Many professional groups use biofeedback for neuromotor rehabilitation, autonomic regulation, psychotherapeutic treatment, pain management, and treatment of vascular problems. In recent years, insurance reimbursement for biofeedback as a separate billing entity in the fields of physical and occupational therapy has diminished. This unfortunate limitation has also restricted reimbursement for home rental units, with the exception of some specific uses. Despite these limitations, biofeedback continues to offer some unique solutions in the management of hand injuries. The value of biofeedback is that it can provide specificity of effort, quantified measurements, outcome criteria, transfer of training effect, and mechanism of action.
In addition, biofeedback can be used as a vehicle to inform the clinician about changes in muscle physiologic activity and levels of muscle activation, from which decisions regarding further instruction, manual contacts, patient positioning, or amount of resistance to elicit a better response can be made.
The purpose of this chapter is to familiarize the therapist with three types of biofeedback used for the hand-injured individual: electromyographic, thermal, and electrokinesiologic biofeedback. Each has special indications and techniques. When used appropriately, biofeedback can assist in the rehabilitation of upper extremity function.
Basmajian defined biofeedback as a technique of using equipment (usually electronic) to reveal to people some of their internal physiologic events (normal and abnormal), in the form of visual and auditory signals, to teach them to manipulate these otherwise involuntary or unfelt events by manipulating the displayed signals. Unlike conditioned responses, a human being must want to voluntarily change the signals because he or she desires to meet some goal. Biofeedback provides avenues to enhance patient motivation and performance and to yield objective data to evaluate treatment effectiveness and efficiency. In addition, clinicians can use the information to alter interactions with their patients.
Electromyographic Biofeedback
Historical Background
Biofeedback emerged in the 1920s from the fields of psychophysiology and electronics. Initially, electromyography (EMG) was used only as a diagnostic test to determine neuromotor function. Only later would EMG activity be applied to patient treatment techniques as biofeedback, a term coined at a 1969 meeting of the Biofeedback Research Society. In the development of EMG as a diagnostic test, Adrian and Bronk, in 1929, demonstrated that the electrical functions in muscles accurately reflected the functional activity of muscles. Smith further clarified EMG signal accuracy through evidence that there is little inherent EMG signal in motor units. This means that the signal monitored will be related to the goal of either muscle facilitation or relaxation and not to background EMG signal noise.
As scientists became assured of the accuracy of EMG measurements when using indwelling needle electrodes, treatment applications of the measurement of motor-unit activity emerged. Over a 20-year span, beginning in the 1950s, Basmajian developed what would become known as biofeedback application principles. Much recognition needs to be given to Basmajian, who has been called the father of EMG biofeedback. His works provided the foundation that has given the field of medicine a valuable adjunct in the restoration and reeducation of neuromotor and musculoskeletal function.
Many studies have been conducted and instructional articles have been written on the use of EMG biofeedback for muscle reeducation, including use in sports performance, muscle strengthening, and relaxation. To serve as a small select sample, these papers support * and outline the limitations of biofeedback. From a theoretic perspective, learning theories, and in particular operant conditioning, continue to be explored as a basis for the success of biofeedback as a clinical tool. Bruckner and Bulaeva identified studies that did not use operant conditioning (e.g., goal setting) in EMG biofeedback. They stated that the reason some studies did not show benefits with biofeedback was because appropriate shaping was not used. In the field of pain management, reduction of pain may result from not only reduction of muscle activity, but also from cognitive variables such as increased self-efficacy resulting from the success in biofeedback tasks.
* References .
The treatment and research applications of biofeedback have continued to grow within many separate fields. In 1969, the Biofeedback Research Society (now known as the Association for Applied Psychophysiology and Biofeedback ) was formed as a source for communication and certification in biofeedback principles. The historical development and research on EMG biofeedback have created a solid foundation on which the strategies for the use of biofeedback are anchored.Purpose and Strategy
EMG biofeedback monitors activity in skeletal musculature. The activities actually monitored are the outputs from the peripheral nerves across the neuromuscular junction to the motor endplate in the muscle. These impulses cause muscle fibers to contract by eliciting motor-unit potentials. The electrical changes from ionic membrane activity are detected through surface electrodes and relayed to the EMG amplifier. The activity of the muscle is translated into visual and auditory signals and is displayed to give the patient increased awareness of skeletal muscle function.
