Antagonist cocontraction of knee extensors during constant velocity muscle shortening and lengthening.

Electromyography (EMG) was used to study the role of antagonist cocontraction of the quadriceps muscles of 24 normal subjects during constant velocity muscle performance tests on a KIN/COM dynamometer. The hypothesis tested the dependence of antagonist cocontraction on joint angle, limb velocity and type of contraction. Seated subjects performed two dynamic tests of resisted muscle shortening and lengthening of the knee flexors through a 65 degrees range of knee motion under two constant velocity conditions in a single session. Each test consisted of four repetitions of maximum voluntary contractions (MVC) of constant velocity muscle shortening and lengthening of the knee flexors; one test was performed at 30 degrees s(-1), the other at 90 degrees s(-1). The sequence of velocity testing was randomized. Normalized (%Max) values of peak amplitude EMG of knee extensors were measured every 5 degrees in the constant velocity phase of each test and compared in a paired manner for each angle, contraction type and velocity, by split-plot two-way analysis of variance (ANOVA). The level of antagonist quadriceps cocontraction was low, ranging from 5-8% Max between 70 degrees and 15 degrees of knee flexion for both velocities and contraction types. Antagonist quadriceps activity was found to be velocity dependent during agonist muscle shortening (P < 0.02). However, no other effects of angle, contraction type, or velocity were found for antagonist quadriceps. It is concluded that antagonist quadriceps and the previously reported hamstrings(46) respond differently under typical constant velocity test conditions, and these differences need to be accounted for when intepreting muscle performance tests.

Elbow joint restriction: effect on functional upper limb motion during performance of three feeding activities.

This study was conducted to quantify and compare changes in upper limb joint motion during different feeding tasks when the elbow joint was restricted. Ten male and nine female volunteer subjects age 18 to 50 years participated; all were healthy, right dominant, with no upper limb pathology. A splint was used to restrict elbow joint motion. Three feeding tasks under both unrestricted and restricted conditions were randomly assigned; motion was recorded by a video-based three-dimensional motion analysis system. Elbow restriction resulted in significantly (p < .05) larger arcs of motion in shoulder flexion and internal rotation. Differences between feeding types were similar during both unrestricted and restricted conditions. Increased shoulder joint motion resulting from elbow joint restriction may require greater activity of shoulder girdle muscles increasing the risk of soft tissue problems and degenerative joint disease. Decisions regarding elbow immobilization should take into consideration potential effects upon total upper limb motion.

Antagonist cocontraction of knee flexors during constant velocity muscle shortening and lengthening.

Electromyography (EMG) was used to study the role of antagonist cocontration of the hamstring muscles of 24 normal subjects during constant velocity muscle performance tests on a KIN COM (™) dynamometer. The hypothesis tests whether antagonist cocontraction varies dependent on joint angle, limb velocity, and type of contraction. Seated subjects performed two dynamic tests of resisted quadriceps muscle shortening and lengthening through a 65° range of knee motion under two constant velocity conditions in a single session. Each test consisted of four repetitions of maximum effort constant velocity muscle shortening and lengthening of the knee extensors; one test performed at 30° s(-1), the other at 90° s(-1). The sequence of velocity testing was randomized. Normalized values of peak amplitude EMG of knee flexors were measured every 5° in the constant velocity phase of each test and compared in a paired manner between each angle, contraction type, and velocity, by split-plot 2-way ANOVA. Antagonist hamstrings cocontraction was found to be contraction type, and velocity dependent. Cocontraction was greater at larger angles of knee flexion and at higher velocity. These results do not support the hypothesis that such activity is a function of muscle moment-arm, but are consistent with the idea that antagonist muscle function is controlled by muscle spindles and perhaps Golgi tendon organs. Because antagonist cocontraction ranged up to a mean of 32% of maximum agonist activity in normal individuals, it should be taken into consideration when interpreting clinical muscle performance tests.

Three-dimensional measurement system for functional arm motion study.

An easy-to-use and inexpensive system for studying human movement is described and applied to the study of arm movement during feeding. A typical time to produce kinematic data for an experiment is one hour, including the experiment. System error was found to be less than three per cent. Besides the kinematic data the system inherently provides for a permanent video copy of the studied movement.

