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At least 955 records · Page 53Linked to original sources
PubMed2002

High torque ultrasonic motors for hand prosthetics: current status and trends.

This paper presents the work carried out at the Instituto de Automática Industrial, in the framework of the EU MANUS project and with the co-operation of the Katholieke Universiteit of Leuven, to develop a specifically designed TWUM for driving our prototype of hand prosthesis. The application of TWUM to prosthetic devices has clear advanteges, namely, noiseless operation, self-braking drive, high torque and low speed characteristics. Here we analyse main actuation advantages, point out main drawbacks of this technology and describe our research in the area of specific design of TWUM for high torque actuation, improved control characteristics and enhanced overall performance. We intend to provide a concurrent approach to the overall actuator design involving electronics, mechanical design as well as improved control strategies having in mind the prosthetic application.

Artificial Limbs↗
PubMed1992

Effect of high velocity resistance training on peak torque, cross sectional area and myofibrillar ATPase activity.

The purpose of this investigation was to determine the effect of high velocity resistance (HVR) training on peak torque (PT), cross sectional area (CSA) and myofibrillar ATPase activity of the knee extensors. HVR training was performed in a circuit on hydraulic exercise equipment, 4 times a week for 5 weeks at an angular velocity of approximately 3.14 rad.s-1. Knee extension PT was determined on a Cybex II isokinetic dynamometer and CSA of the quadriceps femoris muscle was assessed using computer tomography (CT) scanning. Muscle biopsies were obtained from the lateral quadriceps muscle and were analyzed for myofibrillar ATPase activity. Knee extension peak torque was significantly increased at 1.57, 2.09, 3.14, 3.66 and 4.19 rad.s-1. Myofibrillar ATPase activity and CSA was also significantly increased after HVR training. These findings showed that short-term high velocity resistance training enhances the in vivo torque/velocity curve especially at fast angular velocities and these changes are partly attributed to an increase in muscle CSA and activity of myofibrillar ATPase.

Adaptation, Physiological↗
PubMed1992

Value of isokinetic angle-specific torque measurements in normal and injured knees.

This study assessed the relationship between the isokinetic peak torque (PT) (speed of movement 60 and 180 degrees.s-1) and the angle-specific torques (ASTs) at 15 and 75 degrees of knee flexion in multiple contractions of the quadriceps and hamstrings in 80 subjects with a grade I knee injury. At every test speed, the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the PT and ASTs were highly significant (P less than 0.001) for both muscle groups in the uninjured (r = 0.73-0.88, rs = 0.75-0.89) as well as in the injured (r = 0.63-0.91, rs = 0.65-0.91) knees. In both extremities, a great majority of the correlation coefficients exceeded 0.80, which was the predetermined threshold for the coefficients to exceed before the relationship could be considered clinically important. Using regression analysis, both extremities showed completely nonsystematic distribution of the residuals. The variability of the AST measurements was clearly higher than corresponding PT measurements. In conclusion, concerning healthy or grade I injured knees, the predictability of ASTs from PT was good; and, therefore, AST analyses offer little additional information about thigh muscle function than that obtained through the simpler and more commonly used measurement, PT analysis. Because of large variability, the routine use of the AST measurements for grade I knee injuries is not recommended.

Adult↗
PubMed1991

Angle-specific torques of thigh muscles: variability analysis in 200 healthy adults.

This study evaluated the variability of the isokinetic angle-specific torques (ASTs) at 15 and 75 degrees of knee flexion and assessed the relationship between them and the isokinetic peak torque (PT) in 200 healthy adults. The results showed that the value of these AST measurements was lower than of the PT measurements. This was due to larger variability of the AST (male and female coefficient of variation [cv] 34 and 43% in the ASTs vs. 19 and 31% in the PTs); unequal variation in the results between men and women (mean cv 27% in men vs. 34% in women); and fairly poor prediction of the ASTs from the PT (PT accounted for only 39 and 62% for the variation seen in the men's and women's AST results). Furthermore, in regression analysis the standard errors of the estimates were unacceptably high, averaging 26%. AST measurements should not be used routinely.