Based on Basmajian’s research demonstrating that a person could gain control over a single motor unit, contemporary use of EMG biofeedback with hand-injured individuals focuses on gaining control of as many motor units as possible, either to restore functional coordinated movement or to facilitate muscular relaxation. The theory supporting motor-unit training is based on the notion that some type of sensory feedback mechanism must reinforce voluntary effort. Simard and Basmajian state that, “The quality of a motor response is governed by the quality of perception of sensations.” According to Abildness, “EMG biofeedback signals can substitute for inadequate proprioceptive signals by shaping responses more sensitive than the signals generated by a therapist’s observation.”
For the hand-injured patient specifically, EMG biofeedback is used for muscle facilitation, relaxation, or a combination of the two, such as in situations when muscular cocontraction occurs. Patients who could benefit from EMG biofeedback intervention include those with amputation, arthritis, crush injury, fracture, focal dystonia, overuse disorders, pain disorders, peripheral-nerve injury, pollicization, reflex sympathetic dystrophy (RSD), replantation, spinal cord injuries, tendon laceration with subsequent repair, tenolysis, tendon transfer, and toe-to-thumb transfer. Individuals with central nervous system disorders also can benefit from EMG biofeedback.
Strategies and Guidelines
In using EMG biofeedback, clinicians and researchers have noted that a patient initially relies on the visual and auditory cues to condition the random attempts at muscle control. This process then progresses to controlled initiation of a movement or motor response. Brundy notes that with biofeedback, “retention persists even after withdrawal of sensory feedback, suggesting that new sensorimotor integration is taking place as a result of such therapy.”
To learn to control a muscle, a patient must have at least a few functioning motor units in the muscle monitored. Initial and routine EMG and nerve conduction studies to assist treatment planning for muscle reeducation is helpful.
The patient also must understand the link between the biofeedback signals and his or her own muscle activity. This understanding is not difficult—even small children can learn the connection quickly. To facilitate the understanding, electrodes may be placed first on the uninjured extremity to demonstrate the connection between muscle activity and the display signals. Training can also be undertaken using a procedure called motor copy. Using this approach allows the output from one muscle to be matched or “copied” by the output of the less affected homologous muscle of the other upper extremity. Shaping is accomplished through controlling the gains or sensitivities of each channel separately.
In 1984, Ince, Leon, and Chrisidis found that continuous feedback is more effective than intermittent feedback. In addition, the least amount of delay between patient output and machine display of visual or auditory signals is desired. However, some assumptions, in particular how often to provide the patient with the results, have been challenged. In fact, in the absence of knowing comprehension levels of patients, fatigability, or a host of other important variables, the optimal intensity and timing of feedback simply is not yet known. Thus, the purposes of EMG biofeedback span a spectrum of uses and disorders. Specific strategies to enhance the likelihood of success involve assessing the patient for his or her potential to benefit from biofeedback and then presenting the tool in a manner that can be understood easily and used independently.
EMG Biofeedback Equipment
To obtain maximum benefit from biofeedback, the clinician must be aware of the variety of equipment that is currently marketed and must then make a choice based on the purpose of the intervention. The Association for Applied Psychophysiology and Biofeedback provides sources that give complete descriptions of the components and terms associated with biofeedback equipment. Available equipment ranges from portable single-channel units to computerized component systems with multiple physiologic sign monitoring. Regardless of the type of machinery, the equipment should be tested intermittently on a normal individual to ensure that it provides feedback proportionate to and consistent with the measured physiologic response.
Most types of EMG biofeedback equipment have four basic component parts :
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Transducer or sensing elements: The electrodes sense the electrical potential of the ionic membrane activity of muscle fibers.
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Amplifier: These components enlarge the signal for subsequent processing.
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Integrator: This component allows processing and quantification of the signal as well as the timing of the delivery of a visual and/or auditory representation of that signal.
