A prototype for dynamic knee extension: construction, force characterization and electromiographic responses (original) (raw)
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The influences of muscle fibre proportions and areas upon EMG during maximal dynamic knee extensions
European journal of applied physiology, 2000
This study is an investigation of the relationship between muscle morphology and surface electromyographic (EMG) parameters [mean frequency of the power spectrum (MNF), signal amplitude (root mean square, RMS) and the signal amplitude ratio (SAR; i.e. the ratio between the RMS level during the passive part of the contraction cycle and the RMS level during the active part of the contraction cycle)] during 100 maximal dynamic knee extensions at 90 degrees. s(-1). Each contraction cycle comprised of 1 s of active knee extension and 1 s of passive knee flexion. The surface EMG was recorded from the vastus lateralis muscle. Twenty clinically healthy subjects participated in the study, and muscle biopsy samples of the vastus lateralis were obtained from 19 of those subjects. The relationships between muscle morphology and EMG were investigated at three stages of the test: initially, during the fatigue phase (initial 40 contractions), and at the endurance level (the final 50 contractions)....
Clinical Biomechanics, 2004
Objective. Examine two hypotheses: (a) during isometric knee extension contractions the moment measured at the dynamometer is different from the resultant moment in the same plane around the knee joint and (b) during isometric contractions, at the same given resultant moment the knee angle while loading is different from the knee angle while unloading. Design. Comparative study in which the geometrical and the kinetic differences between joint and dynamometer were determined. Background. It is usually assumed that the moment measured by the dynamometer is equivalent to the resultant joint moment. The non-rigidity of the dynamometer-leg system can influence the equivalence of these two moments. Method. Twenty seven subjects performed isometric maximal knee extension contractions and contractions induced by electrostimulation on a dynamometer. The kinematics of the leg were recorded using 8 cameras (120 Hz). Results. The resultant moment at the knee joint and the moment measured by the dynamometer are different. During a knee extension effort the knee angle changes significantly. At identical resultant knee joint moments the knee angles are different when comparing the loading and the unloading phases. Conclusions. The differences between the measured and the resultant joint moments might influence the estimation of parameters as: muscle forces, moment-angle relationship and strain and hysteresis of tendons and aponeuroses. Relevance Torque dynamometers have been often used to estimate muscle forces, to examine neuromuscular processes and to determine the mechanical properties of tendons and aponeuroses.
Biomechanical measures of short-term maximal cycling on an ergometer: a test-retest study
Sports Biomechanics, 2020
Biomechanical measures of short-term maximal cycling on an ergometer: a test-retest study An understanding of test-retest reliability is important for biomechanists, such as when assessing the longitudinal effect of training or equipment interventions. Our aim was to quantify the test-retest reliability of biomechanical variables measured during short-term maximal cycling. Fourteen track sprint cyclists performed 3 x 4 s seated sprints at 135 rpm on an isokinetic ergometer, repeating the session 7.6 ± 2.5 days later. Joint moments were calculated via inverse dynamics, using pedal forces and limb kinematics. EMG activity was measured for 9 lower limb muscles. Reliability was explored by quantifying systematic and random differences within-and between-session. Within-session reliability was better than between-sessions reliability. The test-retest reliability level was typically moderate to excellent for the biomechanical variables that describe maximal cycling. However, some variables, such as peak knee flexion moment and maximum hip joint power, demonstrated lower reliability, indicating that care needs to be taken when using these variables to evaluate biomechanical changes. Although measurement error (instrumentation error, anatomical marker misplacement, soft tissue artefacts) can explain some of our reliability observations, we speculate that biological variability may also be a contributor to the lower repeatability observed in several variables including ineffective crank force, ankle kinematics and hamstring muscles' activation patterns.
