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At least 667 records · Page 37Linked to original sources
PubMed1990

Effects of axis placement on measurement of isokinetic flexion and extension torque in the lumbar spine.

We wanted to ascertain whether changing the machine axis placement relative to the anatomic landmarks of a tested subject in isokinetic flexion and extension trunk strength would influence the measurements obtained. Twenty healthy volunteers were tested with the machine axis intentionally displaced from a reference position at the lumbosacral junction. Displacing the axis 50 mm vertically produced on average 15% increase in the torque produced, and displacing it 10 mm horizontally produced approximately 5% reduction in torque, independent of the direction of displacement from the reference position. The angle at which maximum torque occurred and the ratio of extension to flexion torque were unaffected by axis placement. Intertester reliability in axis placement was found experimentally to produce variations of usually less than 10 mm. We conclude that isokinetic trunk strength measurement is affected by testing axis placement; this should be controlled, especially in repetitive testing of the same individual.

Adult↗
PubMed1990

Lower extremity preference and knee extensor torques in intercollegiate soccer players.

The purpose of this study was to determine whether lower extremity preference influenced the relationship between the dominant and nondominant knee extensors of intercollegiate soccer players. Twelve recreational athletes and 12 soccer players completed isometric contractions at 60 degrees flexion, and concentric-eccentric contraction cycles at angular velocities of 60 degrees and 180 degrees/s through a range of motion from 90 degrees to 10 degrees knee flexion. Although the soccer players demonstrated greater peak and average torques, and greater differences between their dominant and nondominant legs, they responded similarly to recreational athletes during isometric, concentric and eccentric contractions and produced similar torque-velocity patterns. The concentric/eccentric ratios were similar for both legs and both groups, and decreased as angular velocity increased. The nondominant/dominant ratios of the soccer players, however, were significantly lower than those of the recreational athletes when calculated using peak torque (p less than .02) and nearly so when calculated using average torque (p less than .08). Nondominant/dominant ratios were not affected by the type of contraction or by the angular velocity. Further study is required to determine whether the small asymmetry (about 7%) in knee extensor strength of the soccer players is significant with respect to performance or injury rates, or may be inconsequential.

Adult↗
PubMed1990

[Removal torques of small screws of steel and titanium with different surfaces].

This study was designed to investigate the relationship between metal surfaces and bone holding strength and the safety margin against breakage available in small screws at implant removal. Small cortical bone screws of 1.5 and 2 mm outer diameter (mini-screws) made of stainless steel or commercially pure titanium have been mechanically and chemically treated to give different surface conditions. They were implanted in randomized groups of four or five speciments into the proximal halves of rabbit tibiae. Tightening was performed with a standardized torque of 10 or 18 Ncm by means of an instrumented screwdriver. The animals were sacrificed after 12 weeks and screw removal torques were measured. Stainless steel screws used as reference screws were found to have loosened their seat by 27% compared with the original tightening torque. Titanium implants, in contrast, revealed improved bone contact with higher removal torques varying from 130% to 160%. No correspondence could be found between these values and the surface roughness of glass-ball-blasted versus polished screws.

Alloys↗
PubMed1989

Isokinetic muscle torque in the dorsiflexors of the ankle in children 6-15 years of age. Normal values and evaluation of the method.

Isokinetic muscle torque of the dorsiflexors of the ankle was tested in 137 children 6-15 years old. Reference values in different age groups are given for girls and boys separately. Generally, peak torque values increased with age. However, the developed torque/kg bodyweight showed no significant difference in 15-year-old girls compared to 12-year-old girls. For prediction of normal torque the best parameters are age, weight and height. The maximal torque and work values generally increased with increasing weight and height. The prediction was not improved by adding factors like length of the lower leg, calf circumference and length of the foot. In the youngest age groups, the stronger leg, in the highest velocities, was on the dominant side, while in the older groups the strongest leg, at least in slow velocities, was on the non-dominant side. The boys seem to have their most intensive force development between 12 and 15 years while this occurs earlier in girls.

