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PubMed1986

Isokinetic knee flexion and extension torque in the upright sitting and semireclined sitting positions.

We undertook this study to determine whether the isokinetic knee extension and flexion torque generated by 14 young healthy women was greater in the upright sitting test position or in the semireclined sitting test position. Testing was performed at 60 degrees/sec. Knee extension torque did not differ significantly between the two test positions. The subjects, however, did produce significantly greater knee flexion torque when upright compared with when semireclined (p less than .001). Therapists should recognize that the results of testing isokinetic knee extension in the two positions may be similar, but that the results of testing isokinetic knee flexion may be significantly different.

Adult↗
PubMed1987

Diagnostic value of knee extension torque tracings in suspected anterior cruciate ligament tears.

The purpose of this study was to determine the diagnostic accuracy of knee extensor muscle torque tracings in patients suspected of having damage to the anterior cruciate ligament of the knee joint. The knee extensor torque tracings of 30 patients suspected of having anterior instability of the knee joint were reviewed independently for abnormalities believed to be associated with anterior cruciate ligament damage. These results were compared blindly with an arthroscopic evaluation. The diagnostic accuracy of the torque tracing approach was determined by calculating the prevalence, sensitivity, specificity, and positive and negative predictive values. The sensitivity and specificity were calculated to be 25.0% and 85.7%, respectively. These results suggest that the curve patterns examined in this article have poor diagnostic accuracy and are of little benefit as a clinical diagnostic aid.

Adult↗
PubMed1988

Augmenting voluntary torque of healthy muscle by optimization of electrical stimulation.

The purpose of this study was to evaluate the ability of electrical stimulation (2,500-Hz sine waves, interrupted for 50 pulsed bursts per second) to improve muscle torque using low-dosage training characteristics. Fifteen healthy subjects (9 men, 6 women), 20 to 32 years of age, participated in the experiment. All subjects received electrical stimulation of the right anterior thigh musculature while their left leg served as the control. Electrical stimulation was repeated eight times per session, each stimulation producing isometric torque equal to 50% of the subject's maximum voluntary isometric contraction. The sessions were repeated twice a week over a period of five weeks. Results showed that electrical stimulation, when used with the specified low-dosage training characteristics of this study, will augment quadriceps femoris muscle torque of men.

Adult↗
PubMed1989

Relationship between multiple predictor variables and normal knee torque production.

The purpose of this study was to develop predictive models relating isokinetic knee testing performance to anthropometric and demographic variables. The subjects were 134 healthy volunteers (70 female, 64 male) between the ages of 10 and 80 years. The investigators measured subjects' peak knee flexion and extension torque production at two angular velocities. Stepwise regression analyses were used to examine the relationship between each torque-dependent variable and the following potential predictor variables: age, sex, side of lower extremity dominance, height, weight, percentage of body fat, and thigh girth. The investigators generated two sets of models designed to predict preinjury knee strength. Clinicians can use one set of models by assessing predictor variables before or immediately following injury. The second set of models involves the assessment of predictor variables postinjury, excluding an assessment of percentage of body fat and thigh girth. The results indicated that peak knee torque production can be predicted with statistically significant accuracy (multiple R = .78-.87). The predictive models generated in this study can be used to establish muscle strength goals for patient rehabilitative programs.

Adolescent↗
PubMed1992

Linearity and reliability of the IEMG v torque relationship for the forearm flexors and leg extensors.

