Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Torque”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1983

Isometric, isotonic, and isokinetic torque variations in four muscle groups through a range of joint motion.

The purpose of this investigation was to describe and examine variations in maximal torque produced by knee extension, knee flexion, elbow extension, and elbow flexion through a range of joint motion. Subjects were young, healthy men (n = 16) and women (n = 15). Torque was measured isometrically and isokinetically using a modified Cybex apparatus. Isotonic torque was calculated from a one-repetition maximum using a modified N-K device. Joint angles were monitored with an electrogoniometer. Torque-joint angle curves were constructed for both men and women for each muscle group. Isometric torque was highest, followed by isotonic and isokinetic torque. Torque declined with increasing isokinetic velocity. The angle of peak torque was found to be highly variable in individual subjects. Variations in torque curves were explained in terms of mechanical characteristics of the musculoskeletal system. Muscle group capability was generally found to be well matched to the mechanical requirements of the movement.

Adult↗
PubMed1994

Torque of trunk flexion and trunk flexion with axial rotation in healthy men and women.

The purpose of this study was to determine normal values for torque of trunk flexion and trunk flexion with axial rotation. Eighty-two healthy subjects (39 men, 43 women) were tested for isometric torque of trunk flexion at four angles, and eccentric and concentric torque at 30 degrees/sec. All tests were performed in three positions of axial rotation: neutral rotation, trunk rotated 30 degrees to the right, and trunk rotated 30 degrees to the left. The results of two separate three-way analyses of variance (gender vs. position vs. angle/contraction) indicated that the torque of men was greater than that of women, eccentric torque was greater than concentric, and the torque in neutral rotation was greater than in right or left rotation. Isometric torque decreased with increased trunk flexion. Regression and correlation analyses demonstrated that gender was generally the best predictor of torque, and that all the torque measures were significantly correlated.

Abdominal Muscles↗
PubMed1990

Evaluation of a dynamometer measuring torque of uni- and bilateral concentric and eccentric muscle action.

A dynamometer designed for torque measurements of uni- and bilateral concentric and eccentric muscle actions of the quadriceps and hamstring muscle groups is described. Torque reproducibility and control of lever-arm position were studied using known standards. In vivo measurements assessed angular velocity, lever-arm acceleration, variability of torque between limbs and reproducibility of torque. Torque obtained from left and right leg attachments was equal when using weights and during dynamic in vivo conditions. Static torque recorded at different lever-arm positions and known torque were equal. Likewise, lever-arm position output equated with known angles. In vivo test-retest of peak torque was found to be reliable. Acceleration of the lever arm was greater for concentric bilateral than for unilateral muscle actions but equal during eccentric muscle actions. The dynamometer is suggested to provide valid and reproducible torque measurements up to at least 700 N m at constant angular velocities up to 2.62 rad s-1. Besides being a research tool the dynamometer is useful in clinical settings for rehabilitation and evaluation of skeletal muscle function.

Adult↗
PubMed1993

Fatigue in the shoulder muscles during static work at two different torque levels.

The present study aimed to investigate whether and when a shift in the mean power frequency (MPF) of the electromyogram (EMG) occurs at low torque levels during a maximum endurance test of three shoulder flexors. Twelve clinically healthy women performed two endurance tests of the shoulder flexors (at 50% MVC--the high torque level, and at approximately 18% MVC--the low torque level) until maximum exhaustion. Surface EMG were obtained and MPF and signal amplitude (RMS) were computed for the trapezius descendens, the anterior part of the deltoid and the infraspinatus. The subjects also rated the perception of fatigue in the shoulder muscles throughout the two tests using a 10-graded scale. A significantly higher degree of perceived fatigue was found at the low rather than at the high torque level. In contrast significantly lower MPF were found at the end of the endurance times in the three muscles at the high torque level when compared to the low torque level. At the low torque level MPF of the trapezius was constant throughout the test. In the deltoid the most prominent decrease occurred during the initial 30-40% of the endurance time at the low torque level. It is suggested that the MPF shift mainly reflects peripheral fatigue of the type-2 fibres. The results of the present study question the use of the MPF shift to monitor peripheral fatigue in the fibres active (mainly type-1) at low torque levels.

