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PubMed1990

Relationship between trunk muscle torque and bone mineral content of the lumbar spine and hip in healthy postmenopausal women.

The purpose of the study was to determine the relationship between trunk muscle strength and bone mineral density (BMD). Fifty-six postmenopausal women, aged 38 to 73 years, were examined. The BMD of lumbar vertebrae L2-4, the femoral neck, the Ward's triangle, and the greater trochanter was measured with dual-photon absorptiometry. Isometric and isokinetic torque and work measurements obtained on a trunk testing unit were used to assess trunk flexor and extensor strength. Correlation analysis demonstrated a statistically significant relationship between most trunk torque and work measurements and BMD. The trunk extensors generally provided higher correlations with BMD than did the trunk flexors, and the isokinetic extension torque values demonstrated higher correlations than the isometric extension values in every case. Linear backward-regression models, based on the subjects' weight and trunk flexor and extensor torque and work measurements, demonstrated multiple-correlation coefficients of .67, .58, .43, and .65 in predicting the BMD of the L2-4 region, femoral neck, Ward's triangle, and greater trochanter region, respectively. Estrogen therapy status did not affect the linear regression models. These data suggest a positive relationship in postmenopausal women between flexor and extensor torque values and BMD at the lower lumbar spine and proximal femur.

Adult↗
PubMed1991

Test-retest reliability of isokinetic knee extension and flexion torque measurements in persons with spastic hemiparesis.

The purpose of this study was to evaluate and compare the test-retest reliability of isokinetic torque measurements in the involved and uninvolved knee musculature of 20 subjects with spastic hemiparesis. An isokinetic dynamometer was used to measure maximal voluntary knee extension and flexion at 60 degrees and 120 degrees/s. Peak torque (PT) and average peak torque (APT) data were collected from five repetitions on two separate occasions. Average peak torque was defined as the mean of the PT values obtained during each of the five repetitions. Spasticity was measured in the involved knee musculature prior to isokinetic testing using the Ashworth Scale. Pearson Product-Moment Correlation Coefficients and intraclass correlation coefficients (ICCs) were high (greater than or equal to .90) for both knees for PT and APT at both angular velocities. No clinically meaningful differences were found between the Pearson correlation coefficients and the ICCs of the involved versus the uninvolved knee for any testing conditions. We concluded that isokinetic evaluation of torque, as measured by PT and APT in subjects with spastic hemiparesis, can yield reliable results in both extremities.

Adult↗
PubMed1992

The effect of electrical stimulation on quadriceps femoris muscle torque in children with spina bifida.

The effects of neuromuscular electrical stimulation (NMES) on the torque production of the quadriceps femoris muscles were examined in five children with spina bifida. Two male subjects, aged 5 and 12 years, and three female subjects, aged 5, 12, and 21 years, participated in the study. Surface stimulation was applied to the quadriceps femoris muscles of one lower extremity for 30 minutes each day over an 8-week period. At 0, 4, and 8 weeks, maximum isometric voluntary knee extension torques were measured for both control and stimulated lower extremities with a dynamometer at 0, 15, 30, 45, and 60 degrees of knee flexion. The three oldest subjects had torque measurements of acceptable reliability (intraclass correlation coefficient greater than .72). Two of these three subjects also had significant increases in the torque produced by the stimulated limb relative to the torque produced by the control limb. The data were unreliable from the two youngest subjects. Completion times for functional tasks (walking and step ascension/descension) were also recorded before and after the 8 weeks of stimulation. The completion times were lower following stimulation for four subjects.

Adult↗
PubMed1992

Obtaining reliable measurements of knee extensor torque produced during maximal voluntary contractions: an experimental investigation.