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Output displays: These audiovisual elements can be light series, graphic displays, or tones, or can be attached to other electrical equipment.
Surface electrodes are used for clinical EMG biofeedback. The electrode functions as a transducer. It senses the ionic membrane activity of muscle fibers as an electrical potential, which is carried to the amplifier near the electrode or within the biofeedback unit. Electrodes range in diameter from 5 to 15 mm ( Fig. 109-1 ).
The amplifier is the main housing of the biofeedback unit. Here the range of microvolt activity can be enlarged across a series of ranges or scales. These scales display the upper and lower levels of voltage recorded and often are broken into various subcomponents. This arrangement enables the patient, who is reactivating only a few motor units, to work in a high-sensitivity range (from 1 to 10 mV), whereas a patient with greater muscle activity can work in a less sensitive range (from 10 to 100 mV). The range level will vary among biofeedback units ( Fig. 109-2 ) and is displayed so that the patient can successfully work with the feedback. One effective way of interfacing biofeedback with the patient is to periodically remove the visual and auditory cues and use the “freeze” or “stationary” mode of the feedback device. In this situation, the patient is asked to visualize when he or she thinks his or her peak EMG level has reached a target or goal (also called threshold ) on the screen and to tell the clinician as rapidly as possible when that level is achieved. At that precise point, the clinician hits the freeze key, which stops the processing and allows the patient to see subsequently just how close to the actual target level he or she had come. This form of periodic feedback withdrawal and target estimation allows the clinician and patient to comprehend just how much improvement is based on the transition of dependence on exteroceptive cues to proprioceptive cues because the patient would have to rely on a feeling of muscle length changes or effort.
The goal toward which the patient works is determined by output displays. These displays typically are revealed as audio and visual modes. Output displays vary with the type of machinery chosen. The visual displays can be line graphs on a video display monitor, meter deflection, oscilloscope, pen recordings, and light series ( Fig. 109-3 ). Audio feedback can be tones or clicks. Some biofeedback units can be used as bioconverters so that electrical appliances can be run after the patient achieves the goal set. This functional output can be especially motivating for children.
Contemporary EMG Monitoring Equipment
Considerable improvements have been made in clinical EMG biofeedback instruments in the past decade. The devices are more versatile and less expensive, the electronic components and software are relatively sophisticated, and the operating menus (often a source of intimidation to rehabilitation clinicians) are more simplified. The magnitude of memory in these machines now permits training, and storage of acquired data (including, if desired, actual EMG representations of training sessions) has increased exponentially. Therefore information can be retrieved easily and displayed in any of a variety of formats that are comprehensible by other clinicians or third-party payers. The improved electronics, including impedance matching capabilities, no longer require the intensity and time necessary for skin preparation. Furthermore, given the growing appreciation for the complexity with which human skeletal muscles are organized, there is some question about the need for precise surface electrode placement orientation. In short, the time necessary to prepare a patient and acquire data is not that profound and the magnitude of information gathered can be important. In addition, the growth of using alternative medicine (including biofeedback) has made the public more interested in and responsive to these alternatives. Awareness of muscle activity has become important to patients, and the revelation that “awareness of activity” can lead to integration of movement within function lends new appreciation for biofeedback.
Clinical Applications
After the proper equipment is selected, the following steps are taken:
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Preparing the skin and placing the electrode
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Positioning the patient
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Establishing a baseline
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Training techniques for muscular facilitation and relaxation
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Reevaluating the training
Preparing the Skin and Placing the Electrode
Clinical application of EMG biofeedback uses surface electrodes even though research applications may use indwelling needle electrodes. When surface electrodes are being used, the skin may need to be prepared to remove the superficial layer of dead skin and oils, which causes impedance to good electrical monitoring. The skin is scrubbed with an alcohol pad until the skin slightly reddens. The skin must be dry before the electrodes are applied. If high impedance is evident, it may be necessary to reapply the electrodes and wait 10 minutes. If hair is present on the skin surface of the area monitored, shaving the hair will improve the electrical contact. In addition, rubbing a small amount of conductive gel onto the skin at the electrode site will improve the monitoring. Placement of electrodes on bony prominences, scarred areas, and fatty areas should be avoided, if possible.
