Differences between measured and resultant joint moments during voluntary and artificially elicited isometric knee extension contractions (original) (raw)
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Journal of Applied Physiology, 2011
The purpose of this study was to determine the effect of dynamometer and joint axis misalignment on measured isometric knee-extension moments using inverse dynamics based on the actual joint kinematic information derived from the real-time X-ray video and to compare the errors when the moments were calculated using measurements from external anatomical surface markers or obtained from the isokinetic dynamometer. Six healthy males participated in this study. They performed isometric contractions at 90° and 20° of knee flexion, gradually increasing to maximum effort. For the calculation of the actual knee-joint moment and the joint moment relative to the knee-joint center, determined using the external marker, two free body diagrams were used of the Cybex arm and the lower leg segment system. In the first free body diagram, the mean center of the circular profiles of the femoral epicondyles was used as the knee-joint center, whereas in the second diagram, the joint center was assumed ...
Research Square (Research Square), 2023
Isokinetic dynamometers are the gold standard for assessing joint and muscle-speci c kinetics. However, commercial dynamometers are often prohibitively expensive and lack portability. Therefore, we compared kinetic data captured via an affordable and portable strain-gauge with a treatment plinth against a isokinetic dynamometer during maximal isometric knee extensions. Methods Healthy participants (8 males and 6 females; age 30.2 ± 7.1 years) volunteered and performed knee extensions at a 90° knee angle on a dynamometer and a treatment plinth with a portable strain-gauge. Peak force (PF), peak rate of force development (PRFD), rate of force development (RFD 2080) and impulse (IMP 2080) from 20-80% of onset to peak force were assessed. Results No meaningful differences were identi ed between isokinetic and strain-gauge devices (all p ≥ 0.268, ES ≤ 0.35). However, greater (2.5-9.5%) outputs were observed with the isokinetic dynamometer. Very large between-device correlations were found for PF (r = 0.77, p = 0.001) and PRFD (r = 0.73, p = 0.003), while small and moderate between-device correlations were found for RFD 2080 (r = 0.48, p = 0.079) and IMP 2080 (r = 0.59, p = 0.060). Bland-Altman plots did not reveal apparent biases from high to low performers. Conclusions The examined strain-gauge device produces valid maximal and rapid force expression measurements. Similar results can be obtained without extreme rigour and constraint, such as those quanti ed via an isokinetic device. This study's overall ndings support the use of the practically relevant treatment plinth and strain-gauge combination as a suitable alternative to the isokinetic dynamometry for the measurement of PF and PRFD. Therefore, more rehabilitation and sports performance practitioners can con dently assess knee extension kinetics.
A purpose-built dynamometer to objectively measure static and dynamic knee torque
Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine, 2011
This paper reports the development of a purpose-built knee dynamometer (PBKD) to evaluate passive range of motion (ROM) and isometric muscle strength measurements of the knee. The PBKD uses a TorqSense rotary torque transducer and objectively measures isometric knee muscle strength in a valid and reliable manner and passive resistance to motion through range. The device and all associated instrumentation underwent dynamic and static calibration to ensure consistent and accurate measurements were obtained in terms of knee joint angular position, passive torque measures, and isometric torque measures. Eleven healthy male participants performed a knee flexion and extension task designed to evaluate knee function. The validation of the PBKD entailed measuring the consistency of measurement and accuracy of measurement. Accuracy of the PBKD was determined by comparing peak isometric muscle strength measurements against a KIN-COM machine. No significant differences were observed both passi...
Reproducibility of peak moment for isometric and isokinetic knee extension exercise
BMC Sports Science, Medicine and Rehabilitation, 2023
Accurate measurements of muscular performance are important for diagnostics, for example during rehabilitation after traumatic injuries but also in competitive sports. For these purposes, dynamometric devices are widely used and considered the gold standard for muscle strength testing. However, few previous studies have tested the reproducibility of peak moment (PM) at velocities close to the maximum device capability, and in general, reproducibility results cannot be transferred to other devices or test protocols. The purpose of this study was to evaluate the reproducibility of PM for different isometric and isokinetic knee extension exercises using the IsoMed 2000. Thirty subjects volunteered in three repeated test sessions, including isometric knee extension (100° and 140° knee angle) and isokinetic knee extension (30°/s and 400°/s). Statistical analysis for comparison of sessions two and three included paired sample t-test, calculation of intraclass correlation coefficient (ICC) and standard error of measurement (SEM). Additionally, Bland Altman statistics and corresponding plots were created. A significant difference between sessions in PM was found for isometric knee extension in one leg (140° left). Reproducibility was high for all conditions with ICC ranging from 0.964 to 0.988 and SEM in the range of 7.6 to 10.5 Nm. Bland Altman statistics revealed a bias between − 7.3 and 0.7 Nm. Reproducibility of PM using the IsoMed 2000 was good after an initial familiarization trial with high values of relative reproducibility. Absolute reproducibility can be interpreted as appropriate for most common practical applications.
