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Thirty-one dentists were tested relative to the optimal and maximum amount of torque they could deliver to posts in teeth. The mean for the optimal amount of torque was 15.55 ounce-inches, and the mean for the maximum amount of torque was 35.29 ounce-inches. Female dentists showed a statistically significantly lower mean difference of 24.5 ounce-inches on the maximum torque test.
PURPOSE: To compare the torque and flattening effect induced by temporal or on-axis clear corneal incisions (CCIs) for phacoemulsification. SETTING: Moorfields Eye Hospital, London, United Kingdom. METHODS: Randomized controlled clinical trial on 62 eyes with cataract and mild to moderate corneal astigmatism (<2.60 diopters [D]) having phacoemulsification with a temporal CCI (temporal group) or on-axis CCI (on-axis group). Corneal astigmatism was assessed by corneal topography preoperatively and 3 weeks after surgery. The meridian of the incisions was marked on the cornea before local anesthesia was given to avoid anesthesia-related cyclotorsion. The surgically induced astigmatism (SIA) vector, torque, flattening effect, and accuracy of incision placement were analyzed in the 2 groups and compared with a paired t test. RESULTS: Three weeks after surgery, the on-axis CCI induced slightly more flattening of the meridian of the incision (mean -0.63 +/- 0.57 D [SD]) than the temporal CCI (mean -0.50 +/- 0.44 D); however, the differences were not statistically significant (P = .31). Simple algebraic difference showed a mean increase in astigmatism magnitude of 0.12 +/- 0.52 D in the temporal group and a mean reduction of 0.21 +/- 0.53 D in the on-axis group (P = .02). The mean absolute torque was 0.28 +/- 0.27 D and 0.53 +/- 0.37 D, respectively (P<.005). The absolute angle of error of incision placement (alpha) was greater after on-axis CCIs (mean 25.9 +/- 20.1 degrees) than after temporal CCIs (mean 14.5 +/- 14.3 degrees) (P = .01). CONCLUSIONS: In eyes with preoperative astigmatism less than 2.60 D, on-axis CCI phacoemulsification induced slightly more flattening along the incision meridian than temporal CCI phacoemulsification, although the differences were not significant. The on-axis CCI was associated with significantly greater absolute torque and angle of error than the temporal CCI. These factors could limit the benefit of placing the incision on axis when the aim is to reduce preoperative astigmatism in phacoemulsification.
The bacterial flagellar motor couples the flow of protons across the cytoplasmic membrane to the rotation of a helical flagellar filament. Using tethered cells, we have measured the stall torque required to block this rotation and compared it with the torque of the running motor over a wide range of values of proton-motive force and pH. The stall torque and the running torque vary identically: both appear to saturate at large values of the proton-motive force and both decrease at low or high pH. This suggests that up to speeds of approximately 5 Hz the operation of the motor is not limited by the mobility of its internal components or the rates of proton transfer reactions coupled to flagellar rotation.
Using Fuji Prescale Pressure Sensitive Film we evaluated the influence of screw torque, object radius of curvature, mode of bone plate application (compression or neutral loading) and bone plate design on bone-plate interface mechanics. Testing was performed using 4.5 mm and 3.5 mm dynamic compression (DC) (stainless steel) and limited contact-dynamic compression (LC-DC) plates (titanium). Plexiglass tubing, having different radii of curvature, was used to simulate bone but having more uniform geometric and structural properties. With the film interposed between the bone plate and the plexiglass, bone plates were applied at predetermined levels of screw torque. The resultant image was digitized and then underwent computer-assisted analysis to yield the interface contact area (%) and the average force (in Newtons N) between the bone plate and the object to which it was applied. In any given object, screw torque had the most significant influence on both interface contact area (P = 0.0001) and average force (P = 0.0001) at the interface. The bone plates responded differently to dynamization. The DC plate, when applied in compression loading mode, was lifted off the object between the two central screws when compared to the same plate applied in neutral loading mode (P = 0.0001). Conversely, in the LC-DC plate, an increase in the overall interface contact area was observed when applied in compression loading mode (P = 0.0002). At a given level of applied screw torque, the object radius of curvature appeared to be a major determining factor for interface contact area and average force (P = 0.0001, P = 0.0001). We conclude that variables other than bone plate design also influence the interface contact area and average force between a bone plate and object to which it is applied.
