Symmetry of bilateral lower limb during sit-to-stand and stand-to-sit tasks in stroke hemiplegia patients

Abstract

Abstract Background Stroke patients with hemiplegia are at increased risk of falls during sit-to-stand (Si-St) and stand-to-sit (St-Si) tasks. Maintaining bilateral lower limb symmetry during those movements can reduce the incidence of falls. This study aimed to investigate bilateral lower limb symmetries during Si-St and St-Si tasks in stroke patients compared healthy controls.Methods Thirteen stroke patients with hemiplegia and thirteen healthy controls were recruited. The subjects were asked to stand up and sit down naturally from backless and armless chairs. Five Si-St and St-Si trials were collected for each subject. Kinematics and kinetics were calculated using the inverse kinematics and inverse dynamics tools of OpenSim. The Symmetry Index (SI) was used to quantify the symmetries of both sides. The 10% of SI was set as the asymmetry threshold.Results The results showed that there were significant bilateral differences (P < 0.05) in the time to reach the maximum hip and knee moment during the Si-St task in the stroke patients. All spatial-temporal characteristics in the stroke group were greater than (P < 0.05) those in the healthy group. Bilateral ankle angle showed asymmetry during the Si-St and St-Si tasks in stroke group, and the mean ankle angle SI was greater than (P < 0.05) that of the healthy group. The stroke group showed asymmetry for bilateral hip, knee, and ankle moment, vertical ground reaction force, and medial-lateral center of pressure (ML-COP) during the entire Si-St and St-Si movements, and their average SI were significantly different (P < 0.05) from those of the healthy group except the ML-COP.Conclusions Stroke patients demonstrated significant bilateral asymmetry during Si-St and St-Si tasks, which may increase the risk of falls. Targeted lower-limb strength training, especially on the affected side, may improve symmetry and reduce the risk of falls. These findings can inform the development of rehabilitation interventions for stroke patients with hemiplegia.