Adolescent↗
PubMed1988

Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part II, Friction, heating, and torque.

In Part I, (J.A. Davidson and G. Schwartz, "Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part I, A review," J. Biomed. Mater. Res., 21, 000-000 (1987) it was shown that lubrication of the artificial hip joint was complex and that long-term performance is governed by the combined wear, creep, and to a lesser extent, oxidation degradation of the articulating materials. Importantly, it was shown that a tendency for heating exists during articulation in the hip joint and that elevated temperatures can increase the wear, creep, and oxidation degradation rate of UHMWPE. The present study was performed to examine closely the propensity to generate heat during articulation in a hip joint simulator. The systems investigated were polished Co-Cr-Mo alloy articulating against UHMWPE, polished alumina ceramic against UHMWPE, and polished alumina against itself. Frictional torque was also evaluated for each system at various levels of applied loads. A walking load history was used in both the frictional heating and torque tests. The majority of tests were performed with 5 mL of water lubricant. However, the effect of various concentrations of hyaluronic acid was also evaluated. Results showed frictional heating to occur in all three systems, reaching an equilibrium after roughly 30 min articulation time. Ceramic systems showed reduced levels of heating compared to the cobalt alloy-UHMWPE system. The level of frictional torque for each system ranked similar to their respective tendencies to generate heat. Hyaluronic acid had little effect, while dry conditions and the presence of small quantities of bone cement powder in water lubricant significantly increased frictional torque.

Hip Prosthesis↗
PubMed1988

Eccentric and concentric torque and power of the knee extensors of females.

The purpose of this study was to compare differences in eccentric and concentric peak torque and power measurements of knee extensors at different velocities. The subjects included 21 females between the ages of 19 and 28, who had no history of knee pain or abnormality. Eccentric and concentric contractions of the knee extensors of the dominant leg of each subject were tested on an isokinetic dynameter at 60 degrees/s, 120 degrees/s and 180 degrees/s. Eccentric peak torque was greater than concentric at each of the three velocities tested, whereas eccentric power was significantly greater only at the two higher velocities. The lack of change in concentric peak torque between 120 degrees/s and 180 degrees/s contrasted with results of other studies, probably owing to methodological differences. Eccentric torque increased from 60 degrees/s to 120 degrees/s, but decreased again at the highest velocity. Both concentric and eccentric power increased with velocity.

Adult↗
PubMed1985

Isometric torque-angle relationship and movement-related activity of human elbow flexors: implications for the equilibrium-point hypothesis.

Since the moment arms for the elbow-flexor muscles are longest at intermediate positions of the elbow and shorter at the extremes of the range of motion, it was expected that the elbow torque would also show a peak at an intermediate angle provided the activity of the flexor muscles remained constant. We measured the isometric elbow torque at different elbow angles while the subject attempted to keep constant the electromyographic activity (EMG) of the brachioradialis muscle. The torque-angle relationship thus obtained exhibited a peak, as expected, but the shape of the relationship varied widely among subjects. This was due in part to differences in the variation of the biceps brachii EMG with elbow angle among the different subjects. The implications of these observations for the equilibrium-point hypothesis of movement were investigated as follows. The subject performed elbow movements in the presence of an external torque (which tended to extend the elbow joint) provided by a weight-and-pulley arrangement. We found in the case of flexion movements that invariably there was a transient increase in flexor EMG, as would seem necessary for initiating the movement. However, the steady-state EMG after the movement could be greater or less than the pre-movement EMG. Specifically, the least flexor EMG was required for equilibrium in the intermediate range of elbow angles, compared to the extremes of the range of motion. The EMG-angle relationship, however, varied with the muscle and the subject. The observation that the directions of change in the transient and the steady-state EMG are independent of each other militates against the generality of the equilibrium-point hypothesis. However, a form of the hypothesis which includes the effects of the stretch reflex is not contradicted by this observation.