Adolescent↗
PubMed1990

[Changes with time in incomplete root and periodontal tissues of young dog teeth with torque loading applied].

We investigated, using labeling techniques (tetracycline, calcein) and routine histopathological methods (H. E. and Azan stainings), the histological changes with passage of time in incomplete root and the periodontium of young dog teeth with torque loading applied. The maxillary left first, second and third incisor teeth were used as anchorage teeth, and the maxillary right second incisor was loaded with either 3 degrees or 9 degrees torque. The orthodontic forces of these are 20-30 g and 80-90 g, respectively. Some temporal disturbances (such as mild, moderate, or severe bendings of labial and palatal apexes) were observed in certain regions of the apex of the incomplete root. However, with subsequent development of the root, the disturbances were repaired and pulp of the teeth was normally formed. Furthermore, although periodontium was also temporarily disturbed, it developed normally with the passage of time.

Alveolar Bone Loss↗
PubMed1987

The relationship between anaerobic power and isokinetic torque outputs.

Optimal peak and mean power outputs were determined from a 30s anaerobic cycle ergometer test and compared to the isokinetic peak torque outputs for hip and knee flexion and extension. Fifteen male physical education students, mean age 20.9 yrs., mean weight 73.2 kg, performed several 30s all-out ergometer rides to determine individual power curves for the calculation of peak and mean power outputs. Isokinetic exercise at 30 degrees X s-1 for knee flexion and extension and 180 degrees X s-1 for hip and knee flexion and extension was also performed. The peak and mean power outputs were 11.66 and 9.29 watts X kg-1 respectively. Mean power correlated with isokinetic peak torque at 180 degrees X s-1 for knee flexion (r = 0.96) and extension (r = 0.87) and for hip flexion (r = 0.71) and extension (r = 0.68). Due to the significant contribution of knee and hip flexion and extension movements at 180 degrees X s-1, high intensity sports may benefit from incorporation of such movements at high velocities into resistance training programs.

Adult↗
PubMed1987

Application of the halo device for immobilization of the cervical spine utilizing an increased torque pressure.

The rates for loosening and infection of the pins used in the halo apparatus are unfortunately high. The commonly recommended amount of torque to be used in applying the pins is 0.68 newton-meter (six inch-pounds). Forty-two adult patients underwent application of a halo device for immobilization of the cervical spine using an increased torque of 0.90 newton-meter (eight inch-pounds). The rate for loosening of the pins and the rate for infection at the pin site dropped from 36 per cent to 7 per cent and 20 per cent to 2 per cent, respectively.

Adolescent↗
PubMed1986

Optimal filtering of constant velocity torque data.

The purpose of this investigation was to implement an optimal filtering strategy for processing in vivo dynamometric data. The validity of employing commonly accepted analog smoothing methods was also appraised. An inert gravitational model was used to assess the filtering requirements of two Cybex II constant velocity dynamometers at 10 pre-set speeds with three selected loads. Speed settings were recorded as percentages of the servomechanism's maximum tachometer feedback voltage (10 to 100% Vfb max). Spectral analyses of unsmoothed torque and associated angular displacement curves, followed by optimized low-pass digital filtering, revealed the presence of two superimposed contaminating influences: a damped oscillation, representing successive sudden braking and releasing of the servomechanism control system; a relatively stationary oscillatory series, which was attributed to the Cybex motor. The optimal cutoff frequency for any data set was principally a positive function of % Vfb max. This association was represented for each machine by a different, but reliable, third order least-squares polynomial, which could be used to accurately predict the correct smoothing required for any speed setting. Unacceptable errors may be induced, especially when measuring peak torques, if data are inappropriately filtered. Over-smoothing disguises inertial artefacts. The use of Cybex recorder damping settings should be discouraged. Optimal filtering is a minimal requirement of valid data processing.

