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At least 19 recordsLinked to original sources
PubMed1989

Eccentric and concentric torque-velocity characteristics, torque output comparisons, and gravity effect torque corrections for the quadriceps and hamstring muscles in females.

The purpose of this study was to assess and compare eccentric (ECC) and concentric (CONC) torque output of the quadriceps and hamstring muscles and to analyze the effect of gravity effect torque (GET) correction on the calculation of the hamstring/quadriceps peak torque quotient (H/Q quotient). Twenty female subjects performed maximal voluntary CONC and ECC contractions of the quadriceps and hamstring muscles at five isokinetic lever arm velocities from 60 degrees/s to 360 degrees/s. Peak torque was measured and corrected for GET. Mean ECC torque did not significantly change with increasing ECC velocity for either the quadriceps or hamstring muscles (P greater than 0.05). Mean CONC torques were significantly lower than the corresponding ECC torques (P less than 0.05) and decreased with increasing CONC velocity. At each test velocity, the CONC H/Q quotient was significantly lower than the corresponding ECC H/Q quotient (P less than 0.05). Mean H/Q quotients did not significantly change with increasing velocity for either the CONC or ECC tests (means: 0.46 and 0.57; P greater than 0.05). Mean H/Q quotients not corrected for GET significantly increased with increasing velocity for the CONC (0.61 to 0.78; P less than 0.05), but not ECC tests (0.66 to 0.71; P greater than 0.05). The results indicate that the ECC torque-velocity curve is essentially level for both quadriceps and hamstring muscles. The present findings point strongly toward the necessity of correcting for GET when calculating both CONC and ECC H/Q quotients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Uncertainty of knee joint muscle activity during knee joint torque exertion: the significance of controlling adjacent joint torque.

In the single-joint torque exertion task, which has been widely used to control muscle activity, only the relevant joint torque is specified. However, the neglect of the neighboring joint could make the procedure unreliable, considering our previous result that even monoarticular muscle activity level is indefinite without specifying the adjacent joint torque. Here we examined the amount of hip joint torque generated with knee joint torque and its influence on the activity of the knee joint muscles. Twelve healthy subjects were requested to exert various levels of isometric knee joint torque. The knee and hip joint torques were obtained by using a custom-made device. Because no information about hip joint torque was provided to the subjects, the hip joint torque measured here was a secondary one associated with the task. The amount of hip joint torque varied among subjects, indicating that they adopted various strategies to achieve the task. In some subjects, there was a considerable internal variability in the hip joint torque. Such variability was not negligible, because the knee joint muscle activity level with respect to the knee joint torque, as quantified by surface electromyography (EMG), changed significantly when the subjects were requested to change the strategy. This change occurred in a very systematic manner: in the case of the knee extension, as the hip flexion torque was larger, the activity of mono- and biarticular knee extensors decreased and increased, respectively. These results indicate that the conventional single knee joint torque exertion has the drawback that the intersubject and/or intertrial variability is inevitable in the relative contribution among mono- and biarticular muscles because of the uncertainty of the hip joint torque. We discuss that the viewpoint that both joint torques need to be considered will bring insights into various controversial problems such as the shape of the EMG-force relationship, neural factors that help determine the effect of muscle strength training, and so on.

Adult↗
PubMedDate not supplied

Reverse torque failure of screw-shaped implants in baboons: baseline data for abutment torque application.

