Percepttidl and Motor Skills, 1979, 48, 848-850.
@ Perceptual and Motor Skills 1979
BIOFEEDBACK A N D RELAXATION EFFECTS I N ELECTROMYOGRAPHIC BIOFEEDBACK TRAINING: A METHODOLOGICAL NOTE ALEXANDER DALE, DAVID ANDERSON, HERBERT KLIONS, A N D KIMBERLY TANE Allegheny College KIRK BLANKSTElN Universiiy of Toronto Swmmary.-The present study documented progressive reductions of electromyographic potentials in a biofeedback study involving instructions to 11 female and 5 male college srudents to both increase and decrease the feedback (and therefore the muscle tension). W h e n only pre-experimental baselines were employed. electrornyographic reductions were found with instructions to decrease the feedback. W h e n repeated, nontreatment baseline conditions were employed as references for analysis, no electromyographic reductions were detected beyond the progressive reductions chat occurred during those baselines.
Until recently, simple experimental models have been the rule in electromyographic (EMG) biofeedback research. For example, Alexander, French, and Goodman (1975) used independent groups and did not analyze treatmenc changes from an EMG baseline but directly compared differences in EMG levels berween treatment groups. They justified this approach by reporting that there was no difference between the groups in EMG baseline level prior to the experiment. Kinsman and Staudenmayer (1978) recognized that treating baseline data in EMG appropriately is important. However, they failed to point out the necessity of including a number of baselines throughout the treatment, not merely a single baseline before treatmenc is administered. The use of a single baseline can also be seen in the recent work of Ohno, Tanaka, Takeya, Matsubara, Kuriya, and Komemushi (1978) who subtracted pre-training baseline EMG levels from treatment levels and compared the groups on the difference scores. It should be noted, however, that biofeedback effects found using this method could be an artifact of decreasing muscle tension levels over. the course of the experiment. A more complex paradigm was used by Blankstein, Zimmerman, and Egner (1976) in research on heart rate. Their design made use of many nontreatment periods that could be used for reference prior to each trial. They found that pre-experimental baseline measures gave the impression that biofeedback helped subjects slow heart rates. However, when they made use of the multiple baselines the effect of slowing virtually disappeared. Blankstein, et nl. (1976) concluded that the slowing of heart rate was due to the general
MUSCLE TENSION IN BIOFEEDBACK
849
trend of decreasing heart rates over the course of the experiment. In contrast, the magnitude of the heart rate increases was made more evident when the multiple baselines were used. The authors of the present paper have collaborated in designing an experiment to test the hypothesis that the problems Blankstein, et al. (1976) report for research on heart rate are also to be found in electromyographic research. Therefore, the present scudy includes both pre-experimental baselines and nontreatment periods during the course of the experiment (these latter to be referred to as running baselines). Eleven female and five male undergraduite normal subjects participated in two sessions. Subjects sat in an experimental room in a comfortable chair wich eyes open. They were monitored for electromyographic potentials over the frontalis muscles with Beckman silver silver chloride eleccrodes and Redux abrasive electrode cream via a Grass 7P3B amplifier and integrator (lower '/zamp filter set at 1 Hz and upper Yz-amp filter for integrated output set at 75 Hz, 60-Hz filter engaged). Auditory feedback in the subject's earphone was produced by using the integrator's voltage to drive a Couibourn voltage controlled oscillator (VCO) that responded to high EMG levels with a high pitch and low levels wich low picch. The VCO stream was counted by a PDP 8/e05 computer and converted to an'EMG index (VCO count per 700 msec./143). The EMG index was therefore directly proportional to the feedback tone and the EMG potentials. The computer was also used to control trial and intercrial intervals and tape-recorded instructions delivered via earphones. Each subject received instructions prior to the experiment to "not consciously move their muscles to manipulate the feedback." Each subject participated in two sessions of 13 crials that averaged 2 min. k 1 min. separated by 30-sec. intertrial instruction periods. The trials involved instructions to rest and ignore feedback ( R ) , to increase che pitch of the tone, and to decrease the picch of the tone. The design was counterbalanced to reduce any linear order effects; rest ( R1) , increase, rest (R- ) , decrease, decrease, resc ( R : , ) , increase, increase, rest (R, ) , decrease, decrease, resc ( R : ), increase. Therefore, subsequent analyses of variance employ one berween-subjects variable (sex) and three within-subjects variables (instructions, trials, and sessions). Subjects increased the muscle tension during the Increase Condition. They had significantly higher EMG difference scores in the Increase Condicion than the Decrease Condicion whether pre-experimental ( R I ) baselines or running R A ) / 2 or (R4 R6)/2] were subtracced from trial indices baselines [ ( R 2 .01; running baselines F1.14= (pre-experimental baseline F1,14 = 26.67, p 28.15, p .01). Interpretation of relaxation in the Decrease Condition is complicated by the observation of greater decreases in difference scores when the pre-experi-
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@ Perceptual and Motor Skills 1979
BIOFEEDBACK A N D RELAXATION EFFECTS I N ELECTROMYOGRAPHIC BIOFEEDBACK TRAINING: A METHODOLOGICAL NOTE ALEXANDER DALE, DAVID ANDERSON, HERBERT KLIONS, A N D KIMBERLY TANE Allegheny College KIRK BLANKSTElN Universiiy of Toronto Swmmary.-The present study documented progressive reductions of electromyographic potentials in a biofeedback study involving instructions to 11 female and 5 male college srudents to both increase and decrease the feedback (and therefore the muscle tension). W h e n only pre-experimental baselines were employed. electrornyographic reductions were found with instructions to decrease the feedback. W h e n repeated, nontreatment baseline conditions were employed as references for analysis, no electromyographic reductions were detected beyond the progressive reductions chat occurred during those baselines.
