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PubMed1994

Potentiation of concentric plantar flexion torque following eccentric and isometric muscle actions.

In a stretch-shortening cycle (SSC) the concentric muscle action is enhanced by a preceding eccentric muscle action. The hypothesis of the present study is that a preceding isometric action can also have an effect on a following concentric action, but to a lesser degree. A KINetic-COMmunicator II dynamometer was used to test muscle strength of the plantar flexion of the right foot in 20 healthy women. Maximal voluntary torque measurements were made at different angular velocities (120 degrees s-1 and 240 degrees s-1) and the range of motion of the ankle joint was 78-125 degrees. The assessment was based on concentric torque output and EMG recording from the gastrocnemius muscle under three different types of testing conditions (concentric actions with and without preceding eccentric or isometric actions, all with maximal efforts). The results showed that preceding muscle actions led to greater concentric torque output (P < 0.01) between 90 and 99 degrees plantar flexion. However, the increase in the concentric action was significantly (P < 0.01) larger with eccentric than with isometric preceding action, regardless of velocity. The EMG activity of the concentric action showed unchanged or lower values when preceded by a muscle action. In this model our conclusion is that the main reason for larger concentric torque values after a preceding muscle action is that time is sufficient for maximal muscle tension development; in addition, elastic energy is stored, particularly during the preceding eccentric action. Our results show that the effect of preceding muscle actions should be taken into account when measuring isokinetic muscle strength at relatively small angular movements.

Adolescent↗
PubMed1977

Oscillation of the human ankle joint in response to applied sinusoidal torque on the foot.

1. Low-frequency (3-30 Hz) oscillatory rotation of the ankle joint in plantarflexion-dorsiflexion was generated with a torque motor. Torque, rotation about the ankle and electromyograms (e.m.g.s) for the gastrocnemius-soleus and the anterior tibial muscles were recorded.2. Fourier coefficients at each drive frequency were used to calculate the effective compliance (ratio of rotation and torque). The compliance has a sharp resonance when tonic, voluntary muscle activity is present.3. The resonant frequency of compliance is between 3 and 8 Hz. The location of the resonant frequency and the magnitude of the compliance at resonance depend upon both the degree of tonic muscle activity and the amplitude of the driving torque. The resonant frequency increases with increasing tonic activity.4. With tonic muscle activity, the compliance in the frequency range below resonance increases with increasing amplitudes of driving torque.5. The e.m.g., when evoked by the rhythmic stretch, lags the start of stretching by between 50 and 70 msec.6. When tonic muscle activity is present, the resonant frequency of the stretch reflex is between 5 and 6.5 Hz.7. Following the start of driven oscillation at frequencies near resonance, slowly increasing amplitudes of angular rotation (to a limit) are observed.8. Distortion (from the sinusoidal wave shape) of angular rotation is frequently observed with drive frequencies between 8 and 12 Hz during which there sometimes occur spontaneous recurrences of oscillation at the drive frequency. For the angular rotation, a significant portion of the power may be in subharmonic frequency components of the drive frequency when that frequency is between 8 and 12 Hz.9. Self-sustaining oscillation (clonus) near the resonant frequency of the compliance is sometimes observed after the modulation signal to the motor is turned off. This is most often seen when the gastrocnemius-soleus muscles are fatigued. Clonus may be evoked by driven oscillation at any frequency.10. The hypothesis that physiological tremor, which occurs between 8 and 12 Hz, is a consequence of stretch reflex servo properties seems to be at odds with the observations of resonance in the compliance and of self-generated clonus both occurring in the 5-8 Hz region.

Adult↗
PubMed1988

Restoration of torque in defective flagellar motors.

Paralyzed motors of motA and motB point and deletion mutants of Escherichia coli were repaired by synthesis of wild-type protein. As found earlier with a point mutant of motB, torque was restored in a series of equally spaced steps. The size of the steps was the same for both MotA and MotB. Motors with one torque generator spent more time spinning counterclockwise than did motors with two or more generators. In deletion mutants, stepwise decreases in torque, rare in point mutants, were common. Several cells stopped accelerating after eight steps, suggesting that the maximum complement of torque generators is eight. Each generator appears to contain both MotA and MotB.

Bacterial Proteins↗
PubMed1988

Sarcomere length and joint kinematics during torque production in frog hindlimb.

