Motor control strategies to maintain balance in elderly subjects evaluated using wavelet transform

Alex Araneda
Laboratory of Biomechanics, Hospital del Trabajador, Santiago, Chile

Rony Silvestre
Hospital del Trabajador, Santiago, Chile

Rodrigo Guzm
Hospital del Trabajador, Santiago, Chile

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     Last modified: May 13, 2007

Abstract
AIMS: Postural control is provided by complex interactions among proprioceptive, visual, vestibular and somatosensorial systems. Aging has been shown to affect all of these systems causing a poor balance in elderly subjects. Elderly subjects present serious problems due to poor balance such as falls and fractures which increase economical costs in health care. Balance evaluation has been of interest for clinicians and researchers because provides several applications such as predictor of falls, fractures index, and as indicator of treatment success when balance and proprioceptive training has been performed. The objective of this study was evaluate balance in elderly people using Wavelet Transform (WT) in order to provide a new tool to establish normal data for each gender in this population.
METHODS: Balance was evaluated in a probabilistic sample comprised of 50 male and 50 female with an average of 78 and 77 years respectively using a posture platform device. The evaluation consisted of three phases. In the first phase, the subject was asked to maintain the center of pressure (CoP) in the base of support for 30 seconds while a visual feedback of the position of the center of pressure was provided through a computer screen. The second phase was similar to the first phase but the subject had to keep his/her eyes looking to the front without visual feedback, and the last phase was similar to the previous one but with eyes closed. Signals obtained from the diplacement of center of pressure during the three tests for all subjects were analyzed by the Wavelet Transform in order to determine the intensity of each band (4Hz, 2Hz, 1Hz, 1/2Hz, 1/4Hz 1/8 Hz y 1/16Hz) for each gender. The Romberg index was calculated for each gender. SPSS statistical Program was used to evaluate differences in Romberg Index between females and males.
RESULTS: Greater levels of total relative energy were obtained in men when compared with women with eyes closed and eyes open phases. Romberg Index had a normal distribution with a mean of 135.4% (DS: 41.9%). No significant differences in Romberg index between females (124.2%) and males (140.6%) were found (p>0.05). However, there was a tendency for women to have lower Romberg Index values.
CONCLUSIONS: Greater levels of energy obtained with eyes open as well as eyes closed in men could be understood as a difficulty to maintain balance due to a poor interrelationship among visual, vestibular and proprioceptive systems in elderly male subjects. Women obtained lower levels of Romberg index which could indicate that women rely more in the visual system to maintain their balance. This could be associated with a major number of falls and fractures in elderly females.