There are two active (reference) electrodes and one inactive (ground) electrode with EMG biofeedback. Conductive gel must be applied to the electrode’s surface or sponge covering before it is attached to the patient’s skin, or pregelled electrodes must be used. The two active electrodes are most often placed parallel to the muscle fibers. When there is a large distance between the active electrodes, more muscle activity will be recorded. Placing the two electrodes at opposite ends of the muscle belly may be necessary to monitor trace muscle contractions. However, the possibility of inaccurate readings is increased when the electrodes are widely spaced because the volume-conducted activity becomes nonspecific. A shorter distance between the active electrodes provides more accurate muscle-activity readings and may limit the possibility of unintentionally monitoring neighboring muscles. The electrodes may be placed adjacent to each other, but then the patient must recruit a very strong muscle contraction to obtain feedback. Often, this approach is desirable if specificity of training is the primary goal of treatment. In our clinical experience, placement of active electrodes on the forearm muscles 2 cm apart is effective for most patients. The distance between electrodes should be consistent among subsequent sessions if comparative data are collected. The ground electrode is used to decrease electrical artifact and is applied to the patient’s skin before the active electrodes. Sources differ regarding the best placement of the ground electrode. The ground electrode is often placed between or equidistant from the two active electrodes ( Fig. 109-4 ). Once used, if the electrode is not disposable, it must be cleaned completely to prevent conductive-gel buildup. The larger the size of the electrode, the less impedance it produces. However, in hand rehabilitation, the small-sized electrode often is needed for accuracy with electrode placement so that adjacent muscles will not be monitored; skin preparation must be thorough to compensate for the higher impedance with the use of small electrodes. Refer to Kasman, Cram, and Wolf for more detailed information on electrode placements.
The lumbricals and interossei (with the exception of the first dorsal interosseous) cannot be monitored accurately with surface electrodes. In these cases, goniometric feedback is considered a superior treatment intervention. The thenar and hypothenar muscles can be monitored if the electrodes are placed carefully.
Positioning the Patient
The treatment environment should be quiet and free of distractions. This situation is especially true when the patient is working on muscle relaxation. Patients are given a thorough explanation of the process and rationale of biofeedback before treatment is initiated. Biofeedback can be used when active range of motion (AROM) is allowed. The patient’s upper extremity is placed in a position in which the monitored muscle can function optimally. For a muscle graded zero to poor, the patient is placed in a position where gravity is eliminated for that muscle. Muscle function is usually optimal when the muscle is elongated, and the patient is asked to attempt a contraction of the muscle through its full range of motion (ROM). If substitution occurs, placing the extremity in the desired position and asking the patient to hold the position may facilitate use of the appropriate muscle.
Establishing a Baseline
The sensitivity range (low to high) of microvolt activity is set on the amplifier as the patient attempts initial trials to contract or relax a muscle. Some biofeedback units have choices of fixed ranges, whereas other units offer an ability to choose any size range of muscle activity to be monitored. The goal is then set at the midpoint of the range. During the biofeedback session, the patient should be able to reach the goal for at least 50% of the trials.
The assessment of motor behavior during biofeedback sessions should consider four variables:
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Frequency: the number of times a response is performed
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Duration: the length of time a response is maintained (i.e., endurance)
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Intensity: the magnitude or strength of the response
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Latency: the amount of time until a response is performed
The component of motor activity that a therapist chooses to monitor depends on the patient’s presentation. For example, if the patient displays disuse atrophy and is recruiting only a few motor units, intensity and frequency are the most important elements to monitor. When a patient is learning to activate a tendon transfer, the duration and latency are the most important initial foci. These variables can be documented manually, or data can be analyzed from computer printouts when computerized equipment is used.
After baseline measurements are documented, the patient and therapist have a basis for determining the effectiveness of selected treatment techniques. As noted, all treatment sessions should incorporate several efforts at determining patient accuracy in achieving target output levels in the absence of feedback.
