Tanaka Hideyuki, Uetake Teruo, Kuriki Satoshi, Ikeda Satoshi
Department of Human-Computer Interaction Science, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan.
J Hum Ergol (Tokyo). 2002 Dec;31(1-2):1-11.
We investigated the relationships between the ability to maintain balance in an upright stance and center-of-pressure (COP) dynamic properties in young adults. Included in this study were 10 healthy male subjects in each of two groups with respect to balance ability. Balance ability was evaluated according to the length of time a subject stood on one leg with his eyes closed. The means and ranges of this one-leg balancing time were 17.9 s (3-43 s) and 118.3 s (103-120 s) for the off-balance and balance groups, respectively. The time-varying displacements of the COP under a subject's feet during quiet two-leg (normal) standing were measured by an instrumented force platform. Each subject was tested in both the eyes-open and eyes-closed conditions. The COP trajectories were analyzed as fractional Brownian motions according to the procedure of 'stabilogram-diffusion analysis', proposed by Collins and De Luca (1993). The extracted parameters were the effective diffusion coefficients (D) for the short-term (less than about 1.0 s) and long-term intervals, respectively, as well as the Hurst exponents (H) for the short-term and long-term intervals, and some critical-point coordinates (i.e., critical mean square displacements and critical time intervals). The off-balance group showed significantly higher values for short-term D, short-term H, and critical mean square displacements than the balance group. No significant differences between the groups were found in the long-term D and H or in the critical time intervals. That is, for the off-balance subjects, an increase in the stochastic activity and positively correlated (persistent) behavior of the postural sway during shorter timescales may cause postural instability. These results suggest that the difference in balance ability for young adults is related to the open-loop (i.e., short-term) control mechanisms but not to the corrective feedback (i.e., long-term) mechanisms used to maintain balance in an upright stance.
我们研究了年轻人在直立姿势下保持平衡的能力与压力中心（COP）动态特性之间的关系。本研究纳入了两组在平衡能力方面各有10名健康男性受试者。根据受试者闭眼单腿站立的时间长短来评估平衡能力。非平衡组和平衡组单腿平衡时间的平均值及范围分别为17.9秒（3 - 43秒）和118.3秒（103 - 120秒）。在安静的双腿（正常）站立过程中，通过仪器化测力平台测量受试者脚下COP的时变位移。每个受试者均在睁眼和闭眼条件下进行测试。根据Collins和De Luca（1993年）提出的“稳定图 - 扩散分析”程序，将COP轨迹分析为分数布朗运动。提取的参数分别为短期（小于约1.0秒）和长期时间间隔的有效扩散系数（D）、短期和长期时间间隔的赫斯特指数（H）以及一些临界点坐标（即临界均方位移和临界时间间隔）。非平衡组的短期D、短期H和临界均方位移值显著高于平衡组。在长期D和H或临界时间间隔方面，两组之间未发现显著差异。也就是说，对于非平衡受试者，在较短时间尺度上姿势摆动的随机活动增加和正相关（持续）行为可能会导致姿势不稳定。这些结果表明，年轻人平衡能力的差异与用于在直立姿势下保持平衡的开环（即短期）控制机制有关，而与纠正反馈（即长期）机制无关。
