Rogers L M, Brown D A, Gruben K G
Department of Kinesiology and Biomedical Engineering, University of Wisconsin-Madison, 1081 GymNat, 2000 Observatory Drive, Madison, WI 53706-1121, USA.
Gait Posture. 2004 Feb;19(1):58-68. doi: 10.1016/s0966-6362(03)00009-2.
The component of foot force generated by muscle action (F(m)) during pedaling in healthy humans has a nearly constant direction with increasing force magnitude. The present study investigated the effect of stroke on the control of foot force. Ten individuals with hemiparesis secondary to a cerebral vascular accident performed pushing efforts against translationally fixed and moving pedals on a custom stationary cycle ergometer. We found that while F(m) direction remained constant with increasing effort in both the fixed- and moving-crank conditions for both limbs, the orientation of that force component differed between limbs. The non-paretic limb produced the same F(m) orientation as seen previously in healthy humans. However, relative to the non-paretic limb, the paretic limb force line-of-action was shifted away from the hip and closer to the knee in the sagittal-plane for both pedal motion conditions. In the frontal plane, the paretic limb force line-of-action was shifted laterally, closer to parallel to the midline, for both pedal motion conditions. These shifts were consistent with previously reported lower limb muscle weakness and alterations in muscle activation observed during pedaling tasks following stroke. The finding of similar orientations for static and dynamic pushing efforts suggests that limb posture could be a trigger for relative muscle activation levels. The preservation of a constant direction in F(m) with increasing force magnitude post-stroke, despite an orientation shift, suggests that control of lower limb force may be organized by magnitude and direction and that these two aspects are differentially affected by stroke.
在健康人群蹬踏过程中，由肌肉活动产生的足部力量分量（F(m)）随着力量大小的增加，其方向几乎保持不变。本研究调查了中风对足部力量控制的影响。10名因脑血管意外导致偏瘫的个体，在定制的固定自行车测力计上，对平移固定和移动的踏板进行推蹬动作。我们发现，在固定曲柄和移动曲柄两种条件下，双下肢随着用力增加，F(m)方向均保持不变，但该力分量的方向在双下肢之间存在差异。非瘫痪侧下肢产生的F(m)方向与之前在健康人群中观察到的相同。然而，相对于非瘫痪侧下肢，在两种踏板运动条件下，瘫痪侧下肢力的作用线在矢状面内远离髋关节且更靠近膝关节。在额状面内，在两种踏板运动条件下，瘫痪侧下肢力的作用线均向外侧偏移，更接近与中线平行。这些偏移与先前报道的中风后蹬踏任务中观察到的下肢肌肉无力和肌肉激活改变一致。静态和动态推蹬动作方向相似的发现表明，肢体姿势可能是相对肌肉激活水平的触发因素。尽管方向发生了偏移，但中风后随着力量大小增加，F(m)仍保持恒定方向，这表明下肢力量控制可能是按大小和方向进行组织的，且这两个方面受中风的影响不同。
