Ding Qian, Patten Carolynn
Neural Control of Movement Lab, Malcolm Randall VA Medical Center (151A), Gainesville, FL 32608, USA; Rehabilitation Sciences Doctoral Program, Department of Physical Therapy, University of Florida, Gainesville, FL 32608, USA.
Biomechanics and Neural Control of Movement Lab, University of California, Davis School of Medicine, Northern California VA Health Care System, Sacramento, CA 95817, USA.
Clin Biomech (Bristol). 2018 Aug;57:26-34. doi: 10.1016/j.clinbiomech.2018.06.001. Epub 2018 Jun 5.
Grip strength is frequently measured as a global indicator of motor function. In clinical populations, such as hemiparesis post-stroke, grip strength is associated with upper-extremity motor impairment, function, and ability to execute activities of daily living. However, biomechanical configuration of the distal arm and hand may influence the magnitude and stability of maximal voluntary grip force and varies across studies. The influence of distal arm/hand biomechanical configuration on grip force remains unclear. Here we investigated how biomechanical configuration of the distal arm/hand influence the magnitude and trial-to-trial variability of maximal grip force performed in similar positions with variations in external constraint.
We studied three groups of 20 individuals: healthy young, healthy older, and individuals post-stroke. We tested maximal voluntary grip force in 4 conditions: 1: self-determined/"free"; 2: standard; 3: fixed arm-rest; 4: gripper fixed to arm-rest, using an instrumented grip dynamometer in both dominant/non-dominant and non-paretic/paretic hands.
Regardless of hand or group, maximal voluntary grip force was highest when the distal limb was most constrained (i.e., Condition 4), followed by the least constrained (i.e., Condition 1) (Cohen's f = 0.52, P's < 0.001). Coefficient of variation among three trials was greater in the paretic hand compared with healthy individuals, particularly in more (Conditions 3 and 4) compared to less (Conditions 1 and 2) constrained conditions (Cohen's f = 0.29, P's < 0.05).
These findings have important implications for design of rehabilitation interventions and devices. Particularly in individuals post-stroke, external biomechanical constraints increase maximal voluntary grip force variability while fewer biomechanical constraints yield more stable performance.
握力常被作为运动功能的一项综合指标来测量。在临床人群中，如中风后的偏瘫患者，握力与上肢运动损伤、功能以及执行日常生活活动的能力相关。然而，手臂远端和手部的生物力学结构可能会影响最大自主握力的大小和稳定性，并且不同研究结果存在差异。手臂远端/手部生物力学结构对握力的影响仍不明确。在此，我们研究了在外部约束条件不同但姿势相似的情况下，手臂远端/手部的生物力学结构如何影响最大握力的大小以及每次试验之间的变异性。
我们研究了三组，每组20人：健康年轻人、健康老年人和中风后个体。我们在4种条件下测试最大自主握力：1：自主决定/“自由”；2：标准；3：固定扶手；4：握力器固定在扶手上，在优势/非优势手以及健侧/患侧手均使用带传感器的握力计进行测试。
无论手别或组别如何，当远端肢体受到最大约束时（即条件4），最大自主握力最高，其次是约束最小的情况（即条件1）（科恩f值=0.52，P值<0.001）。与健康个体相比，患侧手三次试验之间的变异系数更大，尤其是在约束较多的条件下（条件3和4）与约束较少的条件下（条件1和2）相比（科恩f值=0.29，P值<0.05）。
这些发现对康复干预措施和器械的设计具有重要意义。特别是对于中风后个体，外部生物力学约束会增加最大自主握力的变异性，而较少的生物力学约束则会产生更稳定的表现。