The purpose of this study was to develop and test a protocol that could be used to obtain reliable measurements of knee extensor torque produced during maximal voluntary contractions. On each of 3 days, 10 subjects performed six consecutive maximal voluntary contractions, in the same randomized order, for each of the following 10 conditions: concentric isokinetic contractions at velocities of 30 degrees, 90 degrees, 120 degrees, and 180 degrees/s; eccentric isokinetic contractions at velocities of 30 degrees, 90 degrees, 120 degrees, and 180 degrees/s; and isometric contractions at 40 and 60 degrees of knee flexion. The peak torques produced were examined to determine on which day and during which contraction subjects produced the greatest torques for each condition. This information was used to develop a practice protocol. Fifteen different subjects were tested following this protocol. Subjects participated in two practice sessions, a test session, and a retest session. Intraclass correlation coefficients (ICCs) were calculated to determine the degree of agreement between torques for the test and retest sessions. The ICCs ranged from .87 to .98. The protocol developed appears to be useful for obtaining reliable measurements of knee extensor torque.

Acceleration↗
PubMed1993

Changes in torque and electromyographic activity of the quadriceps femoris muscles following isometric training.

BACKGROUND AND PURPOSE: The purpose of this study was to examine the effect of isometric training of the quadriceps femoris muscles, at different joint angles, on torque production and electromyographic (EMG) activity. SUBJECTS: One hundred seven women were randomly assigned to one of four groups. Three groups trained with isometric contractions three times per week at a knee flexion angle of 30, 60, or 90 degrees. The fourth group, which served as a control, did not exercise. METHODS: Isometric torque was measured using a dynamometer, and EMG activity was measured using a multichannel EMG system. Measurements were obtained during maximal isometric contraction of the quadriceps femoris muscles at 15-degree increments from 15 to 105 degrees of knee flexion. Measurements were taken before and after 8 weeks of training. RESULTS: Following isometric exercise, increased torque and EMG activity occurred not only at the angle at which subjects exercised, but also at angles in the range of motion at which exercise did occur. Further analyses indicated that exercising in the lengthened position for the quadriceps femoris muscles (90 degrees of knee flexion) produced increased torque across all angles measured and appeared to be the more effective position for transferring strength and EMG activity to adjacent angles following isometric training as compared with the shorter positions of the muscle (30 degrees and 60 degrees of knee flexion). CONCLUSION AND DISCUSSION: These findings suggest that an efficient method for increasing isometric knee extension torque and EMG activity throughout the entire range of motion is to exercise with the quadriceps femoris muscles in the lengthened position.

Adult↗
PubMed1994

The relationships among knee extensor torques produced during maximal voluntary contractions under various test conditions.

BACKGROUND AND PURPOSE: The purpose of this study was to describe the relationships among measurements of torque produced during selected maximal voluntary contractions of the quadriceps femoris muscles. SUBJECTS: Twenty nondisabled women, ranging in age from 21 to 33 years (X = 25, SD = 3.5), volunteered to participate in the study. METHODS: The subjects were tested on a dynamometer. Subjects performed isometric contractions at 40 and 60 degrees of knee flexion and concentric and eccentric isokinetic contractions at velocities of 30 degrees, 90 degrees, 120 degrees, and 180 degrees/s. Isometric knee extensor torques, concentric knee extensor peak torques, and eccentric knee extensor peak torques were determined for each subject. Coefficients of determination (r2) and linear regression equations were calculated to determine the strength and nature of the relationships among the measurements. RESULTS: The coefficients of determination ranged from .60 to .94. CONCLUSION AND DISCUSSION: The torque measurements were moderately to highly correlated, suggesting that the measurements obtained during different maximal voluntary contractions may be assessing similar components of performance.

Adult↗
PubMed2000

Effect of oral creatine supplementation on isokinetic torque production.