Adult↗
PubMed1990

Effect of voluntary vs. artificial activation on the relationship of muscle torque to speed.

The speed-torque relationship of the right knee extensor muscle group was investigated in eight untrained subjects (28 +/- 2 yr old). Torque was measured at a specific knee angle during isokinetic concentric or eccentric actions at nine angular velocities (0.17-3.66 rad/s) and during isometric actions. Activation was by "maximal" voluntary effort or by transcutaneous tetanic electrical stimulation that induced an isometric torque equal to 60% (STIM 1) or 45% (STIM 2) of the voluntary isometric value. Torque increased (P less than 0.05) to 1.4 times isometric as the speed of eccentric actions increased to 1.57 rad/s for STIM 1 and STIM 2. Thereafter, increases in eccentric speed did not further increase torque. Torque did not increase (P greater than 0.05) above isometric for voluntary eccentric actions. As the speed of concentric actions increased from 0.00 to 3.66 rad/s, torque decreased (P less than 0.05) more (P less than 0.05) for both STIM 1 and STIM 2 (two-thirds) than for voluntary activation (one-half). As a result of these responses, torque changed three times as much (P less than 0.05) across speeds of concentric and eccentric actions with artificial (3.4-fold) than voluntary (1.1-fold) activation. The results indicate that with artificial activation the normalized speed-torque relationship of the knee extensors in situ is remarkably similar to that of isolated muscle. The relationship for voluntary activation, in contrast, suggests that the ability of the central nervous system to activate the knee extensors during maximal efforts depends on the speed and type of muscle action performed.

Adult↗
PubMed2000

Effects of immobilization on plantar-flexion torque, fatigue resistance, and functional ability following an ankle fracture.

BACKGROUND AND PURPOSE: The goal of this investigation was to study the recovery of ankle plantar-flexor peak torque, fatigue resistance, and functional ability (stair climbing, walking) following cast immobilization in patients with ankle fractures. SUBJECTS: The participants were 10 patients who underwent open reduction-internal fixation and 8 weeks of cast immobilization following a fracture of the ankle mortise and 10 age- and sex-matched, noninjured comparison subjects. METHODS: Plantar-flexor torque and fatigue resistance were measured at 1, 5, and 10 weeks of rehabilitation using an isokinetic dynamometer. Ankle plantar-flexor peak torque and fatigue resistance were correlated to timed ambulation, timed stair climbing, and unilateral heel-rises. RESULTS: Following immobilization, plantar-flexor peak torque was decreased at all angular speeds and positions. The decrease in peak torque was associated with an increase in fatigue resistance. With rehabilitation, ankle plantar-flexor torque and fatigue resistance normalized. Regression analysis revealed a strong relationship between plantar-flexor peak torque and functional measures. By 10 weeks post-immobilization, peak torque, fatigue resistance, and all measures of functional performance had returned to control levels. CONCLUSION AND DISCUSSION: The decrease in muscle performance, functional ability, and fatigue resistance induced by 8 weeks of cast immobilization can be reversed with 10 weeks of supervised physical therapy. In addition, this study demonstrated that ankle-plantar flexor torque is a good predictor of stair-climbing and walking performance in patients with ankle fractures.

Adult↗
PubMed1992

Test-retest reliability of reciprocal isokinetic knee extension and flexion peak torque measurements.

Our purpose in conducting this study was to estimate the reliability of reciprocal concentric knee extension and flexion peak torque obtained in uninjured male athletes using the Biodex isokinetic dynamometer. Twenty-six male intercollegiate athletes (age=19.5+/-4.1 yr; ht=70.3+/-14.9 in; wt=212.9+/-48.5 lb) participated in this study. We used the Biodex to measure peak torque occurring during right knee extension and flexion over 3 consecutive days. Means and standard deviations were calculated for both extension and flexion on each of the 3 days. We observed a significant main effect for days for both extension and flexion. Mean peak torque for the first day was significantly higher (Turkey, p<.05) than the means for the other 2 days, which were not significantly different from each other (Turkey, p>0.05). Intraclass correlation coefficients (ICCs) were estimated for each of the six trials on each of the 3 days. Intraclass correlation coefficients (ICCs) ranged from .88 on trial 1, day 1 for both extension and flexion peak torque to .97 for extension peak torque and .98 for flexion peak torque on day 3, trial 6. The standard error of measurement for extension peak torque was 7.0 ft-lbs and for flexion peak torque was 3.0 ft-lbs. These results indicate that reliable measurements of reciprocal right knee extension and flexion peak torque can be obtained from uninjured male athletes with the Biodex isokinetic dynamometer.

