Dynamic Electromyography Research Articles

Efficiency of gait measurement after complex foot trauma

Summary Four different gait analysis techniques (three-dimensional kinematic analysis, two force plates, dynamic electromyography (EMG), dynamic analysis of plantar pressure distribution) were employed in a study on 10 normal subjects and 12 patients after treatment of displaced calcaneal fractures. The aim was to evaluate each method for accuracy of measurement of the severity of functional impairment. Analysis of ankle joint kinematics revealed that the loss of motion after trauma at the subtalar joint (range of motion after injury 2.9±2.0°, normal subjects 7.5±2.6°) was compensated by an increased inward rotation of the foot. If the foot adduction mechanism did not suffice to prevent lateralization of the resultant force, additional inverting or adducting mechanisms (at the ankle, knee, hip and the pelvic level) could be demonstrated. Generally, three-dimensional joint moments and the shank muscle activity pattern were changed at an insignificant level. Force plate data and the analysis of plantar pressure distribution allowed us to assess gait with an accuracy of 83%. For evaluation of dynamic joint motion at the ankle level or above, classical kinetic-kinematic studies are indispensable but, as the kinetics and kinematics at the examined joint levels are highly complex, they can hardly be used to formulate a simple and reliable measure of gait. As the ground reaction force and the plantar impulse distribution as assessed by dynamic pedography represent the net sum of the effects of both the primary gait disturbance and the existing compensation mechanisms, these methods can easily be used for verification and quantification of gait disturbance with an acceptable cost/effectiveness ratio.

Phasic Relationships of the Intrinsic and Extrinsic Thumb Musculature

Dynamic electromyography has proven to be useful in testing patients with spastic disorders who are candidates for tendon transfer or lengthening operations. The purpose of this investigation was to define the normal phasic activity of the thumb muscles during simple, reproducible activities. Fine wire electrode pairs were inserted into the extensors pollicis longus and brevis, abductors pollicis longus and brevis, flexors pollicis longus and brevis, opponens pollicis, adductor pollicis, and first dorsal interosseus of 5 normal subjects. Motions of the carpometacarpal joint and the interphalangeal joint of the thumb were recorded by electrogoniometer. Proximal joint positions were controlled by the subject at the elbow, forearm, and wrist. Normal timing was described for each muscle during hand opening and closing, key pinch with and without force, and opposition pinch with and without force. The data support the concept of individual motor strategies: normal persons often select different combinations of muscles to accomplish a functional goal.

Findings in post-poliomyelitis syndrome. Weakness of muscles of the calf as a source of late pain and fatigue of muscles of the thigh after poliomyelitis.

The purpose of this study was to identify overuse of muscles and other alterations in the mechanics of gait in twenty-one patients who had muscular dysfunction as a late consequence of poliomyelitis. All of the patients had good or normal strength (grade 4 or 5) of the vastus lateralis and zero to fair strength (grade 0 to 3) of the calf, as determined by manual testing. Dynamic electromyography was used, while the patients were walking, to quantify the intensity and duration of contraction of the inferior part of the gluteus maximus, the long head of the biceps femoris, the vastus lateralis, and the soleus muscles. Patterns of contact of the foot with the floor, temporal-spatial parameters, and motion of the knee and ankle were recorded. The principal mechanisms of substitution for a weak calf muscle fell into three groups: overuse of the quadriceps (twelve patients) or a hip extensor (the inferior part of the gluteus maximus in eight patients and the long head of the biceps femoris in four), or both; equinus contracture (twelve patients); and avoidance of loading-response flexion of the knee (five patients). Most patients used more than one method of substitution. These observations support the theory that post-poliomyelitis syndrome results from long-term substitutions for muscular weakness that place increased demands on joints, ligaments, and muscles and that treatment--based on the early identification of overuse of muscles and ligamentous strain--should aim at modification of lifestyle and include use of a brace.

