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At least 757 records · Page 42Linked to original sources
PubMed2000

Isokinetic torque deficit of the knee extensor muscles after arthroscopic partial meniscectomy.

Isokinetic torque deficit of the knee extensor muscles in the operated leg was measured in 21 male patients (mean age 26.4 +/- 1.9 years) who had undergone arthroscopic partial medial meniscectomy. The isokinetic torque testing was performed 1, 3, and 6 months postoperatively using the Cybex II dynamometer according to standard technique. Isokinetic knee extension peak torque (PT) at angular velocities of 60 degrees and 180 degrees/s was determined in both legs, and the proportional PT deficit in the operated leg was compared with that in the nonoperated leg. A significant (P<0.001) isokinetic PT deficit in the operated leg in testing with angular velocity of 60 degrees and 80 degrees/s was observed at 1 month (28.6% and 31.0%, respectively) and 3 months (19.8% and 15.8%, respectively) postoperatively. At 6 months postoperatively a significant (P<0.001) isokinetic PT deficit (18.2%) of the knee extensor muscles in the operated leg was observed only in testing with angular velocity of 60 degrees/s; no significant differences (P>0.05) in isokinetic PT between the operated and nonoperated leg in testing with angular velocity of 180 degrees/s was found 6 months postoperatively. Thus in patients with arthroscopic partial meniscectomy the postoperative recovery of isokinetic strength of the knee extensor muscles in the injured leg is closely related to testing velocity, while it is more delayed at low than intermediate angular velocities.

Adult↗
PubMed1984

Variability of effective root torque as a function of edge bevel on orthodontic arch wires.

The effective torque delivered by a variety of arch wire-bracket combinations has been measured experimentally in terms of the deviation angle, by means of a torque-meter apparatus, and compared to theoretical values calculated from both nominal and measured bracket slot and wire dimensions. Edgewise brackets with both 0.018 and 0.022 inch slot widths from two manufacturers were used, with three different arch wire sizes for each slot size. Stainless steel, nickel-cobalt, and beta titanium wires from a total of three manufacturers were employed. The present effective torque values were less than the theoretical values previously reported by Dellinger and Creekmore, who had separately focused on manufacturer tolerances associated with the wire cross sections and slot widths, respectively. Differences between the experimental and theoretical values of deviation angle were in agreement with measurements of the wire-bracket tolerances and with microscopic observations of differences in the edge bevel at the corners of the arch wires. The average edge bevel contribution to the measured deviation angle varied from 0.2 degrees to 12.9 degrees for the various wire-bracket groups, and the average percentage contribution from 3 to 63%. The edge bevel contribution to the deviation angle was higher for stainless steel wires than for nickel-cobalt wires marketed as square-cornered. The highest deviation angles and edge bevel contributions were found for the beta titanium wires.

Equipment Design↗
PubMed1994

Agonist and antagonist EMG activation during isometric torque development at the elbow in spastic hemiparesis.

Voluntary isometric step contractions of the elbow flexor and extensor muscles were studied in a group of patients with paresis arising as the result of unilateral cerebral lesion and in a control group of normal subjects. For each subject the maximum isometric torque in flexion and extension was obtained, along with a series of graduated torque steps up to this maximum, in order to perform a regression analysis between torque developed and the associated agonist and antagonist EMG. This relationship proved to be linear in all normal subjects and in all but the most paretic spastic patients. If the patients were grouped according to their ability to make discrete large angle flexion and extension movements at the elbow, a clear correspondence was seen between increasing movement disability and the degree of paresis. No significant differences were found in the torque/EMG relationship of spastic patients when either elbow extensors or flexors were acting as the agonist in a contraction. Similarly, no evidence of exaggerated antagonist co-activation was found. It is concluded that, in the upper arm muscles, hemiparesis following stroke cannot, under isometric conditions, be attributed to hyperactivity of antagonist muscles.

Adult↗
PubMed1989

Relation between electromyogram and torque of isometric reflex contractions in man.