The purpose of this investigation was to examine the linearity and reliability of the surface integrated electromyogram (IEMG) v isometric torque relationship for the leg extensors and forearm flexors. Nine men and four women (mean age +/- SD = 22 +/- 2 yr) volunteered for this investigation. Isometric testing was conducted on a Cybex II isokinetic dynamometer with the lever arm at 0.785 rad (45 degrees) below the horizontal plane for the leg extensors and in the vertical plane for the forearm flexors. Bipolar surface electrodes were used to record IEMG values from the vastus lateralis and biceps brachii. To examine test-retest reliability, two test sessions, separated by a minimum of 48 h, were performed. The test-retest linearity of the IEMG v torque relationship ranged from r2 = 0.77 to 0.96 and 0.55 to 0.94 for the forearm flexors and r2 = 0.81 to 0.98 and 0.83 to 0.98 for the leg extensors. The slope values were not significantly different (P > 0.05) between sessions and were correlated (intraclass correlation coefficients) at R = 0.86 (standard error of estimate (SEE) = 5.77 microV.Nm-1, 31% of the mean) and R = 0.97 (SEE = 0.27 microV.Nm-1, 12% of the mean) for the forearm flexors and leg extensors, respectively. The test-retest maximal torque values were 57.73 +/- 22.57 Nm and 58.14 +/- 22.81 Nm (R = 0.99; SEE = 2.39 Nm) for the forearm flexors and 187.79 +/- 55.98 Nm and 195.42 +/- 56.27 Nm (R = 0.96; SEE = 22.62 Nm) for the leg extensors (nonsignificant differences; P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Ligamentous laxity across C0-C1-C2 complex. Axial torque-rotation characteristics until failure.

The axial torque until failure of the ligamentous occipito-atlanto-axial complex (C0-C1-C2) subjected to axial angular rotation (theta) was characterized using a biaxial MTS system. A special fixture and gearbox that permitted right axial rotation of the specimen until failure without imposing any additional constraints were designed to obtain the data. The average values for the axial rotation and torque at the point of maximum resistance were, respectively, 68.1 degrees and 13.6 N-m. The specimens offered minimal resistance (approximately 0.5 N-m), up to an average axial rotation of 21 degrees across the complex. The torque-angular rotation (T-theta) curve can be divided into four regions: regions of least and steadily increasing resistances, a transition zone that connects these two regions, and the increasing resistance region to the point of maximum resistance. The regions of least and steadily increasing resistances may be represented by two straight lines with average slopes of 0.028 and 0.383 N-m/degree, respectively. Post-test dissection of the specimens disclosed the following. The point of maximum resistance corresponded roughly to the value of axial rotation at which complete bilateral rotary dislocation of the C1-C2 facets occurred. The types of injuries observed were related to the magnitude of axial rotation imposed on a specimen during testing. Soft-tissue injuries alone (like stretch/rupture of the capsular ligaments, subluxation of the C1-C2 facets, etc.) were confined to specimens rotated up to or close to the point of maximum resistance. The specimens that were subjected to rotations up to the point of maximum resistance of the curve spontaneously reduced completely on removal from the testing apparatus. Spontaneous reduction was not possible for specimens tested slightly beyond their points of maximum resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed2000

Lorentz torque on a charged sphere rotating in a dielectric fluid in the presence of a uniform magnetic field

The Lorentz torque exerted by a uniform magnetic field on a charged sphere rotating steadily in a dielectric fluid is calculated to first order in the charge. For a strongly polar fluid and stick boundary conditions the torque is enhanced significantly with respect to its vacuum value. The modification from the vacuum value depends only on the static dielectric constant of the fluid and on the slip parameter. It is independent of the dielectric response of the sphere and of the shape of the radial charge distribution. There is a nonvanishing Lorentz torque, even when the charge is concentrated in the center of the sphere.

Journal Article↗
PubMed2004

Domain-wall dynamics and spin-wave excitations with spin-transfer torques.

A generalization of spin-transfer torques in ferromagnetic structures is proposed. For a spatially nonuniform magnetization, the spin torque has a form nearly identical to that in magnetic multilayers. We show that the domain-wall motion driven by the current has many unique features that do not exist in the conventional domain-wall motion driven by a magnetic field. We also demonstrate that the spin torque can generate bulk and surface spin excitations that have been seen in point-contact experiments.

Journal Article↗
PubMed2006

Torque detection using Brownian fluctuations.

We report the statistical analysis of the movement of a submicron particle confined in a harmonic potential in the presence of a torque. The absolute value of the torque can be found from the auto- and cross-correlation functions of the particle's coordinates. We experimentally prove this analysis by detecting the torque produced onto an optically trapped particle by an optical beam with orbital angular momentum.