Torque failure for endosseous implants has been used as a biomechanical measure of anchorage, though the significance of such data is not known. A practical understanding of the resistance to torque failure of implant-tissue interfaces at stage 2 surgery would help in assigning torque levels for implant abutment-screw fastening. The purpose of this study was to measure torque failure levels of commercially pure (CP) titanium, Ti-6Al-4V, hydroxyapatite-coated (HA-coated) screw-shaped implants placed into the maxillae and mandibles of baboons. Implants identical in size were placed into the edentulous posterior maxillae and mandibles of six female baboons (n = 37 each group) using a standardized surgical protocol. Reverse-torque data were collected at postinsertion time intervals ranging from 3 to 4 months using a counterclockwise torque driver and the data were analyzed (repeated measures ANOVA) for torque differences related to time, biomaterial, and jaw. The HA-coated implants exhibited significantly greater torque-removal values compared to both metallic implants (HA: 186.0 Ncm [50.1]; Ti-6Al-4V: 78.6 Ncm [18.1]; CP Ti 74.0 Ncm [24.4]). Analysis of torque interactions with jaw showed no significant difference; however, the mandible was found to be greater than the maxilla in torque resistance for all groups tested. Understanding the risks in inferring animal data to human application, the clinical implications of these data suggest that the recommended torque level of 35 Ncm for abutment fastening may provide a margin of safety for most implants of similar design and material as used in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Alloys↗
PubMed2005

Ankle eversion torque response to sudden ankle inversion Torque response in unbraced, braced, and pre-activated situations.

In 13 young ankle stable subjects, ankle eversion torque and peroneal EMG were simultaneously recorded in response to sudden ankle inversion. The eversion torque response was bi-phasic. The initial development of torque, which was responsible for 30% of the maximal eversion torque response, was observed 135 ms after the start of platform rotation and correlated well with the onset of the automatic postural peroneal EMG response. The remaining eversion torque response commenced after 305 ms, strongly correlating with the onset of the peroneal long latency voluntary EMG activity. With the ankle unbraced, 66% of the maximal torque level was reached in 326 ms. While braced, the same torque magnitude was reached using 230 ms (p<0.02), and pre-activation of the peroneal muscles allowed the subjects to reach the same level of torque in 89 ms (p<0.0005). Prior to the study, a common reaction pattern to sudden inversion was expected in an ankle stable population, but review of the eversion torque and EMG data from the 13 subjects revealed three different voluntary reaction patterns: 10 subjects showed an efficient activation of evertor muscles; two subjects stiffened their ankles with activation of both in- and evertor muscles; and one subject showed a marginal voluntary activation of the ankle evertors. The results of the study indicate that the reaction to sudden ankle inversion is not solely automatic. The main part of the torque response is voluntarily mediated and inter-individual differences in strategy seem to exist in healthy subjects.

Adult↗
PubMed2000

Cerebellar ataxia: torque deficiency or torque mismatch between joints?

Prior work has shown that cerebellar subjects have difficulty adjusting for interaction torques that occur during multi-jointed movements. The purpose of this study was to determine whether this deficit is due to a general inability to generate sufficient levels of phasic torque inability or due to an inability to generate muscle torques that predict and compensate for interaction torques. A second purpose was to determine whether reducing the number of moving joints by external mechanical fixation could improve cerebellar subjects' targeted limb movements. We studied control and cerebellar subjects making elbow flexion movements to touch a target under two conditions: 1) a shoulder free condition, which required only elbow flexion, although the shoulder joint was unconstrained and 2) a shoulder fixed condition, where the shoulder joint was mechanically stabilized so it could not move. We measured joint positions of the arm in the sagittal plane and electromyograms (EMGs) of shoulder and elbow muscles. Elbow and shoulder torques were estimated using inverse dynamics equations. In the shoulder free condition, cerebellar subjects made greater endpoint errors (primarily overshoots) than did controls. Cerebellar subjects' overshoot errors were largely due to unwanted flexion at the shoulder. The excessive shoulder flexion resulted from a torque mismatch, where larger shoulder muscle torques were produced at higher rates than would be appropriate for a given elbow movement. In the shoulder fixed condition, endpoint errors of cerebellar subjects and controls were comparable. The improved accuracy of cerebellar subjects was accompanied by reduced shoulder flexor muscle activity. Most of the correct cerebellar trials in the shoulder fixed condition were movements made using only muscles that flex the elbow. Our findings suggest that cerebellar subjects' poor shoulder control is due to an inability to generate muscle torques that predict and compensate for interaction torques, and not due to a general inability to generate sufficient levels of phasic torque. In addition, reducing the number of muscles to be controlled improved cerebellar ataxia.

Adult↗
PubMedDate not supplied

Torque generated by handheld screwdrivers and mechanical torquing devices for osseointegrated implants.

