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BioMed Research International
Volume 2014, Article ID 287436, 9 pages
http://dx.doi.org/10.1155/2014/287436
Research Article

Morning/Evening Differences in Somatosensory Inputs for Postural Control

1Armed Forces Biomedical Research (IRBA), Vigilance Team, 91223 Brétigny-sur-Orge, France
2Université Paris Descartes, Sorbonne Paris Cité, EA 7330 VIFASOM Sommeil-Fatigue-Vigilance et Santé Publique, 75181 Paris, France
3Normandie University, 14032 Caen, France
4Unicaen, COMETE, 14032 Caen, France
5INSERM, U 1075, COMETE, 14032 Caen, France

Received 15 March 2014; Revised 24 July 2014; Accepted 24 July 2014; Published 18 August 2014

Academic Editor: Jacob J. Sosnoff

Copyright © 2014 Clément Bougard and Damien Davenne. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The underlying processes responsible for the differences between morning and afternoon measurements of postural control have not yet been clearly identified. This study was conducted to specify the role played by vestibular, visual, and somatosensory inputs in postural balance and their link with the diurnal fluctuations of body temperature and vigilance level. Nineteen healthy male subjects (mean age: 20.5 ± 1.3 years) participated in test sessions at 6:00 a.m. and 6:00 p.m. after a normal night’s sleep. Temperature was measured before the subjects completed a sign cancellation test and a postural control evaluation with eyes both open and closed. Our results confirmed that postural control improved throughout the day according to the circadian rhythm of body temperature and sleepiness/vigilance. The path length as a function of surface ratio increased between 6:00 a.m. and 6:00 p.m. This is due to a decrease in the centre-of-pressure surface area, which is associated with an increase in path length. Romberg’s index did not change throughout the day; however, the spectral analysis (fast Fourier transform) of the centre-of-pressure excursions (in anteroposterior and mediolateral directions) indicated that diurnal fluctuations in postural control may occur via changes in the different processes responsible for readjustment via muscle contractions.