PURPOSE: This study was conducted to examine the effect of oral creatine supplementation on the decline in peak isokinetic torque of the quadriceps muscle group during an endurance test. METHODS: Twenty-three active, but untrained, male subjects performed isokinetic strength tests on a Cybex II dynamometer at 180 degrees x s(-1). The protocol consisted of pre- and post-tests with five sets of 30 maximum volitional contractions with a 1-min rest period between sets. Subjects returned to perform the posttest after 5 d of placebo (4 x 6 g glucose x d(-1), N = 12) or creatine (4 x 5 g creatine + 1 g glucose x d(-1), N = 11) supplementation. Supplements and testing were administered in a double blind fashion. Peak torque was measured during each contraction and the 30 contractions were averaged for each set. RESULTS: A three-way mixed ANOVA with one between factor (placebo vs creatine) and two within factors (pre/post supplementation and sets 1-5) revealed no significant interactions, P > 0.05. The placebo vs creatine main effect was also nonsignificant, whereas the pre/post and set effects were significant (P < 0.05). Peak torque increased (approximately 3%) from pre- to post-testing, (P = 0.04), but the absolute magnitude of the differences is unlikely to be of any practical significance. Peak torque decreased from sets 1 to 4, whereas sets 4 and 5 were not different. A priori contrasts comparing the creatine group's performance pre vs post test for the fourth and fifth sets were nonsignificant (P > 0.05). CONCLUSIONS: Based on within and between group comparisons, we were unable to detect an ergogenic effect of oral creatine supplementation on the decline in peak torque during isokinetic exercise at 180 degrees x s(-1).

Adult↗
PubMed1993

The effect of torque pressure on halo pin complication rates. A randomized prospective study.

At Thomas Jefferson University Hospital, 102 consecutive patients treated in a halo vest orthosis were randomized into one of two torque protocol groups based on their date of birth. The pins of patients who were born in even-numbered months were inserted with 8 inch-lbs of torque and those born in odd-numbered months were inserted with 6 inch-lbs. All patients were placed in an identical model halo using a standardized technique of application. The patients were followed prospectively, and all potential complications were evaluated by a member of the orthopedic attending staff, using protocols established at the onset of the study. Statistical analysis indicated no significant differences in halo pin loosening, infection, pain, or scarring between the torque protocols, but there was a trend toward a higher complication rate in the 8-inch-lbs group. There was no direct evidence of skull penetration in either group, and no patients developed a deep infection. Based on the results of this study, we conclude that insertion torque has no significant effect on halo pin complications within the ranges tested by this study. Our current protocol calls for routine insertion of halo pins with 6 inch-lbs of torque.

Adult↗
PubMed1998

A static dynamometer measuring simultaneous torques exerted at the upper limb.

The majority of available dynamometers are designed to measure force or torque in one specific direction, one joint at a time. For the quantification of motor incoordination in neurological patient populations, these dynamometers provide limited information about the global behavior of the limb under investigation. This report describes the potential use and function of a static dynamometer measuring torques exerted simultaneously at the shoulder (flexion-extension, abduction-adduction, internal-external rotation), elbow (flexion-extension), and forearm (pronation-supination). Orthogonal forces were measured at the arm and wrist using strain gauge transducers interfaced with a laboratory computer. The lever arms were specified to a software program and the joint torques were calculated in real time according to static equilibrium equations. The use of the dynamometer is illustrated by characterizing for one hemiparetic subject, the joints torques recorded at the shoulder, elbow, and forearm during isolated submaximal grip exertions at different force levels on both sides. The torques generated at the shoulder, elbow and forearm during the hand grip tasks on the affected side were significantly higher than those obtained on the nonaffected side and increased with the grip force level. These differences probably reflect the loss of movement selectivity observed following a lesion in the central nervous system. Further studies are currently being undertaken in neurological patient populations to characterize and quantify motor deficits using this dynamometer. As a long term goal, we hope that the method and technologies described here will contribute to the evaluation and rehabilitation of these populations.

Biofeedback, Psychology↗
PubMed1993

Longitudinal study on torque around the sagittal axis in lower distal-extension removable partial dentures.