Journal Article↗
PubMed1993

Comparison of N-k table offset angles with the human knee flexor torque curve.

The purpose of this study was to dynamically examine various offset angles on the N-K table to determine which offset produces a torque pattern corresponding most closely to the isokinetic torque curve of the knee flexor musculature when tested at 60%. Subjects for the study were five college-age male volunteers (age=21.8+/-1.8 yrs, ht=181.9+/-4.3 cm, wt=88.4+/-12.6 kg). Mean peak isokinetic torque values for the five subjects were measured at 5 degrees increments to represent the human knee flexor torque curve. These were converted to relative mean values by dividing each value by the maximum mean peak torque. Torque curves from four offset angles (90 degrees ,110 degrees ,135 degrees , and 160 degrees ) for the N-K table were obtained by using the Kin Com in the passive mode at 20 degrees /s to push the exercise arm of the N-K table through a range of motion of 0 degrees to 90 degrees while recording torque and angular position. The four torque curves were converted to relative values in a similar manner as for the subjects. Qualitative analysis reveals that the 160 degrees offset angle most closely corresponded to the representative knee flexor isokinetic torque curve, while the 90 degrees offset angle corresponded least. Although these findings would seem to support reconsideration of common clinical practice relative to the use of the N-K table for knee flexor strength development, the 160 degrees offset angle is awkward because it has a tendency to force the user into hyperextension at the beginning phase of motion. As such, practical compromises might include the use of the 110 degrees or 135 degrees offset angle in lieu of the traditionally employed 90 degrees offset angle, or the development of an extension stop that would prevent hyperextension of the knee.

Journal Article↗
PubMed1990

Reliability of knee extensor and flexor torques during continuous concentric-eccentric cycles.

Peak and average torques of the knee extensors and flexors were determined on three occasions within ten days. On each occasion, 20 healthy women and 15 healthy men performed three continuous concentric-eccentric cycles with no pause between muscle actions or between cycles at 45 degrees and 90 degrees/sec angular velocities. Peak and average torques did not vary significantly or systematically over the three test occasions. Intraclass correlation coefficients (ICCs), based on one occasion, ranged from 0.79 to 0.91 for peak torques and from 0.75 to 0.88 for average torques. At 45 degrees/sec angular velocity, the ICCs for peak torque tended to be greater than those for average torque, whereas at 90 degrees/sec angular velocity the ICCs were similar whether calculated using peak or average torque. The ICCs during knee extension were greater than those during knee flexion. Eccentric muscle actions produced significantly higher torques than did concentric actions (p less than 0.01). A continuous concentric-eccentric cycle protocol which emphasizes teaching the subject to perform the test maneuvers and using at least three submaximal practice contractions and one maximal practice contraction can produce reliable isokinetic torques.

Adult↗
PubMed1998

Gain of muscle torque at low and high speed after isokinetic knee strengthening program in healthy young and older adults.

Low-speed isokinetic exercise has been recommended to exert a maximal contraction and produce greater muscle torque than high-speed exercise in young adults. The purpose of this study was to compare the effectiveness of low- and high-speed isokinetic exercise programs for increasing muscle torque in young and elderly people. Twenty healthy elderly and 20 young subjects participated. The elderly subjects were divided into two groups. One group performed high-speed (300 degrees/s) isokinetic exercise training three times a week for the dominant-side knee extensor and low-speed (60 degrees/s) exercise for the non-dominant side for 6 weeks. The other group was trained using the reverse exercise regime. The training program for the young subjects was the same as that for the elderly groups. All subjects had their knee extensor torque evaluated with an isokinetic test before and at 2-week intervals during the training program. For young and elderly groups, both high- and low-speed isokinetic exercise training increased extensor torque in low- and high-speed tests. For the young group, low-speed exercise effectively improved muscle torque at low and high speeds. The improvement in slow muscle torque was significantly greater than that in fast muscle torque. For the elderly subjects, high-speed isokinetic exercise produced the greatest muscle torque at high speed in the first 2 weeks of training, and demonstrated a sharp increase in muscle torque in the final 2 weeks. Low-speed exercise frequently caused knee stress and the inability of some elder subjects to continue the exercises with maximal effort. Our findings indicate that high-speed exercise may be more appropriate for the elderly, and low-speed exercise may be more appropriate for younger people.

