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PubMed2002

Torque-EMG relationships in normal and spastic muscles.

The linearity of the relationship between torque and electromyographic (EMG) activation has been widely debated for years, yet remains unresolved. Despite limitations and possible inaccuracies, an assumption of linearity is often made to simplify the relationship between these variables for computational and descriptive purposes. Although typically derived from isometric test conditions, these relationships have also been extrapolated, perhaps invalidly, to conditions where joint velocity and length are changing. The purpose of this study was to examine the degree of linearity between hamstring and quadriceps torques and their respective EMG signals, and to compare the slopes of these relationships in normal and spastic muscles at varying muscle lengths and conditions. We hypothesized that relationships would be linear for all muscles tested in both subject groups; however, slopes would differ across the two muscles, the three muscle lengths tested, and the two subject groups. We further hypothesized that the degree of linearity during an isotonic task would be less than for the isometric one, particularly for patients with spasticity who may demonstrate abnormal responses to changes in muscle length. Results indicated that torque--EMG relationships were linear for all subjects during isometric contractions, regardless of group, muscle, or knee angle. However, the degree of linearity was significantly less in CP in both conditions; and within the CP group, was less during isotonic compared to isometric conditions. Slope values differed between muscles at some lengths, across muscle lengths in the quadriceps, and subjects with CP showed consistently lower slopes for all quadriceps values. These data in general support the robustness of the linear assumption in isometric conditions for the knee musculature, caution against extrapolation to isotonic conditions particularly for those with movement abnormalities, and suggest that slope differences may provide valuable insights into pathology and warrant further investigation.

Adolescent↗
PubMed2003

The relationship of lower-extremity muscle torque to locomotor performance in people with stroke.

BACKGROUND AND PURPOSE: Improved walking is a common goal after stroke. The purpose of this study was to examine the relationship between the torque generated by the muscles of both lower extremities and 2 locomotor tasks: gait on level surfaces and stair climbing in people who had strokes. SUBJECTS: Twenty community-dwelling individuals (mean age=61.2 years, SD=8.4, range=52-82) who had strokes and who were able to walk independently participated in the study. The mean time since stroke was 4.0 years (SD=2.6, range=1.5-10.0). METHODS: Pearson correlations and multiple regression were used to measure the relationship between concentric isokinetic torque of the flexor and extensor muscles of the hip, knee, and ankle bilaterally and locomotor performance (gait on level surfaces and stair-climbing speed). RESULTS: The isokinetic torques of the paretic ankle plantar flexors, hip flexors, and knee flexors had moderate to high correlations (r=.5-.8) with gait and stair-climbing speeds. Muscle force could explain 66% to 72% of the variability in gait and stair-climbing speeds. Correlations for the nonparetic side were as high as or higher than those for the paretic side for some muscle groups. DISCUSSION AND CONCLUSION: Muscle performance measurements of both limbs should be included in the evaluation of locomotion and treatment of people following a stroke.

Aged↗
PubMed2003

[A robot measurement system for spacesuit joint torque].

OBJECTIVE: To measure the joint torque of spacesuit so as to evaluate its dynamic force/torque performance. METHOD: A method for measuring the spacesuit joint torque by use of robot technology was proposed in this paper. The design of the measuring strategy and measuring robot was put forward and a mathematical model of the system was given. Then the working space of the robot was analyzed. RESULT: The robot designed is light, compact, easy to operate, and has a large working space. Experimental results demonstrated the effectiveness of the measuring principle and the reliability of the measuring system. CONCLUSION: The system can satisfy the requirements of the spacesuit joint torque measurement.

Biomechanical Phenomena↗
PubMed2003

Evaluation of the peak torque, total work, average power of flexor-estensor and prono-supinator muscles of the elbow in baseball players.

The Authors, after a short analysis on biomechanics of the elbow during throwing in baseball, show the movements of the elbow during the different phases of the throw and the stabilizing action of the ulnar collateral ligament, flexor-pronator muscles of the wrist, anconeus and brachial triceps muscles. Aim of this study is the evaluation of the peak torque, total work and average power of the flexor-extensor and pronator-supinator muscles of the elbows in professional baseball players. Isokinetic test data show that a mayor peak torque in flexo-extension at power and resistance test in the pitchers compared to the strikers. Whereas the strikers show a higher peak torque in pronation at the resistance test. This may happen because during a baseball match the ball is hit many times by the bat and the pronator muscle of the wrist are notably stimulated and reinforced.

