The effect of age on balancing behavior: complexity analysis of mediolateral force trajectories
1Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, United States of America.
Objective:
We quantified, via complexity analysis, the postural stability of healthy people from a wide age range.
Approach:
Thirty-five healthy people aged 18-72 performed three tasks while balancing on one foot on a force plate: standard balancing task, mental task (balancing while answering basic arithmetic questions), and knot-tying task (balancing while tying two knots in a piece of ribbon). Mediolateral force trajectories were analyzed to determine control strategy via Hurst exponents, Lyapunov exponents, Kolmogorov complexity, root mean square, and phase-space plots.
Main Results:
We found increased pattern repetition in balancing with increased age, as evidenced by the emergence of a double attractor pattern in phase-space plots and the increase of Hurst exponents with age from approximately 0.3 to 0.8.
Significance:
As people age, they tend to develop strong feed-forward control strategies for balancing, and lose the complexity of micro movements intrinsic to young age. There is an open-loop control strategy for balancing that emerges in older adulthood, and there are attractors inherent to balancing which begin to develop in middle age.