Normal functional range of motion of upper limb joints during performance of three feeding activities.

This study was designed to quantify the range of upper limb joint motion required during the performance of a specific type of functional activity. Ten able-bodied men were studied as they performed three feeding tasks--eating with a spoon, eating with a fork, and drinking from a handled cup. Three shoulder joint rotations, one elbow joint rotation, one forearm joint rotation, and three wrist joint rotations were quantified simultaneously using a three-dimensional measurement system. It was found that the required ranges of motion for the feeding tasks were 5 degrees to 45 degrees shoulder flexion, 5 degrees to 35 degrees shoulder abduction, 5 degrees to 25 degrees shoulder internal rotation, 70 degrees to 130 degrees elbow flexion, from 40 degrees forearm pronation to 60 degrees forearm supination, from 10 degrees wrist flexion to 25 degrees wrist extension, and from 20 degrees wrist ulnar deviation to 5 degrees wrist radial deviation. Wrist rotation was also measured, but it was found to be negligible.

An electrogoniometer for the measurement of thoracolumbar rotation.

A simple, noninvasive method of measuring thoracolumbar rotation was developed using an electrogoniometer mounted on thermoplastic girdles. The instrument is designed to adjust to trunk movement that might occur in the sagittal and coronal planes while transmitting the torque that results from rotation in the horizontal plane directly to the active potentiometer of the electrogoniometer. Experiments were carried out to determine the accuracy, validity and reliability of the device and it was concluded that this method of measurement of horizontal trunk movement could be used in kinematic investigations.

The normal peak of electromyographic activity of the quadriceps femoris muscle in the stair cycle.

The quadriceps femoris muscles of 18 subjects with no history of knee joint pathology were analysed climbing stairs. Temporal data was obtained from bilateral contact closing footswitches. Knee joint data was measured using a specially constructed flexible linkage-bar electrogonimeter. Electromyographic activity was obtained from bipolar Beckman surface electrodes placed on four components of the quadriceps femoris, vastus medialis oblique, vastus medialis longus, vastus lateralis and rectus femoris. Results showed that within the stair cycle, stance occupied 60% and swing 40%. Cadence values were greater during descending than ascending stairs. Joint angle data demonstrated 2 changes in direction of the angular motion of the knee joint in both ascending and descending. Electromyographic analysis identified a peak of EMG activity for each component of the quadriceps femoris in both ascending and descending stairs. Results identified the location of peak EMG activity at specific knee joint angles. The quadriceps components also demonstrated a regular sequence of recruitment. EMG amplitude levels obtained were higher in ascending than descending stairs. The results have clinical implications in the design of lower extremity prostheses and in the application of functional electrical stimulation.

The assessment of the internal rotation gait in cerebral palsy: an electromyographic gait analysis.

A study of 12 cerebral palsied children with internal rotation revealed three patterns of electromyographic activity: (1) Diagnostic pattern--where a simple muscle group stood out as the responsible agent--notably the medial hamstrings; (2) Nondiagnostic pattern--nonrecurring pattern; (3) Nondiagnostic pattern--recurring "mass limb reflex" pattern. In all cases, electromyography was useful for: (1) confirmation of clinical impressions. Electromyographic confirmation of phasic hamstring overactivity gives a firm basis for tendon surgery with expectancy of good results. (2) Detection of the responsible muscle group where clinical methods fail to do so. It detects the "at risk" patients, where follow up with tendon surgery at the appropriate time could be performed with predictable results. (3) Selection of patients who are likely to respond to tendon surgery, and those unlikely to benefit from it. The adductors and internal rotators may play only a secondary role in children whose predominant problem is internal rotation during gait. The medial hamstrings stand out as the most important single muscle group causing this problem. Consequently, it is important to analyze gait problems with the patient walking, and examine electromyographs during walking in the overall assessment of a patient with dynamic gait problem.

Paraspinal Muscle Activity During Sports.

Using sophisticated telemetry techniques, the authors studied electrical activity in the paraspinal muscles and found implications not only for analyzing athletic performance, but also for patients with low back pain.

Electromyographic temporal analysis of gait: normal human locomotion.