Adult↗
PubMed2004

Comparison of torque measurements and near-infrared spectroscopy in characterization of a wet granulation process.

The purpose of this study was to compare impeller torque measurements and near-infrared (NIR) spectroscopy in the characterization of the water addition phase of a wet granulation process. Additionally, the effect of hydrate formation during granulation on the impeller torque was investigated. Anhydrous theophylline, alpha-lactose monohydrate, and microcrystalline cellulose (MCC) were used as materials for the study. The materials and mixtures of them were granulated using purified water in a small-scale high-shear mixer. The impeller torque was registered and NIR spectra of wet samples were recorded at-line. The torque and the NIR baseline-corrected water absorbances increased with increasing water content. A plateau in the NIR baseline-corrected water absorbances was observed for wet masses containing MCC. This was at the region of optimal water amount for granulation according to the torque results. In the case of anhydrous theophylline, the slope of baseline-corrected water absorbance values increased at the same water amount as the impeller torque started to increase. The hydrate formation of theophylline during granulation was observed as a slight decrease in the impeller torque. In addition, the hydrate formation during granulation affected the granulation liquid requirement. The liquid requirement was different for monohydrate formed during granulation compared to one formed in high relative humidity before the granulation. The results suggest that NIR spectroscopy may be applicable to process monitoring of wet granulation, also in cases where monitoring of impeller torque is difficult to apply.

Spectroscopy, Near-Infrared↗
PubMed2000

Muscle force arises by actin filament rotation and torque in the Z-filaments.

Actin filament rotation in skeletal muscle is studied by a mechanical model that simulates structure and tension. The four anchoring Z-filaments are twisted around and change the structure of the Z-lattice. The "small square" without twist represents the resting stage of muscle. Torque causes contraction by clockwise rotation (as seen from the Z-band), drilling into the A-band and transition of the "small square" to "basket weave" by increasing the twist and decreasing the torque. Release decreases the torque ("force-depression") by passive clockwise rotation. Stretch causes increased torque ("stretch activation") by passive counterclockwise rotation. Torque arises during Ca(2+)-activation by a conformational change in the highly charged coiled-coils: The four alpha-actinin Z-filaments generate strong torque for the isometric tension. Quick release experiments show that less than one rotation reduces this torque to zero. The 5-12 rotations necessary for isotonic shortening result from torque-generation in the two long tropomyosin coiled-coils. Myosin controls the velocity of active and passive rotations.

Actinin↗
PubMed2000

Torque transmission between square wire and bracket as a function of measurement, form and hardness parameters.

The aim of the study was to investigate the influence of cross section, edge geometry and structural hardness on torque transmission between square wire and bracket. For this purpose, 5 different brands of stainless steel square wire in 3 dimensions (0.016" x 0.016", 0.016" x 0.022" and 0.017" x 0.025") were inserted into edgewise brackets with a slot size of 0.018" and loaded with different torques (1 and 3 Ncm). The slot and wire geometries were analyzed by computer on ground specimens before and after loading. In addition, the Vickers hardness and micro-hardness of the unstressed and stressed metal surfaces were determined. While the slot size was very accurately maintained, the wire dimensions deviated downwards by an average of 10%. Torque transmission led to notching and bending-up phenomena on the bracket slot flanks. A torque loading of 3 Ncm increased the torque play of 0.016" x 0.022" wires by 3.6 degrees, and of 0.017" x 0.025" wires by 3.7 degrees. In the case of 0.016" x 0.016" wires, an effective torque transmission was no longer possible. The average Vickers hardness of the wires was 533 kp/mm2, and that of the brackets 145 kp/mm2. The micro-hardness in the deformation area of stressed internal slot walls increased with increasing load transmission from 204 to 338 kp/mm2. As a result of excessively small wire dimensions and plastic deformation of the brackets, a relatively large torque play occurs. Deformation and notching in the area of the internal slot walls are inconsistent with demands for recycling brackets. A standardization of bracket wire systems stating the actual torque play would be desirable.

