Maria Paterna1, Zeevi Dvir2, Carlo De Benedictis1, Daniela Maffiodo1, Walter Franco1, Carlo Ferraresi1, Silvestro Roatta3. 1. Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy. 2. Department of Physical Therapy, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. 3. Department of Neuroscience, University of Torino, c.so Raffaello 30, 10125, Turin, Italy. silvestro.roatta@unito.it.
Abstract
PURPOSE: Many studies have investigated postural reactions (PR) to body-delivered perturbations. However, attention has been focused on the descriptive variables of the PR rather than on the characterization of the perturbation. This study aimed to test the hypothesis that the impulse rather than the force magnitude of the perturbation mostly affects the PR in terms of displacement of the center of foot pressure (ΔCoP). METHODS: Fourteen healthy young adults (7 males and 7 females) received 2 series of 20 perturbations, delivered to the back in the anterior direction, at mid-scapular level, while standing on a force platform. In one series, the perturbations had the same force magnitude (40 N) but different impulse (range: 2-10 Ns). In the other series, the perturbations had the same impulse (5 Ns) but different force magnitude (20-100 N). A simple model of postural control restricted to the sagittal plane was also developed. RESULTS: The results showed that ΔCoP and impulse were highly correlated (on average: r = 0.96), while the correlation ΔCoP-force magnitude was poor (r = 0.48) and not statistically significant in most subjects. The normalized response, ΔCoPn = ΔCoP/I, was independent of the perturbation magnitude in a wide range of force amplitude and impulse and exhibited good repeatability across different sets of stimuli (on average: ICC = 0.88). These results were confirmed by simulations. CONCLUSION: The present findings support the concept that the magnitude of the applied force alone is a poor descriptor of trunk-delivered perturbations and suggest that the impulse should be considered instead.
PURPOSE: Many studies have investigated postural reactions (PR) to body-delivered perturbations. However, attention has been focused on the descriptive variables of the PR rather than on the characterization of the perturbation. This study aimed to test the hypothesis that the impulse rather than the force magnitude of the perturbation mostly affects the PR in terms of displacement of the center of foot pressure (ΔCoP). METHODS: Fourteen healthy young adults (7 males and 7 females) received 2 series of 20 perturbations, delivered to the back in the anterior direction, at mid-scapular level, while standing on a force platform. In one series, the perturbations had the same force magnitude (40 N) but different impulse (range: 2-10 Ns). In the other series, the perturbations had the same impulse (5 Ns) but different force magnitude (20-100 N). A simple model of postural control restricted to the sagittal plane was also developed. RESULTS: The results showed that ΔCoP and impulse were highly correlated (on average: r = 0.96), while the correlation ΔCoP-force magnitude was poor (r = 0.48) and not statistically significant in most subjects. The normalized response, ΔCoPn = ΔCoP/I, was independent of the perturbation magnitude in a wide range of force amplitude and impulse and exhibited good repeatability across different sets of stimuli (on average: ICC = 0.88). These results were confirmed by simulations. CONCLUSION: The present findings support the concept that the magnitude of the applied force alone is a poor descriptor of trunk-delivered perturbations and suggest that the impulse should be considered instead.
Authors: Zeevi Dvir; Maria Paterna; Martina Quargnenti; Carlo De Benedictis; Daniela Maffiodo; Walter Franco; Carlo Ferraresi; Andrea Manca; Franca Deriu; Silvestro Roatta Journal: Eur J Appl Physiol Date: 2020-04-15 Impact factor: 3.078
Authors: Denise Engelhart; Alfred C Schouten; Ronald G K M Aarts; Herman van der Kooij Journal: IEEE Trans Neural Syst Rehabil Eng Date: 2014-11-20 Impact factor: 3.802