and subsequently the education group which appears to have been maintained over time. This needs to be replicated and examined in light of different theoretical perspectives (i.e., motor control theory) and compared to other forms of treatment. Until then the results should be treated as preliminary only.
REFERENCES 1. Basmajian JV. R e s e a r c h f o u n d a t i o n s o f EMG biofeedback in rehabilitation. Self-Regulation 1988; 13(4): 275-298.
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2. Yates AJ. Biofeedback and the modification of behavior. New York: Plenum, 1980. 3. Basmajian JV. Control and training of individual motor units. In: Peper E, Ancoli S, Quinn M, eds. Mind~body integration: Essential readings in biofeedback. New York: Plenum, 1979, pp. 371-375. 4. Basmajian JV, Baeza M, Fabrigar C. Conscious control and training of individual motor meurons in normal human subjects. J New Drugs 1965; 5: 78-85. 5. Simard TG, Basmajian JV. Methods in training the conscious control of motor units. Arch Phys Med 1966; 48: 12-19. 6. Lloyd A, Leibrecht B. Conditioning of a single motor unit. J Exp Psychol 1971; 88: 391-395. 7. Johnson CP. Analysis of five tests commonly used in determining the ability to control single motor units. Am J Phys Med 1976; 55(3): 113-121. 8. Binder-Macleod SA. Biofeedback in stroke rehabilitation. In: Basmajian JV, ed. Biofeedback." Principles and practice for clinicians (2nd Ed.). Baltimore: Williams and Wilkins, 1983, pp. 73-89. 9. Wolf SL. Electromyographic biofeedback applications to stroke patients: A critical review. J Am Phys Ther Assoc 1983; 63(9): 1448-1455. 10. DeBacher G. Biofeedback in spasticity control. In: Basmajian JV, ed. Biofeedback: Principles and practice for clinicians. Baltimore: Williams and Wilkins, 1983, pp. 111-129. 11. Wolf SL, Binder-Macleod SA. Electromyographic biofeedback applications to the hemiplegic patient: Changes in lower extremity neuromuscular and functional status. J Am Phys Ther Assoc 1983; 63: 1404-1413. 12. Wolf SL, Binder-Macleod SA. Electromyographic biofeedback applications to the hemiplegic patient: Changes in upper extremity neuromuscular and functional status. J Am Phys Ther Assoc 1983; 63: 1404-1413. 13. Brudney J. Biofeedback in chronic neurological cases: Therapeutic electromyography. In: White L, Turskey B, eds. Clinical biofeedback: Efficacy and mechanisms. New York: Guilford, 1982, pp. 249-276. 14. Dale A, Anderson DE, Lutton LM. Agonist-antagonist electromyographic biofeedback and neuromuscular re-education: A case study. Am J Clin Biofeedback 1983; 6(1): 14-18. 15. Mulder T, Hulstijn W. The effect of fatigue and task repetition on the surface electromyographic signal. In: Mulder T, ed. The learning of motor control following brain damage: Experimental and clinical studies. Lisse: Swets and ZeitJinger, 1985, pp. 54-66. 16. Mulder 1", Hustijn W. Delayed sensory feedback in the learning of a novel motor task. In: Mulder T, ed. The learning of motor control following brain damage: Experimental and clinical studies. Lisse: Swets and Zeitlinger, 1985, pp. 44-53. 17. Mulder T, Hustijn W. Sensory feedback in the learning of a novel motor task. In: Mulder T, ed. The learning of motor control following brain damage: Experimental and clinical studies. Lisse: Swets and Zeitlinger, 1985, pp. 29-43. 18. Price JP, Clare MH, Ewerhardt FH. Studies of low backache with persistent muscle spasm. Arch Phys Med 1948; 29: 703-709. 19. Cram JR. Clinical EMG: Muscle scanning and diagnostic manual for surface recordings. Seattle: Clinical Resources, 1986. 20. Janda V. Muscles, central nervous system regulation. In: Korr IM, ed. The neurobiologic mechanisms in manipulative therapy. New York: Plenum, 1978, pp. 27-41. 21. Wolf SL, Basmajian JV. Assessment of paraspinal electromyographic activity in normal subjects and in chronic back pain patients using a muscle biofeedback device. In: Asmussen E, Jorgensen K, eds. International series on biomechanics. V1B, 1978, pp. 319-324. 22. Wolf SL, Basmajian JV, Russe TC, Kutner M. Normative data on low back mobility and activity levels. Am J Phys Med 1979; 58: 217-229. 23. Wolf SL, Nacht M, Kelly JL. EMG feedback training during dynamic movement for low back pain patients. Behav Ther 1982; 13: 395-406. 24. Melzack R. McGill Comprehensive Pain Questionnaire interviewer guide. In: Melzack R, ed. Pain measurement and assessment. New York: Raven, 1983, pp. 10A-14A. 25. Huskisson EC. Visual analogue scales. In: Melzack R, ed. Pain measurement and assessment. New York: Raven, 1983, pp. 33-37. 26. University of Minnesota. Minnesota Multiphasic Personality Inventory group form test booklet. Minneapolis: University of Minnesota Press, 1982. 27. Interstate Commerce Commission. Table of 105,000 random decimal digits. Washington, D.C., 1949. 28. Johnson HE, Hockersmith V. Therapeutic electromyography in chronic back pain. In: Basmajian JV, ed. Biofeedback: Principles and practice for clinicians. Baltimore: Williams and Wilkins, 1983, pp. 306-310. 29. Leary MR, Altmaier EM. Type I error in counselling research: A plea for multivariate analyses. J Counsel Psychol 1980; 27(6): 611-615.