Biomechanical Phenomena↗
PubMed1985

A study of quadriceps excursion, torque, and the effect of patellectomy on cadaver knees.

Ten cadaver legs were mounted on a loading frame, and normal values for quadriceps excursion and tibial force were established with a constant quadriceps tension. The mean excursion of the quadriceps was 66.2 +/- 5.51 millimeters from zero to 90 degrees of knee flexion. After examining each 10-degree increment of motion we found that the maximum excursion of the quadriceps (9.49 +/- 1.35 millimeters) occurred between 30 and 40 degrees. The minimum excursion of 5.40 +/- 0.67 millimeters was found between 80 and 90 degrees of knee flexion. Incremental excursion of the quadriceps during 10-degree increments of knee flexion showed a correlation coefficient of 0.94 when compared with mean tibial torque (p less than 0.001). Patellectomy decreased excursion of the quadriceps to 51.3 +/- 1.30 millimeters from zero to 90 degrees of knee flexion. Torque was decreased by roughly 40 per cent of maximum from zero to 40 degrees of knee flexion.

Cadaver↗
PubMed1978

Lower extremity forces and torques during systematic variation of non-weight bearing motion.

Component and resultant external forces and torques at ankle, knee, and hip joints of unrestrained lower extremity motion were computed as resultant limb velocities were systematically changed. Cinematographic and modeling techniques were used to analyze 45 trials of five skilled soccer players who performed slow, medium and fast velocity kicks. A model of the lower extremity was incorporated, with kinematic data and segment mass estimates, into computer programs to quantify the mechanical variables. Monotonic increases in magnitudes of all kinetic elements occurred as the velocity of kicking was increased. Significant differences were also observed in the maximum values of the net parallel and perpendicular external force actions, and resultant torques at the joints with changes in limb velocity.

Ankle↗
PubMed1982

Changes in length and torque of the masticatory muscles produced by the activator appliance. A cephalometric study.

The purpose of this study was to measure cephalometrically the change in muscle length and torque of the masticatory muscles produced by an activator appliance. The study was based on 10 orthodontic cases with distoclusion. Muscle length and force arm (leverage) were measured on two lateral cephalometric roentgenograms of each subject, one with the teeth in centric occlusion and one with an activator between the teeth. The construction bite of the activator was taken with the mandible repositioned 2-3 mm below and 5-6 mm ahead of resting position. It was found that the temporal masseter and medial pterygoid muscles increased 5-15% in length whereas the lateral pterygoid decreased 25% in length with the activator in place. The effect on the force arm on the temporal muscle was small, a decrease of 3-6%, but that on the masseter was much more dramatic, a decrease of 21-22%. Thus, as far as the torque of the temporal muscle is concerned, the small decrease in force arm is well compensated for by the increased muscle tension due to the stretching by the activator. The clinical significance of the findings for obtaining the best construction bite of the activator is discussed.

Activator Appliances↗
PubMed1995

The quantitative measurements of hip isometric muscle torques in Chinese young adults--a preliminary report.

A standard procedure for measurement of hip muscle strength (maximal isometric torque) with the Cybex 340 isokinetic dynamometer is presented. Twenty-two healthy males aged 30-40 years (average 34.3 years) were tested on hip flexors, extensors and abductors; in which the factors as sex, age, dominant side and testing session were all eliminated. The test was redone two weeks later on the same 10 males to evaluate its reproducibility. The results disclosed the maximal isometric torque of the hip flexors was stronger than that of extensors and abductors in both sides hips. The comparison between two sides hips showed only the abductors of right side hip significantly stronger than that of left side (P = 0.0259). The tests between the two different periods were quite compatible. The results have clinical implications for objective assessment of preoperative and postoperative hip strengths in patients with hip arthropathy and thus giving a reasonable guidance for physiotherapeutic management.

Adult↗
PubMed1994

Isometric shoulder torque in subjects with spinal cord injury.