The telemetered electromyographic (EMG) activity of pretibial muscles (tibialis anterior), triceps surae (lateral gastrocnemius), medial hamstring group and quadriceps (vastus lateralis) of 20 normal subjects was examined during locomotion. The ages of the subjects ranged from 8 to 72 years (mean, 37 years). A microswitch shoe was used to correlate the EMG activity with eight specific components of the gait cycle. Tibialis anterior showed two peaks of activity, the first at the swing-stance transition, the second at the stance-swing transition. Gastrocnemius showed a single peak of activity recorded during push-off. The medial hamstring showed its greatest activity during deceleration in the swing phase. Vastus lateralis demonstrated peak activity at the transition from swing to stance. The mean cadence was 106 steps per minute. Swing phase occupied 39.6% and stance phase 60.4% of the gait cycle.

Electromyographic temporal analysis of gait: hemiplegic locomotion.

The telemetered electromyographic (EMG) activity of quadriceps, hamstrings, triceps surae and pretibial muscles on the affected side of 20 adult hemiplegic subjects was examined during locomotion. The subjects ranged in age from 29 to 68 years (mean, 52.1). Duration of the lesions ranged from 1 month to 8 years: in 11 subjects the duration of the lesions ranged from 1 to 9 months (mean, 4.9 months), and in the remaining 9 subjects from 1 to 8 years (mean, 4 years 2 months). Shoes with five microswitches, two in the heel and three in the sole, were used to correlate the EMG activity with eight specific components of the gait cycle. The results of the study showed a loss of the phasic pattern associated with normal locomotion. The hemiplegic subjects showed the greatest activity in the period of midstance. Expressed as a percentage of the total cycle, the mean stance time of the paretic lower limb was 67% and the mean swing time was 33%. The unaffected lower limb showed a stance phase of 80% and a swing phase of 20%.

Clinical telemetry of EMG and temporal information during gait.

Multichannel telemetry has formed an integral part of the clinical assessment of children's walking problems. EMG signals and temporal information from foot switches are transmitted from a small belt-pack unit which provides almost complete freedom of movement for the child. Although patients with various crippling diseases have been studied, the investigation of problems resulting from cerebral palsy has been most valuable clinically. The effects of orthopaedic surgery to release or transfer muscles can be asssessed more positively and the causes of some unexplained gait patterns can be investigated more thoroughly.

Locomotion studies as an aid in clinical assessment of childhood gait.

A clinical locomotion laboratory has been developed to provide quantitative information in the management of gait disorders. The biomedical engineering development of this system identified two major clinical constraints: (a) the need for instrumentation that would not alter the natural gait of the patient and (b) the need for data-processing techniques that would permit analysis and correlation of the large volume of electromyographic (EMg) and kinematic information. The net result has been a unit that incorporates a multichannel telemetry system to capture the EMG and foot-switch information and a television computer system to handle the kinematic information. Gait studies on children with hemiparesis, muscular dystrophy and cerebral palsy have yielded quantitative EMG and kinematic information on the pathomechanics of ambulation in these disorders. Because the information obtained is quantitative, an accurate measure of improvement (or lack of it) after treatment can be documented. Therefore, the locomotion laboratory may have an important role in the preoperative and postoperative evaluation of children whose abnormal gait may require surgical corrective procedures or rehabilitative treatment including the use of prostheses or orthoses.

A voluntarily controlled electrohydraulic above-knee prosthesis.

Most above-knee amputees to date are using prostheses employing either constant friction or some type of programed hydraulic damping which the wearer has no control over and which limits his gait speeds. A new system was designed and tested in which voluntary control of a lower-limb prosthesis is derived from the EMG signals of residual thigh muscles in the stump. These signals, after suitable conditioning, open or close solenoid valves, which form a closed hydraulic loop around the damping cylinder in the knee joint. Thus, the amputee is able to voluntarily vary the resistance to knee flexion, from free swing to full lock, by operating valves controlling the resistance to flow around a hydraulic cylinder. The main advantages of this system are a variable and more aesthetic gait, stability over uneven terrain, and because the lock prevents only knee flexion, the amputee can rise on his prosthesis and so use a passive appendage as an active element of his skeleton. The results of this project demonstrate that the concept of an EMG voluntarily controlled hydraulic prosthesis is viable; however, continuing effort is required to make this system lighter, more compact, and cosmetically acceptable.