Dynamic electromyography and muscle biopsy changes in a 4‐year follow‐up: Study of patients with a history of polio

Eighteen patients who had had polio 29-56 years prior to the first investigation were studied on two occasions, 4 years apart. Isokinetic and isometric strength measurements and Macro EMG were performed in 28 legs. Muscle biopsy specimens were obtained on both occasions from 11 legs. On average the muscle strength was 56% of control values at the first examination, and decreased by another 8% during the observation period. The muscle fiber area was increased compared to that of controls and did not change significantly. Macro EMG, comprising muscle fiber area and number of muscle fibers, and/or single fiber EMG showed clear signs of reinnervation in all legs. The motor units at the first examination were increased 11-fold, on average, compared with age-matched control values. During the observation period, reinnervation continued and the size of motor units increased by another 56% as a result of ongoing denervation, that is, loss of neurons. This compensation was particularly pronounced in patients with stable conditions. The parameters studied did not reveal any definite pattern predicting future development of new muscle weakness in individual subjects.

Insertion of fine-wire electrodes does not alter EMG patterns in normal adults

Dynamic electromyography (EMG) utilizes either surface or fine-wire intramuscular electrodes to collect data on muscle activity. The question arises whether or not insertion of fine-wire electrodes alters the patterns they are intended to reflect. This study was designed to evaluate the affect of fine-wire electrode insertion on muscle activity during gait in normal adults without muscle tone abnormalities by comparing ensemble-averaged surface EMG patterns and variance ratios (VR) before and after fine-wire electrode insertion. Pearson's correlation coefficients (r) and variance ratios (VR) were determined to assess the degree of similarity between pre- and post-insertion surface EMG patterns and the degree of repeatability of the muscle activity respectively. The ensemble-averaged signals reflect a high degree of pattern similarity as evidenced by high r values (usually greater than 0.90). Pre- and post-insertion VRs are similar. The low mean VRs indicate reasonable reproducibility for both pre- and post-insertion. We concluded that fine-wire electrodes had no significant affect on muscle activity during gait as measured by surface EMG signals under our conditions in normal adults.

Electromyographic analysis of the scapular muscles during a golf swing.

To describe the role of the scapular muscles in the golf swing, we studied 15 competitive male golfers. Four muscles were studied bilaterally using dynamic electromyography and cinematography. In the trailing arm, the levator scapulae elevates while the rhomboid muscles retract the scapula during takeaway; both then stabilize the scapula through the remainder of the swing. In the leading arm, these muscles retract the scapula during forward swing and acceleration. The trapezius muscle in the trailing arm also demonstrates high activity during takeaway to aid in scapular retraction. In the leading arm, trapezius activity is high in forward swing and through the remainder of the swing to promote scapular retraction. The serratus anterior muscle activity is high in the trailing arm during forward swing and through the remainder of the swing to maximize scapular protraction. In the leading arm, the serratus anterior muscle has constant activity through all phases of the swing, which may explain the clinical scenario of muscle fatigue in high demand golfers. The golf swing and uncoiling action requires that the scapular muscles work in synchrony to maximize swing arc and clubhead speed. This study demonstrates the importance of the scapular muscles in the golf swing and the need for specific strengthening exercises.

Surface vs. fine-wire electrode ensemble-averaged signals during gait

Dynamic electromyography (EMG) utilizes either surface or fine-wire intramuscular electrodes. Ensemble-averaging of EMG profiles provides a convenient and commonly performed way to analyse these signals. This study was designed to evaluate the similarities of ensemble-averaged profiles of the two electrode types. We studied two muscles, the right vastus medialis (VM) and the left biceps femoris (BF), at freely-selected speeds of walking and jogging on a treadmill. Both electrodes were simultaneously attached to the subjects' legs. EMG signals were conditioned to produce linear envelopes. Pearson's correlation coefficients ( r) and variance ratios (VR) were determined to assess the degree of similarity in the EMG profiles and the repeatability of the muscle activity, respectively. The ensemble-averaged signals reflect a high degree of pattern similarity as evidenced by high r values (usually greater than 0.90) for both muscles at both speeds. The low mean VRs indicate reasonable reproducibility for both electrode types; fine-wire electrodes in the BF and VM exhibit similar variability to surface electrodes. For the purpose of establishing relative profiles of activation during gait, ensemble-averaged surface and fine-wire signals are closely equivalent.