OBJECTIVE: To study the fatigue process in the calf muscle during a standing heel-rise test. DESIGN: Heel-rises were performed on a force plate measuring development of torque in the ankle joint. BACKGROUND: The heel-rise test is a commonly employed clinical test to evaluate the function of the calf muscle by counting the number of heel-rises before exhaustion. Development of fatigue during other eccentric-concentric actions has earlier been studied as decreases in force, work and EMG. METHODS: Ten healthy males (mean age 25 yr) participated in the study. Torque and work were calculated using measurements from a force plate. Mean power frequency and root-mean-square of the EMG in the triceps surae were evaluated separately in the eccentric and concentric phases. RESULTS: Increases of mean torque during both the eccentric and concentric phases were found. Work performed decreased during the concentric phases due to decreased range of motion. No changes in root-mean-square and decreases in mean power frequency during the concentric phases indicated development of muscular fatigue, whereas decreases in both root-mean-square and mean power frequency during the eccentric phases indicated decreasing muscular activity. CONCLUSIONS: Accordingly, the limiting factor for the heel-rise test was not loss of muscle force at the range of motion used, but rather a failure to maintain the initial range of motion owing to muscle fatigue. RELEVANCE: This method of calculating torque development in the ankle joint provides an opportunity to study the fatigue process in terms of performance. The results show that the heel-rise test reflects muscle endurance rather than strength of the calf muscle.
Twenty-five patients (20 +/- 3 years) with patella tendinitis were followed over an 8-week period in order to study the relation between quadriceps muscle torque, in a Cybex test, and knee pain on exertion. Each patient was examined on three occasions; at 0, 4, and 8 weeks. During the first 5 weeks the patient was put through a treatment program with initial rest, activity modification, and local injection of betamethasone or Arteparon. Half of the patients improved, with less pain and higher torque, and the rest experienced no change. There was a significant negative correlation between pain and torque, stronger to measurements at 30 degrees than at 180 degrees/s (r = -0.59 and -0.40). The linear regression analysis, however, revealed that the same relative difference in pain was equivalent to a bigger difference in torque at 180 degrees than at 30 degrees/s.
PURPOSE: To understand the effect of astigmatism surgery by analyzing astigmatic changes according to their component parts. SETTING: Cheltenham Eye Centre, Melbourne, Australia. METHODS: The component parts of the astigmatic changes considered were flattening, steepening, clockwise torque, and counterclockwise torque. Calculations to determine the astigmatic change were performed by vector analysis using rectangular coordinates after doubling the astigmatism and surgical vector axes. A reference axis was used for the resolution of astigmatic change to ascertain its effect along a selected meridian. RESULTS: When correcting astigmatism, the orientations of incisional (tissue addition) or nonincisional (tissue ablation) techniques in any cornea are at right angles to each other. Since differences exist in the measured astigmatism depending on whether it is measured topographically or by manifest refraction, an on-axis correction in one will occur with an off-axis effect in the other. The net result is a reduced flattening effect and a proportionately increased torque effect for the off-axis component. CONCLUSION: When treatment is applied off one of the four primary axes, the treating vector can be resolved into its component parts of flattening, steepening, and torque. Analyzing changes in this way provides a uniform means of assessing astigmatic changes for all types of cataract and refractive surgery and quantifies the flattening effect when treatment is applied off the intended meridian.
PURPOSE: To analyze possible suture configurations at the haptics of posterior chamber intraocular lenses (IOLs) and estimate the resulting tilt. SETTING: King Khaled Eye Specialist Hospital, Riyadh, Kingdom of Saudi Arabia. METHODS: Using a plastic cylinder with two pairs of holes drilled on opposite sides and an IOL with eyelets in the haptics, we determined possible suture configurations and analyzed them for net torque on the IOL haptics that would result in tilting of the optic. RESULTS: We identified 64 combinations of regular and countless combinations of irregular suture configurations. Among the 16 most likely combinations, only 4 were torque-free (or torque neutral), 2 caused maximum tilt, and 10 induced some tilting. Theoretically, torque could be eliminated by radial suture placement, but this is anatomically undesirable, and by positioning the eyelet perpendicular to the haptic, but this is technically difficult. Longer suture bites tended to lessen the torsion on the haptic but increased the risk of the suture looping around the free end of the haptic. CONCLUSION: Surgeons using scleral fixation of a posterior chamber IOL should be aware of the possibility of inducing tilt and should aim for symmetrical suture configurations at the two haptics.