Hardness↗
PubMed2006

Influence of predominant patterns of coordination on the exploitation of interaction torques in a two-joint rhythmic arm movement.

In this study we investigate the coordination between rhythmic flexion-extension (FE) and supination-pronation (SP) movements at the elbow joint-complex, while manipulating the intersegmental dynamics by means of a 2-degrees of freedom (df) robot arm. We hypothesized that constraints imposed by the structure of the neuromuscular-skeletal system would (1) result in predominant pattern(s) of coordination in the absence of interaction torques and (2) influence the capabilities of participants to exploit artificially induced interaction torques. Two experiments were conducted in which different conditions of interaction torques were applied on the SP-axis as a function of FE movements. These conditions promoted different patterns of coordination between the 2-df. Control trials conducted in the absence of interaction torques revealed that both the in-phase (supination synchronized with flexion) and the anti-phase (pronation synchronized with flexion) patterns were spontaneously established by participants. The predominance of these patterns of coordination is explained in terms of the mechanical action of bi-articular muscles acting at the elbow joint-complex, and in terms of the reflexes that link the activity of the muscles involved. Results obtained in the different conditions of interaction torques revealed that those neuromuscular-skeletal constraints either impede or favor the exploitation of intersegmental dynamics depending on the context. Interaction torques were indeed found to be exploited to a greater extent in conditions in which the profiles of interaction torques favored one of the two predominant patterns of coordination (i.e., in-phase or anti-phase) as opposed to other patterns of coordination (e.g., 90 degrees or 270 degrees). Those results are discussed in relation to recent studies reporting exploitation of interaction torques in the context of rhythmic movements.

Adult↗
PubMed1999

Effects of movement speed and joint position on knee flexor torque in healthy and post-surgical subjects.

Coactivation of knee flexors during knee extension assists in joint stability by exerting an opposing torque to the anterior tibial displacement induced by the quadriceps. This opposing torque is believed to be generated by eccentric muscle actions that stiffen the knee, thereby attenuating strain to joint ligaments, particularly the anterior cruciate ligament (ACL). However, as the lengths of knee muscles vary with changes in joint position, the magnitude of flexor/extensor muscle force coupling may likewise vary, possibly affecting the capacity for active knee stabilization. The purpose of this study was to assess the effect of changes in movement speed and joint position on eccentric/concentric muscle action relationships in the knees of uninjured (UNI) and post-ACL-surgery (INJ) subjects (n = 14). All subjects were tested for maximum eccentric and concentric torque of the contralateral knee flexors and extensor muscles at four isokinetic speeds (15 degrees-60 degrees x s(-1)) and four joint position intervals (20 degrees-60 degrees of knee flexion). Eccentric flexor torque was normalized to the percentage of concentric flexor torque generated at each joint position interval for each speed tested (flexor E-C ratio). In order to estimate the capacity of the knee flexors to resist active knee extension, the eccentric-flexor/concentric-extensor ratios were also computed for each joint position interval and speed (flexor/extensor E-C ratio). The results revealed that eccentric torque surpassed concentric torque by 3%-144% across movement speeds and joint position intervals. The magnitude of the flexor E-C ratio and flexor/extensor E-C increased significantly with speed in both groups of subjects (P < 0.05) and tended to rise with muscle length as the knee was extended; peak values were generated at the most extended joint position (20 degrees-30 degrees). Although torque development patterns were symmetrical between the contralateral limbs in both groups, between-group comparisons revealed significantly higher flexor/extensor E-C ratios for the INJ group compared to the UNI group (P < 0.05), particularly at the fastest speed tested (60 degrees x s(-1)). The results indicate that joint position and movement speed influence the eccentric/concentric relationships of knee flexors and extensors. The INJ subjects appeared to accommodate to surgery by developing the eccentric function of their ACL and normal knee flexors, particularly at higher speeds and at more extended knee joint positions. This may assist in the dynamic stabilization of the knee at positions where ACL grafts have been reported to be most vulnerable to strain.