Muscle pathology and clinical measures of disability in children with cerebral palsy

We performed a histologic and morphometric study of spastic muscle from 10 children with diplegic cerebral palsy, comparing muscle structure with the gait parameters of energy expenditure index and dynamic electromyography. Variations in fiber area within and between fiber types were increased significantly in children with cerebral palsy. In each of the control subjects, the combined coefficient of variation for type-1 and type-2 fiber area was less than 25% and the average was 17%; in the subjects with cerebral palsy, the combined coefficient of variation was more than 25% and the average was 36% (p < or = 0.004). The average difference between the mean area of type-1 and type-2 fibers was 26.7 +/- 18.9% for subjects with cerebral palsy and 4.2 +/- 2.4% for control subjects (p < or = 0.004). There was a 67% predominance of one fiber type in the subjects with cerebral palsy compared with a 55% predominance in the control subjects (p < or = 0.03). The difference between the total area of type-1 and type-2 fibers was 57% in the subjects with cerebral palsy and 17% in the control subjects (p < or = 0.002). There was a significant correlation between the combined coefficient of variation of fiber area and the energy expenditure index (r = 0.77, p < or = 0.03). The difference between the mean area of type-1 and type-2 fibers correlated with prolongation of electromyographic activity (r = 0.69, p < or = 0.05). No abnormalities in fiber ultrastructure were found in the subjects with cerebral palsy. Children with cerebral palsy had abnormal variation in the size of muscle fibers and altered distribution of fiber types. The values for variation in fiber area correlated with the energy expenditure index and with prolongation of electromyographic activity during walking.

Hamstrings in cerebral palsy crouch gait.

After observing patients with increased anterior pelvic tilt following medial hamstring lengthening in cerebral palsy crouch gait, we became concerned that the hamstrings may be functionally important hip extensors. To evaluate this, we studied the three-dimensional motion of the hip and knee, calculated hamstring muscle length, and evaluated dynamic electromyography (EMG) of the medial hamstrings in 16 patients with diplegic cerebral palsy and crouch gait to determine if the hamstrings were extending the hip. Twelve of 16 patients exhibited marked prolongation of electrical activity in the medial hamstrings, and in eight of these 12, the hamstrings were contracting concentrically, thus aiding in hip extension during gait. Hamstrings may be important hip extensors in some cerebral palsy patients with crouch gait; however, other deformities contributing to crouch (such as hip flexion contracture) need to be considered before isolated hamstring lengthening is performed in these patients.

Dynamic Electromyography in Functional Surgery for Upper Limb Spasticity

Surgery to improve upper limb function after stroke, closed head injury, or other causes of acquired spasticity is generally accomplished by a combination of muscle transfer, lengthening, and/or release. Dynamic electromyography can be used to identify voluntary muscle action, delineate the deforming motor forces when spasticity is present, and provide guidance for surgical planning to improve prehensile hand function.

Using Dynamic Electromyography to Guide Surgical Treatment of the Spastic Upper Extremity in the Brain-Injured Patient

Upper extremity deformity after brain injury is frequently complex and dominated by spasticity or contracture. Clinical examination of the limb is often difficult and inaccurate. Dynamic electromyography provides valuable information previously unobtainable. Analysis of this data can facilitate appropriate reconstruction of the deformed limb.

The Use of the Pathokinesiology Laboratory to Select Muscles for Tendon Transfers in the Cerebral Palsy Hand

One hundred nine cerebral palsy hands referred for consideration for tendon transfers were examined clinically and by dynamic electromyography. Wire electromyography as used in gait analysis at the author's institution was employed in each of these cases. Most patients required transfers for release (opening) of the hand. The flexor carpi ulnaris and brachioradialis were the most common muscles active in release, yet even in those muscles, less than half were suitable for transfer. This suggests that the wire electromyogram is helpful in selecting the proper muscle for tendon transfer in the cerebral palsy hand.

