Stackhouse Scott K, Stevens Jennifer E, Johnson Christopher D, Snyder-Mackler Lynn, Binder-Macleod Stuart A
Department of Physical Therapy, 301 McKinly Laboratory, University of Delaware, Newark, Delaware 19716, USA.
Muscle Nerve. 2003 Jan;27(1):40-5. doi: 10.1002/mus.10278.
The purposes of this study were to develop and test a model describing the relationship between the central activation ratio (CAR; a measure of voluntary muscle activation) and percent maximum voluntary contraction (%MVC) force for old adults and to provide a method for more accurate determination of voluntary muscle activation failure. Twenty-one adults (ages 64-81) performed isometric testing of the quadriceps at 25%, 50%, 75%, and 100% MVC. During each contraction, a 100-HZ, 120-ms train of electrical pulses was delivered to the quadriceps muscle to quantify voluntary muscle activation. Similar to a young, healthy population (ages 20-35), a curvilinear relationship existed between the CAR and %MVC force for older adults. Predictions of subjects' MVCs using the linear model of CAR-%MVC force relationship generally demonstrated poor agreement with actual MVCs. Predictions of MVC from submaximal contractions (25%, 50%, and 75%) using a previously identified curvilinear young adult CAR-%MVC relationship were good [ICC (2,1): 0.81, 0.96, and 0.82, respectively]. Similar agreement was obtained from the curvilinear older adult CAR-%MVC relationship. These data suggest that the CAR-%MVC relationship is similar in young and older adult subjects and that curvilinear models of this relationship can predict MVC forces in older adults more accurately. Reexamination of the relationship between the CAR and %MVC force may allow a more accurate determination of how failure of voluntary muscle activation contributes to weakness in old adults.
本研究的目的是开发并测试一个模型，该模型描述老年人的中枢激活率（CAR；一种衡量随意肌激活的指标）与最大随意收缩百分比（%MVC）力量之间的关系，并提供一种更准确地确定随意肌激活失败的方法。21名成年人（年龄在64 - 81岁之间）在25%、50%、75%和100%MVC水平下对股四头肌进行等长测试。在每次收缩过程中，向股四头肌输送一列100赫兹、120毫秒的电脉冲，以量化随意肌激活情况。与年轻健康人群（年龄在20 - 35岁之间）类似，老年人的CAR与%MVC力量之间也存在曲线关系。使用CAR-%MVC力量关系的线性模型预测受试者的MVC，通常与实际MVC的一致性较差。使用先前确定的年轻成年人曲线CAR-%MVC关系，从次最大收缩（25%、50%和75%）预测MVC的效果良好[组内相关系数（ICC，2,1）分别为0.81、0.96和0.82]。从老年人曲线CAR-%MVC关系中也获得了类似的一致性。这些数据表明，CAR-%MVC关系在年轻和老年受试者中相似，并且这种关系的曲线模型可以更准确地预测老年人的MVC力量。重新审视CAR与%MVC力量之间的关系，可能有助于更准确地确定随意肌激活失败如何导致老年人的肌肉无力。