Arm↗
PubMed1980

[Studies on the performance of the dental air turbine handpieces. (Part 3) Torque measurements of the air turbine handpieces (author's transl)].

Air turbine handpieces, electro-micro motors and electric engines are widely used as the dental cutting instruments for the clinical use. So, this paper examined the measurement of rotational torque of the high speed dental instruments used for cutting works. For the measurement of torque of the dental instrument, we have measured the pushing load of the test but as used for cutting tools. But, in this paper, we attempted the new trials which are the measuring the tangential force of test bur rotated with the high speed velocity. And then, the kinetic energy values of rotational bur are obtained with using the value of the test bur's rotational torque. Besides we examined the interrelations of the rotational torque and pushing as the results, and both measurement value show the good relations for air turbine handpieces.

Air↗
PubMed1995

Peak torque per unit cross-sectional area differs between strength-trained and untrained young adults.

It is unclear whether gender differences in the relative strength of the upper and lower body are due to differences in muscle mass distribution or dissimilarity of use. There is also controversy as to whether prolonged resistance training increases strength per unit cross-sectional area (CSA). To help resolve these questions, maximum isometric torque per unit muscle and bone (M+B) CSA was measured in the upper arm and thigh of 26 trained (13 males; 13 females) and 26 untrained (13 males; 13 females) young adults. Muscle and bone CSA values were calculated from limb circumferences and skinfolds. Maximal isometric torque values were recorded by a LIDO isokinetic dynamometer. There was no significant difference (P > 0.05) in mean upper arm or thigh torque per unit M+B CSA between the trained males and trained females, or between the untrained males and untrained females. However, mean torque per unit M+B CSA was significantly higher for the trained subjects of both genders compared with the untrained subjects of both genders for the upper arm (28.9%; P < 0.0001) and thigh (18.8%; P < 0.0001). These results suggest that muscle quality (peak torque/CSA) is equal between genders, and that the increase in muscle strength per unit area that occurs with resistance training is not gender-dependent.

Adolescent↗
PubMedDate not supplied

Torque required to loosen single-tooth implant abutment screws before and after simulated function.

The amount of torque required to loosen screws from three different antirotational screw-retained abutment/implant combinations was compared (with and without adhesive sealant applied) after 6 kg of force was applied during simulated intraoral movements. Movements were generated over two simulated time periods, representing 1 and 6 months. There was no significant decrease (alpha < .05) in the torque required to loosen the screws after either time period when using Calcitek Omnilock or Stryker Minimatic. The Core-Vent Bio-Vent specimens, however, exhibited a significant decrease (alpha < .05) in the amount of torque required to loosen the screws at the 1-month test period only. The addition of adhesive sealant significantly increased (alpha < .05) the amount of torque necessary to loosen the screws only in the Core-Vent specimens.

Analysis of Variance↗
PubMed1993

The influence of conformity and constraint on translational forces and frictional torque in total shoulder arthroplasty.

Glenoid loosening in total shoulder arthroplasty (TSA) may result from translational forces and frictional torque generated at the articular surfaces and transmitted to the fixation interface. The effect of glenohumeral articular design on the magnitude of these translational forces and frictional torques has not been evaluated previously. Seven different glenohumeral designs were evaluated on a specially designed fixture integrated with a materials test system. The degree of conformity and constraint in the glenohumeral designs directly affected the forces generated during translation and rotation of the humeral head. Maximum translational forces occurred close to the midline in the more conforming design. The less conforming designs generated lower translational forces and frictional torques. Because frictional torque and translational forces at the glenohumeral articulation may contribute to glenohumeral loosening, the use of less conforming and less constrained designs is advocated where possible to reduce the potential for mechanical loosening of the glenoid component.

Biomechanical Phenomena↗
PubMedDate not supplied

The reverse-torque test: a clinical report.