The purpose of this study was to examine the longitudinal changes of torque around the sagittal axis in lower distal-extension removable partial dentures. The torque transmitted from the denture base to retainers was measured on several separate occasions from the insertion of new dentures to about 2 months after it. The maximal mean value of torque (Max.MT) was calculated from the magnitude of all chewing strokes of the minimum of the interocclusal distance. The integration values of torque (I) and time (T) from initiation of chewing to swallowing were obtained and then the average value of torque (Ave.T) was calculated (Ave.T = I/T). Subjects could be divided into two groups. Max.MT and Ave.T were almost constant in one group while they were remarkably decreased in another. After 1 month of insertion of new dentures the value of both groups was within the range of less than 3 x 10(-3) kgm (1 kgm = 9.8 Nm) of Max.MT and less than 1 x 10(-3) kgm ss-1 of Ave.T.

Adult↗
PubMed1993

Longitudinal study on torque transmitted from denture base to an abutment tooth of lower distal-extension removable partial dentures with conus crown telescopic system.

The purpose of this study was to make a longitudinal analysis of torque transmitted to a direct abutment tooth of a lower distal-extension removable partial dentures constructed with the conus crown telescopic system. Torque around the vertical and lateral axes of the tooth were measured during chewing of food at the time of insertion of the new dentures to about three months after. The maximal mean value of torque (Max.MT) was calculated from the peak level of all chewing strokes at the minimum of the interocclusal distance. The integration values of torque (I) and time (T) from initiation of chewing to swallowing were obtained, then the average value of torque (Ave.T) was calculated (Ave.T = I/T). The results are summarized as follows: (a) There were no remarkable changes of Max.MT around the both axes; (b) Max.MT around the lateral axis was 7-47 x 10(-3) kgm (mean: 25 x 10(-3) kgm) (1 kgm = 9.8 Nm) in the downward direction and Ave.T around the lateral axis was 6-14 x 10(-3) kgm ss-1 (mean: 10 x 10(-3) kgm ss-1) in the downward direction; (c) There were marked differences of Max.MT and Ave.T around the vertical axis between subjects. Max.MT around the vertical axis was less than 24 x 10(-3) kgm and Ave.T around the vertical axis was less than 6 x 10(-3) kgm ss-1.

Aged↗
PubMed1995

Relation between gait speed, knee muscle torque and motor scores in post-stroke patients.

A study was undertaken to investigate the relation between gait speed, motor function and isokinetic knee muscle torque in stroke victims. Two different gait speeds, freely chosen speed and fastest speed, were measured on a 10-m long walkway in 34 stroke victims (median age 71 years) three months after the stroke. At the same time different motor functions were assessed, and isokinetic knee muscle torque was measured. One year after the stroke 24 of the subjects were again investigated. The two gait speeds measured were both slower than those in normal healthy subjects of the same age. The motor assessment revealed that the group of stroke patients had light to moderately severe stroke symptoms. The isokinetic muscle torque was significantly lower in the paretic than in the non-paretic legs. The non-paretic legs were also weaker than the legs of healthy subjects. No significant changes in any of the measured variables were found between the three months' assessment and the one year post-stroke assessment. There were some significant correlations between gait speed and motor scores and between gait speed and muscle torque, but usually of moderate strength. Multiple regression analysis with gait speed as dependent variable and combined isokinetic muscle torque and three different motor scores as independent variables gave higher R values.

Aged↗
PubMed1984

Resonance at the wrist demonstrated by the use of a torque motor: an instrumental analysis of muscle tone in man.

The resonance of the relaxed wrist for flexion-extension movements in the horizontal plane has been investigated by using rhythmic torques generated by a printed motor. In the normal subject the resonant frequency of the wrist is ca. 2 Hz unless the torque is reduced below a certain critical value when the system is no longer linear and the resonant frequency rises. This critical torque level, and the damping are both less in women than men. The resonant frequency is uninfluenced by surgical anaesthesia. With added bias the increase of resonant frequency at low torques still occurs although the hand is now oscillating about a displaced mean position. It follows that the stiffening implied by this elevation of resonant frequency for small movements is neither the result of pre-stressing of the muscles nor of reflex activity. With velocity feed-back of appropriate polarity the system will oscillate spontaneously at its resonant frequency. If the peak driving torque is progressively reduced the resonant frequency increases abruptly, indicating that the system has stiffened. Perturbations delivered to the wrist may reduce its stiffness. The postural system is thixotropic with a 'memory time' of 1-2 s. The resonant frequency is elevated in voluntary stiffening.

