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At least 811 records · Page 45Linked to original sources
PubMed1986

The effect of external load on torque production by knee extensors.

The kinematics of the knee joint are load-dependent; the length of the lever arm of the extensor mechanism and the pathway of the instant center of rotation vary with external load. This study was conducted to determine if the maximum extensor torque-generating capacity of the knee joint is dependent on the distance from the knee joint at which the external force resisting extension is located. Maximum isometric extensor torques were measured at 90 and 30 degrees of knee flexion while the distance from the knee joint to the resisting force was varied. Our results demonstrated that the subjects generated larger maximum extensor torques, at both 90 and 30 degrees of knee flexion, when the external resisting force was positioned farther distal to the knee joint. This increase was as large as 50 per cent with the knee at 30 degrees of flexion.

Adult↗
PubMed1979

Passive resistive torques about long bone axes of major human joints.

Multisegmented total-human-body models play an important role in studies such as vehicle crash victim simulation, pilot ejection and flailing. Proper biomechanical description of the major articulating joints of these mathematical models require passive resistive torque data for the rotational motions of the body segments about their long bone axes. This paper presents a research program which was developed to collect such data at the shoulder, hip, knee, elbow, and ankle joints. The research was conducted, with some obvious limitations, on live human subjects by means of specially designed experimental apparatus. The numerical results are presented for three subjects for the passive resistive torques about the long bone axes of the major articulating joints. It was concluded that the maximum tolerable passive resistive torques associated with the long bones of the lower extremities are more than twice the ones associated with the long bones of the upper extre mities.

Accidents, Aviation↗
PubMed1982

An in vitro biomechanical evaluation of anterior-posterior motion of the knee. Tibial displacement, rotation, and torque.

We tested the anterior-posterior motion of nine normal cadaver knees in zero to 90 degrees of flexion using a specially designed apparatus. This apparatus applied a dynamic anterior-posterior force to each knee and measured the resulting tibial displacement, rotation, and torque. In the intact knee, an anterior force produced an internal tibial torque and internal tibial rotation, while a posterior force produced an external torque and external rotation. Anterior-posterior displacement increased by 30 per cent when the tibia was allowed to rotate freely about its neutral rotation position. Isolated section of the anterior cruciate ligament produced more than double the amount of anterior displacement without affecting posterior displacement. Isolated section of the posterior cruciate ligament produced almost triple the amount of posterior displacement without affecting anterior displacement. After cutting either the anterior or the posterior cruciate ligament, the resulting internal or external secondary tibial rotation disappeared. It appears, therefore, that the anterior and posterior cruciate ligaments are the primary restraints to motion in the anterior and posterior directions as well as the causes of internal and external tibial rotation during anterior and posterior motion.

Aged↗
PubMed1982

On the relationship between resultant joint torques and muscular activity.

This paper is an investigation of the relationship between resultant joint torques and in vivo muscular activity. This relationship is currently inaccessible by direct experimental measurements due to the limited usefulness of electromyographic (EMG) data to indicate muscle force reliably and to proscriptions and experimental difficulties related to in vivo measurements on human subjects. The standard indirect method for inferring information about this relationship, using model studies in conjunction with temporal EMG data, is discussed. Key assumptions incorporated in these model studies, which lead to values for the joint force and torque resultants, are reviewed. The general distribution problem is formulated, and key assumptions associated with generating the simplified distribution problem that governs muscle activity are described. Two basically different methods for solving the simplified distribution problem and therefore determining the approximate relationship between resultant joint torques and muscular activity, including methods that attempt to account for the effect of antagonistic muscular activity, are discussed.

Biomechanical Phenomena↗
PubMed1981

Relationships between tibial rotary torque and knee flexion/extension after tendon transplant surgery.

