An experimentally based nonlinear viscoelastic model of joint passive moment

Esteki, Ali; Mansour, Joseph M.

doi:10.1016/0021-9290(95)00081-x

Cited by 90 publications

(64 citation statements)

References 14 publications

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“…The dynamometer angle was slowly increased (2°s -1 ) until the gymnast reached the limit of range of motion. Exponential equations were then fitted to the joint angle/torque data (Esteki & Mansour, 1996;Reiner & Edrich, 1999).…”

Section: Data Collectionmentioning

confidence: 99%

Optimal technique for maximal forward rotating vaults in men’s gymnastics

Hiley

Jackson

Yeadon

2015

Human Movement Science

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In vaulting a gymnast must generate sufficient linear and angular momentum during the approach and table contact to complete the rotational requirements in the post-flight phase. This study investigated the optimisation of table touchdown conditions and table contact technique for the maximisation of rotation potential for forwards rotating vaults. A planar seven-segment torque-driven computer simulation model of the contact phase in vaulting was evaluated by varying joint torque activation time histories to match three performances of a handspring double somersault vault by an elite gymnast. The closest matching simulation was used as a starting point to maximise post-flight rotation potential (the product of angular momentum and flight time) for a forwards rotating vault. It was found that the maximised rotation potential was sufficient to produce a handspring double piked somersault vault. The corresponding optimal touchdown configuration exhibited hip flexion in contrast to the hyperextended configuration required for maximal height. Increasing touchdown velocity and angular momentum lead to additional post-flight rotation potential. By increasing the horizontal velocity at table touchdown, within limits obtained from recorded performances, the handspring double somersault tucked with one and a half twists, and the handspring triple somersault tucked became theoretically possible.

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Section: Data Collectionmentioning

confidence: 99%

Optimal technique for maximal forward rotating vaults in men’s gymnastics

Hiley

Jackson

Yeadon

2015

Human Movement Science

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“…Passive torque data were also obtained using the isovelocity dynamometer for shoulder flexion, wrist extension and hip extension. Exponential equations were fit to the passive torque-angle data for each joint (Riener and Edrich, 1999;Esteki and Mansour, 1996).…”

Section: Data Collectionmentioning

confidence: 99%

The influence of touchdown conditions and contact phase technique on post-flight height in the straight handspring somersault vault

Yeadon

Jackson

Hiley

2014

Journal of Biomechanics

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Additional Information:• NOTICE: this is the author's version of a work that was accepted for publication in Journal of Biomechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Biomechanics, vol 47 (12), 2014 DOI: 10.1016/j.jbiomech.2014 ABSTRACTIn vaulting the gymnast must generate sufficient linear and angular momentum during the approach and table contact in order to complete the rotational requirements in the postflight phase. This study investigated the effects of touchdown conditions and contact technique on peak post-flight height of a straight handspring somersault vault. A planar seven-segment torque-driven computer simulation model of the contact phase in vaulting was evaluated by varying joint torque activation time histories to match three performances of a straight handspring somersault vault by an elite gymnast. The closest matching simulation was used as a starting point to optimise peak post-flight height of the mass centre for a straight handspring somersault. It was found that optimising either the touchdown conditions or the contact technique increased post-flight height by 0.1 m whereas optimising both together increased post-flight height by 0.4 m above that of a simulation matching the recorded performance. Thus touchdown technique and contact technique make similar contributions to post-flight height in the straight handspring somersault vault. Increasing touchdown velocity and angular momentum lead to additional post-flight height although there was a critical value of vertical touchdown velocity beyond which post-flight height decreased. INTRODUCTIONThe mechanics of the table contact phase of gymnastics vaulting is dependent on the initial contact conditions and the technique used during the contact phase. Although there are numerous coaching publications on vaulting, there is no general consensus about the importance of table contact phase technique. Some authors hold the view that vaulting performance is primarily determined prior to table contact (Still, 1990) while others have suggested that the gymnast has the ability to change the outcome of the vault via table contact technique (Smith, 1982;Boone, 1976). Takei (1988) used correlational analysis to show that a large pre-flight horizontal velocity is an important determinant of success in the tucked handspring somersault vault. Additionally Takei and Kim (1990) found that a large change in mass centre vertical velocity during contact was beneficial. While the horizontal pre-flight velocity is clearly an aspect of touchdown conditions, it is unclear whether the change in vertical velocity is a function of initial conditions or contact technique or both. King et al. (1999) used a passive (no shoulder torque) two-segment simulation model to determine ...

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“…The large inter-subject variability in the high-pass properties of the MUAP (in particular, standard deviations in cut-off frequency of ~30 Hz) implied that the magnitude of this effect is difficult to predict and that the 7/2/ 7/1 derived from the EMG is therefore not suited for the estimation of the temporal tremor characteristics. The angular velocity, on the other hand, is the result of a low-passed filtered version of the neural drive due to the properties of the motor unit twitch [35,39] and the viscoelastic mechanical properties of muscles [36,46]. Furthermore, this low-pass filtering is highly pronounced in older adults, due to the agerelated slowing of muscle contractile speed [47].…”

Section: Discussionmentioning

confidence: 99%

One central oscillatory drive is compatible with experimental motor unit behaviour in essential and Parkinsonian tremor

et al. 2015

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Objective. Pathological tremors are symptomatic to several neurological disorders that are difficult to differentiate and the way by which central oscillatory networks entrain tremorogenic contractions is unknown. We considered the alternative hypotheses that tremor arises from one oscillator (at the tremor frequency) or, as suggested by recent findings from the superimposition of two separate inputs (at the tremor frequency and twice that frequency). Approach. Assuming one central oscillatory network we estimated analytically the relative amplitude of the harmonics of the tremor frequency in the motor neuron output for different temporal behaviors of the oscillator. Next, we analyzed the bias in the relative harmonics amplitude introduced by superimposing oscillations at twice the tremor frequency. These findings were validated using experimental measurements of wrist angular velocity and surface electromyography (EMG) from 22 patients (11 essential tremor, 11 Parkinson's disease). The ensemble motor unit action potential trains identified from the EMG represented the neural drive to the muscles. Main results. The analytical results showed that the relative power of the tremor harmonics in the analytical models of the neural drive was determined by the variability and duration of the tremor bursts and the presence of the second oscillator biased this power towards higher values. The experimental findings accurately matched the analytical model assuming one oscillator, indicating a negligible functional role of secondary oscillatory inputs. Furthermore, a significant difference in the relative power of harmonics in the neural drive was found across the patient groups, suggesting a diagnostic value of this measure (classification accuracy: 86%). This diagnostic power decreased substantially when estimated from limb acceleration or the EMG. Signficance. The results indicate that the neural drive in pathological tremor is compatible with one central network providing neural oscillations at the tremor frequency. Moreover, the regularity of this neural oscillation varies across tremor pathologies, making the relative amplitude of tremor harmonics a potential biomarker for diagnostic use.

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An experimentally based nonlinear viscoelastic model of joint passive moment

Cited by 90 publications

References 14 publications

Optimal technique for maximal forward rotating vaults in men’s gymnastics

Optimal technique for maximal forward rotating vaults in men’s gymnastics

The influence of touchdown conditions and contact phase technique on post-flight height in the straight handspring somersault vault

One central oscillatory drive is compatible with experimental motor unit behaviour in essential and Parkinsonian tremor

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