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Biomedical subjects

R V Baratta

Publications and source records attributed to R V Baratta.

47 records · Page 3Linked to original sources
PubMed1995

Electromyography and biomechanics of a dynamic knee brace for anterior cruciate ligament deficiency.

Twelve anterior cruciate ligament (ACL)-deficient subjects performed concentric isokinetic knee extensions at maximum effort both with and without the Bledsoe Pro Shifter knee brace. Electromyogram signals from the quadriceps, hamstrings, knee angle, and the extension force were recorded and evaluated to determine the effects of such dynamic bracing on muscle activity and joint stability. High activity, or asymptomatic, subjects (n = 5) experienced no change in muscle activity, but displayed a decrease in extension force throughout the active range of the brace. Low activity, or symptomatic, subjects (n = 7) exhibited increased quadriceps activity and decreased hamstrings activity, and displayed a minor increase in force in the mid-range (80 degrees to 40 degrees flexion). These results indicate that dynamic bracing prevents quadriceps inhibition in symptomatic subjects by exerting a posteriorly directed force to the superior tibia; thus, the brace compensates externally for the absence of the ACL.

Adult↗
PubMed1993

Isotonic length/force models of nine different skeletal muscles.

The isotonic length/force relationships of nine skeletal muscles in the cat's hindlimb were determined using electrical stimulation of the sciatic nerve branches. Large variability in the active, passive, total force patterns and elongation ranges was found. The lateral gastrocnemius (LG), medial gastrocnemius (MG), peroneus longus (PL), flexor digitorum longus (FDL), tibialis posterior (TP) and soleus (Sol) showed symmetric active force curves, whereas those of the extensor digitorum longus (EDL), tibialis anterior (TA) and peroneus brevis (PB) were asymmetric. The total force curves of the EDL, LG, MG, FDL, TP and Sol increased quasilinearly through the elongation range, whereas the PL and PB increased in a nonlinear fashion. The TA had an intermediate plateau. The ranges were generally asymmetric, with a longer shortening range than lengthening past the optimum length. A simple model of the active force was fitted to all except the MG, EDL and TA, which are complex, with at least two compartments. These were successfully fitted with a two-compartment model. The variabilities encountered in the various isotonic length/force curves confirm the need to represent muscles according to their architecture to account for the variety of properties exhibited, which reflect their adaptations to their functions.

Animals↗
PubMed1993

Impact tolerances of the rigidly fixated maxillofacial skeleton.

A study was designed to determine how soon an athlete who undergoes rigid fixation of a facial fracture can return to full competition. The impact resistance of a rigidly fixated malar complex fracture was studied and compared with that of an intact malar complex. Twelve fresh human cadaver heads were used. A custom-designed impact device was used to deliver a blow of a specific energy to each intact malar complex. The subsequent fractures were rigidly fixated at three points using titanium miniplates and screws. A second impact of identical energy was delivered. The forces generated and the subsequent displacement of hard and soft tissues were recorded after each impact. It was concluded from this study that an impact to a rigidly fixated malar complex fracture produced less force and greater displacement of hard and soft tissues than an impact of identical energy to an intact malar complex. The potential for sustaining more severe maxillofacial injuries after an initial facial fracture should be seriously considered. The results suggest that sufficient time should be allowed for the bony healing of a facial fracture to occur, even after rigid fixation, before an athlete can resume full contact activities.

Age Factors↗
PubMed1993

Role of tendon properties on the dynamic performance of different isometric muscles.

The effect of the tendon's viscoelastic stiffness on the dynamic performance of muscles with different architecture was determined using the cat's medial gastrocnemius and extensor digitorum longus. Dynamic response models were derived under sinusoidal contraction-relaxation in the range of 0.4-6.0 Hz and between 20 and 80% of the muscles' maximal isometric tension, manipulated by orderly recruitment-derecruitment of motor units together with firing rate increase-decrease. It was shown that, for isometric contractions at the muscle's optimum length, the dynamic response of the muscles was not significantly different before and after dissection of the tendon. Therefore the conclusion that under these conditions the tendon acts like a stiff force transmitter without significantly modifying the muscle's performance was confirmed and extended to muscles with different architecture.

Action Potentials↗
PubMed1992

The dynamic performance model of skeletal muscle.

Applications of electrical stimulation to the nerve or muscles associated with a defunct limb joint due to stroke or spinal cord injury are a viable means of restoring a certain level of functional movement to the patient. In this article, the currently acceptable physiology of motor control is outlined and used as a criterion for electrophysiological and biomechanical performance evaluation of contemporary electrical stimulation strategies used by various systems attempting to duplicate such motor control in an effort to restore meaningful limb function. Strategies associated with surface, nerve, intramuscular, and reflex stimulation are critically reviewed with special reference to voluntary sensory motor control of a limb joint rather than an isolated muscle.

Animals↗
PubMed1991

Integrating computers into orthopedic research.

The role of computers in orthopedic research and education is expanding rapidly. Its potential to manipulate large amounts of data and execute multiple complex assignments with great speed and accuracy indeed make the computer an awe-inspiring device. An important instrument in research is the computerized database, a collection of related data arranged so that useful information may be retrieved. Computer models derived from classical physics and fluid mechanics have been used to study motion of both extremities and spinal articulations. Computers also have found usefulness in clinical orthopedic research. The orthopedist of the future will use the computer directly in clinics and private practice for patient evaluation, computer-assisted preoperative planning, and financial recordkeeping.