The relationship between semitendinosus muscle force and knee joint kinematics during isometric torque production was examined in the frog (Rana pipiens) hindlimb. Passive muscle sarcomere length was monitored by laser diffraction during knee rotation, and joint center of rotation was determined later using principles of rigid body kinematics. Contractile force at the distal tibia, resulting from semitendinosus contraction, was also measured, and, using the kinematic data, a torque vs. joint angle curve constructed. Muscle sarcomere length varied from 3.6 micron at full knee extension to 2.0 micron at full knee flexion. Effective lever arm varied almost as a sine function, with optimal lever arm at 90 degrees of flexion. Joint torque increased linearly from 0 to 140 degrees of flexion and then sharply decreased to 160 degrees of flexion. Thus the optimal joint angle occurred at an angle (140 degrees) that was neither the angle at which muscle force was maximum (160 degrees) nor the angle at which the effective lever arm was maximum (90 degrees). These data indicate that knee torque production in the frog results from the interaction between muscular and joint properties and not either property alone.

Analysis of Variance↗
PubMed2003

Effects of age on human muscle torque, velocity, and power in two muscle groups.

The purpose of this study was to test the hypotheses that, under isovelocity conditions, older compared with young humans would 1). be slower to reach target velocity and 2). exhibit a downward shift in the torque-velocity and power-velocity relationships in the ankle dorsiflexor and knee extensor muscles. We studied 12 young (26 +/- 5 yr, 6 men/6 women) and 12 older (72 +/- 6 yr, 6 men/6 women) healthy adults during maximal voluntary concentric contractions at preset target velocities (dorsiflexion: 0-240 degrees /s; knee extension: 0-400 degrees /s) using an isokinetic dynamometer. The time to target velocity was longer in older subjects in the dorsiflexors and knee extensors (both P <or= 0.02). Averaged across all velocities, older subjects produced approximately 26% less concentric torque and power in the dorsiflexors (P < 0.01) and approximately 32% less in the knee extensors (P < 0.01). The downward shift in the torque-velocity relationship persisted even when torque was expressed relative to each subject's maximum. In the knee extensors only, the age-related decrement in power increased with increasing velocities, suggesting that this muscle group may be more susceptible to age-related losses of function than the dorsiflexor muscles are. In support of our hypotheses, these results demonstrate an age-related impairment in the dynamic performance of two functionally distinct muscle groups in healthy older adults. With age, the impairment of dynamic performance appears to exceed the loss of isometric performance, particularly in the knee extensor muscles.

Adult↗
PubMedDate not supplied

Shoulder torque changes in the swimming athlete.

Torque production was assessed in the shoulders of competitive men and women swimmers for the motions of abduction, adduction, and external and internal rotation. Testing was performed on the Cybex II dynamometer and the results were compared to controls. In addition, the ratios of torque development for adduction:abduction and external rotation:internal rotation were evaluated. The results demonstrated a statistically significant increase in torque production in swimmers for most motions tested. Statistically significant ratio shifts were also noted. The ratio of adduction:abduction increased and that for external rotation:internal rotation decreased. We think these shifts in the torque ratios in swimmers' shoulders resulted from sport-specific repetitive activity that emphasizes adduction and internal rotation.

Adolescent↗
PubMed1993

Changes in gait and maximum ankle torque in patients with ankle arthritis.

Findings from quantitative gait analysis and maximum ankle torque were used to assess the walking pattern of patients with ankle arthritis and to correlate the changes of gait parameters and muscle strength with severity of arthritis. Gait analysis and the isokinetic maximum ankle torque test were performed in 20 patients with first to fourth degree traumatic ankle arthritis. Six patients without evidence of traumatic arthritis were used as controls. Isokinetic maximum ankle plantarflexion and dorsiflexion torques were determined with Cybex instrumentation. Force plate and foot switch data were gathered during level walking. Maximum ankle plantarflexion and dorsiflexion torques were diminished in the injured ankles. Velocity, stride length, and cadence were decreased in arthritic patients compared with controls. The arthritic limbs had shorter single limb stance and longer double stance during free and fast walking speeds compared with the controls' affected ankles. The patterns of ground reaction forces were similar in the injured and uninvolved limbs as well as the control subjects, except the magnitude of vertical forces during push-off were reduced in arthritic ankles. The gait parameters and muscle strength deteriorated as the arthritis became severe, but they showed significant changes only when the patients had third or fourth degree arthritis.