Anesthesia↗
PubMed1995

Changes in pennation with joint angle and muscle torque: in vivo measurements in human brachialis muscle.

1. Estimates of pennation in human muscles are usually obtained from cadavers. In this study, pennation of human brachialis was measured in vivo using sonography. Effects of static and dynamic changes in elbow angle and torque were investigated. 2. Pennation was measured in eight subjects using an 80 mm, 5 MHz, linear-array ultrasound transducer to generate sagittal images of the brachialis during maximal and submaximal isometric contractions at various elbow angles. It was shown that estimates of pennation were reproducible, representative of measurements made throughout the belly of the muscle and not distorted by compression of the muscle with the transducer or rotation of the muscle out of the plane of the transducer. 3. Mean resting pennation was 9.0 +/- 2.0 deg (S.D., range 6.5-12.9 deg). When the muscle was relaxed there was no effect of elbow angle on pennation. However, during a maximal isometric contraction (MVC), with the elbow flexed to 90 deg, pennation increased non-linearly with elbow torque to between 22 and 30 deg (mean 24.7 +/- 2.4 deg). The effect of increasing torque was small when the elbow was fully extended. The relationship between elbow angle, elbow torque and brachialis pennation suggests that the relaxed brachialis muscle is slack over much of its physiological range of lengths. 4. There was no hysteresis in the relationship between torque and pennation during slow isometric contractions (0.2 MVC s-1), and the relationship between elbow angle and pennation was similar during slow shortening and lengthening contractions. 5. Two consequences follow from these findings. Firstly, intramuscular mechanics are complex and simple planar models of muscles underestimate the increases in pennation which occur during muscle contraction. Second, spindle afferents from relaxed muscles may not encode joint angle over the full range of movement.

Adult↗
PubMed1995

Evaluation of voluntary and elicited dorsiflexor torque-angle relationships.

The purposes of this study were to determine the relative influence of mechanical (muscle force and moment arm) and neural (activation) factors on the shape of dorsiflexor torque-angle relationships and to determine the interday reliability of measurements of such relationships. Dorsiflexor torque-angle relationships produced with maximal voluntary contractions (MVCs) and with electrically elicited contractions (twitch, 20-Hz tetanic, 40-Hz tetanic) were obtained for seven male subjects on 2 separate days. MVC torque-angle relationships were reproducible between days. Elicited relationships were less reproducible than the MVC relationships, with the 40-Hz relationship the most reproducible of the elicited relationships. The shapes of the MVC and elicited twitch torque-angle relationships were significantly different. The shapes of the MVC, 20-, and 40-Hz elicited relationships were similar. The simplest explanation for this latter finding is that the shape the MVC relationship is determined primarily by mechanical factors and is not strongly dependent on neural factors. The results of this study may affect the interpretation of comparisons of torque-angle relationships between subject groups or pre- and posttraining.

Adult↗
PubMed1982

Myoelectric responses at flexors and extensors of human wrist to step torque perturbations.