This study evaluated the ability of practitioners experienced in the use of Brãnemark implant components to impart a desired torque using handheld screwdrivers. The torque output and variability of mechanical torque devices was also examined. For clinicians using handheld screwdrivers, values ranged from 0.7 to 18.1 Ncm, 1.4 to 33.7 Ncm, and 8.2 to 36.2 Ncm for the 10-Ncm, 20-Ncm, and 32-Ncm torques respectively. The manually operated mechanical torquing devices produced torque values within the tolerances specified by their respective manufacturers at all levels. Significant variation from the manufacturer's set values were noted as a function of tightening speed with the electronic torquing device. The data indicate that there is wide variation in the ability of clinicians to perceive adequate torquing forces applied to implant components. Calibrated torquing devices are mandatory if proper torquing procedures are to be accomplished.

Calibration↗
PubMed2003

Right coronary arteriography: experience with standard-torque and limited-torque techniques in children and young adults.

Coronary spasm and intimal injury may occur during selective right coronary arteriography. The safety and efficacy of right coronary arteriography in children and young adults were retrospectively reviewed for this report. Right coronary arteriography was performed in 200 patients. A standard-torque technique was used in 150 patients, a limited-torque technique was used with a reshaped left coronary catheter in 53 patients. The standard-torque technique was associated with proximal coronary spasm in nine patients, nonsustained ventricular tachycardia in one patient, and ST segment changes in one patient. The limited-torque technique was associated with no complications. The standard-torque technique was effective in one patient when the limited-torque technique failed to define distal coronary branches clearly. The limited-torque technique was effective in nine patients when the right coronary artery could not be engaged while attempting the standard-torque technique. In conclusion, right coronary arteriography may be performed in a safe and potentially more effective manner using a new catheter design and a limited-torque technique.

Adolescent↗
PubMed2002

Muscular torque generation during imposed joint rotation: torque-angle relationships when subjects' only goal is to make a constant effort.

It is a reasonable expectation that voluntarily activated spinal motoneurons will be further excited by increases in spindle afferent activity produced by muscle stretch. Human motor behavior attributed to tonic stretch reflexes and to reflexes recruited by relatively slow joint rotation has been reported from several laboratories. We reinvestigated this issue by rotating the elbow joint over the central portion of its range while subjects focused on keeping their elbow flexion effort constant at one of three different levels and made no attempt to control the position, speed or direction of movement of their forearm. There is evidence that subjects' voluntary motor status is constant under these conditions so that any change in torque would be of involuntary origin. On average, torques rose somewhat and then fell as the elbow was flexed through a range of 80 degrees at 10, 20 and 60 degrees/s and a similar pattern occurred during elbow extension; i.e., both concentric and eccentric torque-angle profiles had roughly similar shapes and neither produced consistent stabilizing cross-range stiffness. The negative stiffness (rising torque) during the early part of a concentric movement and the negative stiffness (falling torque) during the later part of an eccentric movement would not have occurred if a stabilizing stretch reflex had been present. Positive stiffness rarely gave rise to torque changes greater than 20% in either individual or cross-subject averaged data. When angular regions of negative stiffness are combined with regions of low positive stiffness (torque change 10% or less), much of the range of motion was not well stabilized, especially during eccentric movements. The sum of the EMGs from biceps brachii, brachioradialis and brachialis showed a pattern opposite to that expected for a stretch reflex; there was an upward trend in the EMG as the elbow was flexed and a downward trend as the elbow was extended. There was little change in the shape of this EMG-angle relationship with either direction or velocity. The individual EMG-angle relationships were distinctive for each of these three elbow flexor muscles in four of the six subjects; in the remaining two, biceps was distinctive, but brachioradialis and brachialis appeared to be coupled. Although the EMGs of individual muscles were modulated over the angular range, no consistent stretch reflexes could be seen in the individual records. Thus, we could find no clear evidence for stretch reflex stabilization of human subjects maintaining a constant effort. Rather, muscle torque appears to be reflexly modulated across a much used portion of the elbow's angular range so that any appreciable stabilizing stiffness that is sustained for more than fractions of a second is associated with a change in effort.