Training Techniques for Muscular Facilitation
Muscular facilitation or reeducation is indicated when patients display minimal active contraction with an identified muscle or muscle group. Causes of these upper extremity muscle disorders may be disuse atrophy, focal dystonia, nerve laceration or compression, pain, scar adherence, a patient’s inability to isolate a specific movement because of cocontraction of the antagonist muscle, or substitution of other muscles performing inefficient joint motion (i.e., finger extensors substituting for wrist extension). The goal of reeducation is for the patient to reactivate voluntary control of the muscle. Brown and Nahai state, “EMG biofeedback is not a muscle strengthener as much as it is an aid in reeducation. By gaining more appropriate feedback the patient can then work on strengthening his muscles.”
When the patient is working with a weak muscle, the intensity of the motor-unit activity and the frequency of the muscle contraction are emphasized initially. The active electrodes may be placed further apart to obtain pickup from a larger volume of muscle. Treatment sessions should be short and should end when fatigue is noted by the patient’s decreasing ability to achieve the set goal level. Rest periods lasting 30 seconds between 10-second muscle contractions are recommended. The patient should be working within a microvolt range that is challenging enough such that the recorded muscle activity does not consistently exceed 75% of the total range.
Case Example
The patient sustained a median-nerve laceration and multiple flexor tendon lacerations at zone V. The tendons and nerve were repaired with microsurgical technique. At 10 weeks after surgery, no muscle activity could be elicited from the abductor pollicis brevis (APB) or opponens pollicis muscles in the thumb. When trace (grade 1 of 5) muscle strength was observed, the electrodes were placed on the APB, and EMG biofeedback training was initiated to facilitate active control of the muscle. The initial range was set at 0 to 35 mV, with a goal of 20 mV. The patient attempted place and hold muscle contractions for 10 seconds and rested for 30 seconds. At the third session, the range and goal were increased. As the patient’s APB strength increased to fair (grade 3 of 5), activities, such as grasping around a glass and turning coins, were monitored with biofeedback to increase muscle activity during functional tasks ( Fig. 109-5 ).
Case Example
Muscular cocontraction can occur often after an upper extremity injury. The patient develops a motor pattern of contracting the muscle or muscle group antagonistic to the desired action. In other instances, there is a substitution of other muscles, resulting in inefficient joint motion. Such maladaptive motor patterns can be seen after tendon repair, tenolysis, in overuse disorders, and in RSD. A biofeedback machine with two input channels can be an effective treatment intervention when one is attempting to decrease abnormal muscle cocontraction ( Fig. 109-6 ). The patient then can observe the level of activity in the opposing muscle group as he or she attempts to activate the desired muscle.
Four weeks after flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) repair for digits II and III at zone II, the patient began active finger flexion exercises. With flexion attempts, the patient could not obtain active flexion even with the uninjured digits. EMG biofeedback electrodes were placed on the extensor digitorum communis (EDC) and the FDS. As the patient attempted active flexion, the EDC level of contraction was two times higher than the FDS. A series of exercise techniques were attempted while the levels of muscle contraction were monitored. With place-and-hold exercises and light dowel squeezing, the level of EDC contraction decreased. The patient was instructed to increase the intensity of flexor muscle activity only if the EDC activity remained at a minimum. Biofeedback monitoring was discontinued after seven sessions when the patient was able to initiate composite flexion with minimal EDC muscle contraction. This case example points out that control must be learned before strength is emphasized.
Apart from case examples, as the patient gains muscle strength, he or she is encouraged to sustain the muscle contraction for a longer period to work on endurance. The range and goal can then be increased. If the patient has difficulty recruiting the muscle activity initially, several conjunctive treatment techniques may be used to facilitate muscle function. For example, the patient may be able to hold the shortened position of the muscle action after the therapist places the extremity in the desired position (i.e., place-and-hold exercises). The therapist can slowly carry the patient’s extremity through desired motion as the patient attempts to perform the muscle action. Muscle facilitation techniques as described by Brunnstrum and Rood also can be used, including tapping over the muscle belly or resisting the opposite extremity in the desired motion. However, in these situations, considerable care must be taken to ensure that movement artifact does not develop while instituting these procedures. This artifact could result in spuriously high and transient increases in muscle responses, sensed by the microprocessor as motor activity rather than external, nonphysiologic events.
