Treatment Parameters of High Frequency Electrical stimulation as Established on the Electro-Stim 180

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1 /83/ $02.00/0 THE JOURNAL OF ORTHOPAEDIC AND SPORTS PHYSICAL THERAPY Copyright by The Orthopaedic and Sports Physical Therapy Sections of the American Physical Therapy Association Treatment Parameters of High Frequency Electrical stimulation as Established on the Electro-Stim 180 JEFF OWENS, BS,* TERRY MALONE, MS, PT* Copyright All rights reserved. Tremendous interest has developed regarding the use of electrical stimulation in both treatment and strengthening regimens. The Electro Stim 1 80 (Numed, Joliet, IL) is manufactured in Canada and imported into the United States. This unit functions at 2500 cycles per second with output similar to that developed by a Russian electrical stimulation device. A paucity of treatment parameters exists regarding this apparatus. Fifteen normal subjects participated in this study to establish treatment parameters in an exercise regimen. All subjects (mean age, 24) were pretreated isometricly and isokineticly in knee extension bilaterally using a Cybex I1 (Cybex, Ronkonkama, NY). The subjects were divided into three groups with group one receiving stimulation each day during a 10-day period and group two receiving stimulation on alternate days of a 10-day period, while group three served as a control. All treatment sessions consisted of 10 isometric contractions of 15 seconds duration, interspaced with 50 seconds of rest. Current was applied as tolerated to the left knee extensor mechanism during each trial. Current accommodation, strength of generated contraction, other associated treatment effects and strength differences were recorded. It was concluded that the Electro- Stim 180 is capable of generating greater than 60% of the maximal isometric voluntary knee extension, that stimulation is somewhat unpleasant, and that a tremendous degree of current accommodation is possible. Although strength gains were not significnt in this particular study, they approached significance and, hence, indicate the need for further study in this area. In lecture notes from the 1977 Canadian-Soviet Exchange Symposium on Electrical Stimulation of Skeletal Muscles, Dr. Kots of the USSR described treatment techniques and expectations concerning the use of high frequency electrical stimulation. Included in his lectures were techniques for the reduction of pain, edema, gains in muscular strength and endurance, and pain-free muscular contractions in excess of maximal voluntary effort using high frequency electrical stimulation. It must be noted that limited documentation of methodology, procedures, and statistical analysis impedes the reproducibility of Dr. Kots' result^.^ Standish et al.3 examined the use of high frequency electrical stimulation in the prevention of atrophy in immobilized muscle. Two groups of six patients were immobilized following knee sur- * From The Physical Therapy Department, Indiana Central University, Indianapolis, IN gery for a period of 6 weeks. After 10 days of immobilization, one group received electrical stimulation at a 2500-hertz frequency, with each treatment consisting of second contractions. Onset time was 5 seconds and current was administered to tolerance to the knee extensor musculature. Following cast removal, both groups underwent rehabilitative exercise. Biopsies of the vastus lateralis muscle showed that the ATPase levels of the stimulation group increased slightly, whereas the ATPase levels in the control group decreased significantly. No change in muscular glycogen levels was noted. These findings are supportive of the work of other authors.' The Electro-Stim 180 is a high frequency electrical stimulator, manufactured in Canada and imported into the United States (Fig. 1). This unit functions at 2500 cycles per second involving 10 microseconds of stimulation followed by 50 microseconds of rest. This maintains a tetany within the muscle while decreasing the percep-

