Comparison of Trunk and Leg Sway During Single Leg Stance

Abstract

Background: Singe leg stance (SLS) is a commonly used assessment of balance, but there is lack of knowledge of how different body part may be involved in the SLS maintenance. The purpose of this study was to utilize small inertial measurement unit (IMUs) to investigate how different body segments respond during static SLS.Methods: This was a cross-sectional study with two IMU sensors utilized to compare two body locations. The sensors were placed at two flat areas -on L4-5 spinous processes for the trunk segment, and at the left popliteal fossa immediately below the knee joint line for the leg segment. All subjects recruited had the left leg as the nondominant leg. These subjects were asked to perform a SLS on a flat hard surface with their non-dominant leg. Subjects held this position for 30 seconds, while data of body sway parameters (range, angular velocity, and acceleration) were recorded and transmitted wirelessly to a computer for storage and analysis.Results: Compared with the leg sway, the trunk displaying a larger range in faster speed and greater acceleration than the leg primarily in the sagittal (anterior-posterior) direction (all p <.05). Also, quicker speed in axial plane, and greater acceleration in both axial and frontal planes were observed in trunk than in leg (p <.05); but no obvious differences were identified in range of sway in these two planes (P>.05). Conclusions.During SLS on the non-dominant left leg, the whole body stays more toward left in frontal and axial planes but sways more in sagittal plane. These data may provide baseline information for future studies in more body segments and in elderly people as well.