Training Techniques for Muscular Relaxation
Muscular relaxation techniques can be used in the presence of abnormally increased muscle activity. This increase in muscle activity is seen during guarding one or more joints of an extremity. Even before the EMG monitoring is started, patients often are asked to listen to a relaxation tape to facilitate a decrease in overall muscle tension. The training strategies initially involve patients actively contracting and then relaxing the muscle with increased activity. As patients understand the process, specific relaxation training begins. If one set of electrodes is used, the pair is placed on the muscle that the patient needs to relax. In some cases, two sets of electrodes may be used to monitor both the muscle that needs to be relaxed and its antagonist. Patients attempt to maintain a low level of microvolt activity with the limb at rest. As this level of rest is accomplished, the patient attempts to move the opposing muscle group while maintaining a low level of microvolt activity in the muscle with increased tension.
The therapist should be aware that eccentric muscle activity also would be monitored through EMG biofeedback. What may appear as increased muscle concentric contraction could, in reality, be the monitoring of an eccentric contraction. The eccentric contraction tends to be displayed by the biofeedback unit as a low and constant level of microvolt activity, whereas the concentric contraction displayed by the unit tends to have a quality of spiking integrals of motor-unit activity. As the patient learns how to use biofeedback and benefits from it, reevaluation of progress and subsequent modification of the biofeedback program should be undertaken.
Case Example
The patient, a computer operator and amateur pianist, described a 10-year history of progressive muscle pain in the forearm extensor muscle mass in both upper extremities. The discomfort limited his ability and duration of piano playing. EMG, nerve conduction, and magnetic resonance imaging (MRI) tests were normal. Muscle weakness was noted in scapular stabilization muscles, lumbricals, and interossei. EMG biofeedback was applied to the EDC as the patient attempted lumbrical strengthening, and he was instructed to keep the biofeedback signal low. As lumbrical strength improved, he attempted the same goal while placing fingers on the keys of the piano. Over the next 8 months, as scapular stabilization musculature and lumbrical strength improved, the overuse of the EDC and associated muscular pain diminished.
Reevaluating the Training
The measurements of frequency, duration, and latency can be compared between sessions. Thus EMG biofeedback provides measurable data to assess the effectiveness of the treatment intervention. Use of clinical tests such as ROM, manual muscle testing, dynamometer testing, and coordination testing to provide a view of biofeedback’s effect on the patient’s functional abilities are also important.
The intensity levels of microvolt activity may be compared at the beginning and end of each biofeedback session. In our clinical experience, a 10% improvement in microvolt activity seen with one session justifies continued use of this treatment modality. A comparison of intensity levels between sessions should be avoided. Varying electrode placements and skin preparation between sessions may result in different baseline microvolt activity. The maximum microvolt activity may appear to be higher in one session if the baseline resting microvolt activity was high during that session.
If EMG biofeedback has been effective in clinic treatment, using biofeedback on a home program basis is appropriate. Using rental units or teaching the patient the area to palpate where muscle activity can be felt are ways to facilitate carryover outside clinical treatment time.
In response to reevaluation findings, EMG biofeedback programs can be modified to more effectively and efficiently enhance patient function. At this time in the evolution of rehabilitation services, use of EMG monitoring can be beneficial provided this activity is quantified and related to measurable changes in functional tasks that involve the impaired musculature.
EMG Biofeedback: Additional Perspectives
There may be situations in which the sequencing of facilitation for one muscle group and inhibition of another muscle group may not be clear-cut, and the hand therapist must consider the attitudes and behaviors of patients in planning the best treatment strategy. For example, Cannon and Strickland have observed that after tendon repairs, real or anticipated pain might affect movement capabilities profoundly. Thus, in patients who anticipate pain in attempting finger flexion exercises to increase mobility, using EMG biofeedback to relax the tense wrist and finger extensors might be far more productive than driving output to the finger flexors in the presence of “guarding” precipitated by anticipated discomfort. Seeing low levels of extensor activity during flexion efforts might suffice to increase movement. Alternatively, for patients without pain, simply providing feedback from finger flexor muscles (reference electrode just proximal to the distal palmar crease [DPC] and to the ulnar side of the flexor carpi radialis or palmaris longus, and ground electrode more proximal) might augment AROM.
