Reference Reference - Gait & Posture

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use of aids and/or orthotic devices to compensate for the effects of spasticity ... (dotted line); in the apnea movement test the PSD showed only one peak.
Abstracts of the 2007 SIAMOC congress / Gait & Posture xxx (2008) xxx–xxx with impairment and disability indicators may be explained by an effective use of aids and/or orthotic devices to compensate for the effects of spasticity or muscles weakness. Acknowledgement: This study was financed by StartER funds provided by the “Regione ” of Emilia Romagna.

Reference [1] Flansbjer UB, Downham D, Lexell J. Knee muscle strength, gait performance and perceived participation after stroke. Arch Phys Med Rehabil 2006;87:974–80. doi:10.1016/j.gaitpost.2007.12.044

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to define a low pass filter that could remove the artefact component during normally breathing exercise. Finally, we defined an algorithm that identifies as cut-off frequency (fc) the first local minimum following the respiratory frequency; this frequency was supposed to delimit the spectrum related to the useful signal. The performance of the above-described signal processing procedure was quantified by the signal-to-noise ratio (defined as the ratio between the areas under the PSD, on the left and on the right of fc), before and after filtering.

Results and discussion: The identification of the frequency peaks associated to breathing (fr) and to locomotor movement artefacts (fma) did not show any problem in all subjects. In particular, as expected, it was found that for each test fma frequency corresponded to the locomotion frequency calculated on the vertical displacement of the estimated body center of mass. The identification of the cut-off frequency was robust as well. In the 6 subjects the signal-to-noise ratio improved from 31% (minimum) to 139% (maximum) in the walking tests. In the running tests, where a greater artefact power than in walking was expected, the improvement was even more relevant, from 120% to 1219%. The robustness of the present approach’s assumption derives from the empiric observation that the walking/running subject normally takes one breath every N (N > 1) locomotor acts (steps).

Optoelectronic plethysmography and locomotion: Identification and filtering of the movement artefacts P. Mazzoleni ∗ , M. Rabuffetti, P. Castiglioni, M. Di Rienzo, M. Ferrarin Polo Tecnologico, IRCCS S. Maria Nascente, Fondazione Don Carlo Gnocchi ONLUS, Milan, Italy Introduction: The kinematic analysis of the thoracic movement (optoelectronic plethysmography, OEP) during complex motor acts, as walking or running, is important for the functional evaluation of the respiratory system, and for the interference between breathing and inertial stress on tissues. Despite the undoubted advantage of OEP use in comparison with other instruments [1], its application on moving subjects quantifies a volume variation of the chest wall V, that adds an artefact component produced by the locomotor movement to the breathing contribution. In this study, we analysed on the basis of experimental data, the possibility to elaborate the signal in order to remove the movement artefacts (ma). For this purpose, we characterized the frequency contents of the V signal and of the artefact in different conditions, and we proposed an algorithm for the signal filtering. Methods: We analysed breathing in six healthy subjects (age = 23 ± 5 years) by an optoelectronic system OEP (BTS, Italy) with 9 tvc. We considered six experimental conditions, 20 s long, on a tapis roulant: static straight posture, 3 km/h walking and 7 km/h running, both normally breathing and without breathing (apnea). For each test, we obtained volume variations of the chest wall V, and the correspondent power spectral density (PSD) through Welch periodogram. The PSD obtained in the breathing static test is characterized by only one peak in the respiratory frequency frpost resp (dotted line); in the apnea movement test the PSD showed only one peak in the movement artefact frequency, fmamov apnea (dashed line); during the breathing movement test both peaks frmov resp and fmamov resp (solid line) were identified. Finally, the PSD of the static test without breathing showed no peak, because of the absence of the two determining factors (breathing and locomotor movement). Having verified that frequencies related to breathing and to locomotor movement were clearly distinct (fr < fma), it was possible

Reference [1] Aliverti A, et al. Mechanics of breathing. Milano: Springer-Verlag Italia; 2002. doi:10.1016/j.gaitpost.2007.12.045 Head stabilization and body coordination induced by horizontal oscillation M. Petrarca 1,∗ , P. Cappa 1,2 , F. Patan`e 1,2 , S. Rossi 1,2 , A. Colazza 1 , E. Castelli 1 , A. Berthoz 3 1

Pediatric Neuro-Rehabilitation Division, Children’s Hospital “Bambino Ges`u” IRCCS, Via Torre di Palidoro, 00050 Passoscuro (Fiumicino), Rome, Italy 2 Department of Mechanics and Aeronautics, “Sapienza” University of Rome, Via Eudossiana, 18-00184 Rome, Italy 3 Laboratoire de Physiologie de la Perception et de l’Action, Coll` ege de France, 11, rue Marcelin Berthelot 75005, Paris, France Introduction: It is known that during gait there is a trend to stabilize the head [1], the trunk and to oscillate the arms in opposite phase respect to the lower limbs [2]. These movements are compromised in children with cerebral palsy. With the aim to study balance strategies and to individualize therapeutic indications, we trained normal subjects in trials of balance task on an ad hoc built rotating platform. Methods: Ten subjects, three males and seven females, 30 ± 9 years old, standing on a platform of 0.5 m × 0.5 m at which was imposed sinusoidal rotations of ±45◦ of amplitude at frequencies of 0.25, 0.50 and 0.75 Hz, that lasted 25 s each. Kinematic data are collected by means of opto-electronic system (Vicon 512. UK, six cameras) operating at 120 Hz. Thirty-eight

GAIPOS 2534 1–38