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30. Tabachnick B, Fidell LS. Using multivariate statistics. New York: Harper and Row, 1983. 31. Reading AE. The McGill Pain Questionnaire: An appraisal. In: Melzack R, ed. Pain measurement and assessment. New York: Raven, 1983, pp. 55-61. 32. Swenson WM, Pearson JS, Osborne D. An MMPI source book: Basic item, scale and pattern data on 50,000 medical patients. Minneapolis: University of Minnesota Press, 1973. 33. Melzack R, Wall PD. The challenge of pain. New York: Basic Books, 1982. 34. Shellenberger R, Green JA. From the ghost in the box to successful biofeedback training. Greeley, CO.: Health Psychology Publications, 1986. 35. Kottke F. From reflex to skill: The training of coordination. Arch Phys Med Rehab 1980; 61: 551-561.
Randomized Study of the Application of Single Motor Unit Biofeedback Training to Chronic Low Back Pain Stuart Donaldson, 1,4 David Romney, 2 Mary Donaldson, 1 and Daniel Skubick 3
The application of single motor unit biofeedback training (SMUBT) techniques was compared to traditional therapies in treating chronic low back pain (CLBP). Thirty-she volunteers (who experienced daily pain for 7 years in the T8 to $1 area) were randomly assigned to one of three treatments; SMUBT, relaxation training, or an educational program. The pain level and electromyographic activity of all subjects were assessed by a person blind to the treatment; before, immediately after, and 90 days after treatment. The SMUBT group reported immediately decreased pain which was maintained at 90 days, the relaxation group showed no changes, while the education group reported decreased pain at 90 days. The EMG results showed decreased amplitude and bilateral differences for the SMUBT and education groups. A 4-year follow-up revealed the SMUBT group remained symptom free. Implications and discussion of the results concludes the paper. KEY WORDS: single motor unit; EMG biofeedback; chronic low back pain.
INTRODUCTION Muscles are innervated by single motor units (SMUs) which arise from the ventral horn of the spinal column (1). Training (increasing and/or decreasing the activity) of the motor unit represents one of the most unequivocal examples of the importance of feedback in the development of specificity of motor control (2). Numerous authors (3-6) have studied acquired control of the SMU with Johnson (7) demonstrating that (a) the ability to develop on-off control, (b) control the rhythm of activity, and (c) maintain isolation from other SMUs, were the best predictors of successful training. 1Behavioral Health Consultants, Calgary, Alberta, Canada. 2Department of Educational Psychology, University of Calgary, Calgary, Alberta. 3Neurologie Group, North Wales, Pennsylvania. 4Correspondence should be directed to Dr. S. Donaldson, Behavioral Health Consultants, 560-10655 Southport Rd. S.W., Calgary, Alberta T2W 4YI Canada. 23 1053-0487/94/0300-0023507.00/0O 1994PlenumPublishingCorporation
Donaldson, Romney, Donaldson, and Skubick
24
The application of the SMU principles to the retraining of muscles is not definitive. A few uncontrolled studies (8-14) and controlled studies (11-13) indicate that electromyographic (EMG) biofeedback is effective in increasing motor activity and decreasing spasticity. Mulder (15-17), in a series of controlled studies, demonstrated that the critical variable in learning motor control was the specificity of the information. Otherwise the application to muscle activity of the SMU techniques [referred to as Single Motor Unit Biofeedback Training (SMUBT) in this paper] has not been studied. Price et al. (18) suggested that chronic low back pain (CLBP) is caused by biomechanical factors (unequal in strength) acting on the vertebrae. Following this theme several authors (19-23) suggested that an imbalance of muscle activity during standing and when moving produces the biomechanical imbalance which may lead to pain and muscle strain. The purpose of this study was to" (1) determine if the principles of S M U B T training [following the criteria of Johnson (7)] could be applied to muscles, (2) determine if application of these principles would impact upon muscle activity, (3) determine if this impact would affect CLBP, and (4) compare the outcome to other standard forms of treatment.