Human subjects maintained isometric plantar or dorsal flexions of the ankle in a matching task. H-reflexes of different sizes were superimposed on the steady activity. The peak-to-peak amplitude of the reflexes was measured on the electromyogram (EMG) of the soleus muscle. The size of the corresponding muscle contractions was determined on the isometric torque signal in relation to the maintained flexion force. The EMG-torque relation which was defined as the reflex muscle contraction as a function of the EMG reflex signal approximated a square root function for a given steady contraction level. It was not modulated by steady dorsal flexions, but it decreased continuously with stronger plantar steady torques. This dependence was caused by the silent period following the reflex discharge. Since the reflex discharge and the silent period were near in time to the duration of the contraction, the silent period had a direct effect on the reflex contraction amplitude.

Electromyography↗
PubMed2006

Design of a torque-controlled manipulator to analyse the admittance of the wrist joint.

This paper describes the design of a torque-controlled manipulator to identify the dynamics of the wrist joint. With torque disturbances, the subject can actively control the joint angle, giving a natural task. The application of a hybrid haptic controller guarantees linearity over a large bandwidth and adjustable virtual dynamics. The haptic controller has a bandwidth of 50 Hz, meaning that the virtual dynamics are realistically felt at up to 50 Hz. To let the subject 'feel' the torque, disturbances as well as possible the apparent, or virtual, dynamics of the device must be small. The minimal apparent inertia of the device is 1.6 g m(2), which is of the same order as for a normal wrist, and the minimal damping and stiffness are negligible. To judge the accuracy of the manipulator, loads of known physical properties were attached and their parameters were quantified. The parameters of the loads were estimated with a maximum error of 5%. As the eigenfrequency of a (co)-contracted human wrist is approximately 15 Hz, the 50-Hz bandwidth of the haptic device is sufficient to measure all relevant dynamics of the human wrist. With this device, the dynamics of the human wrist joint can be measured under varying virtual dynamics, as well as the effect of neurological dysfunction on human motor control, for example.

Algorithms↗
PubMed2006

A traveling wave ultrasonic motor of high torque.

A traveling wave ultrasonic motor of high torque with a new configuration is proposed in this paper. In the new design, a part of the motor serves as the stator. The rotor is the vibrator consisting of a toothed metal ring with piezoelectric ceramic bonded, which generates ultrasonic vibration. The rotor is in contact with the shell of motor and is driven by the friction between the rotor and the stator. This configuration not only removes the rotor in a conventional type of traveling wave ultrasonic motor but also changes the interaction between the rotor and the stator of the motor so that it improves the output performance of the motor. Although an electric brush is added to the ultrasonic motor, it is easy to be fabricated because of the low speed of motor. The finite element method was used to compute the vibration modes of an ultrasonic motor with a diameter of 100mm to optimize the design of the motor. A 9th mode was chosen as the operation mode with a resonance frequency about 25 kHz. According to the design, a prototype was fabricated. Its performance was measured. The rotation speed-torque curves for various frequencies were obtained. The result shows that its stall torque is greater than 4 Nm within a range of 400 Hz. This ultrasonic motor was used to drive the window glass of a mobile car and the result was satisfactory. In the further the research on the friction material between the stator and the rotor is under way to improve the efficiency of the ultrasonic motor.

Journal Article↗
PubMed2001

Postural control and torque of the knee joint after healed tibial shaft fracture.

Muscular atrophy occurs as a consequence of trauma and immobilisation. This cohort comparison study was conducted to evaluate the limb function after healed tibial shaft fractures, which were treated by casting versus nailing. Balance (as centre of pressure) and muscle strength (as torque of the knee joint during knee extension) have been measured in 27 patients with tibial shaft fractures with a mean age of 39 (19-73) years, 1 year after fracture healing. Fourteen patients were treated by intramedullary nailing 'nailed group' and 13 by plaster cast with or without minimal internal fixation 'casted group'. Centre of pressure was measured on a force platform. Knee extension torque was measured during isometric and concentric muscle actions by an isokinetic dynamometer. Centre of pressure tended to be more towards the uninjured leg in patients who had been treated by plaster cast (P<0.05). Side-to-side differences for isometric torque were significantly higher within the casted group (P<0.05). Patients with tibial shaft fractures treated by intramedullary nailing showed better postural control, one-leg standing test, and side-to-side differences for isometric muscle strength compared with patients treated by cast. Therefore, we recommend intramedullary nailing as a better method of treatment for tibial shaft fractures, with regard to recovery of muscle function.