The aim of this study was to investigate the reliability of peak torque and surface electromyography (EMG) variable's root mean square (RMS) and mean frequency (MNF) during an endurance test consisting of repetitive maximum concentric knee extensions. Muscle fatigue has been quantified in several ways, and in isokinetic testing it is based on a set of repetitive contractions. To assess test-retest reliability, two sets of 100 dynamic maximum concentric knee extensions were performed using an isokinetic dynamometer. The two series were separated by 7-8 days. The subjects relaxed during the passive flexion phase. Twenty (10 men and 10 women) clinically healthy subjects volunteered. Peak torque and EMG from rectus femoris, vastus medialis, vastus lateralis and biceps femoris were recorded. RMS and MNF were calculated from the EMG signal. The reliability was calculated with intraclass correlation coefficient ICC (1.1) and standard error of measurements (SEM). The reliability of peak torque was good (ICC=0.93) and SEM showed low values. ICC was good for absolute RMS of rectus femoris (ICC>/=0.80), vastus medialis (ICC>/=0.88) and vastus lateralis (ICC>/=0.82) and MNF of rectus femoris (ICC>/=0.82) and vastus medialis (ICC>/=0.83). Peak torque, and MNF and RMS of rectus femoris and vastus medialis are reliable variables obtained from an isokinetic endurance test of the knee extensors.
Because the relations between electromyographic signal (EMG) and anisometric joint torque remain unpredictable, the aim of this study was to determine the relations between the EMG activity and the isokinetic elbow joint torque via an artificial neural network (ANN) model. This 3-layer feed-forward network was constructed using an error back-propagation algorithm with an adaptive learning rate. The experimental validation was achieved by rectified, low-pass filtered EMG signals from the representative muscles, joint angle and joint angular velocity and measured torque. Learning with a limited set of examples allowed accurate prediction of isokinetic joint torque from novel EMG activities, joint position, joint angular velocity. Sensitivity analysis of the hidden node numbers during the learning and testing phases demonstrated that the choice of numbers of hidden node was not critical except at extreme values of those parameters. Model predictions were well correlated with the experimental data (the mean root-mean-square-difference and correlation coefficient gamma in learning were 0.0290 and 0.998, respectively, and in three different speed testings were 0.1413 and 0.900, respectively). These results suggested that an ANN model can represent the relations between EMG and joint torque/moment in human isokinetic movements. The effect of different adjacent electrode sites was also evaluated and showed the location of electrodes was very important to produce errors in the ANN model.
A high-shear mixer was instrumented with a new capacitive sensor, a watt meter, and a strain-gage torque sensor. The output from the capacitive sensor was split into two channels, which monitor both resistive and capacitive changes during the granulation process. The outputs of the devices were related to properties of the wet granulation. The percentage moisture content related linearly to the amplitude channel response. Yield values provided a rheological property to relate with power consumption and torque measurement. Power consumption and torque furnished a similar map of the granulation process. The amplitude channel of the capacitive sensor appears to be more clearly differentiated between binder levels in hydrous lactose-HPMC granulations than either power consumption or torque measurement, based on particle size distributions.
1. The present experiment was undertaken to investigate the influence of oral creatine supplementation, shown previously to increase the total creatine content of human skeletal muscle (Harris RC, Soderlund K, Hultman E. Clin Sci 1992; 83: 367-74), on skeletal muscle isokinetic torque and the accumulation of plasma ammonia and blood lactate during five bouts of maximal exercise. 2. Twelve subjects undertook five bouts of 30 maximal voluntary isokinetic contractions, interspersed with 1 min recovery periods, before and after 5 days of placebo (4 x 6 g of glucose/day, n = 6) or creatine (4 x 5 g of creatine plus 1 g of glucose/day, n = 6) oral supplementation. Muscle torque production and plasma ammonia and blood lactate accumulation were measured during and after exercise on each treatment. 3. No difference was seen when comparing muscle peak torque production during exercise before and after placebo ingestion. After creatine ingestion, muscle peak torque production was greater in all subjects during the final 10 contractions of exercise bout 1 (P < 0.05), throughout the whole of exercise bouts 2 (P < 0.01), 3 (P < 0.05) and 4 (P = 0.057) and during contractions 11-20 of the final exercise bout (P < 0.05), when compared with the corresponding measurements made before creatine ingestion. Plasma ammonia accumulation was lower during and after exercise after creatine ingestion. No differences were found when comparing blood lactate levels.(ABSTRACT TRUNCATED AT 250 WORDS)
The purposes of this study were to investigate the effect of movement repetitions on resistive torque during passive isokinetic dynamometry of the knee and to determine the role of electromyographic activity in the stretched muscles on the torque measurements. Ten persons with multiple sclerosis and hypertonia of the knee muscles were compared with 10 healthy age- and gender-matched control subjects. During series of 10 flexion and extension movements of the knee at 60, 180 and 300 degrees/s, torque and electromyographic activity in the stretched muscles were registered. The persons with hypertonia presented a significantly larger torque reduction (p < 0.05) than the control subjects in all test conditions except for repeated knee flexion at 300 degrees/s. Electromyographic activity in the stretched muscles was not identified as the only explanatory mechanism for the reduction in hypertonia during the movement repetitions, suggesting that other factors were also involved.