Adult↗
PubMed1994

A comparison of the forces required to produce tooth movement ex vivo through three types of pre-adjusted brackets when subjected to determined tip or torque values.

Friction in fixed appliance systems has received considerable attention in recent literature, although that attributable to varying second order (tip) and third order (torque) adjustments in either the bracket or the archwire has not been fully investigated. The ex vivo study of 0.022 x 0.028-inch slot Minitwin, Activa, and Standard Straight Wire brackets investigates friction when known values of tip or torque were applied to 0.018 x 0.025-inch stainless steel wires. The resistance to sliding of the wire through the ligated brackets was measured on a vertically-mounted Instron testing machine. The results showed that the self-ligating Activa brackets consistently produced less friction than the other conventionally tied brackets. Minitwin brackets were slightly more resistant to movement than the Standard brackets during torquing, but the converse was found when tip was applied. Increasing tip and torque (ranges tested 0-6 degrees and 0-25 degrees, respectively) produced almost linear increases in friction for all brackets, although increasing tip had the more profound effect on friction, particularly in Activa brackets.

Analysis of Variance↗
PubMed2005

Calculation of the torque on dielectric elliptical cylinders.

We present our investigation of the torque exerted on dielectric elliptical cylinders by highly focused laser beams. The calculations are performed with rigorous diffraction theory, and the size-dependent torque is analyzed as a function of the axis ratio. It is found that highly elongated particles will experience a reversal of the torque for a radius that is approximately one third of the wavelength. This effect is attributed to interference effects inside the structure due to multiple reflections of the incoming wave. The evolution from a perfectly sinusoidal angular dependence of the torque to a more complicated pattern for increasing particle size is presented in detail.

Journal Article↗
PubMed1996

The contribution of frictional torque to loosening at the cement-bone interface in Tharies hip replacements.

We evaluated the results in a series of 170 osteoarthrotic hips (156 patients) at a median of 10.0 years (range, 3.0 to 16.4 years) after a Tharies resurfacing arthroplasty performed with cement. Our purpose was to assess the role of frictional torque in loosening at the cement-bone interface. The hips were divided into three groups on the basis of the diameter of the bearing surface: small (thirty-six, thirty-nine, or forty-three millimeters), medium (forty-seven millimeters), and large (fifty-one or fifty-four millimeters). Comparisons were made with Kaplan-Meier survivorship analysis, with stepwise discriminant analysis of risk factors for aseptic loosening. Revision for aseptic loosening was the end point for survivorship analysis. Despite higher frictional torques due to the increased diameter of the bearing surface and the increased average load, the larger prostheses survived significantly longer than the smaller ones (p=0.002). Stepwise covariate discriminant analysis indicated that the size of the bearing surface was the only factor identified that significantly affected survival. In six patients who had had a bilateral surface replacement with a component of a different size in each hip, the smaller prosthesis always failed first (p=0.001), at an average of seventy-seven months; the larger prosthesis failed at an average of 113 months. Nine patients had had a bilateral replacement with components of the same size, and there was no significant difference in the durations of survival of the two prostheses. Analysis of radiographs and retrieved specimens indicated that, regardless of the size of the component, the mechanism of loosening on both the acetabular and the femoral side of this so-called double-cup replacement was progressive resorption of bone induced by polyethylene wear particles that compromised the fixation of the components. More time was required for the process to disrupt++ the larger fixation area of the larger components. These data indicate that frictional torque was not the primary factor in the loosening of these prostheses with a large bearing surface and that higher friction and frictional torques can be tolerated if the generation of wear debris is sufficiently limited. These findings may be important as alternatives to polyethylene bearing surfaces are investigated.

Acetabulum↗
PubMed1990

[A transducer for the measurement of torque transmitted to abutment teeth of removable partial dentures].