Adult↗
PubMed1997

Neuromuscular trunk performance and spinal loading during a fatiguing isometric trunk extension with varying torque requirements.

A novel testing protocol was used to investigate changes in neuromuscular performance, muscle recruitment, and spinal loading as subjects became fatigued while performing an isometric endurance test of varying torque requirements. There was decreased accuracy in maintenance of a reference torque but no change in response time as subjects became fatigued. The study of trunk-muscle recruitment indicated significant increases in internal oblique and latissimus dorsi muscle activity. This change in recruitment led to changes in spinal loading despite a relatively constant torque output. The use of an electromyogram (EMG)-assisted model demonstrated that when subjects are expected to become fatigued during test performance, the assumption of a constant maximal stress capacity of the muscle may not be robust.

Adult↗
PubMedDate not supplied

Reverse-torque failure of screw-shaped implants in baboons after 6 months of healing.

Mechanical testing of the implant-tissue interface has been the focus of numerous investigations concerning the anchorage capacity of implants. The purpose of this study was to measure reverse-torque failure after 6 months of healing for three different biomaterials in the posterior jaws of four adult female baboons. The animals had all of their posterior teeth surgically extracted and, following 10 weeks of healing, 7 implants were placed in each quadrant. The biomaterials included titanium plasma-sprayed surfaces, titanium-aluminum-vanadium surfaces (both 3.8 mm x 10 mm), and a commercially pure titanium surface (3.75 mm x 10 mm). After 6 months, torque data were collected using a counterclockwise computerized torque driver and were analyzed by repeated measures analysis of variance for differences related to biomaterial, jaw, and biomaterial/jaw. Post-hoc Tukey Kramer analysis was also performed for within-group differences (alpha = .05 level). The biomaterial comparison revealed a significant difference between the titanium plasma-sprayed and the combined commercially pure titanium/titanium -aluminum-vanadium groups (analysis of variance, Tukey Kramer, P < .05). The jaw comparison showed no significant difference, although the data suggest that higher forces may be required for mandibular torsional failure. The biomaterial/jaw comparison revealed that jaw differences for the mean values of commercially pure titanium and titanium-aluminum-vanadium implants were greater than jaw differences for mean values of titanium plasma-sprayed implants, although these differences were not statistically significant. Because of the lack of correlation between single-cycle biomechanical tests and clinical performance, it is necessary to be selective in assigning usefulness to data of this type.

Alloys↗
PubMed1999

Measurement of insertion torque of tapered external fixation pins: A comparison between two experimental models.

The aim of this study was to compare an in vitro versus an ex vivo experimental model to test the insertion torque of two different types of external fixation pins. A torque measuring machine was developed in order to perform accurate measurements. Forty tapered pins made of stainless steel were utilized. Half of the pins were plasma-spray coated with hydroxyapatite (HA) and the other half remained uncoated. For the in vitro model 20 cylinders were used that were made of synthetic polymer according to ASTM standards. For the ex vivo model 10 fresh femora harvested from adult sheep were used. All the pins were implanted after predrilling, and insertion torque was measured. Statistical analysis of the in vitro versus the ex vivo model showed significant differences in both coated (p < 0. 0005) and uncoated (p = 0.002) external fixation pins. These results may be due to the surface roughness that caused significant friction between the HA coating and the polyvinylchloride in the in vitro model. The significant difference between the in vitro and ex vivo results lead us to state that the in vitro model does not realistically simulate the behavior of external fixation pins implanted in bone.

Animals↗
PubMed1985

Reliability after repeated use of a torque screwdriver employed for halo pin fixation.

It has been recommended that halo torque screwdrivers be used only once. To determine if this advice is justified on biomechanical grounds, five commercially available torque screwdrivers were cycled 1,600 times each in an Instron testing machine over a 7-day period. The screwdrivers displayed an initial error from the dial reading at both 6 and 10 in-lb of only +/- 0.3 in-lb. After cyclic loading and retesting, the percent deviation from original calibration was 8% at both 6 and 10 in-lb. These data demonstrate the accuracy and dependability of the torque screwdrivers and imply that repeated use of these devices should be safe.

Biomechanical Phenomena↗
PubMed1995

Thermal response and torque resistance of five cortical half-pins under simulated insertion technique.