Journal Article↗
PubMed1996

Do neural factors underlie age differences in rapid ankle torque development?

OBJECTIVES: Rapid torque development is substantially slower in healthy old adults compared with young adults, but the underlying cause of this age-related loss remains unclear. Measurements of myoelectric signals in ankle dorsi- and plantarflexor muscles during rapid exertions were used to explore the extent to which the loss might be attributed to neural factors. METHODS: Myoelectric signals were measured in a laboratory setting in 24 healthy young and 24 healthy old adult volunteers during rapid isometric and isokinetic torque development. Premotor times, muscle activation rates, and myoelectric activity levels of agonistic and antagonistic muscles were quantified. RESULTS: There were few marked age differences in the premotor times or in the onset rates or magnitudes of agonistic muscles activities during maximum isometric and during isokinetic exertions. Premotor times were statistically associated with age but, in the mean, were only approximately 10 to 25 ms longer in the old. Age effects on agonist muscle activity magnitudes were significant only in the lateral gastrocnemius. Small decreases in antagonistic muscle activity levels with age were found. CONCLUSIONS: Given the outcomes of this study, the differences observed previously in rapid torque development abilities in healthy older adults, compared with healthy younger adults, seem attributable largely to differences in muscle contraction mechanisms rather than to differences in speeds of stimulus sensing or central processing of motor commands, or to differences in muscle recruitment strategies.

Adult↗
PubMed1989

Enzyme activities in type I and II muscle fibres of human skeletal muscle in relation to age and torque development.

The quadriceps muscles from 20- 30- and 70-year-old clinically healthy men and women were studied regarding maximal isometric and isokinetic muscle torque in Newton metres (Nm), morphology and enzyme activity. Biopsy specimens were taken from the vastus lateralis muscle and freeze-dried, and individual fibres were dissected out and identified as type I or type II. The activities of citrate synthase (CS), 3-OHacyl-coA dehydrogenase (HAD), lactate dehydrogenase (LDH), myokinase (MK) and creatine phosphokinase (CPK) were determined in pools of type I and type II fibres. In both age groups a higher oxidative (CS, HAD, 1.3-1.5 x) and a lower glycolytic (LDH, 0.7 x) capacity was found in type I than in type II fibres. The myokinase activity was higher in type II (2 x) than in type I, whereas CPK activity was similar. The young men showed higher CS activity in both type I and type II fibres (1.5 x) and higher CPK activity in type I fibres (1.4 x) than the young women. There were only minor changes in oxidative or glycolytic capacities in relation to age. Myokinase was the only enzyme that decreased markedly with age in both pools of fibre types. Type II fibre area and mean fibre area correlated significantly to muscle torque in both sexes. In men, myokinase activity in type II fibres was significantly correlated to type II fibre area and to maximal muscle torque.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1994

Intramuscular pressure, torque and swelling for the exercise-induced sore vastus lateralis muscle.

This study investigated changes in intramuscular fluid pressure (IMP), torque and swelling related to delayed onset muscle soreness (DOMS) of the vastus lateralis muscle. IMP was measured via catheterization in the unstretched (0 degree, full extension) and stretched (90 degrees of knee flexion) muscle at rest; then IMP and knee extension torque were determined during maximal contractions pre and 2 d after (post) repetitive eccentric activity in one leg for eight male subjects. DOMS of the vastus lateralis muscle was associated with a significant elevation in IMP at rest as indicated by pre (0 degree: 5.4 mmHg, 90 degrees: 80 mmHg) and post (0 degree: 8.4 mmHg, 90 degrees: 13.2 mmHg) comparisons (P = 0.02). Soreness symptoms were aggravated when the muscle was stretched and this was accompanied by a significantly higher post IMP at 90 degrees vs. 0 degree (P = 0.01). During maximal contractions, peak torque declined by 15% relative to pre and peak IMP declined by 26%; DOMS symptoms, however, were most severe during this manoeuvre. Biopsies from the sore vastus lateralis muscle revealed significantly larger fibre areas for all fibre types as compared with contralateral controls (P < 0.01); however, no differences were detected for extracellular volume percent comparisons. This study shows that DOMS of the vastus lateralis muscle is associated with extensive intracellular swelling and with elevated IMP. In line with previous studies, fibre swelling may be a common subsequence to repetitive eccentric activity; the ability of IMP measurements to detect this swelling at rest and during various manoeuvres for other muscles may depend on compartmental compliance.