2 JOSPT Winter 1983 PARAMETERS OF ELECTRICAL STIMULATION 163 Copyright All rights reserved. tion of pain. This modulation pattern was most comfortable and, therefore, chosen for this particular stimulation device. Because a paucity of treatment parameters exists regarding this form of electrical stimulation, the purpose of this study was to develop treatment parameters regarding young, healthy adults. As this form of electrical stimulation is new to this country, verjt little reserch or treatment information regarding its use is available. That information which is available is quite limited in its scope and application. It must be emphasized that treatment of pathologic conditions may require different protocols and may not respond in a similar fashion. METHOD Fifteen normal subjects (nine males, six females, average age, 24) were selected for the study. Each subject was measured to determine thigh girth using a steel tape (approximately an inch and a half above the medial joint line). Subjects were tested for strength in knee extension bilaterally utilizing the Cybex II via three isometric contractions at 35' of knee flexion. Hip flexion was maintained at approximately 115" throughout the treatment and testing. The subjects were divided into three groups. Fig. 1. Nu-Med's TS-180 Fig. 2. Electrode placement

3 1 64 OWENS AND MALONE JOSPT Vol. 4, No. 3 Copyright All rights reserved. Group one received treatment for 10 consecutive days, group two received treatment on alternating days over the 10-day period, and group three served as a control. All muscular contractions were generated via the stimulation unit, at 35" of knee flexion, isometrically utilizing the left knee extensor musculature. The circular electrodes (4 inches in diameter) were placed over sponges moistened in tap water in a bipolar configuration with the first electrode over the left femoral triangle and the second electrode over the left vastus lateralis muscle (Fig. 2). This combination was secured with Velcro straps (Fig. 3). Treatment consisted of second stimulations which included a 3.5-second onset time. Each stimulation was interspaced with 50 seconds of rest. Current was increased as tolerated during the second, fourth, sixth, and eighth stimulation. All subjects were retested to determine strength of knee extension bilaterally using the same procedure as the pretest upon conclusion of their protocol after 10 days. RESULTS Current accomodation appeared to be greatest for group one (daily) during sessions nine and ten (day 9-1 O), while group two (every other day) appeared to have the greatest accommodation during treatment session number five (day 10). Group one presented the greatest overall current accommodation (Figs. 4 and 5). The range of current tolerated during the initial treatment ranged from 16 to 38 milliamperes. Milliamperage tolerated during the final treatment session ranged from 34 to 82 milliamperes. Maximal isometric muscular contraction elicited by the stimulation unit was determined during the last stimulation of treatment five for group one (daily) and during the last stimulation of treatment three for group two (every other day). Percentages of maximal contraction were determined by comparing the muscular contraction elicited by the unit to the initial maximal isometric muscular contraction. Average muscular con- Fig. 3. Final treatment position

4 JOSPT Winter 1983 PARAMETERS OF ELECTRICAL STIMULATION CROUP ONE-CURRENT ACCOrOlODATION Current (ma) Copyright All rights reserved. traction elicited by the unit for group one (daily) was 60% of maximum and the average muscular contraction for group two (every other day) was 39% of maximum. A wide range of variance was seen individually (Fig. 6). A two-tailed t test and an F test applied to final strength levels of all groups showed no significant strength gains (Fig. 7). It must be noted that muscular strengthening was not the primary thrust of the study, but rather a determination of treatment parameters that should be considered to elicit changes in strength readings. In addition, no significant group changes or girth changes were noted. All subjects treated with the unit reported that the stimulation was somewhat uncomfortable with the actual muscular contraction decreasing in intensity at the end of the stimulation period. It was obvious that accommodation to the unit allowed a decrease in the sensation of pain and an increase in the tolerance to stimulation. Indi- Fig. 4. Group one: average current accommodation viduals in group one reported general soreness at the negative electrode site, with one individual presenting a sympathetic pain reaction during the sixth treatment session period. This individual exhibited increased sweating, increased salivation, and complained of nausea following completion of the treatment session period. Eight of the 10 subjects stimulated with the unit also exhibited involuntary contralateral knee extension during stimulation during each treatment period. To further validate the output of the stimulation unit, an oscilloscope was used to demonstrate the actual output of the unit. Frequency was determined via examination of the output to be constant at 2500 hertz. Waveform was determined, through observation of the output, to be sinusoidal with a 0.2-millisecond pulse duration (Fig. 8). Maximum output obtained was 400 volts, as determined through the use of a voltmeter.