Joint Motions of the Lower Limb During Ergometer Cycling
Journal of Orthopaedic & Sports Physical Therapy, 1988
The purpose of the study was to study the utilization of range of motion at the hip, knee, and ankle joints during exercise on a bicycle ergometer. Six healthy subjects biked at different workloads, pedaling rates, saddle heights, and pedal foot positions. The subjects were filmed in the sagittal plane with a cine-film camera at 60 frames/ sec. The mean hip range of motion (ROM) during normal cycling was 38" ranging from 32-70 hip flexion. The mean knee ROM was 66 " ranging from 46-1 12 knee flexion, and the ankle ROM was 24 " ranging from 2" plantarflexion to 22 " dorsiflexion. The hip, knee, and ankle joint motions were influenced by changes of the saddle height or pedal foot position. Different workloads had a small but statistically significant influence on the joint motions while different pedaling rates did not significantly change the lower limb joint motions. The range of motion utilized during cycling is approximately equal to, but more flexed compared to level walking and stair walking. The most effective way of increasing the ROM and obtaining more extension of the lower limb joints is to change the saddle height. ' Kinesiology Research Group, Department of Anatomy and Depart-variation (95, 100, and 105Oh trochanteric height) ment of Physical Medicine 8 Rehabilitation, Karolinska Institute. Stockupon lower limb kinematics. She found that the holm. Sweden. t Kinesiology Research Group, Department of Anatomy. Karolinska ROM at the hip does not change, while the major Institute. Stockholm, Sweden.
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.
The Effect of Measurement Technique and Load on Lower Limb Kinematics in Cycle Ergometry
ISBS - Conference Proceedings Archive, 1994
D~pnno l~i d J b y C d k~ dl hmm P t r f m n c c d(todnpment I!niwruity of Kwada, Lm b7c~as tNTRODUCTIUN Mwy dudie~ involving cycle ergcm~v often provide a description of lfiwer l i b kitwmkk 'L'his description h s W n uSCJ 1v provide inli#nu~aticrr~ regarding: body position rurd co&mt bn 1 ha1 mariini~or wnhic energy apcdicurr: [Nordm 1976. VgrdeCn-Snyder 1977, and T m lW: 1991); o p t i d s w lo pedal diaarut k r anaembi and aerobic work (Gregw 1676.199 1. Harnlq 1967, Nardeen-Snyder 1977); and simrltatims 01-lowel' limb kincnmtks [t Legor 1976). Howcvcr, joint angle msuretrrerrts are af&en &ne lrtatjcdly Cl'oo I YY I h and rrmy not tef'lw~ the mud jdnt kinunatim during the assigned task. This is a
A split-crank, servomotor-controlled bicycle ergometer design for studies in human biomechanics
IEEE/RSJ International Conference on Intelligent Robots and System, 2002
This paper presents a novel computer-controlled bicycle ergometer, the Tiltcycle, for use in human biomechanics studies of pedaling. The Tiltcycle has a tilting (reclining) seat and backboard, a split crank to isolate the left and right loads to the feet of the cyclist, and two belt-driven, computer-controller motors to provide both assistance and resistance loads. Sensors measure the kinematics and force production of the pedaling work performed, as well as goniometer and electromyography signals from the lower limbs. The technical description includes the mechanical design, low-level software and control algorithms designed for studies in human lower-limb biomechanics and bilateral coordination, and concludes with validation testing and system identification results.
Journal of Electromyography and Kinesiology, 2003
Frequency analysis of myoelectric (ME) signals, using the mean power spectral frequency (MNF), has been widely used to characterize peripheral muscle fatigue during isometric contractions assuming constant force. However, during repetitive isokinetic contractions performed with maximum effort, output (force or torque) will decrease markedly during the initial 40-60 contractions, followed by a phase with little or no change. MNF shows a similar pattern. In situations where there exist a significant relationship between MNF and output, part of the decrease in MNF may per se be related to the decrease in force during dynamic contractions.
Acta Physiologica Scandinavica, 1997
This study investigated the relationship between muscle morphology and surface electromyographic parameters (mean frequency, f mean ; and signal amplitude, RMS) during sustained static knee extension to exhaustion at 25% maximal voluntary contraction (MVC) and at 70% MVC. Twenty clinically healthy subjects participated. EMGs were registered from the quadriceps. Muscle forces during knee extension at a 90°joint angle were maintained at the respective levels throughout the measurement periods. A biopsy was obtained of the vastus lateralis muscle. The total time to exhaustion was normalized for each subject. By means of regression analysis, the intercept (i ) (i.e. the unfatigued state) and the regression coef®cient (k ) were determined for each EMG parameter.