Biomechanical Phenomena↗
PubMed1990

Energy consumption in paraplegic ambulation using the reciprocating gait orthosis and electric stimulation of the thigh muscles.

The energy consumption of six thoracic paraplegic persons ambulating in the reciprocating gait orthosis (RGO) with and without functional electric stimulation (FES) of their thigh muscles was determined as a function of walking speed. Plots of Kcal/kg-min and Kcal/kg-m vs walking speed in the RGO and RGO & FES were experimentally determined in this study and compared with the energy cost of walking in the long leg brace (LLB), the hip guidance orthosis (HGO), and an FES walking aid from data available in the literature. The RGO powered with electric stimulation of the thigh muscles required the lowest energy expenditure in Kcal/kg-m across the full range of walking speeds. The RGO, HGO, LLB, and FES walking orthoses ranked second, third, fourth, and fifth respectively. The lowest energy costs in Kcal/kg-min were associated with the RGO & FES, followed by the RGO, HGO, LLB, and FES for walking speeds below .28m/sec. At walking speeds higher than .28m/sec the HGO demonstrates lower energy cost followed by the RGO & FES, RGO, FES, and LLB. At the end of a 30-m walk, patients using the RGO & FES had a mean heart rate (HR) which was 12 beats/min less than the mean HR when using the RGO without FES, 31 beats/min less than the HR when using the LLB, and 42 beats/min less than the HR when using FES only. It was concluded that the FES-powered RGO combines the advantages of a passive mechanical orthosis with those of FES to provide substantial improvements in energy cost which may provide paraplegic persons with a mode of independent ambulation superior to the wheelchair.

Adult↗
PubMedDate not supplied

Role of the tendon in the dynamic performance of three different load-moving muscles.

The effect of the tendon's viscoelastic properties on the dynamic performance of three different load-moving muscles was determined. The frequency response models of the cat's medial gastrocnemius (MG), extensor digitorum longus (EDL), and tibialis anterior (TA) with and without their tendons were derived under sinusoidal shortening-lengthening, manipulated by orderly recruitment and derecruitment of motor units together with firing rate increase and decrease. The passive load sizes applied to the muscles were approximately 30%-40% of each muscle's maximal isometric force. It was shown that the tendon has a moderate effect on the dynamic response of muscles while moving loads of fixed mass. The MG and EDL without their tendons show a decrease in high frequency gain (2-5 dB) and increasing phase lag angles (7 degrees-9 degrees). In contrast, the TA without its tendon shows an increase in high frequency gain (2 dB) and decreasing phase lag angles (20 degrees) compared with the same muscle with the tendon. It was concluded that tendon's viscoelastic properties have a moderate effect during load-moving contractions, influencing the dynamic performance of different muscles in a different manner.

Animals↗
PubMedDate not supplied

Mechanoreceptors and reflex arc in the feline shoulder.

A reflex arc from the glenohumeral capsule to the biceps, infraspinatus, supraspinatus, and subscapular muscles was shown in a feline preparation. Branches of the suprascapular and subscapular nerves terminating in the capsule were identified and then stimulated with a 100 microseconds supramaximal pulse at 10 pulses per second. Stimulation of the suprascapular articular nerve elicited electromyographic discharge in the biceps and infraspinatus muscles, whereas stimulation of the subscapular articular nerve elicited electromyographic discharge in the biceps, subscapularis, infraspinatus, and supraspinatus muscles. When the articular nerves were transected between their emergence from the main nerve trunk and the stimulation electrodes, the electromyographic discharge was abolished confirming the afferent nature of the nerves. The mean time delay ( +/- SD) from application of the stimulus to the peak of the recorded electromyographic activity was 3.2 +/- 0.27 msec. Anatomic dissection and staining of the capsule segments where the articular nerves terminated revealed mechanoreceptors consisting primarily of free nerve endings and Golgi tendon organs, Ruffini's endings, and pacinian corpuscles. The existence of a ligamento-muscular reflex arc in the glenohumeral joint extends the concept of passive and active restraints of a joint by virtue of the synergy between ligaments and muscles. That such a reflex exists may advocate modification of surgical repairs of the capsule, leading to preservation of as many neurologic structures as possible; it may also form the foundation for new postsurgical therapeutic modalities.

Animals↗
PubMedDate not supplied

Motor unit recruitment strategy of antagonist muscle pair during linearly increasing contraction.

The motor unit recruitment control strategy of the antagonist thigh muscles was determined during linearly increasing isometric flexion and extension of the knees. The median frequency (MF) of the power density spectrum of surface electromyograms recorded from eighteen subjects was used as an indicator of motor units recruitment. The results showed that different recruitment strategies were used by the muscles that are antagonist to each other. When quadriceps and hamstrings acted as agonist most of the motor units were recruited in a linear manner up to 60% of maximal voluntary contraction (MVC). When the muscles acted as antagonist, quadriceps motor units were recruited up to 40% MVC during flexion while during extension the antagonist hamstrings recruited motor units up to 60% MVC. In both muscles, when acting as antagonist, the MF decreased after the recruitment phase, whereas when functioning as agonists, the MF remained relatively constant past the recruitment phase. The results suggested that a single muscle can employ different motor units recruitment strategies in accord with the type of contraction it performs and while acting as an agonist muscle as well as an antagonist.

Adult↗