An analysis of the effect of lower extremity strength on impact severity during a backward fall
An analysis of the effect of lower extremity strength on impact severity during a backward fall
复制标题
DOI：
10.1115/1.1408940
复制
发表时间：
2001-12-01
影响因子：
1.7
通讯作者：
Robinovitch, S
中科院分区：
文献类型：
--
作者：
Sandler, R;Robinovitch, S
美国每年至少发生28万例髋部骨折，估计耗资90亿美元。虽然超过90%的这些是由福尔斯引起的，但只有大约2%的福尔斯导致髋部骨折。有证据表明，跌倒时髋部骨折风险的最重要决定因素是身体的撞击速度和结构。因此，降低撞击速度的保护性反应以及直接撞击髋关节的可能性强烈影响骨折风险。一种用于降低跌倒期间的身体冲击速度和动能的方法是在下降期间吸收下肢肌肉中的能量，如在坐和蹲期间发生的。在本研究中，我们采用了一系列的倒立摆模型，以确定：（a）该机制的理论效果石油的影响严重程度在一个落后的秋天，和（B）的影响石油的影响严重程度的年龄相关的下降（或运动引起的增强）下肢力量。与下肢关节零能量吸收的跌倒情况相比，最好的情况是福尔斯（其中涉及81%的踝关节和臀部肌肉的激活，比尔只有23%的膝盖肌肉激活）涉及79%的衰减撞击时，身体的垂直动能（KEv）衰减（从352 J到74 J），撞击时毛皮的下降速度（vv）衰减48%（从3.22 m/s到1.68 m/s）。其中的机制是：（1）在下降过程中下肢肌肉的离心收缩，这导致了嘴唇吸收150 J的能量;（2）在直立配置中与躯干的碰撞，这减少了与下降相关的势能变化100 J;以及（3）在下降的最后阶段期间的膝盖伸展，其将高达90 J的冲击能量“转移”成水平（与垂直相对）动能。关节强度的下降降低了机制（1）和（3）的有效性，从而增加了冲击的严重性。然而，即使有效扭矩减少了80%，KEv也衰减了50%。这表明了技术和强度在降低冲击强度方面的重要性。这些结果提供了动力，试图通过结合安全跌倒技术和增强下肢力量的练习来降低老年人跌倒相关损伤的风险。
At least 280,000 hip fractures occur annually in the U.S., at an estimated cost of $9 billion. While over 90 percent of these are caused by falls, only about 2 percent of all falls result in hip fracture. Evidence suggests that the most important determinants of hip fracture risk during a fall arc the body's impact velocity and configuration. Accordingly, protective responses for reducing impact velocity, and the likelihood for direct impact to the hip, strongly influence fracture risk. One method for reducing the body impact velocity and kinetic energy during a fall is to absorb energy in the lower extremity muscles during descent, as occurs during sitting and squatting. In the present study, we employed a series of inverted pendulum models to determine: (a) the theoretical effect of this mechanism oil impact severity during a backward fall, and (b) the effect oil impact severity of age-related declines (or exercise-induced enhancements) in lower extremity strength. Compared to the case of a fall with zero energy absorption in the lower extremity joints, best-case falls (which involved 81 percent activation of ankle and hip muscles, bill only 23 percent activation of knees muscles) involved 79 percent attenuation (from 352 J to 74 J) in the bod ys vertical kinetic energy at impact (KEv), and 48 percent attenuation (from 3.22 to 1.68 m/s) in the downward velocity of the pelt-is at impact (vv). Among the mechanisms responsible for this were: (1) eccentric contraction of lower extremity muscles during descent, which resulted in lip to 150 J of energy absorption; (2) impact with the trunk in an upright configuration, which reduced the change in potential energy associated with the fall by 100 J; and (3) knee extension during the final stage of descent, which "transferred" up to 90 J of impact energy into horizontal (as opposed to vertical) kinetic energy. Declines in joint strength reduced the effectiveness of mechanisms (1) and (3), and thereby increased impact severity. However even with reductions of 80 percent in available torques, KEv was attenuated by 50 percent. This indicates the importance of both technique and strength in reducing impact severity. These results provide motivation for attempts to reduce elderly individuals' risk for fall-related injury through the combination of instruction in safe falling techniques and exercises that enhance lower extremity strength.