METHODOLOGY
Subjects The subjects (all volunteers) were recruited through advertisement. The acceptance criteria included: (1) CLPB in the area from T8 to S1, (2) pain for at least 1 year, (3) experience daily pain, (4) not be involved in litigation, and (5) be between the ages of 18 and 55. Initially 69 people volunteered, but 18 did not meet the criteria. Fifty-one subjects were screened by a physician (blind to the study) and excluded for any of the following reasons: (1) a history of back surgery, (2) a straight leg raise which produced pain at less than 70 degrees, (3) a loss of reflexes, (4) weakness in the lower limbs, (5) a severe scoliosis, (6) a gait abnormality affecting the biomechanics of the spine, and (7) any significant disease (i.e., lupus). On this basis, a further two subjects were rejected. Following the physician's assessment and before the pre-treatment assessment, another 13 dropped out for various reasons (i.e., illness, receiving other treatment, death in the family, car accident, back surgery) leaving a total of 36 subjects.
Procedure Assessment
All assessments were conducted by the same person who was blind to the treatment assignments. Three assessments were conducted on each subject: (a) pre-
Biofeedback and Low B a c k Pain
2s
treatment, (b) post-treatment (within 7 days of completing treatment), and (c) follow-up (90 days after treatment). All assessment were identical in procedure. Demographic data were collected, then the subject was instructed to complete the McGill Pain Questionnaire (MPQ) following standard instructions (24). A measure of the general level of the intensity of the pain was obtained using a Visual Analogue Scale (VAS---General) as outlined by Huskisson (25). An MMPI was then completed following standard directions (26). Finally an E M G assessment was completed in four different positions (lying, sitting, standing, and movement). Subjects located the spot on their backs that presented the greatest amount of pain. The distance form this spot to the top of the sacrum was recorded for future assessments. The skin on either side of the spine over the paraspinals was abraded, then cleaned with rubbing alcohol. Four 10 mm silver/silver chloride electrodes were attached using double sided adhesive collars, two on either side of the spine, 2.5 cms from the spineous processes, 3 cm center to center. Resistance was measured using an ohm meter with any placement showing a reading of greater than 50,000 ohms replaced. A universal reference was located on the spineous processes. Analogue data was transmitted to a BIOCOMP 2001TM (Biocomp Research Institute 216, 3710 South Robertson, Culver City, CA 90232) system through infrared signal (90 Hz) and converted to digital signal at a rate of 15 samples per second using root mean square procedures, with a bandpass filter setting of 80-400 Hz. For the lying assessment, the subject lay supine on a massage table with pillows under the head, lower back, and knees. For the sitting assessment, the subject sat fully supported in a chair, feet flat on the floor, and arms on the arm rest. For standing, the subject was instructed to stand in what they considered a normal, comfortable position, hands at the side staring straight ahead. Each part of the assessment lasted for 6 minutes with the average EMG score for either side recorded. For the movement assessment the subject was instructed to bend forward from the waist as far as was comfortable, pause, and then return to the upright position. The movement required about 7 seconds with the maximum amplitude for either side recorded, as was the corresponding value for the side opposite. At the end of each part of the E M G assessment the subject filled in a VAS indicating the amount of pain involved for that section. These were labeled VAS--lying VAS sitting, V A S standing, and VAS--movement. Treatment
The subjects were randomly assigned (27) to one of three treatment conditions: (a) SMUBT, (b) relaxation training, (c) education. All subjects received ten 35 minute sessions: session 1, orientation to the treatment, sessions 2--9, treatment, and session 10, assessment of learning. No other treatment was received during the study. The SMUBT group was first instructed in the concepts of SMUBT and muscle symmetry. In sessions 2-9, electrodes were placed over the painful site in an manner identical to the assessment. The subject was instructed while standing, to increase the activity of the low side while keeping the high side quiet, by using visualization tech-
26
Donaldson, Romney, Donaldson, and Skubtck