In a report offered by Hirasawa, Uchiza, and Kusswetter, EMG biofeedback has proven successful in five patients who had repairs of lacerated extensor pollicis longus tendons. Electrode placements oriented toward the tendon just proximal to the dorsum of the wrist joint or just proximal to that location, but aligned longitudinally toward the middle digits, permit recording of thumb and finger extensor activity. Extension lag of the thumb, functional use, strength, and ROM all were improved. A far more unique use of EMG biofeedback has been offered in teaching piano performance, where feedback is used for the APB muscle activity during specific piano playing activities. The group that received feedback was able to increase peak muscle output and improve relaxation times significantly more than the group that did not receive this form of training.
Recently, Deepak and Behari reported considerable success in using EMG biofeedback for patients with hand dystonia. To down-train hyperactive responses among 13 patients, muscle selection was based on the most elevated EMG response during writing activity compared with normal activities in the impaired limb. Many proximal muscles were monitored concurrently during the training sessions. Variable numbers of treatment sessions were provided for the 10 patients who completed the program. Interestingly, the target muscle was predominantly the triceps or brachioradialis. Nonetheless, 9 of 10 patients improved their pain rating by 50% and handwriting samples demonstrated profound differences. The unique aspect of this approach was to train proximal muscles rather than distal muscles, most notably the ulnar or radial deviators.
There is little doubt that “repetitive use syndrome” is attracting attention in the clinical arena, especially among keyboard operators and machinists. A recent report places a different twist on the application of EMG feedback for such patients. Barthel et al. demonstrated that 24 patients who were recalcitrant to conventional treatment for repetitive use syndrome improved in pain symptoms and hand use after a comprehensive treatment program not previously instituted. Among the components was EMG biofeedback both for general relaxation training and in the context of occupational workplace simulations and job-site evaluations. In these circumstances, patients were shown how muscles could be used with less effort.
Not all applications of muscle feedback for hand-related impairments have revealed favorable outcomes, however. Kohlmeyer et al. could not demonstrate that muscle feedback produced a more favorable improvement in strength or activities of daily living among 45 patients with tetraplegia assigned to conventional strengthening programs, electrical stimulation procedures, biofeedback, or biofeedback with electrical stimulation. All patients showed improvement, but the magnitude of difference was not significant between treatment approaches. Feedback was provided to the extensor carpi radialis for 20 minutes each weekday for 5 to 6 weeks, with instruction to increase output. This approach highlights the need to perform more detailed assessment of patients such as these before biofeedback-based treatments are instituted. In the absence of more detailed evaluation, a more logical approach might have been to undertake concurrent down-training of flexors (flexor carpi radialis and/or ulnaris) with up-training of what apparently were the wrist extensor and radial deviator groups. Had patients shown cocontraction efforts during attempts to engage very weak muscles, this approach might have led to more substantial gains in movement.
A bold effort to apply EMG biofeedback in the workplace has been reported by Thomas et al. for patients with carpal tunnel syndrome. In this study, subjects were trained to place electrodes on wrist flexor and extensor muscles during working situations. The instruction was to avoid deviating the hands “significantly” from neutral and to minimize “excessive” forces through the fingers. The feedback group did not show changes in nerve conduction velocity or subjective discomfort levels that differed from the control group, and their grip strength was less. This study emphasizes the importance of bringing measurements and training “on-line” in the workplace while also requiring that clinicians be aware of how feedback training is to enact. Here the instructions were remarkably vague, and the rationale for their institution never was explained in terms of kinematic or kinetic principles. The reduced levels in grip among the biofeedback group was not surprising in light of their instruction not to pinch excessively. Another option in approaching this situation would have been to select a muscle group more carefully and instruct subjects about what levels to achieve in the context of task-specific use of the muscle. Alternatively, subjects could have been taught to down-train more proximal muscles in the hope of relaxing distal muscles that presumably were hyperactive and contributory to the carpal tunnel symptoms.
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