Adult↗
PubMed2006

A comparison between insertion torque and resonance frequency in the assessment of torque capacity and primary stability of Brånemark system implants.

The aim of this study was to determine primary stability and insertion torque of Brånemark System implants placed in the anterior mandible, and to evaluate a possible correlation between primary stability and insertion torque. Thirty edentulous patients were treated with 60 Brånemark System implants using a one-stage technique. The insertion torque values of all implants were recorded with the Osseocare equipment. Immediately after implant placement, each implant was connected to the transducer of an Osstell machine to measure the primary implant stability. The average insertion torque and resonance frequency values were 41.5 +/- 5.8 and 74.1 +/- 3.8 for 30 implants. The correlation between insertion torque and resonance frequency values indicated a statistical significance (P < 0.001). The difference between mean insertion torque values for female and male patients was statistically significant (P < 0.001). No significant difference (P > 0.05) was found between younger and older patients with mean insertion torque values of 43.1 +/- 4.7 and 40.1 +/- 6.5 respectively. The results of this study showed a strong correlation between the primary stability and insertion torque values of Brånemark System TiUnite MKIII implants at the time of implant placement.

Age Factors↗
PubMedDate not supplied

A comparison between cutting torque and resonance frequency in the assessment of primary stability and final torque capacity of standard and TiUnite single-tooth implants under immediate loading.

PURPOSE: In this study, standard Brånemark System implants and Brånemark TiUnite implants were evaluated regarding primary stability and placement torque. The correlation between placement torque and primary stability as well as the influence of implant design on placement torque and primary stability were examined. MATERIALS AND METHODS: Twelve patients who presented bilateral loss of either maxillary lateral incisors or premolars were treated with 24 immediately loaded dental implants. Each patient received 1 standard 3.75 x 13-mm Brånemark System implant and one 3.75 x 13-mm TiUnite Mk III implant. One at a time, each implant was connected by a transducer to an Osstell machine that automatically translated a resonance frequency value for the implant into an implant stability quotient value. Osseocare equipment was used to measure the placement torque for both types of implants. RESULTS: Statistical analysis showed higher mean values for standard implants in relation to placement torque and resonance frequency values. DISCUSSION: There was no overall correlation between placement torque and resonance frequency values; this finding supported previous studies. CONCLUSION: Stability was shown to be higher for the standard implants. Mean values of torque resistance were higher for the standard implants than for the TiUnite implants. Implant design appeared to influence primary stability and placement torque.

Adult↗
PubMed1991

Relationship between insertion torque and removal torque analyzed in fresh temporal bone.

Insertion torque and removal torque of fixtures were measured using human cadaver temporal bone and human living bone. The torque level for fracturing the threads of the bone was also measured. The maximum insertion torque exerted without causing a break in bone threads was 70.0 Ncm in bicortical bone and 50.0 Ncm in unicortical bone. The relationship between insertion torque and removal torque indicated a positive correlation between both sites. However, removal torque was lower than insertion torque in all measurements. The fracture points of bone threads were 77.0 Ncm in bicortical bone and 57.7 Ncm in unicortical bone by mean. Microfractures were observed mainly in the thread bases and were directed upward in the histologic specimens examined.

Aged↗
PubMed1998

The influence of target torque and torque build-up time on physical stress in right angle nutrunner operation.