niques and gentle contraction of the low side. Feedback from the computer was utilized to document the correctness of the muscle activity. During the trials, the trainer offered encouragement when the correct muscle activity was demonstrated. A trial consisted of six 1-minute subtrials with the first 10 seconds of the subtrial used to increase the actMty and the last 50 seconds used to rest. The 10/50 timing was utilized as Mulder (15) demonstrated a change in recruitment patterns occurred after 10 seconds of contraction, and the first author's clinical observations that 50 seconds was necessary for the EMG patterns to stabilize after contraction. Each session involved two trials for a total of 12 subtrials. When symmetry was obtained no further training was completed since the continuation of training would reverse the symmetry. All subjects met this criteria after six sessions. At the start of each session subjects were given a VAS and asked to indicate their present level of pain and on a second VAS asked to rate their change in pain from the previous day. These were labeled VAS-Intensity and VAS-Change. During session 10, the two VASs were completed and then all subjects were asked to demonstrate learning by increasing then decreasing the muscle activity upon command following the training protocol and matching Johnson's criteria. The relaxation group was first instructed in the concepts of relaxation and muscle symmetry and a baseline of level of muscle activity was obtained following the cross-body procedures of Johnson and Hockersmith (28). In sessions 2-9, the subject was talked through a modified version of progressive relaxation training in which the subject tensed and relaxed 16 muscle groups following the format of Lehrer and Woolfolk (29). Each muscle received 1 minute of training in the following manner. The subject tensed the muscle for 7 seconds, relaxed it for 10 seconds, tensed it again for 7 seconds, and relaxed for 25 seconds, with the remaining time spent in instruction. At the end of the training any muscles that felt tense (as indicated by the subject) were trained again. The 16 muscle groupings included: (1) dominant forearm and hand, (2) dominant upper arm, (3) nondominant forearm and hand, (4) nondominant upper arm, (5) forehead, (6) upper cheeks and nose, (7) lower face, (8) neck, (9) chest, shoulders and upper back, (10) abdomen and lower back, (11) dominant upper leg, (12) dominant calf, (13) dominant foot, (14) nondominant upper leg, (15) nondominant calf, and (16) nondominant foot. During session 10, all subjects received the relaxation training, but were then asked to demonstrate learning by relaxing to the best of their ability while the E M G cross-body activity was monitored in a manner identical to the first session. The VASs were administered in the same manner as they were for the SMUBT group. The education group was first instructed in the theories of pain, the relationship of pain to CLBP, the orientation of the program, the purpose of the research, and the outline of the course. In sessions 2-9, the subjects received instruction on various topics as related to CLBP. These included anatomy, posture, causes of muscle imbalance (i.e., chronic repetitive actions, lifting), exercise, depression, stress, stress management, and 25 tips to a better back. Modeling of various topics by the instructor was also performed. In session 10, a review of the course was completed after the subjects completed a ten-question test of knowledge. The VASs were administered as outlined above.
27
Biofeedback and Low Back Pain
Data For the MPQ the total score (PRI-T) was utilized as it demonstrates good testretest reliability and face validity (31). For all VAS analyses (except change) the lines were measured with the results averaged for each group. For the VAS-change midway on the line was scored as zero (no change), to the left of center scored as decreased functioning (maximum score of -5) and to the right of center scored as improved functioning (maximum score of +5). These scores were averaged as well. For the E M G values, the average scores for the 6-minute sample was averaged for each side for three conditions (lying, sitting, and standing) and then subtracted to obtain the difference. For the movement condition, the maximum score for either side was located, as was the corresponding value. These were labeled movement-high and movement-low, respectively. The low side was then subtracted from the high side producing the bilateral difference. These scores were averaged for each group by time condition. Statistical Analysis The basic statistical analysis employed was a 3 x 3 repeated measures analysis of variance where one factor was group and the other was time. In order to protect against inflated Type I error rates, multivariate analysis of variance was used when the measures appeared to be related (29). When significant results were obtained univariate analyses of the measures were then performed. For those scales which appeared to differ from each other a two-way A N O V A (group by time) was utilized. Long-Term Follow-Up Effort was made to contact the subjects 4 years after completion of the study. Of the 36 subjects 26 were located. They were interviewed by the first author's secretary (who was blind to the treatment) via telephone and asked the following question. Since your involvement in the study, have you experienced any ongoing back pain similar in manner to what you had before the study? They were also asked if they had received any treatment for their back pain since the study? If they indicated that they had received treatment or had experienced back pain similar to what they had prior to the study they were assigned to the negative category. If they indicated that they had not experienced any back pain nor received any other treatment then they were assigned to the positive category. These results were then subjected to Chi-Square analysis to test for significance.
