Phase-Specific Biomechanical Characterization of Upper Limb Movements in Stroke.

Area of Science:

• Biomechanics
• Neurorehabilitation
• Motor Control

Background:

• Stroke frequently causes lasting upper limb dysfunction, impacting daily activities.
• Objective biomechanical markers for precise stroke-related motor impairment assessment are limited.
• The hand-to-mouth (HTM) task is crucial for evaluating upper limb function post-stroke.

Purpose of the Study:

• To characterize phase-specific impairments in energy output, torque stability, and muscle coordination during the HTM task in stroke survivors.
• To assess the potential of these phase-specific biomechanical metrics for improving rehabilitation evaluation.
• To explore the utility of machine learning models for classifying stroke patients based on these metrics.

Main Methods:

• Collected motion data from 20 stroke patients and 20 healthy controls using wearable electromyography and inertial measurement units.
• Applied a musculoskeletal model to compute joint torque, mechanical work, torque smoothness, and a novel torque-based co-contraction index across four movement subphases.
• Developed machine learning models using selected phase-specific dynamic features for group classification.

Main Results:

• Phase-specific biomechanical metrics significantly correlated with clinical motor impairment scores, validating their clinical relevance.
• Stroke patients exhibited reduced output capacity, increased torque fluctuations, and abnormal co-contraction patterns that differed across movement subphases.
• A quadratic support vector machine model achieved 84.6% accuracy and 0.853 AUC, outperforming models using whole-task features.

Conclusions:

• Phase-specific biomechanical features effectively capture subtle neuromuscular deficits in stroke survivors during the HTM task.
• These detailed movement analyses provide sensitive and objective indicators for assessing motor impairment.
• Phase-specific biomechanics hold significant potential for informing individualized stroke rehabilitation assessment and treatment planning.