BACKGROUND: The advent of highly crosslinked polyethylene has allowed the re-evaluation of the use of femoral heads larger than 32 mm for metal-on-polyethylene total hip arthroplasties. However, the effect of larger heads on the frictional torque of highly crosslinked polyethylene is unknown. METHODS: We performed an in vitro examination of the effect of larger chrome cobalt femoral heads (40 mm diameter) on the frictional torque and torsional resistance of hip articulations on aged liners of polyethylene that were sterilized by gamma rays while in nitrogen, and aged highly crosslinked polyethylene. The frictional torque at the femoral head articulation was usually higher for the highly crosslinked polyethylene than for the conventional polyethylene. The aged conventional liners oxidized considerably, which led to gross failure of the polyethylene at the anti-rotation portion of the rim. The aged crosslinked polyethylene showed no such failures despite the higher frictional torque. INTERPRETATION: Our findings suggest that in terms of torsional resistance to fatigue when studied as a device, rather than as an isolated material, under these conditions, aged highly crosslinked polyethylene is preferable to aged conventional polyethylene.
Plantar flexor torque was measured in 24 young (25 +/- 1.4 y) and older (62 +/- 2 y) untrained and endurance-trained men to test the hypothesis that age-associated declines in muscle function would be attenuated in older men who also endurance trained. Endurance-trained subjects averaged 7-9 h/wk of aerobic activity for 10-12 years. These subjects had not engaged in resistance training previously in the past 10 years. Plantar flexor torque was measured at velocities between 0 and 5.23 rads. s-1. In absolute terms, maximal isometric torque was 23% lower in older men compared to young men, regardless of their training status. On the other hand, relative measures of isometric strength (i.e., torque.muscle cross-sectional area-1 and torque.muscle volume-1) were similar in young and older men but were higher in trained than in untrained men. Isokinetic torque.muscle cross-sectional area-1 and torque.muscle volume-1 was greater at contraction velocities of 0.26-2.09 rads.s-1 for trained subjects. These data suggest that endurance training does not attenuate the age-associated loss of muscle mass or absolute strength. However, endurance training might reduce the extent of loss of relative strength because torque-muscle cross-sectional area-1 and torque.muscle volume-1 are greater in endurance-trained older men than in untrained older men.
The purposes of this study were to determine the test-retest reliability of isometric hip abductor torques in elderly females, to compare two assessment protocols, and to compare the performances of elderly and young females. Twenty elderly and 20 young women were tested on two occasions. During the examiner-resisted test the examiner provided the resistance, and during the belt-resisted test the subject's contralateral leg provided the resistance while the examiner positioned the dynamometer. A four-way ANOVA indicated no occasion effects (p greater than .05). Within each group, similar torques were produced by both legs (p greater than .05). Test-retest intraclass reliability coefficients were good-to-high, ranging from 0.84 to 0.98 for the eight combinations of group-method-leg. The elderly females produced 61% of the torques produced by young females (p less than .01), and the examiner-resisted method produced 65% of the torques produced using the belt-resisted method (p less than .01). The belt-resisted method required less physical effort on the part of the tester, provided greater stabilization of the pelvis, and was preferred by 95% of the subjects.
I measured the knee extension torque, produced by eight hemiparetic patients during repeated knee extension-flexion reversals and during separated knee extension-flexion dyads, to determine the effect of "reversal of antagonists" on knee extension torque. The hemiparesis in these eight patients was secondary to intracranial lesions. I tested their involved lower extremity on an isokinetic dynamometer at 60 degrees/sec. Using a sequential medical-trials design, I found knee extension torque to be significantly greater during repeated knee extension-flexion reversals than during separated knee extension-flexion dyads (p less than .05). I, therefore, concluded that reversal of antagonists may facilitate knee extension torque production in the type of patients tested, under the specific conditions of their testing.
The purpose of this study was to investigate whether the tonic neck reflex affects elbow flexor muscle torque production in healthy, young adults and which head-neck (H-N) positions have the greatest influence. Forty-eight male and female students between the ages of 18 and 35 years volunteered as subjects. Head-neck positions involving the sagittal and horizontal planes and combinations of these were tested. The nondominant hand was used to apply tension to the lever of an isokinetic analyzer under both isometric (static) and isotonic (dynamic) conditions. Peak torque was determined for each H-N position under each condition. Differences in peak torque were elicited more easily from the female subjects than from the male subjects. Head-neck rotation (horizontal plane) appeared to have a greater influence on elbow flexor muscle torque production than movements in the sagittal plane, particularly when movements in the two planes were combined. We concluded, therefore, that H-N position must be considered during rehabilitation of the upper extremity.