Biomechanical analysis of movement time and center of pressure during single-leg and double-leg sit-to-stand in healthy adults
Authors:   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand., Inthana Naphat , Orhirun Thanakorn ,   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand., Jankaew Amornthep ,   Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan., Chamnongkich Samatchai ,   Department of Physical Therapy, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai Province, Thailand.
Published: February 2025

Background: The sit-to-stand (STS) task is a fundamental movement integral to daily activities and is widely used as a functional test to evaluate lower limb strength, balance, and postural control across various populations. However, limited literature provides biomechanical analysis comparisons between traditional double-leg STS tasks and single-leg STS tasks.

Objective: This study aimed to compare muscle strength, movement times, and center of pressure (COP) variables across three STS conditions: single-leg STS on the dominant limb, single-leg STS on the non-dominant limb, and double-leg STS.

Materials and methods: Twenty healthy participants (10 males and 10 females; 21.60±1.14 years old) participated in a cross-sectional study. Maximal voluntary isometric contraction of the knee extensors and hip abductors was assessed for both the dominant and non-dominant limbs. Participants performed the three STS testing conditions on the Zebris FDM pressure plate. Movement time and COP outcome variables (sway area, total path length, velocity, and path length in anteroposterior and mediolateral directions) were recorded and analyzed across the three STS tasks. A paired t-test was used to compare the means of the primary outcome variables within groups. A one-way repeated measures ANOVA was conducted to assess outcome differences among the testing conditions, with significance set at p<0.05.

Results: Findings indicated no significant difference in knee extensor or hip abductor muscle strength between the dominant and non-dominant limbs. Movement times for the single-leg STS tasks on both limbs were significantly longer than for the double- leg STS task (p<0.001), with no difference between dominant and nondominant limbs. Additionally, COP variables (sway area, total path length, mean velocity, and mediolateral path length) were significantly lower in the single-leg STS tasks on both limbs compared to the double-leg STS task (all p><0.001), with no differences observed between dominant and non-dominant limbs.><0.001), with no difference between dominant and nondominant limbs. Additionally, COP variables (sway area, total path length, mean velocity, and mediolateral path length) were significantly lower in the single-leg STS tasks on both limbs compared to the double-leg STS task (all p<0.001), with no differences observed between dominant and non-dominant limbs.

Conclusion: Compared to double-leg STS tasks, single-leg STS tasks are associated with longer movement times and reduced COP measures. These findings provide preliminary reference values for STS tasks and suggest that the single-leg STS may serve as a potentially useful tool for assessing balance impairments and functional mobility. Further research is required to validate its sensitivity in pathological populations.