RESULTS Demographics The subjects were on the average 38.0 years old (standard deviation = 7.5) with a range from 25 to 54 years. There were 17 males with most individuals em-
28
Donaldson, Romney, Donaldson, and Skubick
ployed at the same job for an average of 8.8 (6.9) years. All subjects continued to work or go to school throughout the study. Occupations were varied and included such jobs as laborer, secretary, physiotherapist, student, and housewife. The subjects reported being in pain on the average for 83.4 (80.3) months with a range of 72-360 months. The back pain was reported as occurring daily, varying in intensity (mainly with fatigue), and usually involved the neck. Trauma (a motor vehicle accident) was the cause in 21 cases, with lifting involved in nine others. All subjects had previously received several courses of treatment including physiotherapy, chiropractic, medication, and hospitalization. The physician reported muscle spasm in half the cases, with range of motion and Schober's test of skin distraction not significant. All lab tests, neurological findings and X-rays (when available) were within normal limits. The results of the MMPI were within normal T score limits with the first three scales (hypochondriasis, depression, and hysteria) approaching significance. These results correspond to those reported by Swenson (32) indicating individuals with demonstrable physical pathology show this pattern.
Pain Measures
Global Measures
As the MPQ (PRI-T) and VAS-General were thought to measure related concepts these two scales were analyzed using a two-way MANOVA (group by time). Pillai's criterion was selected in view of its robustness with a smaller sample (30). Significant results were revealed for the effect of time [F(4, 30) = 8.62, p < .01], and the interaction of group by time [F(8, 62) = 2.12, p < .05], but not for group. A two-way repeated measures ANOVA was then conducted on each of the pain measures. Results for the MPQ revealed significant results for groups over time [F(2, 105) = 7.30, p < .01] and for groups by time [F(4, 103) = 2.60, p < .05]. A test for simple main effects employing a one-way (between groups) A N O V A showed no significant differences pre-treatment or post-treatment, but showed significant results at follow-up [F(2, 33) = 3.53, p < .04]. Post hoc analysis using the Tukey HSD procedure revealed the SMUBT group mean was significantly (p < .05) lower than the relaxation group, with the education group not significantly different from either group. An identical procedure was followed for the VAS-General scores. Results of the two-way A_NOVA showed no significant differences between groups or for the group by time interaction with a significant difference noted for time [F(2, 105) = 9.32,p < .01]. A one-way repeated measures ANOVA for time showed the SMUBT group significantly IF(2, 33) = 5.50, p < .01] decreased between pre- and posttreatment which was maintained at follow-up, the relaxation group did not significantly change, while the education group decreased between post-treatment and follow-up. Table I highlights these results.
Biofeedback and Low Back Pain
29
Table I. Average Pain Measure Scores by Group over Time
Group Biofeedback
Measure MPQ VAS-G
Relax
MPQ
VAS-G Education
MPQ VAS-G
Pre
Post
Follow-up
28.75 (15.11)
16.08 (14.98)
15.33 (15.66)
2.23 (1.59)
1.26 (1.57)
0.72 (1.32)
31.08 (12.39)
27.67 (12.63)
32.33 (11.31)
2.51
1.90
1.78
(2.17)
(1.27)
(1.31)
34.50 (14.43)
28.58 (16.07)
20.08 (20.28)
3.48 (2.83)
2.47 (1.76)
0.87 (1.26)
Table Ii. Significant Changes for VAS Positions Measures for Different Treatments Pre
Post
Follow-up
Sitting
Position
Education
3.12 (2.03)
1.91 (1.88)
0.95 (1.31)
Standing
Biofeedback
2.08 (1.77)
0.87 (1.05)
0.97 (1.44)
Education
2.78 (2.99)
2.10 (2.01)
1.01 (1.36)
Biofeedback
3.33 (2.43)
1.25 (1.20)
1.05 (1.40)
Education
2.80 (2.40)
2.60 (2.06)
1.10 (1.37)
Movement
Group
VAS Measures by Position For all four positions (lying, sitting, standing, and movement) no significant VAS results were obtained when analyzed using a two-way ANOVA for group or group by time, but time showed significant differences. The results for time were: (a) lying [F(2, 105) = 9.32, p < .01], (b) sitting [F(2, 105) = 6.47, p < .01], (c) standing [F(92, 105) = 6.06, p < .01], and (d) movement IF(2, 105) = 9.82, p < .01]. A one-way repeated measures ANOVA for each treatment was then performed. The results of this analysis showed no significant differences for lying for any of the treatments. Significant decreases in pain levels were obtained for the SMUBT treatment group for standing IF(2, 33) = 3.67, p < .05], and movement [F(2, 33) 8.48,
Donaldson, Romney, Donaldson, and Skublck
30
p < .01]. The education treatment group showed significant decreases for sitting IF(2, 33) = 5.28, p < .02], standing IF(2, 33) = 4.27, p < .05], and movement [F(2, 33) = 3.31, p < .05]. Table II illustrates the means and standard deviations for the significant findings.
