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Biomedical subjects

G L Soderberg

Publications and source records attributed to G L Soderberg.

At least 19 recordsLinked to original sources
PubMed1992

Age-related changes in postural responses preceding rapid self-paced and reaction time arm movements.

The electromyographic responses in postural (thigh and trunk) and primary agonist (shoulder) muscles were examined in standing young and older adults prior to rapid self-paced (SP) and simple reaction time (RT) arm flexion movements. In contrast to younger subjects, older adults demonstrated significantly lower frequencies of trials for self-paced movements in which thigh muscle responses preceded the activation of the shoulder muscle. Furthermore, younger adults showed more frequent early lower limb postural responses for SP versus RT movements, whereas older subjects retained comparable frequencies between task conditions. Overall, a significantly shorter intermuscular timing interval between leg and arm muscle onsets was also found for the older group.

Adult↗
PubMed1991

The effect of muscle length on motor unit discharge characteristics in human tibialis anterior muscle.

Muscle length influences the contractile properties of muscle in that when muscle is lengthened the relaxation phase of the muscle twitch is prolonged and when muscle is shortened, the relaxation phase is shorter in duration. As a result, the force exerted by active motor units varies with muscle length during voluntary contractions. To determine if motoneuron spike trains were adjusted to accommodate for changes in the contractile properties imposed by shortened and lengthened muscle, motor unit action potentials were recorded from the tibialis anterior muscle at different muscle lengths. Twenty subjects performed isometric ramp contractions at ankle angles of 20 degrees dorsiflexion, neutral between dorsiflexion and plantar flexion, and 30 degrees plantar flexion, which put the tibialis anterior muscle in a shortened, neutral, or lengthened condition, respectively. During isometric contractions where torque increased at 5% MVC/s, motor unit discharge rate at recruitment was greater in shortened muscle than in lengthened muscle (P less than 0.05). Brief initial interspike intervals (less than 40 ms) occurred more frequently in shortened muscle than in either neutral length or lengthened muscle. During steady contractions, motor unit discharge rate was greater per unit torque (N.m) in shortened muscle than in neutral length or lengthened muscle (P less than 0.05). These findings indicate that muscle length does influence the discharge pattern of motor unit spike trains during isometric ramp contractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1991

A comparison of motor unit behaviour in young and aged subjects.

We evaluated motor unit behaviour in young and aged subjects during ramped tension development and release to 10% maximum voluntary contraction requiring 10 seconds to complete. Six young and six elderly adults performed isometric abductor digiti minimi muscle contractions while motor units were recorded with implanted fine wire electrodes. Computer interactive programs yielded interspike interval (ISI) data for 16 units from the young and for 15 units from the aged subjects. Mean ISIs for young were 88.4 ms for shortening and 96.5 ms for lengthening contractions. Units from the aged had ISIs of 110.5 ms and 117.1 ms for shortening and lengthening contractions. Some evidence for between-group differences in firing pattern during ascending and descending ramps was also found.

Adult↗
PubMed1991

Reliability of performance measurements obtained using the stability testing and rehabilitation station (STARStation).

The purpose of this study was to determine within- and between-day reliability of measurements of nondisabled subjects for the variables of force and velocity when a balance board (STARStation) was positioned at heights of 4.5 and 7.5 cm from the supporting surface. Twenty-four nondisabled subjects each completed six trials of board rotation at a self-selected velocity. Each trial consisted of 10 revolutions in a clockwise direction. Measurements were repeated within the same day for a second board position, and all tests were completed again on a second day. Descriptive statistics were computed for force and velocity, and intraclass correlation coefficients (ICCs) were calculated. Data were submitted to analyses of variance and follow-up tests. Results showed slight differences between the first three and last three trials. Intraclass correlation coefficients for within-subject reliability for the independent variable day ranged from .72 to .81, and ICCs for within-day reliability for the independent variable trial ranged from .46 to .81. Clinicians using such protocols should be aware of differences within and between days and recognize that measurements will be influenced by the number of trials completed.

Adult↗
PubMed1991

Modeling physical therapy clinical research centers.

Because the establishment of physical therapy clinical research centers (PTCRCs) has been of interest to the profession, this project was undertaken to (1) assess the available resources, (2) complete a systems analysis, and (3) apply the results of a Delphi survey to the resulting clinical research center models. The methodology included several techniques. First, a questionnaire that addressed the status and elements of organization of PTCRCs was distributed to 118 academic institutions and 22 other facilities. A systems analysis of clinical research centers supported by various institutes at the National Institutes of Health was then completed. A Delphi procedure was also used to query a panel of physical therapy researchers regarding the components of a PTCRC. Site visits were conducted at three facilities to assess the possibility of those facilities becoming PTCRCs. From the data derived via these methods, models for PTCRCs were developed. Results showed that as many as 40 facilities reported the capability of becoming a PTCRC, but the data also showed that only four sites had extensively contributed by means of publication in peer-reviewed journals. The Delphi survey produced a number of items regarding characteristics and foci on which consensus was reached. Considering all the data, several models for PTCRCs were developed. Allowance for diversity in the structure and focus of PTCRCs appears to be a critical factor if the development of PTCRCs is to be encouraged.