Inertial effects on moment curves and angle of peak moment during isokinetic knee extension
Isokinetics and Exercise Science, 1998
The various isokinetic parameters are in uenced by inertial moments developed during the acceleration and deceleration periods. Hence the purpose of this study was to examine inertial e ects on moment v ersus angular displacement curves and on the angle of peak moment. Seven young adults performed 5 repetitions of concentric knee extension on the Lido isokinetic dynamometer at 30, 165 and 300 deg s. The angular displacement and moment signals were collected and A D converted via a 16 channel A D card independently from the dynamometer software. Angular displacement data were smoothed using a second order Butterworth lter. The cut-o was approximately 5 Hz and was based on power spectrum assessment. Knee joint moment w as calculated taking into account the inertial e ects of the limb-lever arm system. Di erences on the moment v ersus angular displacement curves were found before and after correction for the inertial effects. These di erences were limited at medium to high velocities and during the initial and nal parts of the movement. Angle of peak moment uncorrected and corrected for inertial e ects decreased closer to full extension or increased closer to full exion respectively as the velocity increased. It was concluded that erroneous moment curves and angle of peak moment are obtained at high velocities when the inertial e ects are ignored. Therefore it is essential at high velocities to correct for inertial e ects in order to obtain valid and comparable results and hence to achieve a more accurate approach t o m uscle and joint function assessment using these parameters.
An Objective Method to Evaluate Force and Knee Joint Moments During Isometric Extension
2008
A simple method to evaluate force and moments of knee joint during isometric extension has been developed and provides to the physicians a fast and objective tool for the evaluation of patients before and after a surgery or rehabilitative program. The experiment was made on normal young patients. Graphs of angle-moment were obtained. The patients started from 90° of knee flexion and extended step-by-step the knee joint until the maximum knee extension was achieved. Force, angle and moment were measured at each step. In comparison with literature, even if significant differences of technical instrumentation, age and activity of the patients are present, the maximum moment-angle behaviour during extension is the same but different magnitude. Future development of this device is to make it easy to use directly in clinical applications.
Brazilian Journal of Motor Behavior
Background: In the dynamic knee extension (DKE), a metal bar is positioned parallel to bicycle frame, replacing the pedal of a cycle ergometer, which allow consecutives extensions instead of pedaling movement. Considering the fixed ratchet of cycle ergometer, the knee joint returns to its initial position passively, isolating the quadriceps group during the exercise. Thus, DKE can be used to investigate the role of the anterior thigh muscles for the locomotion or balance, for example. However, the DKE ergometer is not commercially available. Aim: to describe the construction of a prototype ergometer for DKE and characterize the force signal and electromyography responses. Methods: Six participants underwent a progressive effort to exhaustion. The electromyography signal of Vastus Lateralis and Biceps Femoris were monitored. The last 10 extensions of each stage were used for analyzes. Results: the force signal has three phases: I: knee extension moment; II: crank draws the metal rod ...
Predicting 1-RM isotonic knee extension strength utilizing isokinetic dynamometry
Isokinetics and Exercise Science, 1998
The purpose of this study was twofold: determine which isokinetic determinants correlated best with an isotonic one-repetition maximum (1-RM) and to generate, based on these determinants a formula that will allow clinicians to utilize isokinetic testing to predict an isotonic 1-RM. Fifty female subjects, ranging from 18-35 years of age, participated in this study. Strength measurements using a Cybex II isokinetic dynamometer (peak torque, average peak torque, peak torque:body weight, work per repetition, and total work) and a Cybex isotonic knee extension machine were performed. The subject's height and body weight were recorded. Through linear regression analysis the variables peak torque and body weight were determined to be the best predictors of an isotonic 1-RM. These variables were incorporated in the following formula: Predicted 1-RM = 21.38 + (0.24 x Peak Torque) + (0.18 x Body Weight) which may used utilized by clinicians to predict an isotonic 1-RM.
Test-retest reliability of reciprocal isokinetic knee extension and flexion peak torque measurements
Journal of athletic training, 1992
Our purpose in conducting this study was to estimate the reliability of reciprocal concentric knee extension and flexion peak torque obtained in uninjured male athletes using the Biodex isokinetic dynamometer. Twenty-six male intercollegiate athletes (age=19.5+/-4.1 yr; ht=70.3+/-14.9 in; wt=212.9+/-48.5 lb) participated in this study. We used the Biodex to measure peak torque occurring during right knee extension and flexion over 3 consecutive days. Means and standard deviations were calculated for both extension and flexion on each of the 3 days. We observed a significant main effect for days for both extension and flexion. Mean peak torque for the first day was significantly higher (Turkey, p<.05) than the means for the other 2 days, which were not significantly different from each other (Turkey, p>0.05). Intraclass correlation coefficients (ICCs) were estimated for each of the six trials on each of the 3 days. Intraclass correlation coefficients (ICCs) ranged from .88 on t...