A transducer for the measurement of torque transmitted to abutment teeth of removable partial dentures was newly developed. The transducer was composed of a right cylinder (12.0 mm x 3.5 mmø) made of phosphor bronze as the torsion bar, to the surface of which two strain gauges (KFC-2-D2-11, KYOWA) are adhered symmetrically about the axis of the bar. Torque transmitted to the transducer was detected and evaluated as tensile strain and compressive strain on the torsion bar surface by means of strain gauges. The transducer was small enough to be easily applied to removable partial dentures for the measurement of torque transmitted to crowns of abutment teeth, and showed satisfactory precision (The instrumental error in measurement was within 3%). In the present study, the newly developed transducer was revealed to be useful for the measurement of torque transmitted to crowns of abutment teeth by removable partial dentures.

Dental Abutments↗
PubMed1990

Hemisphericity style, sex, and torque: an exploratory study.

A sample of 139 male and 218 female college students were given the Preference Questionnaire and a torque test to assess (a) whether subjects who prefer a left hemisphericity style would show a higher incidence of torque than those who prefer a right hemisphericity style and (b) whether men would yield a higher incidence of torque than women. The first hypothesis received limited support. Men with a left hemisphericity style yielded a higher incidence of torque than men with a right style, however, the difference was only marginally significant.

Adolescent↗
PubMed1997

A trend analysis of the in vivo quadriceps femoris angle-specific torque-velocity relationship.

To adequately assess isokinetic human muscle performance, it is important for clinicians to understand how the muscle functions across a range of velocities. Thus, the purpose of this study was to re-examine the in vivo quadriceps torque-velocity relationship using trend analysis. Twelve uninjured university-age females performed three concentric and eccentric contractions at velocities of 0, 25, 50, 75, 100, 125, 150, 175, and 200 degrees/sec on the Kin-Com isokinetic dynamometer. A trend analysis was performed on the angle-specific torques at 30, 60, and 75 degrees of knee flexion. The results indicated that the concentric and eccentric relationships at 30 degrees and the concentric relationship at 60 degrees were represented by a third-order polynomial, and a linear relationship was found for concentric contractions at 75 degrees. There were no significant trends for the eccentric relationship at 60 and 75 degrees, suggesting that they were best described by the grand mean. These results suggest that muscular torque production varies across velocities and contraction modes and that this relationship varies depending on the joint angle of torque measurement.

Adult↗
PubMed1997

Isokinetic torque, average power, and flexion/extension ratios in nondisabled adults and adults with mental retardation.

For successful placement of individuals with mental retardation into community environments, a minimal amount of functional strength is required to promote self-independence. Since muscular strength and power are commonly deficient in these groups, the purpose of this study was to compare isokinetic elbow flexion and extension peak torque (Nm), average power (W), and corresponding flexion/extension ratios of adults males with Down syndrome, with mental retardation without Down syndrome, and sedentary adult males without mental retardation. Subjects with Down syndrome (N = 9), mental retardation without Down syndrome (N = 13), and without mental retardation (N = 13) were tested for elbow flexion and extension peak torque and average power at 60 and 90 degrees/sec on a Cybex 340 isokinetic dynamometer. Results indicated: 1) subjects without mental retardation displayed significantly greater ( p < 0.01) peak torque and average power elbow flexion and extension than subjects with Down syndrome and subjects with mental retardation without Down syndrome at speeds of 60 and 90 degrees/sec, and 2) there were no significant differences between groups in peak torque and average power elbow flexion/extension ratios at both angular velocities. The results of the data analysis support the premise that adults with mental retardation are in need of exercise programs to improve muscular strength.

Adult↗
PubMed1999

The effects of rest interval on quadriceps torque and perceived exertion in healthy males.

BACKGROUND: The ability to generate maximal muscular force is dependent upon time mediated mechanisms of fatigue. Interset rest interval length may not only affect force production but may also manifest changes in ratings of perceived exertion (RPE). The purpose of this study was to examine the effects of rest interval on quadriceps torque and RPE during multiple sets of resisted knee extensions. METHODS: 14 healthy male volunteers were assessed for concentric isokinetic quadriceps peak torque, total work, and average power on the Biodex System II Isokinetic Dynamometer at a preset angular velocity of 180 deg.sec-1. Perceived exertion was measured with a modified category-ratio scale (CR-10). Under isometric conditions the perceptual range was anchored with one high and two low anchors. Subjects were randomly assigned to one of two groups: short rest interval (Group 1, 40 sec) and long rest interval (Group 2, 160 sec). All subjects performed 4 sets of 20 maximal isokinetic contractions with an inter-set rest interval that corresponded to their group assignment. Following the completion of each set subjects were asked to assign a rating out of 10 to the feelings in their quadriceps by visually observing a chart of the CR-10 scale. RESULTS: The results demonstrated a significantly greater decline in quadriceps peak torque (p < 0.05), total work (p < 0.05), and average power (p < 0.05) by Group 1 as compared to Group 2. Changes in RPE across the 4 sets of exercise did not show a significant difference between the 2 groups. CONCLUSIONS: The generation of quadriceps torque is a function of rest interval length, whereas perceived exertion appears to be unaffected.

