Postural Control Adaptability to Floor Oscillation in the Elderly

Abstract

We established a method to evaluate postural control adaptability, applying it to 341 subjects, aged 18-29 years (young subjects) and 50-79 years, in order to investigate the influences of age and gender on adaptability. Subjects stood with eyes closed on a force plate fixed to a floor oscillator, which was sinusoidally oscillated in the anteroposterior direction with 0.5 Hz frequency and 2.5 cm amplitude. Five trials of 1-minute oscillation were conducted, with a short rest between trials. The mean speed of fluctuation of the center of foot pressure (CFP), as detected by the force plate, was calculated as an index of postural steadiness. Mean CFP speed decreased significantly in all age groups with trial repetition. The adaptability capability of elderly subjects was categorized as "good," "moderate," or "poor," as evaluated against a standard value, based on the variation of the regression of mean CFP speed between the 1st and 5th trials in young subjects. Results showed that the magnitude of reduction in the mean speed, with practice, was linearly related to the initial mean speed. We found a general decline in adaptability, and increase in initial mean speed, in subjects aged 60 years and older, with no gender difference detected in any age group. The proportion of subjects exhibiting moderate and poor adaptability increased gradually with age. In conclusion, age, but not gender, appears to affect adaptation of postural sway with short-term practice, although some elderly subjects maintain postural sway velocity and adaptability capabilities similar to those of young subjects.

Age-related Changes and Sex Differences in Postural Control Adaptability in Children during Periodic Floor Oscillation with Eyes Closed

“…To eliminate the influence of height on center of mass, we corrected the CoPy speed measurements for subject height and converted measurements into values per 100 cm. These formulas have been described in our previous study (Fujiwara et al, 2007). If subjects opened their eyes during table oscillation and again closed them, then the data from 10 seconds after they closed their eyes were used.…”

“…The experimental setup is described in detail in our previous study (Fujiwara et al, 2007). In brief, a force platform (S110; Patella, Japan), which is composed of three load cells, was used to record CoPy fluctuations.…”

“…Under a dynamic balanced condition, when subjects are exposed to a postural disturbance, it is important to anticipate the disturbance in order to control posture. Previous studies have introduced periodic postural disturbances to investigate the adaptability of anticipatory postural control (Buchanan and Horak, 1999;Nardone et al, 2000;Earhart et al, 2004;Fujiwara et al, 2007).…”

“…The mean speed of the center of pressure in the anteroposterior direction (CoPy) was used to evaluate postural steadiness, which improved rapidly by the third trial and reached a plateau by the fifth trial (Fujiwara et al, 1994). In addition, we established a method of evaluating adaptability of anticipatory postural control to floor oscillation with eyes closed, based on a standard value derived from the CoPy speed in young adults (Fujiwara et al, 2007). These studies indicate that when 1-minute periodic floor oscillation is applied as a postural disturbance, adaptation of postural control based on the nonvisual system can be assessed relatively rapidly, enabling the evaluation of the developmental process for adaptability.…”

Adaptation and vision change the relationship between muscle activity of the lower limbs and body movement during human balance perturbations

“…In current approaches to motor learning, adaptation is viewed as a process in which prediction errors result in proportional changes in parameter estimates (Krakauer et al, 2006). More recently, studies have indicated that adaptation through motor learning can be applied to the human standing posture during balance perturbations (Fransson et al, 2007b;Fujiwara et al, 2007). As such, repeatedly perturbing balance could be one way of decreasing the number of falls in those at risk.…”