The hamstring muscles play an important role in decelerating and checking tibial rotation before excessive stresses are applied to knee support structures. The purpose of this study was to determine the relationships between standard flexion/extension rehabilitative techniques and tibial rotary torque among subjects who had received pes anserinus transfers at least 1 year prior. Postsurgical and healthy contralateral limbs of 15 males were tested for maximum, isokinetic knee flexion/extension and internal/external tibial rotation. An adjustable chair and stabilizing boot were used to minimize extraneous hip, thigh and subtalar movements. Product-moment correlation coefficients were computed to determine the relationships between muscle forces generated during tibial rotation and knee flexion/extension. Relatively small relationships were found between rotation and flexion. Tibial rotation and flexion were more highly correlated in the nonsurgical than in the surgical limbs. The results also revealed that peak torque was generated within the first 5-10 degrees of motion for tibial rotation and within the first 20-30 degrees of motion for knee flexion and extension. The data indicate that measures of maximal knee flexor torque cannot be used to predict the rotational capabilities of the same muscle group and that separate measurement and rehabilitative techniques are necessary. Further analyses of postsurgical knees revealed force deficits among knee flexors and extensors when compared to nonsurgical counterparts. The findings suggest long-term sensitivity of the quadriceps to immobility.

Adolescent↗
PubMed1980

A force and torque analysis of giant swings on the horizontal bar.

The purpose of this study was to make a kinetic comparison of backward and forward giant swings on the horizontal bar. Six Canadian gymnasts of national calibre were filmed using a high speed camera during the performance of giant swings on a horizontal bar which was equipped with strain and torque gauges. Prior to filming, the horizontal bar was calibrated by force application at various angles. During the performances, voltage outputs representing force and torque were amplified and recorded on tape. The force/torque data were then subjected to computer analysis. Forces were plotted circularly against the angle at which the forces acted on the bar using an x-y plotter. Maximum forces and torques for both forward and backward giant swings were compared. Polar force plots were then normalized by dividing force by body weight. A superposition of curves for 11 backward giant swings and 12 forward giant swings has produced two models representing good performance of giant swings by national gymnasts. Deviations from the models may be useful in correction of errors in execution of the swings. This method could provide instantaneous feedback on performance technique without requiring film analysis.

Biomechanical Phenomena↗
PubMed1994

Isokinetic torques and kicking maximal ball velocity in young soccer players.

The purpose of this study is to assess if there is any correlation between isokinetic testing and field performance of young soccer players. The isokinetic peak torques of the knee extensor muscles in sitting position (TKE), and those of the hip flexor muscles in standing position (THF) were measured in 24 junior soccer players. Four angular velocities (omega = 1.05, 3.14, 4.19, 5.23 rad.s-1 or 60, 180, 240, 300 deg.s-1) were used for the knee extensors and three (1.05, 3.14, 4.19 rad.s-1) for the hip flexors. On the field the subjects were asked to kick a stationary soccer ball as fast as possible against a barrier and the mean linear velocity over a 10 m path (v) was measured. TKE of the non dominant limb were higher than those of the opposite one at the three highest omega (p < 0.05). On the contrary the THF of the dominant limbs were higher than those of the controlateral, at the two highest omega. When the ball was kicked by the dominant or non dominant limbs, the mean values and standard deviations (+/- SD) of v were 23.6 (+/- 2.5) and 21.4 (+/- 2.6) m.s-1. Torques and v were always positively correlated to each other; however, only in few cases was this relationship statistically significant. In conclusion the isokinetic torques do not seem to be good predictors of v, one of the several factors which determine the global performances of the soccer players.

Adolescent↗
PubMed1993

Comparison of experimental and analytical torque-angle relationships of the human elbow joint complex.

The human elbow joint complex (EJC) is an intricate joint that is currently being modeled with eight musculotendon actuators for the analysis of flexion-extension and pronation-supination movements. The musculotendon length (LMT), musculotendon velocity (VMT), and muscular moment arm (MA) for each actuator have been investigated based on joint anatomy and joint angle position. Musculotendon parameters necessary for the muscle model have been collected from various sources. These parameters, along with the musculoskeletal geometry, are used in a static muscle model to compute the force and joint torque generated by each muscle. The results are plotted as torque-angle curves and compared with experimental joint torque data.