Adult↗
PubMed2003

Torque-speed relationship of the Na+-driven flagellar motor of Vibrio alginolyticus.

The torque-speed relationship of the Na(+)-driven flagellar motor of Vibrio alginolyticus was investigated. The rotation rate of the motor was measured by following the position of a bead, attached to a flagellar filament, using optical nanometry. In the presence of 50mM NaCl, the generated torque was relatively constant ( approximately 3800pNnm) at lower speeds (speeds up to approximately 300Hz) and then decreased steeply, similar to the H(+)-driven flagellar motor of Escherichia coli. When the external NaCl concentration was varied, the generated torque of the flagellar motor was changed over a wide range of speeds. This result could be reproduced using a simple kinetic model, which takes into consideration the association and dissociation of Na(+) onto the motor. These results imply that for a complete understanding of the mechanism of flagellar rotation it is essential to consider both the electrochemical gradient and the absolute concentration of the coupling ion.

Culture Media↗
PubMed1995

Implant stability related to insertion torque force and bone density: An in vitro study.

Seventy-five implants were installed in 12 fresh ethanol-treated bovine ribs by use of a torque gauge manometer to measure the force needed to screw the implants fully into the bone. Digital radiographs were taken and a density histogram of the bone at the implant/bone interface was obtained. The damping characteristics of the implant/bone interface were assessed by tapping the abutment with the Periotest (PT) device. Abutments of several lengths screwed at 20 N/cm were used to conduct PT measurements and the PT values (PTVs) were related to the insertion torque force, the bone density, and implant and abutment length. The results indicated that high correlations exist between PTVs and insertion torque force (R value -0.74579), and PTVs and bone density (R value -0.83031). There was also a significant difference (p 0.001) among the PTVs of the different abutment lengths used. Implant length did not demonstrate influence on PTVs (p 0.3847).

Analysis of Variance↗
PubMedDate not supplied

Circumferential finger measurements utilizing a torque meter to increase reliability.

The purpose of this study was to compare the reliabilities of two methods of measuring finger circumference. Traditionally, finger circumference is determined clinically by the use of a tape measure. In this study, a tape-measure device for recording finger circumference utilizing a torque meter was compared with the traditional method to determine reliability differences. Ninety-two occupational therapists and occupational therapy students obtained circumferential measurements of the author's left index finger at the middle of the proximal phalanx utilizing the two methods. The readings obtained for each method were analyzed to determine the coefficient of variation and to compare their variances. The coefficient of variation for the traditional method was 2.92 and for the device utilizing the torque meter was 0.75. The F ratio was 15.63, which is significant at the 0.01 level. The results of this study indicate greater interrater reliability using a device that can accurately measure torque and allow the therapist to control the amount of tension applied when obtaining circumferential measurements using a tape measure.

Aged↗
PubMed2000

Transcutaneous FES of the paralyzed quadriceps: is knee torque affected by unintended activation of the hamstrings?

This study addresses the question whether unintended response of the knee flexors (hamstrings) accompanies transcutaneous functional electrical stimulation (FES) of the quadriceps and whether the knee torque is hereby affected. Transcutaneous FES of the right quadriceps of two paraplegic subjects was applied and measurements were made of the net torque and of the myoelectric activities of the quadriceps and hamstrings muscles of the right leg. A low correlation was obtained between the peak-to-peak amplitudes of the M-waves of the two muscles. This correlation decreased further with the development of fatigue, which indicated that the electromyography (EMG) signals from the hamstrings were not the result of cross-talk between adjacent recording sites. The force profile of each muscle was determined from a developed model incorporating EMG-based activation, muscle anthropometry as obtained from in vivo magnetic resonance imaging of the thigh, and metabolic fatigue function, based on data acquired by 31P nuclear magnetic resonance spectroscopy. A sensitivity analysis revealed that the muscle specific tension and the muscle moment arms have a major influence on the resulting muscle forces and should therefore be accurately provided. The results show that during the unfatigued phase of contraction the estimated maximal force in the hamstrings was lower than 20% of that in the quadriceps and could be considered to be practically negligible. As fatigue progressed the hamstrings-to-quadriceps force ratio increased, reaching up to 45%, and the effect of co-activation on the torque partition between the two muscles was no longer negligible.