Adult↗
PubMed1993

A comparison of the mechanogram of the ankle jerk in men and women: observations using an adjustable dorsiflexing torque, high inertia mechanical filter and automatic readout system.

An instrument of new design has been constructed to measure the contractions of the calf musculature resulting from a tap on the Achilles tendon. The instrument provides a predetermined and adjustable dorsiflexing torque from a printed motor, but the contractions are virtually isometric as the system is one of high inertia. Peak force, half-contraction time and half-relaxation time are monitored by electronic circuits equipped with digital output meters. Observations have been made on fifty-two male and forty-five female medical students. There were no significant differences in the peak torques generated by the contractions between the men and women students and no difference in the half-contraction times. The half-relaxation times of the women were, however, significantly longer than those of the men (P = 0.0001). In another group of students the EMG discharges following a tendon tap were recorded, there was no significant difference in the duration of the activity in men and women. Observations have also been made on twenty-three male and seventy female subjects whose mean ages were in the mid-sixties. The peak torques generated by the contractions were significantly higher in the women (P = 0.03). There was no difference in the half-contraction times, but the half-relaxation times of the women were significantly longer (P = 0.001). Possible reasons for the differences are discussed.

Adolescent↗
PubMed2001

The generalized torque approach for analyzing the results of pedaling tests.

This paper deals with the analysis of experimental data obtained using an ergometer apparatus. A straightforward analysis method based on the power equation and the concept of generalized torques is presented. This method makes it possible to study the influence of the net muscle joint torques and gravity and inertia forces on the crank torque. The assumptions and limitations of the proposed method are discussed and this method is compared with the methods of analysis proposed by other researchers. In order to assess the validity of the method, some experimental data are elaborated. Results show that the method can highlight the effect of training and the pedaling technique of an athlete.

Ankle Joint↗
PubMed1995

Regulated underexpression of the FliM protein of Escherichia coli and evidence for a location in the flagellar motor distinct from the MotA/MotB torque generators.

The FliM protein of Escherichia coli is essential for the assembly and function of flagella. Here, we report the effects of controlled low-level expression of FliM in a fliM null strain. Disruption of the fliM gene abolishes flagellation. Underexpression of FliM causes cells to produce comparatively few flagella, and most flagella built are defective, producing subnormal average torque and fluctuating rapidly in speed. The results imply that in a normal flagellar motor, multiple molecules of FliM are present and can function independently to some degree. The speed fluctuations indicate that stable operation requires most, possibly all, of the normal complement of FliM. Thus, the FliM subunits are not as fully independent as the motility proteins MotA and MotB characterized in earlier work, suggesting that FliM occupies a location in the motor distinct from the MotA/MotB torque generators. Several mutations in fliM previously reported to cause flagellar paralysis in Salmonella typhimurium (H. Sockett, S. Yamaguchi, M. Kihara, V.M. Irikura, and R. M. Macnab, J. Bacteriol. 174:793-806, 1992) were made and characterized in E. coli. These mutations did not cause flagellar paralysis in E. coli; their phenotypes were more complex and suggest that FliM is not directly involved in torque generation.

Bacterial Proteins↗
PubMed1979

Activity of precentral neurons during torque-triggered hand movements in awake primates.