Biomechanical Phenomena↗
PubMed2002

Contractile muscle volume and agonist-antagonist coactivation account for differences in torque between young and older women.

It is controversial whether specific tension (the ratio between muscle strength and size) declines with aging. Therefore, contractile muscle volume was estimated separately from the intramuscular noncontractile tissue by magnetic resonance imaging, and maximum isometric torque was measured in the knee extensors and flexors of 10 young (22.8 +/- 5.7 years) and 10 older (69.5 +/- 2.4 years) healthy active women. Specific tension was lower in the older women both in the extensors (93.1 +/- 20.1 kN x m(-2) vs. 112.1 +/- 12.3 kN x m(-2); P < 0.05) and in the flexors (100 +/- 31 kN x m(-2) vs. 142.7 +/- 23.9 kN x m(-2); P < 0.01). This was accompanied by an increase in the percentage coactivation of the knee flexors during knee extension. These data suggest that the lower level of muscle torque in the older women can be explained not only by smaller contractile muscle mass but also by increased coactivation of the antagonist muscles during knee extension.

Adult↗
PubMedDate not supplied

Torque teno virus (TTV): current status.

Torque teno virus (TTV), currently classified into the family Circoviridae, genus Anellovirus, was first found in a patient with non-A-E hepatitis. TTV has a single stranded circular DNA of approximately 3.8 kb. TTVs are extraordinarily diverse, spanning five groups including SANBAN and SEN viruses. Torque teno mini virus (TTMV) with approximately 2.9 kb genome also has wide variants. Recently, two related 2.2- and 2.6-kb species joined this community. Recombinations between variants are frequent. This extensive TTV diversity remains unexplained; it is unclear how TTVs could be viable, and why they require such genetic variation. An unequivocal culture system is still not available. TTVs are ubiquitous in > 90% of adults worldwide but no human pathogenicity of TTV has been fully established. Epidemiological surveys need to specify the variants being studied and clinical targets, and must calibrate the sensitivity of the assay used. Potentially interesting observations include a higher viral load in patients with severe idiopathic inflammatory myopathies, cancer and lupus. Active replication was also found in infants with acute respiratory diseases. TTV/TTMV-related viruses were found in chimpanzees, apes, African monkeys and tupaias, and also in chickens, pigs, cows, sheep and dogs. Experimentally, rhesus monkeys were persistently infected by TTV, but only 1/53 chimpanzees. TTV transcribes three species of mRNAs, 3.0-, 1.2- and 1.0-kb in the ratio of 60:5:35. Recently, at least three mRNAs were shown in chicken anaemia virus. The genomic region -154/-76 contains a critical promoter. TTV seems to have at least three proteins; however, the definite functions of these proteins await further research work.

Adult↗
PubMed1996

Impaired stretch reflex and joint torque modulation during spastic gait in multiple sclerosis patients.

The modulation of the short latency stretch reflex of the soleus muscle during walking was investigated in seven spastic multiple sclerosis (MS) patients and nine healthy control subjects. Ankle joint stretches were applied by a system which can rotate that ankle joint in any phase of the step cycle during treadmill walking. The torque related to the muscle fibres contracting prior to the stretch and the passive tissues around the ankle joint were measured as the "non-reflex torque". At the same time the short latency stretch reflex-mediated EMG response was measured. The findings show that the stretch reflex modulation was impaired in spastic patients during walking. The stretch reflex modulation was quantified by a modulation index of an average 50% (range -5 to 100%) in the patients and 93% (78-100%) in the control subjects (P < 0.05). The passive stiffness of the ankle joint was at the same time increased in the patients (P < 0.05). It is proposed that the impaired modulation of the stretch reflex along with increased ankle joint stiffness contribute to the impaired walking ability in spastic MS patients.