Electromyographic Analysis and Its Role in the Athletic Shoulder

In 1944, Inman made some conclusions regarding shoulder function that have become the foundation of a classic model. Clinical observations of the athletic shoulder and its associated common injuries have demonstrated selective weakness of specific rotator cuff muscles rather than generalized muscle impairment. Shoulder mechanics during athletic activities have been evaluated dynamically with electromyography (EMG), which has helped to formulate a base for optimal rehabilitation. Dynamic EMG and high-speed film analysis have been used to evaluate the shoulder during throwing, swimming, tennis, and golf. Evaluation of shoulder function in these various sports revealed that although rotator cuff function is important in all, the emphasis and role of individual muscles varied. The importance of serratus anterior muscle activity to stabilization and protraction of the scapula has been consistently reported. The muscles about the shoulder act according to their mechanical qualities and are function- or sport-specific. A thorough understanding of the mechanics of the normal and pathologic shoulder constitutes the foundation for training and rehabilitation strategies.

Gait Analysis in Pediatric Rehabilitation

Three-dimensional gait analysis has evolved over the past century to allow accurate recording and measurement of human walking. Kinematic analysis allows quantification of the motion of joints; dynamic electromyography shows how muscles firing abnormally affect this motion. Gait analysis has been successfully applied in the evaluation and treatment of cerebral palsy, myelomeningocele, muscular dystrophy, and limb-deficient states. Formal gait analysis allows improved classification of patients with walking disabilities, a more thorough understanding of the problems seen, and a more coherent and comprehensive treatment plan.

Evaluation of upper extremity motor control in spastic brain-injured patients using dynamic electromyography

The assessment of limb motion and motor control In the spastic, brain-injured patient is complex. More diverse patterns of movement are seen in the upper extremity compared with the lower extremity— especially in movement of the thumb and fingers. The variance can be attributed to the fact that the functional use of the hand requires more precise and independent movement of adjacent structures or digits than use of the lower extremity. The diversity of upper extremity motion requires the careful combination of clinical assessment and laboratory investigation for accurate understanding of function. Treatment strategies based on such detailed investigation can lead to improved function in the spastic hand.

Dynamic electromyography to assess elbow spasticity

Control of elbow motion was evaluated in 45 extremities of adults with spasticity resulting from traumatic brain injury with use of dynamic electromyography. Simultaneous recording of elbow motion was obtained using a double parallelogram goniometer. Thirty-four male and 9 female patients were studied. Mean elbow flexion was 85 degrees and mean extension was 20 degrees. The average time of elbow flexion was 1.8 seconds. Extension time was prolonged to a mean of 4.0 seconds. Dynamic electromyography revealed a consistent pattern of muscle activity. Severe spasticity was noted in the brachioradialis muscle. Moderate spasticity was present in the biceps and only mild spasticity was seen in the brachialis muscle. Normal phasic muscle activity was the rule in the triceps. All patients had active elbow flexion, but the flexor spasticity limited smooth extension. Elbow flexor spasticity, especially of the brachioradialis and biceps muscles, commonly interferes with hand placement. Lengthening of the biceps and brachialis tendons combined with release of the brachioradialis enhances elbow motion and improves hand placement.