VAS-Daily Scores The daily scores were averaged over 3-day periods producing three time intervals (days 2--4, 5-7, and 8-10). Analysis utilizing a two-way A N O V A (group by time) revealed no significant effects for any of the measures although time approached significance. The S M U B T group showed the greatest decrease in reported pain [2.63 (1.86), 2.26 (1.09), and 1.41 (1.47)], with little reported for the relaxation group [2.33 (1.68), 2.14 (1.16), and 1.89 (1.19)], and none for the education group [2.23 (0.66), 2.39 (1.67), and 2.12 (1.69)].
VAS-Perceived Change Scores Similar procedures as outlined above using a two-way A N O V A (group by time) showed a significant IF(2, 105) = 2.86, p < .01] change for time, but not for group or group by time. Table III shows the S M U B T group reported the greatest change in days 8-10, the relaxation group in days 5-7, while the education group was constant throughout. EMG Results
Amplitude Results of a two-way A N O V A (group by time) showed no significant differences except for sitting for the group by time interaction [F(4,103) = 3.00, p < .05] and for the movement-low condition for time [F(4,103) = 3.04, p < .05]. ExTable IlL VAS Perceived Change Scores for Each Treatment Days Treatment
2-4
5-7
8-10
Biofeedback
0.06a (0.91)
0.48 (0.71)
1.40 (1.05)
Relax
-0.22 (0.65)
0.21 (0.56)
0.28 (0.72)
Education
0.24 (0.98)
0.39 (1.50)
0.71 (1.25)
score indicates no change, a negative score increased pain, a positive score decreased pain (range - 5 to +5).
aA zero
Biofeedback and Low Back Pain
31
amination for simple main effects showed no significant effects for either variable. Inspection of the data revealed the S M U B T group scores decreased for all positions, the relaxation group increased for all conditions, while the education group decreased for all positions except movement. These changes are illustrated in Table IV.
Bilateral Difference Results of a two-way A N O V A (group by time) showed no significant differences although there was a tendency for the S M U B T and education groups' scores to decrease over time. Table V reports these results.
Table IV. E M G Amplitude Scores over Time for Each Condition a Time Condition Lying
Group Blot'. Relax. Educ.
Sitting
Biot'. Relax. Educ.
Standing
Biol. Relax. Educ.
Movement High
Biol. Relax. Educ.
Low
Biol. Relax. Educ.
Pre
Post
Follow-up
M SD M SD M SD
3.14 (2.69) 1.30 (0.53) 2.86 (3.79)
2.04 (0.97) 1.87 (1.13) 2.17 (0.85)
2.37 (2.36) 2.93 (5.49) 1.82 (1.15)
M SD M SD M SD
6.13 (5.71) 3.77 (4.17) 3.73 (2.97)
4.27 (2.97) 4.83 (4.19) 5.60 (4.33)
3.08 (2.27) 6.22 (7.03) 3.45 (3.16)
M SD M SD M SD
8.20 (6.35) 6.04 (4.64) 7.44 (3.68)
7.76 (7.58) 5.86 (ado) 7.02 (3.09)
6.15 (3.63) 6.11 (6.14) 6.55 (4.47)
M SD M SD M 8D
49.01 (30.33) 42.78 (28.01) 47.28 (18.56)
57.61 (31.15) 47.99 (21.91) 49.02 (17.13)
43.00 (20.90) 44.33 (21.97) 48.65 (25.35)
M SD M SD M SD
39.33 (18.34) 35.08 (25.53) 34,95 (10.65)
44.26 (25.98) 41.01 (18.71) 40.65 (14.66)
38.98 (19.88) 37,05 (18.62) 41,37 (22.56)
aUnderlined scores indicate significant differences, pre = pre-treatment, and post = post-treatment.
