Search

Postural responses are usually investigated as reflexes. Several trials are averaged, and trial-to-trial variations are interpreted as noise. Several studies providing single-trial data plots revealed oscillations that may be cancelled out in averaged time series. Variations between single trials may also be interpreted as a consequence of changed dynamic properties of the neural circuitries. Therefore, we propose a Matsuoka oscillator model to describe single-trial postural responses to external perturbations. The applicability of the model was demonstrated by a comparison between simulations and experimental electromyographic (EMG) data. Vertical force perturbations of durations 0.4 s and 0.2 s were applied via a handle to 10 subjects. Handle force was used as model input, and EMG data from the external oblique muscles was compared with simulation output. Model coefficients were optimized by a least-squares algorithm. The optimization produced a good similarity between simulation and experimental data with determination coefficients of r 2 = 0.7 and greater. Furthermore, as a model validation, the model coefficients were used to predict other perturbation trials with similarities between predictions and respective EMG data of about r 2 = 0.45 , which was in the range of trial-to-trial EMG variability. The observed oscillations are assumed to originate from the central nervous system with changes in the neural circuitries between trials. Hence, the oscillations in single trial responses which are usually regarded as noise might be generated by the dynamics of a neural oscillator.

Bourdiol developed an insole concept with so called Neuromuscular Operating Elements (NME). By influencing the plantar foot sensibility with NME, reflexes should activate so called muscle chain reactions and as a result of that, malposition of the whole locomotors system should be treated. New footorthoses(FO)-concepts use the NME. But they are controversially discussed, cause of the missing scientific background. In contrast to these FO, classical ones like Custom Moulded FO (CMFO) focus on lower limb problems [Collins et al]. Their effects are quiet validated [Murley et al]. So the aim of this study was to test the influences of CMFO with NME (Figure 1; total left) on muscle activation and plantar pressure distribution.