The biomechanics of hemiplegic stroke survivors′ upper limb motor function

Objective To document the kinematics of upper-limb motor dysfunction among hemiplegic stroke survivors. Methods Thirty-nine stroke survivors with hemiplegia were selected as the experimental group, while twenty-five healthy counterparts were chosen as the control group. Reaching movements performed in the sagittal plane were divided into an anteflexion phase and a holding phase. Three-dimensional kinematics data were captured using a micro-sensor motion capture system, and surface electromyograms (sEMGs) were recorded synchronously from the upper trapezius (UT), the anterior (AD) and middle (MD) segments of the deltoid, the biceps brachii (BB) and the triceps brachii (TB). The torso twist (TTD), the range of motion (ROM) of the shoulder, movement velocity (MV), isotonic instability degree (IT) and isometric instability degree (IM) were extracted. Integrated electromyography (iEMG) and work ratios were chosen as indicators to compare the two groups. The experimental group′s kinematic indicators were correlated with that group′s sEMG parameters. Results The average TTD, IT and IM in the experimental group were significantly larger than those of the control group, while the ROM of the shoulder and the MV were significantly smaller. During the anteflexion phase, the average iEMG from the UT in the experimental group was significantly larger than that of the control group, while the average iEMGs from their AD and TB were significantly smaller; The BB/TB work ratios in the experimental group were significantly greater than those of the control group, while the AD/UT and AD/MD ratios were significantly smaller. The results during the holding phase were similar. In the experimental group, torso twist was found to be positively correlated with the iEMG of the UT, and the ROM of the shoulder and movement velocity were also positively correlated with the iEMG of the AD. Conclusions Kinematics variables and sEMG features can be used to evaluate the motor dysfunction of hemiplegic stroke patients′ affected upper limbs quantitatively and provide guidance for rehabilitation. Key words: Hemiplegia; Stroke; Reaching; Kinematics; Electromyography