A model was developed that can quantitate heat generation during placement of half-pins in cortical bone. Five half-pins were tested to assess differences in insertion torque, heat generation, and micro-damage at the pin-bone interface. Thin thermocouple probes were placed 0.5 mm from the track of the pin and within the pin to measure its temperature during insertion. Scanning electron microscopy was used to view the pin-bone interface to assess the microdamage during placement. The design of the tip of the pin influenced insertion torque and heat generation. Higher heat generation was measured when a thermocouple was placed within the pin itself and less was measured when thermocouple probes were placed within bone samples 0.5 mm from the impending pin track. Furthermore, insertion torque and thermal responses were related, but there were no significant differences in microdamage to bone when different pins and drilling/tapping techniques were used. Due to the significant heat generation at the pin-bone interface, proper cooling with saline irrigation should be applied during pin insertion regardless of the design of the pin. The microdamage observed at the surface of the pin track may have significant implications with regard to loosening of pins, but such effects must be studied with in vivo models.

Animals↗
PubMed1996

Orientational steering in enzyme-substrate association: ionic strength dependence of hydrodynamic torque effects.

The effect of hydrodynamic torques on the association rate constants for enzyme-ligand complexation is investigated by Brownian dynamics simulations. Our hydrodynamic models of the enzyme and ligand are composed of spherical elements with friction forces acting at their centers. A quantitative measure of hydrodynamic torque orientational effects is introduced by choosing, as a reference system, an enzyme-ligand model with the same average hydrodynamic interactions but without orientational dependence. Our simple models show a 15% increase in the rate constant caused by hydrodynamic torques at physiological ionic strength. For more realistic hydrodynamic models, which are not computationally feasible at present, this effect is probably higher. The most important finding of this work is that hydrodynamic complementarity in shape (i.e. like the fitting together of pieces of a puzzle) is most effective for interactions between molecules at physiological ionic strength.

Chemical Phenomena↗
PubMed1990

Trajectory formation of arm movement by cascade neural network model based on minimum torque-change criterion.

We proposed that the trajectory followed by human subject arms tended to minimize the time integral of the square of the rate of change of torque (Uno et al. 1987). This minimum torque-change model predicted and reproduced human multi-joint movement data quite well (Uno et al. 1989). Here, we propose a neural network model for trajectory formation based on the minimum torque-change criterion. Basic ideas of information representation and algorithm are (i) spatial representation of time, (ii) learning of forward dynamics and kinetics model and (iii) relaxation computation based on the acquired model. The model can resolve ill-posed inverse kinematics and inverse dynamics problems for redundant controlled object as well as ill-posed trajectory formation problems. By computer simulation, we show that the model can produce a multi-joint arm trajectory while avoiding obstacles or passing through viapoints.

Algorithms↗
PubMed1991

Phasic and tonic responses of premotor and primary motor cortex neurons to torque changes.

Responses to torque step perturbation of the wrist were compared in premotor area (PMA) and motor cortex (MI) neurons of the monkey. A substantial portion (39%) of cells recorded from the PMA had phasic responses with onset latencies as short as those found in MI (mostly between 15 and 50 ms). Responsiveness to small perturbations, directional specificity and linear correlation of phasic responses with the velocity of displacement are properties that were essentially present in the PMA. A role of somatosensory feedback to the PMA in accurate and fast up-dating of movement is suggested. Tonically sustained responses to torque change (mean latency around 60 ms) were encountered in both areas and preferentially in neurons that had a monotonic load-relationship under steady-state condition. Such cortical responses did not exhibit reflex-like features, i.e. no correlation with amplitude of torque step and resulting displacement. Instead, the new load condition seemed to be represented by the tonic response of any particular neuron in accordance with its individual firing rate-load characteristics. These tonic cortical responses may be involved in the swift and effective adaptation to the actual load.

Animals↗
PubMed1981

[The experimental measurement of torque and axial force of 6.5 mm ASIF lag screws in fixation of femoral neck fractures (author's transl)].

An experimental study was undertaken to evaluate the torque and axial force of the 6.5 mm ASIF lag screw implanted in the femoral neck after a subcapital osteotomy. The experiments were carried out on autopsied bones of more than 60 years of age. The average torque was 204 cmN, the screws in the upper half of the femoral head showing a higher torque than those in the lower half. The axial tension was measured by strain gauge transducer. Depending on the length of the thread of the screw (16 or 32 mm) the average tension reaches 1162 N or 1960 N. By tightening the screw until the impression of optimum fit is obtained, 70% of the maximum axial force is reached. It can therefore be estimated that at the beginning an interfragmentary pressure of 4000 to 8000 N is exerted on a medial femoral neck fracture fixed by four ASIF lag screws.

