Single-Leg Squat Delicacies-The Position of the Nonstance Limb is an Important Consideration

Context: The single-leg squat task is often used as a rehabilitative exercise or as a screening tool for the functional movement of the lower limb. Objective: To establish the effect of 3 different positions of the nonstance leg on 3-dimensional kinematics, muscle activity, and center of mass displacement during a single-leg squat. Design: Within-subjects, repeated-measures design. Setting: Movement analysis laboratory. Participants: A total of 10 participants, aged 28.2 (4.42) years performed 3 squats to 60 degrees of knee flexion with the nonstance (1) hip at 90 degrees flexion and knee at 90 degrees flexion, (2) hip at 30 degrees flexion with the knee fully extended, or (3) hip in neutral/0 degrees and the knee flexed to 90 degrees. Main Outcome Measures: Trunk, hip, knee and ankle joint angles, and center of mass displacement were recorded with inertial sensors while muscle activity was captured through wireless electromyography. Results: Most trunk flexion (21.38 degrees [18.43 degrees]) occurred with the nonstance hip at 90 degrees and most flexion of the stance hip (23.10 degrees [6.60 degrees]) occurred with the nonstance hip at 0 degrees. Biceps femoris activity in the 90 degrees squat was 40% more than in the 0 degrees squat, whereas rectus femoris activity in the 0 degrees squat was 29% more than in the 90 degrees squat. Conclusion: The position of the nonstance limb should be standardized when the single-leg squat is used for assessment and be adapted to the aim when used in rehabilitation.