Academies and Institutes↗
PubMed1991

Electromyographic activity of selected leg musculature in subjects with normal and chronically sprained ankles performing on a BAPS board.

The purpose of this study was to evaluate the magnitude and temporal features of tibialis anterior, peroneus longus, and gastrocnemius muscle activity during exercises performed on a Biomechanical Ankle Platform System (BAPS) board by subjects with normal and chronically sprained ankles. Fourteen participants in each of the two groups rotated the platform in both clockwise and counterclockwise directions at self-selected velocities. Trials were completed with both medium- and large-sized hemispheres under the platform while electromyographic surface recordings were made from the three muscles of interest. Electromyographic values, normalized within individuals as a percentage of maximal voluntary isometric contraction (MVIC), ranged from 20% to 80% of MVIC. An analysis of variance for the average myoelectric signals from all three muscles revealed no differences between the two groups. Effects of direction and hemisphere size were shown for all muscles. The large hemisphere produced significantly greater average activity and a more pronounced effect on the tibialis anterior muscle. The data provide information on the level of muscle activity required for conditions used in this study and may assist the physical therapist with making judgments about the use of this device in rehabilitation programs.

Adult↗
PubMed1989

Electromyographic analysis of hip abductor musculature in healthy right-handed persons.

The right hip abductor (HA) musculature has been reported to demonstrate stretch weakness attributable to chronic elongation imposed by standing posture common to right-handed healthy individuals. Research has shown side-specific differences in maximal isometric torque-hip abduction angle curves for the HA muscles in a similar population. The purposes of this study were to assess isometric hip abduction torque in a sample of 40 healthy right-handed persons and to compare side differences in the HA muscles' neural drive index across a wide range of hip abduction angles. The neural drive index was defined as the magnitude of the normalized surface electromyographic activity divided by the absolute magnitude of a submaximal (20% of maximal) isometric HA muscle torque. Data were collected while subjects were positioned supine with trunk and pelvis stabilized. Statistical analysis of the data did not support earlier research on right HA muscle stretch-weakness; however, trends in the data suggest the need for further research. We also discuss the functional role of the passive noncontractile elements of the HA musculature.

Adult↗
PubMed1988

Comparison of maximal isometric hip abductor muscle torques between hip sides.

A posturally induced "stretch weakness" of the right hip abductor muscles has been reported in many healthy right-handed persons in the literature. The purpose of this study was to test for differences in the maximal isometric hip abduction torque produced between hip sides across multiple hip abduction angles. The torques were measured on 40 healthy right-handed individuals using a specialized torque-testing table at hip abduction angles of -10, 0, 10, 20, 30, and 40 degrees. Statistical analysis of the results did not demonstrate a specific "weakness" of the right hip abductor muscles at the hip angle used to clinically test them. The results, however, did demonstrate statistically significant differences in the torque-hip angle slopes across hip sides. We hypothesized that these slope differences may result from muscle adaptation to lengths imposed by standing posture. We discuss how manual muscle testing procedures may bias the likelihood of encountering stretch weakness in muscles that are habitually maintained at near-maximal elongation.

Adult↗
PubMed1987

Postural adjustments preceding rapid arm movements in parkinsonian subjects.

The electromyographic (EMG) responses in postural (thigh and trunk) and agonist (shoulder) muscles were examined in standing parkinsonian subjects and healthy controls prior to visual reaction time and self-paced rapid arm flexion movements. Recruitment of postural muscles typically preceded arm displacement in normals, but was less frequent, of shorter duration, and characterized by multiple EMG bursts which extended to the agonist in parkinsonians. Moreover, parallel delays in EMG recruitment times relative to the visual signal for both postural and agonist muscles were observed in akinetic patients. These abnormalities suggest that the basal ganglia may serve a preparatory motor function, by linking synergistic muscles through a common selection process.

Aged↗
PubMed1987

Electromyographic analysis of knee exercises in healthy subjects and in patients with knee pathologies.

Little information exists about the intensity of contraction required from knee and hip musculature during common therapeutic exercises used for patient populations. This study, therefore, was designed to compare electromyographic data obtained from the vastus medialis, rectus femoris, gluteus medius, and biceps femoris muscles during maximally resisted straight-leg-raising (SLR) exercises with EMG data obtained from the same muscles during quadriceps femoris muscle setting (QS) exercises in healthy subjects and in patients with knee pathologies. Of the 30 participants in the study, 16 had a history of knee injury or surgery. All participants performed randomly ordered trials of the SLR and QS exercises while the EMG data were recorded from surface electrodes and normalized to values derived from maximal effort isometric contraction trials. An analysis of variance demonstrated significantly greater activity (p less than .05) of the vastus medialis, biceps femoris, and gluteus medius muscles during QS exercises than during SLR exercises. The rectus femoris muscle was significantly more active (p less than .05) during SLR exercises than during QS exercises. The study demonstrated remarkably different degrees of muscle activation between the SLR and QS exercises, indicating that the exercise selected will affect the therapeutic intention.

Adult↗
PubMed1986

Technique for EMG fine wire connections.

