Effect of strength and speed of torque development on balance recovery with the ankle strategy
Effect of strength and speed of torque development on balance recovery with the ankle strategy
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DOI：
10.1152/jn.2002.88.2.613
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发表时间：
2002-08-01
影响因子：
2.5
通讯作者：
Cortez, J
中科院分区：
文献类型：
--
作者：
Robinovitch, SN;Heller, B;Cortez, J
在平衡受到意外干扰的情况下，恢复稳定直立姿势的能力不仅应取决于跨越下肢关节的肌肉收缩所产生的扭矩大小，还应取决于这些扭矩产生的速度。在本研究中，我们使用了平衡恢复摇摆（脚到位反应）的实验和数学模型的组合来测试这一假设。23名年轻的受试者参加了一项实验，他们被一根水平的绳子支撑在一个倾斜的站立位置，并被要求通过收缩脚踝肌肉来恢复平衡。在不释放系绳的情况下恢复平衡的最大倾斜角（静态恢复极限）平均为14.9+/-1.4度（平均值+/-SD）。在系绳意外释放和踝关节最初放松后，他们可以恢复平衡的最大初始倾斜角（动态恢复极限）平均为5.9+/-1.1度，或比静态恢复极限小60+/-11%。峰值踝关节扭矩在两种情况下没有显著差异（平均为116+/-32 Nm），表明在扭矩产生的开始和随后的速率（分别平均为99+/-13 ms和372+/-267 N.m/s）中，对膝关节的恢复能力有很强的影响。另外的实验表明，动态恢复极限随着释放前基线踝关节扭矩的增加而增加11+/-14%（从平均值31+/-18到54+/-24 N.m）。这些趋势与基于倒立摆模型的计算机模拟的预测一致，该模型说明了达到目标恢复极限所需的基线踝关节扭矩、扭矩产生速率和峰值踝关节扭矩的特定组合。
In the event of an unexpected disturbance to balance, the ability to recover a stable upright stance should depend not only on the magnitude of torque that can be generated by contraction of muscles spanning the lower extremity joints but also on how quickly these torques can be developed. In the present study, we used a combination of experimental and mathematical models of balance recovery by sway (feet in place responses) to test this hypothesis. Twenty-three young subjects participated in experiments in which they were supported in an inclined standing position by a horizontal tether and instructed to recover balance by contracting only their ankle muscles. The maximum lean angle where they could recover balance without release of the tether (static recovery limit) averaged 14.9+/-1.4degrees (mean+/-SD). The maximum initial lean angle where they could recover balance after the tether was unexpectedly released and the ankles were initially relaxed (dynamic recovery limit) averaged 5.9+/-1.1degrees, or 60+/-11% smaller than the static recovery limit. Peak ankle torque did not differ significantly between the two conditions (and averaged 116+/-32 Nm), indicating the strong effect on recovery ability of latencies in the onset and subsequent rates of torque generation (which averaged 99+/-13 ms and 372+/-267 N.m/s, respectively). Additional experiments indicated that dynamic recovery limits increased 11+/-14% with increases in the baseline ankle torques prior to release (from an average value of 31+/-18 to 54+/-24 N.m). These trends are in agreement with predictions from a computer simulation based on an inverted pendulum model, which illustrate the specific combinations of baseline ankle torque, rate of torque generation, and peak ankle torque that are required to attain target recovery limits.