5 - 90. OWENS AND MALONE GROUP TWO-CURRENT ACCOM1.IODATION JOSPT Vol. 4, No. 3 80,, Current (ma) Copyright All rights reserved , _- 20. (26) / / (37.4) / % PRE_-TEST LEFT-ISSMQRIC M&X I ~ig L3.1"i' TREATMENT (26.8) Fig. 5. Group two: average current accommodation DISCUSSION./. (39.8) A 0 1 The tremendous interest regarding the use of I electrical stimulation in both strengthening and 1 73% injury rehabilitation regimens has primarily revolved around the Russian claims of its effective- I 63% ness. A problem of documenting Russian claims 1, 156% -, has involved the lack of suitable electrical stimulation devices able to duplicate the treatment 4 6% - parameters produced by their equipment. The Electro-Stim 180 purports to generate electro- 31% 33% galvanic stimulation similar to the parameters recommended by Russian authors. The paucity of treatment parameters severely limits the utilization of the unit presently. Examination of the waveform and frequency developed by the Electro-Stim 180 indicates consistency with specifications recommended by the Russians for the greatest effectiveness. I 'IL During treatment, it was determined that the 6. Table three: percentage of maxrmal voluntary con- Electro-Stim 180 is capable of generating traction attained via stimulation greater than 60% of the maximal isometric vol- / / /* (44.6) (34)

6 JOSPT Winter 1983 PARAMETERS OF ELECTRICAL STIMULATION 167 Copyright All rights reserved. e=lr A=nr Left Left Right Right Isokinet ic Isometric Isokinet ic Isometric TESTS - Fig. 7. Final values with 1 SD indicated Fig. 8. Waveform of TS-180 as shown via oscilloscope

7 168 OWENS AND MALONE JOSPT Vol. 4, No. 3 Copyright All rights reserved. untary knee extension contraction. A generally accepted figure of greater than 65% of maximum isometric contraction being required for strength gains is thus being approached. This indicates that further work in the area of strengthening regimens utilizing this unit are in order. All subjects indicated that the stimulations were somewhat uncomfortable. In an attempt to minimize pain, the positioning of the knee was dictated to be 35". This was predicated on the fact that this was determined to be less painful than numerous other positions through trial sessions. Although this position minimized the pain, it is notable that there is a degree of pain present and perceived by the individual with the use of this modality. Current accommodation increases during each treatment session as well as during the treatment protocols. The increased tolerance may be indicative of decreasing resistance, and thus facilitating an increased contraction. Current accommodation may also be related to the decreasing apprehension as the subject becomes familiar with the stimulation unit. CONCLUSIONS It was concluded that the Electro-Stim 180 is capable of generating greater than 60% of the maximal isometric voluntary contraction of the knee extensor mechanism. Although stimulation is somewhat unpleasant, a tremendous degree of current accommodation occurs that further enhances the possibility of utilizing the Electro- Stim 180 as a strengthening modality. Although significant strength gains were not found in the present study, strength gains were approaching the level of significance. In conclusion, it must be noted that the study is of a preliminary nature and that a longer treatment period with a larger sample size should be performed to further elucidate the future uses of the Electro-Stim 180. REFERENCES 1. Ericksson E, Haggmark T: Comparison of isometric muscle training and electrical stimulation supplementing isometric muscle training in the recovery after major knee ligament surgery. Am. J. Sports Med.. 7: Kots YM: Lectures and Laboratory Periods, Canadian-Soviet Exchange Symposium on Electrostimulation of Skeletal Muscles, Concordia University, December 6-1 5, Standish WD, Valiant G, Bonen A, Belcastro A: The Effects of Immobilization and of Electrical Stimulation on Muscle Glycogen and Myofibrillar ATP-ase. Paper presented at American Academy of Orthopedic Surgeons, 1981, Las Vegas. Material available from Numed Surgical/Dental Supply, Joliet, IL.