Bilateral lower limb symmetry during sit-to-stand and stand-to-sit tasks in stroke patients with hemiplegia

 With NO fix suggested for this problem, this was totally fucking useless for survivors!

Bilateral lower limb symmetry during sit-to-stand and stand-to-sit tasks in stroke patients with hemiplegia

Meijin Hou^1,2†Jian He^3†Dongwei Liu^4*Chenyi Guo⁵Ye Ma^3*Xiaobo Luo⁶

• ¹National Joint Engineering Research Centre of Rehabilitation Medicine Technology, Fujian University of Traditional Chinese Medicine, Fuzhou, China
• ²Key Laboratory of Orthopaedics and Traumatology of Traditional Chinese Medicine and Rehabilitation (Fujian University of TCM), Ministry of Education, Fuzhou, China
• ³Research Academy of Grand Health, Faculty of Sports Sciences, Ningbo University, Ningbo, China
• ⁴School of Information Technology and Artificial Intelligence, Zhejiang University of Finance and Economics, Hangzhou, China
• ⁵Department of Electronic Engineering, Tsinghua University, Beijing, China
• ⁶Department of Orthopedics, The 4th Medical Center of the Chinese PLA General Hospital, Beijing, China

Introduction: Stroke patients with hemiplegia are at an increased risk of falling during sit-to-stand (Si-St) and stand-to-sit (St-Si) tasks, partly due to impaired bilateral lower limb symmetry. Maintaining symmetrical movement between the limbs in these tasks can help reduce fall incidence.

Method: This study aimed to investigate bilateral lower limb symmetry during Si-St and St-Si tasks in stroke patients with hemiplegia to compare their performance with healthy controls. Thirteen stroke patients and 13 healthy controls participated in the study. Participants were instructed to perform the 30-s chair stand test at their self-selected pace. Kinematic and kinetic parameters were calculated using OpenSim's inverse kinematics and inverse dynamics tools. Bilateral symmetry was quantified using the symmetry index (SI), with an asymmetry threshold set at 10%.

Results: The stroke group exhibited significantly greater lower limb asymmetry in both kinematic and kinetic parameters during Si-St and St-Si tasks compared to the healthy controls, with the kinetic parameters being more pronounced. In the stroke group, notable bilateral asymmetry (SI > 10%) was observed in the ankle joint angle (P < 0.05) during both tasks. Furthermore, severe asymmetry (SI > 30%) was identified joint moments across all lower limb joints, vertical ground reaction forces, and medial-lateral center of pressure.

Discussion: These findings highlight the need for targeted rehabilitation programs focusing on improving strength, coordination, and balance. Close monitoring of SI values, particularly for kinetic parameters, is recommended to guide and evaluate the effectiveness of these interventions.

1 Introduction

Standing up from a seated position and sitting down from an upright posture, commonly referred to as Sit-to-Stand (Si-St) and Stand-to-Sit (St-Si), are fundamental activities of daily living for humans (1, 2). These movements are frequently performed, with estimates suggesting they occur more than 50 times per day (3, 4). Si-St and St-Si tasks are prerequisite for walking, bed-chair transfers, and maintaining living independence (5, 6). Over recent decades, many studies have examined the biomechanical characteristics of Si-St and St-Si movements in younger and healthy elderly subjects (7–9). These studies have provided normative data on movement patterns and functional performance, which can serve as benchmarks for assessing individuals with movement impairments, such as those following a stroke.

Stroke patients often present various motor deficits, including spasticity, muscle weakness, or hemiplegia (10, 11). These impairments impede stroke patients from performing Si-St and St-Si tasks (12). Instability in the lower limbs, arising from abnormal muscle synergies and weakness, further complicates the execution of these movements (13). To compensate, stroke patients frequently modify their movement strategies (14, 15). These adaptations may include altering chair height, increasing trunk flexion, or changing foot positioning prior to movement (12, 13, 16). Ensuring the safety of stroke patients during Si-St and St-Si tasks is critical, with many relying on their non-paretic leg due to functional limitations on the paretic side (13). However, this compensation can increase the risk of falling (17). Maintaining symmetry between the lower limbs may reduce fall risk during these tasks (18).

While several studies have explored the biomechanical characteristics of Si-St and St-Si tasks in stroke patients using kinematic, kinetic or surface electromyography (EMG) analyses (19–22), relatively few have specifically focused on bilateral lower limb symmetry. (14) identified asymmetry in knee extensor moments during Si-St and St-Si tasks in stroke patients, which was linked to knee extensor weakness and the imbalances in muscle strength on the paretic side (14). Foot position also plays a role in symmetry, with initial positioning affecting vertical ground reaction force (VGRF) symmetry between the limbs (23). For instance, positioning the non-paretic foot behind increases VGRF asymmetry during Si-St or St-Si tasks (12), while positioning the paretic foot behind decrease this asymmetry (24). However, existing research has largely foucued on VGRF, peak joint moments, or symmetry during isolated Si-St task.

Although biomechanical differences in Si-St and St-Si tasks between stroke patients and healthy subjects have identified, few have focused on bilateral lower limb symmetry differences. Understanding these asymmetry is essential for developing effective rehabilitation protocols aim at preventing falls in stroke patients, thereby supporting the recovery of their independence in daily activities. Therefore, this study aims to investigate the bilateral symmetry in both lower limb kinematic and kinetic measures during Si-St and St-Si tasks in stroke patients, with comparison made to healthy controls. We hypothesized that stroke patients with hemiplegia exhibit pronounced bilateral asymmetries in kinematic and kinetic parameters during both Si-St and St-Si tasks, with the asymmetries being more pronounced in the kinetic parameters.

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