In monkeys performing a handle-repositioning task involving primarily wrist flexion-extension (F-E) movements after a torque perturbation was delivered to the handle, single units were recorded extracellularly in the contralateral precentral cortex. Precentral neurons were identified by passive somatosensory stimulation, and were classified into five somatotopically organized populations. Based on electromyographic recordings, it was observed that flexors and extensors about the wrist joint were specifically involved in the repositioning of the handle, while many other muscles which act at the wrist and other forelimb joints were involved in the task in a supportive role. In precentral cortex, all neuronal responses observed were temporally correlated to both the sensory stimuli and the motor responses. Visual stimuli, presented simultaneously with torque perturbations, did not affect the early portion of cortical responses to such torque perturbations. In each of the five somatotopically organized neuronal populations, task-related neurons as well as task-unrelated ones were observed. A significantly larger proportion of wrist (F-E) neurons was related to the task, as compared with the other, nonwrist (F-E) populations. The above findings were discussed in the context of a hypothesis for the function of precentral cortex during voluntary limb movement in awake primates. This hypothesis incorporates a relationship between activities of populations of precentral neurons, defined with respect to their responses to peripheral events at or about single joints, and movements about the same joint.

Animals↗
PubMed1998

A stimulating nerve cuff for chronic in vivo measurements of torque produced about the ankle in the mouse.

Specific muscle training and chronic contractile measurements are difficult in rodents, especially in the mouse. The primary reason for this is the lack of a means for stimulating the motor nerve that does not damage the nerve and that permits reproducible measurements of contractility. In this paper, we describe procedures for the construction and implantation of a stimulating nerve cuff for use on the mouse common peroneal nerve. We demonstrate that nerve cuff implantation success rates can be high (i.e., 75-93%), as determined from measurements of maximal isometric torque produced by the anterior crural muscles. Isometric torque production is not adversely affected by the nerve cuff because the torque produced matches that observed in our established percutaneous stimulation model. We also demonstrate that use of the nerve cuff for stimulation is compatible with electromyographic measurements made on the tibialis anterior muscle, with no sign of stimulation artifact in the electromyographic signal.

Animals↗
PubMed1996

Modulation of the human vestibuloocular reflex during saccades: probing by high-frequency oscillation and torque pulses of the head.

1. We probed the gain and phase of the vestibuloocular reflex (VOR) during the execution of voluntary gaze saccades, with continuous oscillation or acceleration pulses, applied through a torque helmet. 2. Small-amplitude (< 1 degree), high-frequency (10-14 Hz) head oscillations in the horizontal or vertical plane were superimposed on ongoing horizontal gaze saccades (40-100 degrees). Torque pulses to the head ("with" or "against" gaze) were superimposed on 40 degrees horizontal saccades. Eye and head movements were precisely measured with sensor coils in magnetic fields. 3. Techniques were developed to separate the oscillatory (horizontal or vertical) component from the gaze shift and obtain VOR gain and phase with Fourier techniques from the relation between eye-in-head and head oscillations. These involved either subtraction of exactly matching saccades with and without oscillation (drawback: low yield) or time shifting of successive trials to synchronize the oscillations (drawback: slight time blurring of saccades). 4. The results of these matching and synchronization methods were essentially identical and consistent. Presaccadic gain values of the horizontal VOR (typically about unity) were reduced by, on average, approximately 20 and 50% during horizontal saccades of 40 and 100 degrees, respectively. These percentages may be truncated because of methodological limitations, but even after taking these into account (on the basis of simulation experiments with 2 different, theoretical profiles of suppression) our results do not support a complete saccadic VOR suppression for any substantial fraction of saccadic duration. Qualitatively similar changes were found when the vertical VOR was probed during 100 degrees horizontal saccades. 5. Concomitantly with the reductions in gain, VOR phase was advanced by approximately 20 degrees during the saccade. 6. In the wake of gaze saccades, VOR gain was consistently elevated (to approximately 1.0) above the presaccadic level (approximately 0.9). We submit that this mechanism ensures stable fixation of the newly acquired target at a time when the head is still moving substantially. 7. Although the responses to head torque pulses showed idiosyncratic asymmetries, analysis of the differences in eye and head movements for pulses with and against consistently showed a sharp fall of VOR gain at saccadic onset, following an approximately exponential course with a time constant of approximately 50 ms. This decay may be assumed to reflect VOR gain for a period of approximately 50 ms, after which secondary gaze control mechanisms become dominant. 8. The time course of the gain decay and phase shift of the VOR suggest that suppression of the "integrative (position) loop" of the VOR circuit was more complete than suppression of the direct, "velocity" pathway.

Female↗