The etiology of shoulder pain in spinal cord injured (SCI) patients has been attributed to overuse, with dysfunction being more prevalent as the time since injury increases. Impingement syndrome, the most common diagnosis in this population, may be related to weakness of the rotator cuff and shoulder girdle musculature. Shoulder dysfunction is greater in subjects with SCI than in able-bodied patients; consequently, this study compares isometric strength of quadriplegic and paraplegic subjects to able-bodied controls. Peak isometric torque for internal rotation, external rotation, and scapular elevation was assessed using a Lido isokinetic dynamometer. The strength (torque) values of the quadriplegic group were significantly lower than the control group and paraplegic group for all motions tested (p < .0005). The only significant difference between the paraplegic and able-bodied groups was found with internal rotation (p < .0001). These results indicate that quadriplegic patients may be at greater risk for shoulder pathology because of both muscular limitation and increased functional demand.

Adult↗
PubMed1996

The generation of torque in the horizontal plane at the foot-base during laterally directed manual exertions.

Two experiments were carried out to investigate the mechanisms by which both translational forces and a turning moment in the horizontal plane at the foot-base are transmitted by the lower limb during laterally directed manual exertions. The first used a force plate to measure forces and moments exerted by the feet separately or together in order to investigate the contribution of each foot to the moment. The second examined the role of flexors and extensors of the hip, knee and ankle in the transmission of torque. The results suggest that approximately half of the moment is generated by each foot exerting a translational force at a distance from, and in the opposite direction to, the other. The other half is by each foot exerting an individual torque upon the floor. It is suggested that biomechanical models of asymmetric exertion should take these mechanisms into account.

Biomechanical Phenomena↗
PubMed1997

New corneal marker for passing a 24-bite anti-torque corneal transplant single continuous suture.

The use of a single continuous-suture closure technique allows the surgeon to minimize corneal transplant astigmatism within 1 month of surgery. Passage of this suture in a precise, anti-torque pattern is difficult. A new surgical instrument has been designed to place 24 equidistant dots on both the recipient and the donor tissues after the cardinal sutures have been placed. The surgeon simply must "connect the dots" to achieve a rapid, precise anti-torque closure. The instrument is easy to use and should prove helpful to surgeons who perform the single, continuous-suture closure technique.

Cornea↗
PubMed1976

Influence of mechanical properties on the relation between EMG activity and torque.

An attempt was made to determine the average stiffness and viscosity of the muscle groups responsible, in human subjects, for the flexion and extension of the forearm, when these movements are produced intentionally. To this end, the subjects were instructed to produce sinusoidal movements by tracking acoustic and visual signals. 1. By recording simultaneously the sinusoidal angular variations and the EMG activity of both triceps and biceps it was possible to determine the phase angle between EMG and inertial torque at different frequencies (between 0.2 and 5 Hz). 2. The known phase relations between EMG and torque were then subtracted from this plot obtaining, therefore, the phase characteristics of the mechanical system (forearm-lever complex). 3. The average resonant frequency for different amounts of intentional contraction of the muscles responsible for the motion was 0.8 Hz, leading to an estimate of the average stiffness of 2.57 kgw.m/rad. 4. The slope of the phase in proximity of the resonant frequency lends an estimate for the viscosity of 0.85 kgw.m.sec/rad. 5. The contribution to the motion by elastic forces and the active contraction due to intentional motor commands was also considered.

Arm↗
PubMed1976

Influence of a rigid plate for internal fixation on the maximum torque capacity of long bones.

The unfavourable effect of the rigid internal fixation plate on the strength (measured as maximum torque capacity) of the diaphyseal bone, with due attention to the importance of the screw holes, has been studied on the femora of 7 dogs. When the plates that had been applied for 7 months without previous osteotomy were removed, a significantly reduced maximum torque capacity was observed, as also a significantly reduced maximum angle of torsion, and a significantly changed distribution of the amount of bone mineral.

Animals↗