Cerebral Palsy

Although only a small number of children with cerebral palsy have indications for surgical treatment of dynamic or structural upper-extremity deformities, orthopedic surgery does improve function and appearance of the involved hand, particularly in spastic hemiplegia. For further assessment of the patient after careful physical examination, myoneural nerve blocks and dynamic electromyography are useful. Physical and occupational therapists have an important role as crucial links among parents, patients, and physicians. Surgeons can try to prevent deformity with splints; however, their use in prevention of deformities of the hand has not been validated by scientific studies. Shoulder deformities can be managed with myotomies, tendon transfers, and (if fixed) osteotomies; rarely is arthrodesis used. Elbow flexion and dynamic or fixed deformities greater than 60 degrees are treated by lengthening of the muscles and tendons. Pronation deformities of the forearm are managed by myotomies, lengthenings, and tendon transfers. Wrist flexion deformities can be corrected with tendon lengthenings and transfers. The best results have been obtained with transfer of the flexor carpi ulnaris to the extensor digitorum communis. Finger flexion deformities can be managed satisfactorily with Z-lengthenings of the flexor digitorum superficialis in the forearm; rarely is it necessary to lengthen the flexor digitorum profundus. For adduction deformity of the thumb, division of the proximal or distal insertions of the adductor pollicis and release of the first dorsal interosseus muscle from the first and second metacarpals are preferred.

Dynamic electromyography. I. Numerical representation using principal component analysis

A complete description of human gait requires consideration of linear and temporal gait parameters such as velocity, cadence, and stride length, as well as graphic waveforms such as limb rotations, forces, and moments at the joints and phasic activity of muscles. This results in a large number of interactive parameters, making interpretation of gait data extremely difficult. Statistical pattern recognition techniques can simplify this problem. For this approach to be successful, first it is necessary to reduce the number of interactive parameters to a manageable set. In this study, we present an application of principal component analysis as a means for representing graphic waveforms in a parsimonious manner. In particular, we concentrate on representing the phasic muscle activity recorded using surface electrodes from ten major muscles of the lower extremity of 35 normal subjects during level walking. A 32 point vector is created in which each point of the vector represents the normalized area under the curve of a portion of rectified and smoothed electromyographic signal, expressed as a function of gait cycle. Principal components are computed and the first few weighting coefficients are retained as features to represent the original EMG data. We show that the corresponding basis vectors span parts of the gait cycle where the most variability between individual subjects exists. We also show that the basis vectors can be used to represent the EMG data of subjects not originally used to generate the basis vectors.

Dynamic electromyography. II. Normal patterns during gait

Human gait is a complex phenomenon. Many descriptors are needed to completely describe gait in terms of the biomechanics involved. The descriptors, when expressed as a function of the gait cycle, are complex waveforms. For each of these variables, a single "normal" pattern with bands of deviation has generally been accepted as a reference in clinical/research use to explain the abnormalities in a patient's walking pattern. In fact, one observes many "normal" patterns, and a body of research has been devoted to explaining the differences between these patterns in terms of walking speed, age, cadence, sex, etc. It would be simpler in one sense to start with the fact that different people walk with different patterns, not one pattern with bands of deviation. Numerical representation of the waveforms simplifies the analysis and interpretation of waveform data and facilitates comparison between subjects or groups of subjects. When combined with pattern recognition techniques, it also is useful for identifying subpatterns within a group. In this article, the numerical representation of electromyographic data by Karhunen-Loeve expansion are combined with cluster analysis to obtain patterns of dynamic phasic activity of 10 muscles of the lower extremity. From the 35 normal subjects walking at self-selected speed, two to four patterns are developed for each of the muscles and the physiological significance of the patterns are discussed.

The use of dynamic electromyography to evaluate motor control in the hands of adults who have spasticity caused by brain injury.

A dynamic electromyographic analysis of grasp and release, performed on forty-eight upper extremities of forty-two adults who had had injury to the brain causing spasticity, showed volitional motor control of the finger flexors in 80 per cent and active extension of the fingers in 60 per cent. The flexor pollicis longus showed volitional control in 75 per cent of the hands and the extensor pollicis longus showed active control in 50 per cent. The extensor carpi radialis longus acted as an appropriate stabilizer of the wrist in 85 per cent of the extremities. Fourteen muscles had out-of-phase activity that could not be detected on clinical examination. The position of the elbow did not appreciably influence the electromyographic pattern of motor control in the hand.