Donaldson, Romney, Donaldson, and Skubick
32
Table V. E M G Bilateral Difference Scores over Time for Each Condition Time Condition Lying
Group Biof. Relax. Educ.
Sitting
Biol. Relax Educ.
Standing
Blot'. Relax. Educ.
Pre
Post
Follow-up
M SD M SD M SD
1.96 (2.05) 0.70 (0.55) 1.50 (0.99)
1.70 (1.94) 1.09 (1.00) 1.53 (0.91)
0.96 (1.09) 2.02 (5.18) 0.82 (0.95)
M SD M SO M SD
2.29 (1.98) 1.80 (2.34) 1.58 (1.28)
1.94 (1.51) 2.04 (2.65) 2.19 (1.36)
0.90 (0.61) 3.35 (5.82) 0.75 (0.59)
M SD M SD M SD
2.13 (1.86) 2.34 (1.95) 3.16 (2.96)
3.46 (4.35) 1.95 (1.96) 2.47 (1.94)
1.61 (1.76) 2.87 (5.62) 1.80 (1.86)
M SD M SD M SD
9.73 (21.82) 8.50 (7.70) 12.33 (12.34)
13.27 (13.40) 6.98 (5,43) 8.12 (8.56)
4.03 (5.04) 7.23 (7.31) 7.31 (8.86)
Movement Biot'. Relax. Educ.
Summary In view of the amount and complexity of the data a summary of the group by time changes between pre-treatment and follow-up is contained in Table VI. This table shows the S M U B T and education groups decreased the amplitude and bilateral differences, while the relaxation group did not.
Learning Learning of the S M U B T principles was deemed to have occurred if the subject was able to upon command increase and decrease the E M G activity 6 times consecutively as per Johnson's criteria (7). Of the 12 subjects, 11 performed to this level on the first attempt, while the other did on the second attempt. Thus all were considered to have learned the task. For the relaxation group, the criteria as developed by Johnson and Hockersmith (28) was employed. On this basis, 11 of the 12 subjects were deemed to have learned relaxation. The knowledge acquired by
33
Biofeedback and Low B a c k Pain Table VI. E M G Score Changes over Time for Each Group and Condition a
Group Biofeedback Condition
Relaxation
Education
Amp.
Bil. dif.
Amp.
Bil. dif.
Amp.
Bil. dif.
Lying Sitting Standing
-0.8 -3.0 -2.0
-1.0 -1.4 -0.5
+ 1.6 +2.5 + 0.1
+ 1.4 + 1.6 + 0.6
-1.2 -0.3 -0.9
-0.7 -0.8 -1.4
Movement High Low
-6.0 -0.4
-5.7 NA
+ 1.6 +2.0
-1.3 NA
+ 1.4 +6.42
-5.0 NA
aLegend: - decrease in activity, + increase in activity, 0 no change, NA not applicable.
Table VII. Long-Term Follow-Up Group Biofeedback Relaxation Education
Number
Positive
Negative
11/12 8/12 7/12
9 4 4
2 4 3
the education group was measured by paper and pencil test. When compared to naive subjects all participants demonstrated a higher score indicating knowledge acquisition. Long-Term Follow-Up A long-term 4-year follow-up was conducted. Of the 36 subjects, 26 were located: 11 from the SMUBT group, eight from the relaxation group, and seven from the education group. Of the 11 in the SMUBT group, nine reported that they were virtually symptom free with the other two reporting that their symptoms had returned within a few months of the end of the study. The relaxation group indicated that four of the eight were still symptom free. The four who experienced a return in symptoms reported they all were receiving ongoing treatments since the study. The education group reported that four of the seven were improved while three reported that the long-term benefits were minimal. Differences in the expressed reactions of the different groups was reported, with the SMUBT group really clear in their responses (i.e., I've had no pain since the study), while the other two groups required more probing and clarification to their responses (i.e., some days I feel good but that's usually after a treatment). Chi-Squared analysis of the entire sample showed a score of 4.68 (dr = 2) which approached but was not significant. The results of the long-term follow-up are highlighted in Table VII.