1. Torque-step perturbations were applied to flex or extend the wrists of normal human subjects. The electromyographic activity (EMG) of two of the stretched muscles, flexor carpi radialis and extensor carpi radialis, was monitored. 2. Based on functional characteristics and temporal bursting patterns, the EMG responses were partitioned into four distinct temporal intervals : 30-60, 60-120, 120-200, and greater than 200 ms after the onset of the torque step. The last interval continues for the duration of the step input: 200- 400 ms was chosen to represent activity in this interval. 3. EMG responses in the first two intervals show short, stable latencies and amplitudes that depend on the level of muscle contraction prior to the torque step. They are facilitated by any instruction requiring a reaction by the subject. They are reflexes that cannot be voluntarily suppressed by instruction to the subject. 4. The third EMG response is a triggered response. It is not a reflex because its appearance or absence is absolutely under voluntary control. Unlike true voluntary responses, there exists no dichotomy in responses latency or variability between known versus unknown directions of torque steps. 5. We consider that a truly voluntary response to a torque perturbation does not begin until about 200 ms after the step, which is on the order of visual or auditory reaction times. 6. The EMG responses were similar in both the wrist flexor and extensor studied. Ankle flexors and extensors do not show such similarity. 7. The EMG responses at the wrist and ankle are compared and shown to have many similarities. A general scheme for their classification is discussed.

Adult↗
PubMed1983

Response to sudden torques about ankle in man: V effects of peripheral ischemia.

Sudden dorsiflexions and plantar flexions of the foot were imposed by a torque motor while blood flow to the lower leg was occluded by a sphygmomanometer cuff. Seated subjects were instructed to resist the torques and restore the foot to its original position as rapidly as possible. Measurements of the first two electromyographic (EMG) responses were made in the soleus (SOL) and anterior tibial (TA) muscles. These are the myotatic reflex at about 40 ms and the postmyotatic response at about 120 ms. In the anterior tibial muscle, the myotatic component often occurs at 60- to 90-ms latency and is continuous with the postmyotatic component. After about 20 min of ischemia, there is a rapid and eventually complete loss of the myotatic component of the response in the stretched muscle. Concurrent with the loss of the myotatic reflex there is usually a reduction of the postmyotatic component. The latency of postmyotatic component remains unchanged, even after the myotatic reflex is abolished. Voluntary restoration of the foot to its original position in opposition to the motor torque is delayed and slowed by the time that the myotatic reflex has vanished. By measuring electromyographic responses to visually triggered reactions, we demonstrate that the reduction of the postmyotatic response is not due to failure of the efferent pathway. On this basis we discuss the possible contributions made by myotatic mechanisms to the tasks of load compensation and maintenance of muscle tone. Hoffmann reflexes were evoked in similar experiments with stimulation of the posterior tibial nerve at the popliteal fossa, distal to the cuff. The maximal direct motor response and muscle twitch are unaffected by loss of the H-reflex. Myotatic and Hoffmann reflexes were both evoked with torque perturbations and with a stimulating electrode proximal to a below-the-knee cuff. In this case, the myotatic reflex failed while the maximal H-reflex was slightly facilitated. The loss of the myotatic reflex was accompanied by a modest reduction in the direct motor response to electrical stimulation and a somewhat greater reduction in the postmyotatic response to torque perturbation. The data are interpreted to support a dual role for the primary afferent pathway in the control of voluntary movements. It provides the fastest path for the activation of a stretched muscle to initiate a load-compensating contraction. It also provides a form of servo assistance in modulating descending control signals. The degree of this assistance is estimated. In this simple experimental paradigm, functional contributions of the reflex arc are demonstrated.

Ankle Joint↗
PubMedDate not supplied

Torque developed at simulated sliding between sport shoes and an artificial turf.

Rotation torque is known to be one of many factors affecting the risk of injury in athletics. Experiments were performed to examine the torque and friction on different sport shoes when sliding on an artificial turf. An apparatus was constructed in which it is possible to measure simultaneously the torque and the frictional force developed when a shoe slides on a surface. Measurements were made for 25 different shoes on an artificial turf. The frictional force was independent of the speed in the range 1 to 5 m/s. The torque was dependent on the physical distribution of the texture of the sole and slightly dependent on the frictional force. The results indicate that the physical distribution of the sole at the heel and toe, as well as the material, is of great importance for the torque developed.

Ankle Injuries↗