Adult↗
PubMed2002

A method for estimating torque-vector directions of shoulder muscles using surface EMGs.

In this study, a new method is proposed to estimate the torque-vector directions of each shoulder muscle. The method is based on a multiple regression model that reconstructs shoulder torque, which is calculated from the hand force and posture, from the surface EMG of many muscles recorded simultaneously. The torque-vector directions of eleven shoulder muscles of four subjects were obtained at up to 30 different arm postures with this method. The mean confidence interval ( p< 0.05) of the estimated torque-vector direction of each subject was 7.7-10.6 degrees. The correlation coefficient between the measured shoulder torque and reconstructed shoulder torque was between 0.76-0.84. The results for majority of the muscles were in accordance with previous studies, and reasonable from the viewpoint of anatomy. The torque-vector directions of a muscle, which are estimated with this method, have more of a functional meaning than a pure anatomical or mechanical one. These indicate the direction of the shoulder torque accompanying the muscle activation for a normal shoulder action that involves the cooperative contraction of many muscles.

Adult↗
PubMed2005

Moderate-heeled shoes and knee joint torques relevant to the development and progression of knee osteoarthritis.

OBJECTIVE: To determine if women's dress shoes with heels of just 1.5 in (3.8 cm) in height increases knee joint torques, which are thought to be relevant to the development and/or progression of knee osteoarthritis (OA) in both the medial and patellofemoral compartments. DESIGN: Randomized controlled trial. SETTING: A 3-dimensional motion analysis gait laboratory. PARTICIPANTS: Twenty-nine healthy young women (age, 26.7+/-5.0 y) and 20 healthy elderly adult women (age, 75.3+/-6.5 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak external varus knee torque in early and late stance and prolongation of flexor knee torque in early stance. Three-dimensional data on lower-extremity torques and motion were collected during walking while (1) wearing shoes with 1.5-in high heels and (2) wearing control shoes without any additional heel. Data were plotted and qualitatively compared; major peak values and timing were statistically compared between the 2 conditions using paired t tests. RESULTS: Peak knee varus torque during late stance was statistically significantly greater with the heeled shoes than with the controls, with increases of 14% in the young women and 9% in the elderly women. With the heeled shoes, the early stance phase knee flexor torque was significantly prolonged, by 19% in the young women and by 14% in elderly women. Also, the peak flexor torque was 7% higher with the heeled shoe in the elderly women. CONCLUSIONS: Even shoes with moderately high heels (1.5 in) significantly increase knee torques thought to be relevant in the development and/or progression of knee OA. Women, particularly those who already have knee OA, should be advised against wearing these types of shoes.

Adult↗
PubMed2006

Feasibility of estimating isokinetic knee torque using a neural network model.

Many studies have investigated the relationships between electromyography (EMG) and torque production. A few investigators have used adjusted learning algorithms and feed-forward artificial neural networks (ANNs) to estimate joint torque in the elbow. This study sought to estimate net isokinetic knee torque using ANN models. Isokinetic knee extensor and flexor torque data were measured simultaneously with agonist and antagonist EMG during concentric and eccentric contractions at joint velocities of 30 degrees /s and 60 degrees /s. Age, gender, height, body mass, agonist EMG, antagonist EMG, joint position and joint velocity were entered as predictive variables of net torque. A three-layer ANN model was developed and trained using an adjusted back-propagation algorithm. Accuracy results were compared against those of forward stepwise regression models. Stepwise regression models included body mass, body height and joint position as the most influential predictors, followed by agonist EMG for concentric and eccentric contractions. Estimation of eccentric torque included antagonist EMG following the agonist activation. ANN models resulted in more accurate torque estimation (R=0.96), compared to the stepwise regression models (R=0.71). ANN model accuracy increased greatly when the number of hidden units increased from 5 to 10, continuing to increase gradually with additional hidden units. The average number of training epochs necessary for solution convergence and the relative accuracy of the model indicate a strong ability for the ANN model to generalize these estimations to a broader sample. The ANN model appears to be a feasible technique for estimating joint torque in the knee.

Adult↗