This study used a computer-controlled electric right angle nutrunner to investigate the relative effects of different power hand tool and process parameters on operator muscular exertions, handle stability and subjective ratings of perceived exertion. Target torque (25, 40 and 55 Nm), torque build-up time (35, 150, 300, 500 and 900 ms), and workstation orientation (horizontal and vertical) were studied. Dependent variables included EMG activity of the finger flexors, biceps, and triceps, handle velocity and displacement, work done on the tool-hand system and power involved in doing work, subjective ratings of perceived exertion, and task acceptance. Six inexperienced subjects (three females and three males) participated. Ten replications were performed for each combination of experimental conditions. The consequences of increasing the torque reaction force were greater handle instability and perceived exertion. The effect of torque build-up time on handle kinematics, muscular activity and perceived exertion was not monotonic. Among five build-up times tested, the hand was most unstable (greater peak handle velocity and power against the operator) for a 150 ms build-up time. Greater peak handle displacement, total work against the operator and average EMG were observed for 150 and 300 ms build-up times than for other build-up time conditions. Integrated EMG and EMG latency significantly increased as build-up time increased. Average EMG latency between the onset of EMG burst and the onset of torque build-up was 40 ms for a 35 ms build-up time and 330 ms for a 900 ms build-up time. Subjective ratings of perceived exertion were the least when torque build-up time was 35 ms, however greater peak torque variance was associated with this condition.

Adult↗
PubMed2001

Advantages and disadvantages of new torque-controlled endodontic motors and low-torque NiTi rotary instrumentation.

The main problem with the NiTi rotary instrumentation technique is instrument failure. During shaping procedures, rotary instruments might lock and/or screw into canals and, consequently, be subjected to high levels of stress. This may frequently lead to instrument separation or deformation. If a high-torque motor is used, the applied forces are usually very high and the instrument-fracture limit is often exceeded, thus increasing the risk of intracanal failure. A possible solution of this problem is to use a low-torque endodontic motor, which operates below the maximum permissible torque limit of each and every rotary instrument. During clinical instrumentation of root canals, if a torque-controlled motor is loaded right up to the instrument-specific torque, the motor stops momentarily and/or starts rotating counter-clockwise (auto-reverse function) to disengage the locked instrument. These safety mechanisms were developed to reduce the risk of instrument fracture. The author fully discusses the rationale for selecting lower torque values in everyday endodontic practice, and provides clinicians with useful information on the advantages and disadvantages of new endodontic motors with torque control.

Dental Instruments↗
PubMed2003

Improving elbow torque output of stroke patients with assistive torque controlled by EMG signals.

This paper develops an assistive torque system which uses homogeneic surface electromyogram (EMG) signals to improve the elbow torque capability of stroke patients by applying an external time-varying assistive torque. In determining the magnitude of the torque to apply, the incorporated assistive torque algorithm considers the difference between the weighted biceps and triceps EMG signals such that the applied torque is proportional to the effort supplied voluntarily by the user. The overall stability of the assistive system is enhanced by the incorporation of a nonlinear damping element within the control algorithm which mimics the physiological damping of the elbow joint and the co-contraction between the biceps and triceps. Adaptive filtering of the control signal is employed to achieve a balance between the bandwidth and the system adaptability so as to ensure a smooth assistive torque output. The innovative control algorithm enables the provision of an assistive system whose operation is both natural to use and simple to learn. The effectiveness of the proposed assistive system in assisting elbow movement performance is investigated in a series of tests involving five stroke patients and five able-bodied individuals. The results confirm the ability of the system to assist all of the subjects in performing a number of reaching and tracking tasks with reduced effort and with no sacrifice in elbow movement performance.

Aged↗
PubMed1983

Relationship of isokinetic torque to isometric torque.

Isokinetic muscle testing has become an increasingly popular method for measuring muscle performance. However, the relationship of isokinetic strength measurements to static strength measurements remains unclear. The relationship between maximal isokinetic and maximal isometric torque was investigated at angular velocities of 24, 48, 96, and 192 degrees/s for both flexion and extension of the elbow joint. Twenty-four subjects were tested bilaterally, and discrete torque values at the positions of 60 and 90 degrees of flexion were obtained from the continuous isokinetic records for comparison with isometric torques recorded at the same two positions. Data were analyzed using an analysis of covariance with isokinetic torque, the dependent variable, expressed as a function of isometric torque and as a function of the design variables side and position. The results demonstrated significant effects of side and position and also demonstrated the dependence of isokinetic strength on velocity. Confidence intervals were determined for the prediction of isokinetic torque from observed isometric torque for normal individuals, providing a potentially useful tool to aid in the diagnosis of muscular disorders.

