Liang Ding, Ivanov Kamen, Li Huiqi, Ning Yunkun, Zhang Qi, Wang Lei, Zhao Guoru
Shenzhen Key Laboratory for Low-cost Healthcare and Shenzhen Institute s of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
Biomed Mater Eng. 2014;24(1):279-88. doi: 10.3233/BME-130809.
Research on falls in elderly people has a great social significance because of the rapidly growing of the aging population. The pre-impact lead time of fall (PLT) is an important part of the human fall theory. PLT is the longest time for a person who is going to fall to take action in order to prevent the fall or to reduce bodily injuries from the fall impact. However, there is no clear definition of PLT so far. There is also no comparative study for active and passive falls. In this study, we proposed a theoretical definition of the PLT, based on a new method of fall event division. We also compared the differences of PLT and the related angles between active and passive falls. Eight healthy adult subjects were arranged to perform three kinds of activities of daily living (sitting, walking and lying), and two kinds fall activities (active and passive) in three directions (forward, backward and lateral fall). Nine inertial sensor modules were used to measure the body segmental kinematic characteristics of each subject in our experimental activities. In this paper, a fall event was suggested to divide into three or four phases and then the critical phase could be divided into three periods (pre-impact, impact, and post-impact). Two fall models were developed for active and passive falls using acceleration data. The average value of PLT for active falls is about 514 ± 112 ms and it is smaller than the value for passive falls, which is 731 ± 104 ms. The longest PLTs were measured on the chest or waist instead of other locations, such as the thigh and shank. The PLTs of the three kinds of fall activities were slightly different, but there was a significant difference between two fall modes. The PLT showed the correlation to the body angle at the start of PLT, but it was uncorrelated at the end of PLT. The angles at the start of PLT had slight variations (<10 degrees) from the steady standing state except in passive forward falls (max 16 degrees) due to the self-control. The landing angles were significantly different in the both fall modes in all the three directions of fall, indicating the state of the trunk was uncertain when the hip contacted the ground. It can be concluded that it is feasible to prevent falls by using an early pre-impact fall alarm device; the present study provides important reference for development of pre-impact fall alarm devices.
由于老年人口的迅速增长，对老年人跌倒的研究具有重要的社会意义。跌倒前导时间（PLT）是人体跌倒理论的重要组成部分。PLT是即将跌倒的人采取行动以防止跌倒或减少跌倒冲击造成身体伤害的最长时间。然而，到目前为止，PLT尚无明确的定义。对于主动跌倒和被动跌倒也没有比较研究。在本研究中，我们基于一种新的跌倒事件划分方法，提出了PLT的理论定义。我们还比较了主动跌倒和被动跌倒在PLT及相关角度上的差异。安排了八名健康成年受试者进行三种日常生活活动（坐、走和躺），以及在三个方向（向前、向后和侧向跌倒）上的两种跌倒活动（主动和被动）。在我们的实验活动中，使用了九个惯性传感器模块来测量每个受试者的身体节段运动学特征。本文建议将跌倒事件分为三个或四个阶段，然后将关键阶段分为三个时期（跌倒前、跌倒时和跌倒后）。利用加速度数据为主动跌倒和被动跌倒建立了两种跌倒模型。主动跌倒的PLT平均值约为514±112毫秒，小于被动跌倒的731±104毫秒。在胸部或腰部测量到的PLT最长，而不是在大腿和小腿等其他部位。三种跌倒活动的PLT略有不同，但两种跌倒模式之间存在显著差异。PLT在开始时与身体角度相关，但在结束时不相关。除了被动向前跌倒（最大16度）由于自我控制外，PLT开始时的角度与稳定站立状态相比有轻微变化（<10度）。在所有三个跌倒方向上，两种跌倒模式的着地角度都有显著差异，表明当髋部接触地面时，躯干状态不确定。可以得出结论，使用早期跌倒前报警装置预防跌倒是可行的；本研究为跌倒前报警装置的开发提供了重要参考。
