Santhiranayagam Braveena K, Lai Daniel T H, Sparrow W A, Begg Rezaul K
Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, PO Box 14428, Melbourne, Victoria, 8001, Australia.
College of Sport & Exercise Science, Victoria University, PO Box 14428, Melbourne, Victoria, 8001, Australia.
J Neuroeng Rehabil. 2015 Jul 12;12:58. doi: 10.1186/s12984-015-0052-2.
Falls in older adults during walking frequently occur while performing a concurrent task; that is, dividing attention to respond to other demands in the environment. A particularly hazardous fall-related event is tripping due to toe-ground contact during the swing phase of the gait cycle. The aim of this experiment was to determine the effects of divided attention on tripping risk by investigating the gait cycle event Minimum Toe Clearance (MTC).
Fifteen older adults (mean 73.1 years) and 15 young controls (mean 26.1 years) performed three walking tasks on motorized treadmill: (i) at preferred walking speed (preferred walking), (ii) while carrying a glass of water at a comfortable walking speed (dual task walking), and (iii) speed-matched control walking without the glass of water (control walking). Position-time coordinates of the toe were acquired using a 3 dimensional motion capture system (Optotrak NDI, Canada). When MTC was present, toe height at MTC (MTC_Height) and MTC timing (MTC_Time) were calculated. The proportion of non-MTC gait cycles was computed and for non-MTC gait cycles, toe-height was extracted at the mean MTC_Time.
Both groups maintained mean MTC_Height across all three conditions. Despite greater MTC_Height SD in preferred gait, the older group reduced their variability to match the young group in dual task walking. Compared to preferred speed walking, both groups attained MTC earlier in dual task and control conditions. The older group's MTC_Time SD was greater across all conditions; in dual task walking, however, they approximated the young group's SD. Non-MTC gait cycles were more frequent in the older group across walking conditions (for example, in preferred walking: young - 2.9 %; older - 18.7 %).
In response to increased attention demands older adults preserve MTC_Height but exercise greater control of the critical MTC event by reducing variability in both MTC_Height and MTC_Time. A further adaptive locomotor control strategy to reduce the likelihood of toe-ground contacts is to attain higher mid-swing clearance by eliminating the MTC event, i.e. demonstrating non-MTC gaits cycles.
老年人在行走过程中摔倒经常发生在执行并发任务时，即在分散注意力以应对环境中的其他需求时。一个与跌倒特别相关的危险事件是在步态周期的摆动阶段由于脚趾与地面接触而绊倒。本实验的目的是通过研究步态周期事件最小脚趾间隙（MTC）来确定分散注意力对绊倒风险的影响。
15名老年人（平均年龄73.1岁）和15名年轻对照组（平均年龄26.1岁）在电动跑步机上进行三项行走任务：（i）以偏好步行速度行走（偏好步行），（ii）以舒适步行速度手持一杯水行走（双重任务步行），以及（iii）速度匹配的无水杯对照行走（对照步行）。使用三维运动捕捉系统（加拿大的Optotrak NDI）获取脚趾的位置-时间坐标。当存在MTC时，计算MTC时的脚趾高度（MTC_Height）和MTC时间（MTC_Time）。计算非MTC步态周期的比例，并在非MTC步态周期中，在平均MTC_Time提取脚趾高度。
两组在所有三种情况下均保持平均MTC_Height。尽管在偏好步态中MTC_Height标准差更大，但老年组在双重任务行走中降低了其变异性以与年轻组匹配。与偏好速度行走相比，两组在双重任务和对照条件下更早达到MTC。老年组的MTC_Time标准差在所有条件下都更大；然而，在双重任务行走中，他们接近年轻组的标准差。在所有行走条件下，老年组的非MTC步态周期更频繁（例如，在偏好步行中：年轻组-2.9%；老年组-18.7%）。
为应对注意力需求增加，老年人保持MTC_Height，但通过降低MTC_Height和MTC_Time的变异性来更好地控制关键的MTC事件。一种进一步的适应性运动控制策略，以降低脚趾与地面接触的可能性，是通过消除MTC事件来获得更高的摆动中期间隙，即表现出非MTC步态周期。
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