Adult↗
PubMedDate not supplied

A removal torque and histomorphometric study of commercially pure niobium and titanium implants in rabbit bone.

Screw-shaped commercially pure (c.p.) niobium and c.p. titanium implants were inserted in rabbit bone. After a healing period of 3 months, a significantly higher removal torque was demonstrated to unscrew the niobium implants (average 32.9 Ncm) compared to the c.p. titanium implants (average 25.3 Ncm). In the histomorphometric part of the study, there were no significant differences in bone-to-metal contact between the 2 implant materials. An average of 41.1% bony contact was demonstrated for the niobium screws compared to an average of 37.2% for the c.p. titanium ones. Our removal torque findings could be related to the differences that we observed between the 2 implant surfaces as indicated by SEM. Since niobium implants showed a more irregular surface topography and niobium is a softer metal than c.p. titanium, this seems the most probable reason for the differences observed in removal torque between the 2 metals. Hypothetically, a more "positive biocompatibility" of the c.p. niobium in comparison to the c.p. titanium remains as another possible reason for the observed differences. However, against such a difference in biocompatibility between c.p. niobium and c.p. titanium, there is the very similar amount of bony contact registered in the histomorphometric analysis.

Animals↗
PubMed2005

Spin-torque diode effect in magnetic tunnel junctions.

There is currently much interest in the development of 'spintronic' devices, in which harnessing the spins of electrons (rather than just their charges) is anticipated to provide new functionalities that go beyond those possible with conventional electronic devices. One widely studied example of an effect that has its roots in the electron's spin degree of freedom is the torque exerted by a spin-polarized electric current on the spin moment of a nanometre-scale magnet. This torque causes the magnetic moment to rotate at potentially useful frequencies. Here we report a very different phenomenon that is also based on the interplay between spin dynamics and spin-dependent transport, and which arises from unusual diode behaviour. We show that the application of a small radio-frequency alternating current to a nanometre-scale magnetic tunnel junction can generate a measurable direct-current (d.c.) voltage across the device when the frequency is resonant with the spin oscillations that arise from the spin-torque effect: at resonance (which can be tuned by an external magnetic field), the structure exhibits different resistance states depending on the direction of the current. This behaviour is markedly different from that of a conventional semiconductor diode, and could form the basis of a nanometre-scale radio-frequency detector in telecommunication circuits.

Journal Article↗
PubMed1994

Normal values of isokinetic maximum strength, the strength/velocity curve, and the angle at peak torque of all degrees of freedom in the shoulder.

Many acute and chronic complaints in the shoulder joint are due to a reduced active stabilization capacity. Procedures to measure isokinetic strength are used to objectify the muscle deficits and imbalances of various muscle groups. In this study, standard values and reference ranges were determined for peak torque (PT), strength/velocity curve, and range of motion (ROM) at peak torque in the shoulder in 19 untrained women and 32 men. Differentiation was made by the individual degrees of freedom of the shoulder joint and the various types of work (concentric, isometric, eccentric). Moreover, the influence of height, body weight, and body mass index on isokinetic maximum strength development was investigated. It was found that it is necessary to distinguish between the various movements and types of work in development of peak torque. A decrease in maximum strength is observed in the sequence extension, adduction/flexion, abduction/internal rotation, external rotation. The maximum strength of men was determined to be higher than that in women. ROM shows a wide fluctuation and does not possess high validity. Height, as well as body weight and body mass index have only slight influence on the isokinetic maximum strength in the shoulder of untrained men and women.