Adult↗
PubMed1998

Incisor torque by means of a modified Teuscher activator. Three case reports.

It is generally accepted that in the treatment of Class II, 1 malocclusion classical activators may tip the upper incisors considerably. In comparison, in the cases described, an even better torque control was obtained. It has been our clinical experience that with the modified Teuscher activator it is possible to control upper incisor inclination and in some cases it is even possible to induce active palatal root torque. The appliance is relatively comfortable with good vertical retention even without headgear.

Activator Appliances↗
PubMed2002

Quadriceps torque curve pattern in patients with anterior cruciate ligament injury.

We measured torque curve pattern and quadriceps muscle strength with the knee slightly flexed in 48 patients with an anterior cruciate ligament injury, and analyzed the factors associated with reduced quadriceps strength. Strength was measured under isokinetic contraction, and concentric and eccentric contractions were studied. Strength was significantly lower in the injured knee, which also showed abnormal patterns of torque curve. In addition to the rapid downward slope pattern usually associated with concentric contraction, there was a concave pattern during eccentric contraction.

Adolescent↗
PubMed2003

Local tissue temperature effects on peak torque and muscular endurance during isometric knee extension.

The aim of the study was to investigate the relationship between local tissue temperature, peak torque and time to fatigue during isometric knee extensions. Nine males performed maximum voluntary contractions (MVCs) and isometric knee extensions at 70% MVC to exhaustion after 30 min of hot [H, 47.7 (1.3) degrees C; mean (SD)], warm [W, 34.6 (0.4) degrees C], temperate [T, 24.5 (1.3) degrees C], and cold [C, -11.9 (1.8) degrees C] localized temperature applications. Isometric peak torque was not significantly affected by temperature. Time to fatigue was strongly and negatively correlated ( r=-0.98) to temperature, with endurance after H [46.99 (4.98) s] and W [54.36 (9.18) s] significantly shorter than after C [73.27 (13.43) s]. We conclude that local tissue temperature does not impair peak force production but may change muscular endurance through local factors.

Adult↗
PubMed2000

Energy cost of front-crawl swimming at supra-maximal speeds and underwater torque in young swimmers.

The energy cost of front-crawl swimming (Cs, kJ x m(-1)) at maximal voluntary speeds over distances of 50, 100, 200 and 400 m, and the underwater torque (T') were assessed in nine young swimmers (three males and six females; 12-17 years old). Cs was calculated from the ratio of the total metabolic energy (Es, kJ) spent to the distance covered. Es was estimated as the sum of the energy derived from alactic (AnA1), lactic (AnL) and aerobic (Aer) processes. In turn, AnL was obtained from the net increase of lactate concentration after exercise, AnA1 was assumed to amount to 0.393 kJ x kg(-1) of body mass, and Aer was estimated from the maximal aerobic power of the subject. Maximal oxygen consumption was calculated by means of the back-extrapolation technique from the oxygen consumption kinetics recorded during recovery after a 400-m maximal trial. Underwater torque (T' x N x m), defined as the product of the force with which the feet of a subject lying horizontally in water tends to sink times the distance from the feet to the center of volume of the lungs, was determined by means of an underwater balance. Cs (kJ x m(-1)) turned out to be a continuous function of the speed (v, m x s(-1)) in both males (Cs = 0.603 x 10(0.228v), r2 =0.991; n = 12) and females (Cs = 0.360 x 10(0.339r), r2 = 0.919; n = 24). A significant relationship was found between T' and Cs at 1.2 m x s(-1); Cs = 0.042T' + 0.594, r = 0.839, n = 10, P<0.05. On the contrary, no significant relationships were found between Cs and T' at faster speeds (1.4 and 1.6 m x s(-1)). This suggests that T' is a determinant of Cs only at speeds comparable to that maintained by the subjects over the longest, 400-m distance [mean (SD) 1.20 (0.07) m x s(-1)].

Adolescent↗
PubMed2002

Force and torque production in static multifinger prehension: biomechanics and control. II. Control.