Biomechanical Phenomena↗
PubMed1976

[The dependence of the removal torque of a leg screw a screw surface and implantation time (author's transl)].

The experiment was performed on 17 sheep tibiae in vivo. 4.5 mm ASIF leg screws with a constant insertion torque (68.6 Ncm) but different surfaces (smooth or rough) were removed after 3 s, 7, 28, 56 and 112 days after insertion. The screws with a rough surface which were implanted for 28 days and longer exhibited a significantly greater removal torque. For instance rough screws which were implanted for 112 days displayed a removal torque eight times greater than after 3 s.

Animals↗
PubMed1977

To what extent is the tibia-calcaneum angle a reliable measurement of the triceps surae length? Radiological correction of the torque-angle curve (III).

Previous papers gave some methods for the reliable measurement of the tibia-calcaneum angle. It is of common use to evaluate the physical properties of triceps surae on the basis of torque-angle curves. However this method is reliable only if each tibia-calcaneum angle corresponds to a defined distance between the insertions of the muscle in subjects of the same height. Evidence is given by radiological measurements that this correspondance is correct in normal children. However, this is no longer true in certain cerebral palsied children because of abnormal translation of the calcaneum and/or abnormal ratio of bone sizes. In this case the torque-angle curves do not define properly the torque-length curves. A method of correction is given. This correction may be as high as 15 degrees.

Ankle Joint↗
PubMed1981

Effects on torque angle curve of differences between the recorded tibia-calcaneal angle and the true anatomical angle.

The present study gives the results of a comparison of the recorded and true tibia-calcaneal angles in 17 normal subjects and in 14 patients with abnormally hypoextensible non contracting triceps. 1. For a minimal passive torque, the difference between true and recorded angles varied considerably from one individual to another. The mean and ranges for the two groups were respectively: -8 degrees (+7 degrees, -21 degrees) and -7 degrees (+5 degrees, -20 degrees). 2. When the passive torque increased as a result of slow passive lengthening of the muscle, the true curve was steeper than the recorded one, owing to differences between the two angle measurements. For each of the two groups the differences in means and ranges were respectively: 6 degrees (0 degrees, +13.5 degrees) and 8 degrees (3 degrees, 12 degrees). 3. Subjects made isometric voluntary contractions of the triceps surae at fixed angles which corresponded to step by step muscle lengthening. The resulting true curve was much steeper than the recorded curve. The differences in means and ranges were: 7 degrees (1.5 degrees, +15 degrees) in children of the two groups and respectively 3 degrees (0 degrees, +9 degrees) and 12 degrees (10 degrees, 14 degrees) in adults of the two groups. The present results show that this methodology was the only reliable way of correctly obtaining passive and active torque-angle curves, measuring differences between subjects, appreciating the effects of treatments and these by ascertaining whether or not trophic muscle regulation was defective.

Adult↗
PubMed1995

Force-length, torque-angle and EMG-joint angle relationships of the human in vivo biceps brachii.

The relationships of EMG and muscle force with elbow joint angle were investigated for muscle modelling purposes. Eight subjects had their arms fixed in an isometric elbow jig where the biceps brachii was electrically stimulated (30 Hz) and also in maximum voluntary contraction (MVC). Biceps EMG and elbow torque transduced at the wrist were recorded at 0.175 rad intervals through 1.75 rad of elbow extension. The results revealed that while the torque-length relationship displayed the classic inverted "U" pattern in both evoked and MVC conditions, the force-length relationship displayed a monotonically increasing pattern. Analyses of variance of the EMG data showed that there were no significant changes in the EMG amplitudes for the different joint angles during evoked or voluntary contractions. The result also showed that electrical stimulation can effectively isolated the torque-angle and force-length relationships of the biceps brachii and that the myoelectric signal during isometric contraction is uniform regardless of the length of the muscle or the joint angle.

Adult↗
PubMed1990

The loop-torque maneuver: a method to facilitate intubation for enteroclysis.

The loop-torque maneuver is a simple technique used to facilitate intubation with an enteroclysis catheter. A braided stainless steel guidewire, 26 cm longer than the one provided with the commercially available set, is used. A loop is formed in its proximal end to facilitate torquing if the catheter engages the greater curvature or coils up in the fundus. The loop-torque maneuver led to successful intubation of all patients in this series and produced less discomfort than the double-back maneuver.

Contrast Media↗