Abstract
The single leg squat and single leg step down are two commonly used functional tasks to assess movement patterns. It is unknown how kinematics compare between these tasks. The purpose of this study was to identify kinematic differences in the lower extremity, pelvis and trunk between the single leg squat and the step down. Fourteen healthy individuals participated in this research and performed the functional tasks while kinematic data were collected for the trunk, pelvis, and lower extremities using a motion capture system. For the single leg squat task, the participant was instructed to squat as low as possible. For the step down task, the participant was instructed to stand on top of a box, slowly lower him/herself until the non-stance heel touched the ground, and return to standing. This was done from two different heights (16cm and 24cm). The kinematics were evaluated at peak knee flexion as well as at 60° of knee flexion. Pearson correlation coefficients (r) between the angles at those two time points were also calculated to better understand the relationship between each task. The tasks resulted in kinematics differences at the knee, hip, pelvis, and trunk at both time points. The single leg squat was performed with less hip adduction (p ≤ 0.003), but more hip external rotation and knee abduction (p ≤ 0.030), than the step down tasks at 60° of knee flexion. These differences were maintained at peak knee flexion except hip external rotation was only significant in the 24cm step down task (p ≤ 0.029). While there were multiple differences between the two step heights at peak knee flexion, the only difference at 60° of knee flexion was in trunk flexion (p < 0.001). Angles at the knee and hip had a moderate to excellent correlation (r = 0.51–0.98), but less consistently so at the pelvis and trunk (r = 0.21–0.96). The differences in movement patterns between the single leg squat and the step down should be considered when selecting a single leg task for evaluation or treatment. The high correlation of knee and hip angles between the three tasks indicates that similar information about knee and hip kinematics was gained from each of these tasks, while pelvis and trunk angles were less well predicted.
Highlights
With increasing interest in injury prevention, functional “screening” tests have become more commonly used to evaluate the movement system [1]
The three single leg tasks resulted in kinematic differences at the knee, hip, pelvis and trunk (Fig 3)
The Greenhouse-Geisser correction was applied to trunk extension at peak knee flexion and to knee abduction, knee rotation, hip flexion, pelvic tilt and drop, and trunk extension at 60 ̊ of knee flexion
Summary
With increasing interest in injury prevention, functional “screening” tests have become more commonly used to evaluate the movement system [1]. For these tests, a clinician observes as the participant performs a task and notes any abnormal movement patterns. Two frequently used functional tasks for the lower extremity are the single leg squat [2,3,4,5] and the step down [6,7,8,9]. The participant lowers him/herself until the non-stance heel touches the ground and returns to upright standing on top of the box
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