Adult↗
PubMed1988

Relationship between peak torque and total work in an isokinetic contraction of the medial collateral ligament insufficient knee.

The aim of this study was to assess the relationship between the isometric and isokinetic peak torques (speed of movement 0, 60, and 180 degrees/s) and the total work output of multiple contractions (180 degrees/s) of the quadriceps and hamstrings in 25 subjects having a chronic, complete insufficiency of the medial collateral ligament of the knee. At every test speed the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the peak torque and total work were highly significant for both muscle groups in the uninjured (r = 0.75-0.96, rs = 0.72-0.95) as well as in the medially unstable (r = 0.79-0.93, rs = 0.76-0.92) knees. In both knees and in both muscle groups, the correlation coefficients increased toward the highest speed of the isokinetic movement, obviously since the total work was registered at that speed. The author concludes that in the medial collateral ligament insufficient knees the total work analysis offers little additional information to that attained by more simple measurement, the peak torque analysis.

Adult↗
PubMed1983

The torque test as a measure of lateral dominance.

The present study was designed to assess the validity of the Torque Test as a measure of functional lateral dominance in children. One hundred forty-nine children were administered the Torque Test and The Harris Test of Lateral Dominance. A low but statistically significant correlation was found between torque and total lateral dominance.

Adolescent↗
PubMed1993

Stretch-induced electromyographic activity and torque in spastic elbow muscles. Differential modulation of reflex activity in passive and active motor tasks.

Stretch-evoked electromyographic (EMG) activity and torque signals have been studied in elbow joint muscles of both sides of patients with spastic hemiparesis and healthy subjects. In order to reveal differences in the generation of muscle tone between clinical assessment and functional movement, stretches of different velocities and amplitudes were applied during passive and quasi-functional active motor tasks. In spastic patients the strength and duration of the EMG responses following stretching of flexor and extensor muscles during both passive and active tasks were dependent on the stretch velocity and duration, respectively. This effect was seen on both the spastic and unaffected side. Under passive conditions EMG activity after stretching was negligible in the limb muscles of healthy subjects, of small amplitude in unaffected limbs of the patients, but was strong in affected muscles. Under active conditions, the amplitude of the early (M1) component of the EMG signal was larger, while the later components (M2 and M3) were smaller. These differences were due more to a change in reflex gain than to a change in reflex threshold when the stretch velocity signal was the basis for calculation. It is suggested that in spastic paresis, modulation of stretch-induced EMG activity in the spastic limb becomes restricted to a smaller range with a poor ability to switch off under passive conditions. Furthermore, the reflex EMG activity suffers a reduced facilitation under active conditions. In comparison with unaffected limbs the stretch-evoked torque on the affected side was increased under passive conditions (due to the extra EMG activity) and decreased under active conditions (due to a reduced EMG activity). An increased torque to EMG ratio was found in spastic flexor and extensor muscles during active tasks. This is thought to be due to changes in mechanical muscle fibre properties suffered as a consequence of defective muscle activation following cerebral lesions. The consequences for clinical assessment of muscle tone and therapy of spastic movement disorder are discussed.

Adult↗
PubMed1983

Electromyographic, peak torque, and power relationships during isokinetic movement.

The use of isokinetic measurements for research and clinical practice becomes more meaningful when it can be demonstrated that subjects being tested at multiple velocities are making similar efforts and when the relationships between various biomechanical measures are understood. The purpose of this study was to examine 1) integrated electromyographic activity per second of the quadriceps femoris muscle at four isokinetic speeds (30, 60, 90, and 120 degrees/sec) and 2) the relationship of power to peak torque at each speed. Two groups were tested: "normals" (healthy subjects) and patients undergoing long-term steroid therapy for rheumatic diseases. The integrated electromyographic activity per second did not vary significantly across speeds, indicating that subjects in each group made equivalent efforts at all four speeds. At each speed, for each group, high correlations were found between peak torque and power. Population-specific and speed-specific linear regression equations were calculated that allowed for predictions of power from the more easily obtained clinical measure of peak torque.

Adult↗