Adult↗
PubMed2003

Counteractive relationship between the interaction torque and muscle torque at the wrist is predestined in ball-throwing.

Many investigators have demonstrated that in swing motions such as ball-throwing, the motion of the proximal joint (shoulder) produced assistive interaction torque for the distal joint (elbow). In line with these studies, the shoulder and elbow motions would be expected to produce the assistive interaction torque for the wrist joint as well. However, we recently showed that the interaction torque at the wrist was always counteractive to the wrist muscle torque during ball-throwing. The purpose of this study is to clarify, by means of computer simulation, whether the counteractive relationship at the wrist during ball-throwing is caused by the neural contribution or the musculoskeletal mechanical properties of the human arm. First, we simulated the throwing motions of the normal forearm-hand model by systematically changing the proximal-to-distal delay of muscle activities and could line up two candidates for the determinant of the counteractive relationship: the rest angle (neutral angle) of the wrist and the length and mass of the hand. Second, we simulated the throwing motions of the virtual forearm-hand models, showing that only nonrealistic elongation of these two parameters produced the assistive relationship between the interaction torque and muscle torque. These results suggested that the mechanical properties of the human wrist are the main determinant of the counteractive relationship, which is advantageous for keeping the state of the wrist joint stable in multi-joint upper-limb movements and would lead to avoidance of excessive wrist extension or flexion and simplification of extrinsic finger control.

Adult↗
PubMed1996

The effect of extraneous movements on peak torque and constant joint angle torque-velocity curves.

During isokinetic knee testing, some subjects flex the trunk and contralateral knee during knee extension and the trunk and contralateral knee during knee flexion. This investigation assessed the effect of these extraneous movements on peak and constant joint angle torque (15 degrees below horizontal). Twenty-one subjects performed isokinetic knee extensions and flexions at 60, 180, and 300 degrees/sec under stabilized and nonstabilized conditions. The nonstabilized testing was performed with intentional trunk and contralateral leg movements. The stabilized condition resulted in greater torque values than the nonstabilized condition for extension and flexion for both peak torque and constant joint angle torque. The angle at which flexion peak torque occurred was further from full extension at 60 and 180 degrees/sec under the nonstabilized condition, while no differences were found for extension. These results indicate that extraneous movements can decrease torque output, which may be due to changes in muscle length caused by the extraneous movements.

Adult↗
PubMed2003

Gender-specific knee extensor torque, flexor torque, and muscle fatigue responses during maximal effort contractions.

The purpose of this study was to examine gender differences in knee extensor and flexor peak torque, work, power, and muscle fatigue during maximal effort isokinetic contractions. Subjects included 19 healthy male and 20 healthy female volunteers. Following a dynamic warm-up period, subjects performed 30 reciprocal, concentric maximal knee extension and flexion contractions at a pre-set angular velocity of 3.14 rad x s(-1) on the Biodex Isokinetic Dynamometer. Values for knee extensor peak torque, work, and power were calculated for each repetition over an angular displacement of 1.05 rad for each repetition. The single highest repetition value for knee extensor and flexor peak torque, work, and power was then calculated relative to body mass (N x m x kg(-1), J x kg(-1), W x kg(-1)) and allometric-scaled (N x m x kg(-) (n), J x kg(-) (n), W x kg(-) (n)) units. The allometric-scaled units were derived from a log-log transformation and linear regression analysis to calculate the exponent to which body mass is raised. The rate of quadriceps femoris muscle fatigue was calculated as the decline in each isokinetic variable by the linear slope from the single highest repetition value through the 30th repetition, and by two different fatigue indexes. The results demonstrate higher knee extension and flexion peak torque, work, and power in absolute, relative, and allometric-scaled units for males compared to females. Males exhibited higher fatigue rates for both muscle groups of each isokinetic variable than females, as described by the slope and the fatigue index, except when adjusted for peak values via analysis of covariance. The findings suggest that during maximal-effort muscle contractions, males exhibit a higher susceptibility to muscle fatigue than females, a phenomenon that may be related to an inherent ability to generate higher knee extensor and flexor torque.

Adult↗