Reverse torque to failure on implants has been studied in animals. Three implants were reverse torqued to failure in a human volunteer, with failure rates between 45 and 58 Ncm. Clinical data are presented on 404 implants examined after reverse-torque testing and loading, with no increase in failure rates. Reverse-torque testing at 20 Ncm appears to be a safe, reliable method for verifying osseointegration with pure titanium screw-shaped implants.

Animals↗
PubMed1977

Isokinetic and isometric torque force relationships.

The torque forces of elbow extensor musculature of 28 men were tested with an isokinetic dynamometer to determine the relationships between maximal isokinetic torque generated at various speeds and maximal isometric forces at specified angles in the arc of elbow extension. The men were tested at constant velocities ranging from 5 to 25 rpm and at angles of elbow extension ranging from 10 degrees to 90 degrees. Product-moment correlation coefficients were calculated between the maximum isometric torque developed at each of the measured angles and the isokinetic torque generated at each of the predetermined speeds. Of the 81 correlation coefficients calculated, 13 differed significantly from zero. There were slight tendencies for the significant correlations to cluster toward the slower speeds and toward the greater angles of elbow flexion. It was suggested that the slight tendency for higher correlations to cluster toward the slower speeds may be due to slower speeds stimulating isometric effort. The slight tendency for the higher correlations to cluster toward the greater angles of elbow flexion may be due to variances in the consistency of muscular strength at different muscle lengths. Since the highest correlation attained yielded a common variability of less than 24% between the two variables tested, it was concluded that measures of isokinetic strength cannot be used to predict isometric strength capabilities.

Adult↗
PubMed1995

Changes in the hemiparetic limb with training. I. Torque output.

The study concerns eleven patients who had suffered from a cerebro-vascular accident (CVA) less than 6 months previously and who were hospitalized for treatment. In addition to their multidisciplinary rehabilitation treatments, the patients consented to participate in an electromyographic (EMG) biofeedback program designed to increase their shoulder activity. From blocks of five individual isometric contractions, curves of both the mean torque and of its standard deviation (SD) were generated and from each of these, a mean value was obtained. These two measures were used to analyze the effects on the biofeedback training had induced on shoulder activity. The training induced negligible changes on the contralateral (CL) side. The mean torque value for the group was 31.02 post vs 30.99 Nm pre-training. However, for the hemiplegic (HEMI) limbs, some patients showed improvement while others did not. The treatment was considered a success when the mean torque values obtained in the last 2/3 of the training or at the post-training session were > or = 1.5 the values obtained during the pre-training session. Based on this criteria, it was found that six out of eleven patients did improve their muscular activity through the training. Among these, the improvement of four was greater during the 2/3 session than that observed at the post-training session. The six successful patients were found to have a pre-training upper extremity Fugl-Meyer score < or = 13. Two patients had a similar pre-training score of 11, and met the criteria of success, but the younger patient performed better than the older one. Patients with scores of 20 and higher did not meet the 1.5 criteria. A correlation (r = 0.80) was found between post/pre ratios of Fugl-Meyer scores and those of the mean torque: the test thus seems to have a limited usefulness for assessing local changes such as the effects of the biofeedback treatment on the shoulder.

Adult↗
PubMed2002

Hydroxyapatite-based composite for dental implants: an in vivo removal torque experiment.

Screw-shaped dental implants were fabricated from commercially pure Ti (c.p. Ti) and HA-based composites. The HA-based composites were fabricated by mixing HA with Al(2)O(3)-coated ZrO(2) powders. The mechanical properties of these composites were enhanced by a factor of 3. These were implanted into the rabbit tibiae and the removal torque to loosen the implants in vivo was measured in order to investigate the osteointegration. After a healing period of 6 weeks, the implants were retrieved with a torque gauge instrument. The HA-based composite implants showed an almost 2-times-higher removal torque when compared to the Ti implants (ANOVA, p < 0.05), indicating excellent biocompatibility to bone. Thus, HA-based composites had not only better mechanical properties but also similar bioactivity as HA itself. It is believed that a HA-based composite is suitable for artificial dental implants.