Until recently, simple experimental models have been the rule in electromyographic (EMG) biofeedback research. For example, Alexander, French, and Goodman (1975) used independent groups and did not analyze treatmenc changes from an EMG baseline but directly compared differences in EMG levels berween treatment groups. They justified this approach by reporting that there was no difference between the groups in EMG baseline level prior to the experiment. Kinsman and Staudenmayer (1978) recognized that treating baseline data in EMG appropriately is important. However, they failed to point out the necessity of including a number of baselines throughout the treatment, not merely a single baseline before treatmenc is administered. The use of a single baseline can also be seen in the recent work of Ohno, Tanaka, Takeya, Matsubara, Kuriya, and Komemushi (1978) who subtracted pre-training baseline EMG levels from treatment levels and compared the groups on the difference scores. It should be noted, however, that biofeedback effects found using this method could be an artifact of decreasing muscle tension levels over. the course of the experiment. A more complex paradigm was used by Blankstein, Zimmerman, and Egner (1976) in research on heart rate. Their design made use of many nontreatment periods that could be used for reference prior to each trial. They found that pre-experimental baseline measures gave the impression that biofeedback helped subjects slow heart rates. However, when they made use of the multiple baselines the effect of slowing virtually disappeared. Blankstein, et nl. (1976) concluded that the slowing of heart rate was due to the general
MUSCLE TENSION IN BIOFEEDBACK
849
trend of decreasing heart rates over the course of the experiment. In contrast, the magnitude of the heart rate increases was made more evident when the multiple baselines were used. The authors of the present paper have collaborated in designing an experiment to test the hypothesis that the problems Blankstein, et al. (1976) report for research on heart rate are also to be found in electromyographic research. Therefore, the present scudy includes both pre-experimental baselines and nontreatment periods during the course of the experiment (these latter to be referred to as running baselines). Eleven female and five male undergraduite normal subjects participated in two sessions. Subjects sat in an experimental room in a comfortable chair wich eyes open. They were monitored for electromyographic potentials over the frontalis muscles with Beckman silver silver chloride eleccrodes and Redux abrasive electrode cream via a Grass 7P3B amplifier and integrator (lower '/zamp filter set at 1 Hz and upper Yz-amp filter for integrated output set at 75 Hz, 60-Hz filter engaged). Auditory feedback in the subject's earphone was produced by using the integrator's voltage to drive a Couibourn voltage controlled oscillator (VCO) that responded to high EMG levels with a high pitch and low levels wich low picch. The VCO stream was counted by a PDP 8/e05 computer and converted to an'EMG index (VCO count per 700 msec./143). The EMG index was therefore directly proportional to the feedback tone and the EMG potentials. The computer was also used to control trial and intercrial intervals and tape-recorded instructions delivered via earphones. Each subject received instructions prior to the experiment to "not consciously move their muscles to manipulate the feedback." Each subject participated in two sessions of 13 crials that averaged 2 min. k 1 min. separated by 30-sec. intertrial instruction periods. The trials involved instructions to rest and ignore feedback ( R ) , to increase che pitch of the tone, and to decrease the picch of the tone. The design was counterbalanced to reduce any linear order effects; rest ( R1) , increase, rest (R- ) , decrease, decrease, resc ( R : , ) , increase, increase, rest (R, ) , decrease, decrease, resc ( R : ), increase. Therefore, subsequent analyses of variance employ one berween-subjects variable (sex) and three within-subjects variables (instructions, trials, and sessions). Subjects increased the muscle tension during the Increase Condition. They had significantly higher EMG difference scores in the Increase Condicion than the Decrease Condicion whether pre-experimental ( R I ) baselines or running R A ) / 2 or (R4 R6)/2] were subtracced from trial indices baselines [ ( R 2 .01; running baselines F1.14= (pre-experimental baseline F1,14 = 26.67, p 28.15, p .01). Interpretation of relaxation in the Decrease Condition is complicated by the observation of greater decreases in difference scores when the pre-experi-
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