Ding Li, Yang Feng
School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China.
Department of Kinesiology, University of Texas at El Paso, 1851 Wiggins Rd, Rm-452, El Paso, TX 79968, USA.
J Biomech. 2016 Jan 25;49(2):238-43. doi: 10.1016/j.jbiomech.2015.12.009. Epub 2015 Dec 11.
The purposes of this study were (1) to investigate the relationship between muscle weakness and slip-related falls among community-dwelling older adults, and (2) to determine optimal cut-off values with respect to the knee strength capacity which can be used to identify individuals at high risk of falls. Thirty-six healthy older adults participated in this study. Their muscle strength (torque) was assessed at the right knee under maximum voluntary isometric (flexion and extension) contractions. They were then moved to a special treadmill. After walking regularly five times on the treadmill, they experienced an identical and unannounced slip during walking on the treadmill with the protection of a safety harness. This treadmill could be considered a standardized platform, inducing an unexpected slip. Accuracy of predicting slip outcome (fall vs. recovery) was examined for both strength measurements (i.e., the strength capacity of knee extensor and flexor) using univariate logistic regressions. The optimal cutoff values for the two strength measurements were determined by the receiver operating characteristic analysis. Results showed that fallers displayed significantly lower knee strength capacities compared to their recovery counterpart (1.10 vs. 1.44Nm/kg, p<0.01, effect size Cohen׳s d=0.95 for extensor; 0.93 vs. 1.13Nm/kg, p<0.05, d=0.69 for flexor). Such results suggested that muscle weakness contributes to falls initiated by a slip during gait. Our findings could provide guidance to identify individuals at increased risk of falling using the derived optimal cutoff values of knee strength capacity among older adults.
（1）调查社区居住的老年人中肌肉无力与滑倒相关跌倒之间的关系；（2）确定膝关节力量能力的最佳临界值，以用于识别跌倒高风险个体。36名健康老年人参与了本研究。在最大自主等长收缩（屈伸）时评估他们右膝的肌肉力量（扭矩）。然后他们被转移到一台特殊的跑步机上。在跑步机上正常行走5次后，他们在跑步机上行走时在安全带保护下经历了一次相同且未事先通知的滑倒。这台跑步机可被视为一个标准化平台，会引发意外滑倒。使用单变量逻辑回归分析两种力量测量值（即膝伸肌和屈肌的力量能力）对滑倒结果（跌倒与恢复）的预测准确性。通过受试者工作特征分析确定两种力量测量值的最佳临界值。结果显示，与恢复组相比，跌倒者的膝关节力量能力显著更低（伸肌：1.10对1.44Nm/kg，p<0.01，效应量Cohen's d=0.95；屈肌：0.93对1.13Nm/kg，p<0.05，d=0.69）。这些结果表明，肌肉无力会导致步态中因滑倒引发的跌倒。我们的研究结果可为利用得出的老年人膝关节力量能力最佳临界值来识别跌倒风险增加的个体提供指导。