Adult↗
PubMed2002

Removal Tools are Faster and Produce Less Force and Torque on the Helmet Than Cutting Tools During Face-Mask Retraction.

OBJECTIVE: To investigate the retraction time, forces, and torques applied to the football helmet during removal of the face mask with different face-mask removal tools. DESIGN AND SETTING: Subjects retracted the face mask of a football helmet mounted to a force platform in a laboratory setting. They removed a standard face mask by cutting or removing (or both) the lateral plastic loop straps using 4 different tools: the Trainer's Angel (TA), FM Extractor (FM), power screwdriver (SD), and Quick Release System (QR) in a counterbalanced fashion. SUBJECTS: Eighteen certified athletic trainers participated in this study. MEASUREMENTS: We started measuring time when the subject picked up the tool and ended when the face mask was in a fully retracted position. Maximum forces and torques were measured from the force platform during the retraction process. RESULTS: The SD and QR retracted the face mask significantly faster than the TA and FM. Forces producing superior-inferior translation were least with the SD. The SD and QR produced less lateral translation and rotation and lateral flexion moment than the TA and FM. The FM produced less torque in the lateral flexion moment than the TA. CONCLUSIONS: Tools that removed the loop straps (SD, QR) were faster and produced less force and torque on the helmet than the tools that cut through the loop straps (TA, FM).

Journal Article↗
PubMed1993

The Reliability Of Three Isokinetic Knee-extension Angle-specific Torques.

To determine the reliability of concentric quadriceps muscle torque at 30 degrees , 60 degrees , and 75 degrees of knee extension, 25 female university students were studied. Each subject was tested on the Kin-Com isokinetic dynamometer on 2 separate days, 7 days apart. The dynamometer's speed was set at 60 degrees ls. Intraclass correlation coefficients for 30 degrees , 60 degrees , and 75 degrees were 0.84 (p<.01), 0.87 (p<.01), and 0.83(p<.01), respectively. The standard errors of the measure were 5.92 N.m, 7.65 N.m, and 7.35 N.m, respectively. Based on the instrumentation and protocol used in this study, we believe angle-specific torques have good reliability. Because of the error size, clinicians using similar methodology to determine angle-specific torques should be cautious when comparing differences between angle-specific torques of less than 12 to 16 N.m.

Journal Article↗
PubMed1992

Reliability of knee flexor peak torque measurements from a standardized test protocol on a Kin/Com dynamometer.

The test-retest reliability of a specific test protocol for the measurement of peak torque of the knee flexors using a Kin/Com dynamometer was evaluated. The maximum voluntary torque generated by the left knee flexors during constant velocity resisted-muscle shortening (RMS) and muscle lengthening (RML) was measured in a sitting position in 11 healthy women with no history of knee pathology. Each subject performed two tests at each of two velocities (30 degrees/sec and 180 degrees/sec) in a single session. All subjects repeated these four tests one week later. A test consisted of four complete RMS/RML cycles through a range of 65 degrees. The peak torque generated from each test was used to measure test-retest reliability. All data were gravity compensated. Intraclass correlation coefficients (ICCs) were calculated from ANOVA tests for RML and RMS at both velocities. The within sessions ICCs ranged from .94 to .98 for 30 degrees/sec and from .92 to .97 at 180 degrees/sec. The ICCs between sessions were generally lower and ranged from .79 to .90 for 30 degrees/sec, and from .75 to .88 for 180 degrees/sec. It is concluded that using these test protocols, peak torques for both RMS and RML can be measured with a high degree of reliability at two commonly used velocities.

Adult↗