Enders Leah R, Seo Na Jin
Department of Industrial and Manufacturing Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI, 53211, US.
Exp Brain Res. 2015 Jun;233(6):1677-88. doi: 10.1007/s00221-015-4241-9. Epub 2015 Mar 21.
Many stroke survivors with severe impairment can grasp only with a power grip. Yet, little knowledge is available on altered power grip after stroke, other than reduced power grip strength. This study characterized stroke survivors' static power grip during 100 and 50 % maximum grip. Each phalanx force angular deviation from the normal direction and its contribution to total normal force was compared for 11 stroke survivors and 11 age-matched controls. Muscle activities and skin coefficient of friction were additionally compared for another 20 stroke and 13 age-matched control subjects. The main finding was that stroke survivors gripped with a 34 % greater phalanx force angular deviation of 19° ± 2° compared to controls of 14° ± 1° (p < .05). Stroke survivors' phalanx force angular deviation was closer to the 23° threshold of slippage between the phalanx and grip surface, which may explain increased likelihood of object dropping in stroke survivors. In addition, this altered phalanx force direction decreases normal grip force by tilting the force vector, indicating a partial role of phalanx force angular deviation in reduced grip strength post-stroke. Greater phalanx force angular deviation may biomechanically result from more severe underactivation of stroke survivors' first dorsal interosseous and extensor digitorum communis muscles compared to their flexor digitorum superficialis or somatosensory deficit. While stroke survivors' maximum power grip strength was approximately half of the controls, the distribution of their remaining strength over the fingers and phalanges did not differ, indicating evenly distributed grip force reduction over the entire hand.
许多严重受损的中风幸存者只能采用强力抓握方式。然而，除了抓握力量减弱外，关于中风后抓握方式改变的了解甚少。本研究对中风幸存者在最大抓握力的100%和50%时的静态强力抓握进行了特征描述。比较了11名中风幸存者和11名年龄匹配的对照组人员每个指骨力与法线方向的角度偏差及其对总法向力的贡献。另外还比较了另外20名中风患者和13名年龄匹配的对照受试者的肌肉活动和皮肤摩擦系数。主要发现是，与对照组14°±1°相比，中风幸存者抓握时指骨力角度偏差为19°±2°，大34%（p<0.05）。中风幸存者的指骨力角度偏差更接近指骨与抓握表面之间23°的滑动阈值，这可能解释了中风幸存者物体掉落可能性增加的原因。此外，这种指骨力方向的改变通过使力矢量倾斜而降低了正常抓握力，表明指骨力角度偏差在中风后抓握力减弱中起到了部分作用。与对照组相比，中风幸存者的第一背侧骨间肌和指总伸肌激活不足更严重，或者存在体感缺陷，从生物力学角度来看，这可能导致指骨力角度偏差更大。虽然中风幸存者的最大强力抓握力约为对照组的一半，但他们剩余力量在手指和指骨上的分布并无差异，表明整个手部的抓握力均匀降低。