Aluminum Oxide↗
PubMed2002

Effect of moderate dehydration on torque, electromyography, and mechanomyography.

The purpose of the present investigation was to test the hypotheses that the mechanomyographic (MMG) signal would be affected by hydration status due to changes in the intra- and extracellular fluid content (which could affect the degree of fluid turbulence), changes in the filtering properties of the tissues between the MMG sensor and muscle, and changes in torque production that may accompany dehydration. Ten subjects (age 22.5 +/- 1.6 years) were tested for maximal isometric (MVC), submaximal isometric (25, 50, and 75%MVC), and maximal concentric isokinetic muscle strength of the biceps brachii in either a euhydrated or dehydrated state while the electromyographic (EMG) and MMG signals were recorded. Separate three-way and two-way ANOVAs indicated no change in torque, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF with dehydration. The lack of dehydration effect suggests that MMG may be more reflective of the intrinsic contractile processes of a muscle fiber (torque production) or the motor control mechanisms (reflected by the EMG) than the tissues and fluids surrounding the muscle fiber.

Adult↗
PubMed2004

Compensation of limb weight on interfaced raw torque signals from a KIN-COM dynamometer to an AMLAB workstation.

The effect of gravity should be considered when using isokinetic devices to measure human movement performance. In most isokinetic dynamometers gravity compensation is controlled by software through a gravity correction option. However in some complex research protocols the dynamometer signal acquisition and processing capability is not adequate to effectively synchronize or process a wide range of captured signals. Therefore when the force/torque signals from a commonly used dynamometer such as KIN-COM are interfaced into a signal processing workstation such as AMLAB, it is necessary to further process the received raw signals for gravity correction. The aim of this study was to evaluate the effectiveness of an AMLAB-based instrument designed for gravity compensation of raw torque signals acquired from a KIN-COM dynamometer. To check the accuracy of weight compensation within the AMLAB, environment, torque signals produced by a known weight during a 180-degree range of KIN-COM lever arm movement were compared with and without weight compensation. The results indicated that this technique is an accurate means for weight compensation when raw torque signals from a KIN-COM dynamometer are interfaced to an AMLAB workstation.

Biomechanical Phenomena↗
PubMed2006

The fixation strength of hydroxyapatite-coated Schanz screws and standard stainless steel Schanz screws in lower extremity lengthening : a comparison based on a new torque value index: the fixation index.

INTRODUCTION: Lengthening procedures are often complicated by loosening of pins. It has been reported that coating with hydroxyapatite improves fixation and reduces the rate of pin-track infection. MATERIALS AND METHODS: We compared 47 hydroxyapatite-coated Schanz screws (HA screws) in 12 monolateral fixators mounted at the University Hospital Hamburg-Eppendorf with 45 standard stainless steel screws in 9 monolateral fixators mounted at the St Josefs-Hospital Wiesbaden by measuring the insertion and extraction torque values. The average implantation period was 7 months for the hydroxyapatite-coated screws and 5.4 months for the uncoated screws. We established the quotient of the maximum extraction torque over insertion torque which shows the change in the fixation strength with respect to time, the fixation index. It eliminates the influence of the varying pin-bone contact. RESULTS: There was no significant difference in the rate of infection. In the Schanz screws without signs of infection the index was 1.92 for the HA screws and 0.76 for the stainless steel screws (P = 0.0002) giving evidence of the improvement of the fixation by the coating. CONCLUSION: HA coating resulted in improved fixation of Schanz screws in bone and may be useful in prolonged external fixation of the lower leg. The fixation index proved to be a simple tool for the evaluation of the fixation strength of Schanz screws.

Bone Lengthening↗