The coordination of digits during combined force/torque production tasks was further studied using the data presented in the companion paper [Zatsiorsky et al. Biol Cybern this issue, Part I]. Optimization was performed using as criteria the cubic norms of (a) finger forces, (b) finger forces normalized with respect to the maximal forces measured in single-finger tasks, (c) finger forces normalized with respect to the maximal forces measured in a four-finger task, and (d) finger forces normalized with respect to the maximal moments that can be generated by the fingers. All four criteria failed to predict antagonist finger moments when these moments were not imposed by the task mechanics. Reconstruction of neural commands: The vector of neural commands c was reconstructed from the equation c=W(-1)F, where W is the finger interconnection weight matrix and F is the vector of finger forces. The neural commands ranged from zero (no voluntary force production) to one (maximal voluntary contraction). For fingers producing moments counteracting the external torque ('agonist' fingers), the intensity of the neural commands was well correlated with the relative finger forces normalized to the maximal forces in a four-finger task. When fingers produced moments in the direction of the external torque ('antagonist' fingers), the relative finger forces were always larger than those expected from the intensity of the corresponding neural commands. The individual finger forces were decomposed into forces due to 'direct' commands and forces induced by enslaving effects. Optimization of the neural commands resulted in the best correspondence between actual and predicted finger forces. The antagonist moments are, at least in part, due to enslaving effects: strong commands to agonist fingers also activated antagonist fingers.

Biomechanical Phenomena↗
PubMed2005

Handle displacement and operator responses to pneumatic nutrunner torque buildup.

The objective of this study is to investigate the workstation and tool effects on the responses of the powered hand tool operator reacting against the impulsive reaction forces that may be associated with upper extremity musculoskeletal disorders. The study demonstrated a means of direct measurement of force at the interface between the tool and the operator. Fifteen experienced male operators performed three independent work configurations: pistol grip and right angle tools used on the horizontal surface and pistol grip tools used on the vertical surface, in the laboratory. A full factorial experiment consisting of 36 conditions was designed to examine the effects of working height, distance, tool, and fastener joint hardness on handle displacement and grip forces. The results indicate that operator responses were affected by different factors depending on the work configuration. When pistol grip tools were used on the vertical surface, the mean handle displacement decreased from 9.9 degrees to 7.3 degrees as the working height increased from 30 cm below shoulder to 30 cm above shoulder. When right angle tools were used, the greatest handle displacement (51.1mm) and grip force (84.7% MVC) during torque reactions were measured at 30 cm below elbow and 40% forward reach away from the operator. This study provides quantitative information that can be used for workstation design and tool selection to reduce the torque reaction experienced by powered nutrunner operators.

Adult↗
PubMed2004

The influence of soft tissue movement on ground reaction forces, joint torques and joint reaction forces in drop landings.

The aim of this study was to determine the effects that soft tissue motion has on ground reaction forces, joint torques and joint reaction forces in drop landings. To this end a four body-segment wobbling mass model was developed to reproduce the vertical ground reaction force curve for the first 100 ms of landing. Particular attention was paid to the passive impact phase, while selecting most model parameters a priori, thus permitting examination of the rigid body assumption on system kinetics. A two-dimensional wobbling mass model was developed in DADS (version 9.00, CADSI) to simulate landing from a drop of 43 cm. Subject-specific inertia parameters were calculated for both the rigid links and the wobbling masses. The magnitude and frequency response of the soft tissue of the subject to impulsive loading was measured and used as a criterion for assessing the wobbling mass motion. The model successfully reproduced the vertical ground reaction force for the first 100 ms of the landing with a peak vertical ground reaction force error of 1.2% and root mean square errors of 5% for the first 15 ms and 12% for the first 40 ms. The resultant joint forces and torques were lower for the wobbling mass model compared with a rigid body model, up to nearly 50% lower, indicating the important contribution of the wobbling masses on reducing system loading.

Adult↗