A fine wire electrode connector has been developed to incorporate the benefits of on-site pre-amplification, while concurrently providing the ease of repeatable quick connections for fine wires. Results show artifact-free electromyograms in studies of single motor unit action potentials or during functional activities.

Electromyography↗
PubMed1986

Transcutaneous electrical nerve stimulation characteristics for altering pain perception.

The purpose of this study was to determine the effect of conventional low-intensity transcutaneous electrical nerve stimulation (TENS) waveform and frequency characteristics on experimentally induced acute pain. Each of 28 male subjects received six forms of TENS and one control treatment during a single testing session. Treatments used one of two waveforms (monophasic or biphasic) and one of three frequencies (30, 60, or 85 Hz) administered to the forearm. Treatment effects were ascertained from alterations in pain-threshold and pain-tolerance responses induced by noxious electrical stimulation of the ipsilateral fifth digit. The TENS waveform and frequency had a negligible effect on pain threshold. The results indicated that waveform did not influence pain tolerance significantly. Pain tolerance, however, increased significantly at the frequency of 60 Hz but decreased significantly at both 30 and 85 Hz (p less than .05). We concluded that TENS frequency is an important factor in altering the subjects' perception of experimentally induced pain.

Adult↗
PubMed1986

Actions of hip muscles.

This article describes and explains the moment arm vector (MAV) concept, uses the concept for the quantitative classification of hip muscles according to action, and applies the findings to selected clinical problems. A three-dimensional, straight-line model of hip musculature was used. Measurements made on a matched, dry bone specimen provided muscle attachment point location data for the model. Straight lines of muscle action between attachment sites were simulated for a variety of hip configurations during simple hip motions in three principal anatomical planes. We used the MAV concept to identify the three contributions of a muscle (flexion-extension, abduction-adduction, and internal-external rotation) tending to rotate the thigh segment relative to the pelvis. Muscles were classified according to their action or turning effect at 0, 40, and 90 degrees of hip flexion. Certain muscles exhibited significant changes in their action during these simple motions. Model results were verified using an articulated, dry bone specimen with elastic strings stretched between muscle attachment sites. Based on this geometrical model, a "pathological posture" of hip flexion, adduction, and internal rotation was identified, which is a posture prevalent in spastic, brain damaged patients.

Biomechanical Phenomena↗
PubMed1984

Electromyography in biomechanics.

The purpose of this paper is to discuss the use of EMG as related to biomechanical function and dysfunction. The uses and limitations of this technique are described and instrumentation features and methods of data collection and interpretation are presented. We also discuss factors that influence the relationship of EMG to biomechanical measurements and cite as examples studies that have used EMG. Emphasis is placed on improving the ability of the physical therapist to use and interpret EMG data in kinesiology and biomechanics.

Biomechanical Phenomena↗
PubMed1983

Laser etched bifilar fine wire electrode for skeletal muscle motor unit recording.

To selectively record a limited number of skeletal muscle motor unit action potentials, a bifilar fine wire electrode was developed. Two 8 micrometers wires were braided together, a hook formed, and ends insulated. A round beam, pulsed laser, etched a 5 micrometers piece of insulation from each wire near the hooked end. Bipolar recordings from a select number of skeletal muscle motor units were obtained from these two uninsulated 5 micrometers areas. Reactive and capacitative components for each set of electrodes were measured. These electrodes were selective in recording from 3 to 5 single motor unit action potentials at low isometric tension levels.

Electrodes↗
PubMed1983

Comparison of skeletal muscle motor unit discharge characteristics in young and aged humans.

The purpose of this study was to determine the discharge characteristics of motor unit action potentials. Three decades of aged subjects ranging from 60 to 90 yr of age were compared to a group of 20-35 yr olds. Motor unit behavior was described by the interspike interval (ISI) and expressed statistically as a mean, a floating standard deviation (FSD), and a floating serial correlation (FRHO). The 70- to 79-yr-old group tended to have a slow motor unit discharge rate, an increased variability of discharge (FSD) and a negative serial correlation coefficient (FRHO). All three factors describing motor unit discharge behavior possibly suggest substitution of larger motor units for small motor units normally active at low tensions for the 70-79 age group.

Action Potentials↗
PubMed1983

Ultrasound effects on electroneuromyographic measures in sensory fibers of the median nerve.

The purpose of this study was to clarify the available literature and study the influence of ultrasound on the conduction velocity and amplitude of evoked sensory potentials in the median nerve. Thirteen subjects were assigned to either Experimental or Control Groups for ultrasound or placebo treatments. We compared sensory-nerve conduction velocity in the median nerve after 10 minutes of ultrasound treatment at three intensity levels (0.5, 1.0, and 1.5 W/cm2) with sensory-nerve conduction velocity in the median nerve after 10 minutes of placebo ultrasound treatment (0.0 W/cm2). No significant differences were noted between groups at any of the three ultrasound intensity levels, nor were the interaction effects significant. A hypothetical model, based on the available literature, proposes that ultrasound-induced changes in sensory-nerve conduction velocity may not progress in a direct linear fashion relative to the duration of treatment.

Adult↗