34
Donaldson, Romney, Donaldson, and Skubick
DISCUSSION The primary purpose of this study was to examine the application of single motor unit biofeedback training (SMUBT) principles to muscle activity and investigate the impact on same. The results indicate that the ability to increase and decrease the level of muscle activity as per the picket fence criteria developed by Johnson (7) can be easily understood and quickly learned by naive subjects. The application of this principle appears to impact upon muscle activity by changing the amplitude and bilateral imbalance in CLBP subjects. Concurrently with the EMG changes the CLBP subjects reported a decrease in their pain. This decrease was immediate (within six treatments), affected most body positions (sitting, standing, and movement), and was maintained over the length of the study. Follow up (telephone contact) indicated that these changes were permanent. What is particularly striking about this study is the rapid decrease in reported pain for the SMUBT and education groups. The sample had on the average been in pain almost 7 years, which was significantly decreased within six appointments for the SMUBT groups, and within 90 days for the education group. While it is possible to attribute the decreased pain to placebo, the power of the computer or some other nonspecific factor, the length of time in pain, the number of previous treatments and the 4-year follow-up results makes this doubtful. The SMUBT and education groups both appear to have achieved the return to symmetry. Mulder (17) indicated that the specificity of the information was the critical variable in the learning of motor control. For the SMUBT group, the EMG information allowed the therapist and subject to clearly identify the muscle imbalance and target specifically on this. The immediate feedback from the computer allowed for immediate adjustments in the training protocol facilitating learning. Daily monitoring documented the accuracy of the training as well. The education group was trained in specific muscle activity and how specific movements affected same. It is believed that this increased awareness of the muscles and the need to maintain symmetry resulted in a change in work habits and how to function at the worksite. The SMUBT and education training significantly impacted upon the pain in most positions except lying. The SMUBT training was completed in the standing position only, suggesting the technique generalized to the other positions. The education program was not taught in any specific position, but emphasized knowledge of activity in various positions. Lying appears not to be significant as the EMG values were low to begin with, not allowing room for much change. It is interesting to speculate about the physical reason(s) for the decreased pain. The change(s) in degrees of asymmetry (bilateral difference) and in the high side EMG readings (amplitude) would suggest an association between these findings and the reported pain, although this needs further research. While EMG readings reflect the electrical activity occurring in the muscle, they also reflect the neurological and joint activity affecting the muscle. In this case it is thought that the EMG readings reflect neurological or joint involvement, rather than muscular, as muscle strengthening (of the low side) would take longer. In personal communications with
Biofeedback and Low Back Pain
35
S. Wolf (University of Calgary, April 21, 1990) it was suggested that the rapidity of the changes would lend support to the idea of a change in a joint position. An alternative explanation is the EMG imbalances reflect a disturbance in the engram (35) which is altered in the dysfunction and restored by the treatment programs. However, these ideas should be considered only as speculative at the present time. The SMUBT and education groups appeared to have impacted upon the reported pain in a manner different from the relaxation training. Both the SMUBT and education groups were designed to return the muscle activity to symmetry and indirectly reduce the muscle activity, whereas relaxation training is reported to improve the subject's ability to cope and decrease muscle spasm (33). If the return to symmetry is responsible for the decreased pain, it would lend support to the biomechanical theory of chronic pain first suggested by Price et al. (18). The similar decreases in EMG data for the education and SMUBT groups appear to have negated the obtaining of significant statistical results at the 90-day interval. Although the trends in the data are quite clear, the point at which sampling of the data occurred would have produced differing results. The SMUBT group appeared to respond to treatment within the treatment time period (14 days), while the education group took longer to respond (90 days). Sampling at different time intervals would have produced different results. A larger sample and/or differing treatment techniques (those which do not stress muscle symmetry) might clarify the issue of time vs. treatment. This study is unique in that it carefully controlled for learning. As Shellenberger and Green (34) indicated, the active component of treatment in EMG biofeedback (SMLIBT) is learning. Careful control for this variable demonstrated that it had occurred and could be related to the change in pain. Research in the area of EMG biofeedback needs to carefully control for and emphasize this variable. This study needs to be viewed as exploratory in nature. A larger sample size would reduce the susceptibility to Type II error. There are several different issues which were introduced which need further investigation. The relationship of symmetry to CLPB and its impact upon the worksite needs to be studied. Can the worksite be modified, can SMUBT be taught to high risk injury situations, or can workers be taught the concepts of symmetry thus altering their function? These questions need further investigation. Will all of these changes or one more effectively than the others impact upon the time lost injury rate and the related costs? Which procedure is the most economical remains to be determined? The striking feature of this study however is the rapid decrease in the level of reported pain in the SMUBT group and subsequently the education group which appears to have been maintained over time. This needs to be replicated and examined in light of different theoretical perspectives (i.e., motor control theory) and compared to other forms of treatment. Until then the results should be treated as preliminary only.
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