What Is the Relationship Between Ankle Dorsiflexion Range of Motion and Squat/Landing Depth? A Computer Simulation Study

Background/Objectives: Decreased ankle dorsiflexion range of motion (DFROM) is thought to negatively impact lower extremity flexion patterns, which use the coordinated flexion of the hips, knees, and ankles in activities such as the eccentric phase of a squat and landing from a jump. However, the results from experiments using human subjects to ascertain the relationship between DFROM and the mechanics of these flexion patterns are not clear. The purpose of this study was to elucidate the relationship between DFROM and the depth of the flexion pattern via computer simulations. Methods: The human body was represented as a planar model with four segments connected by three revolute joints. The ankle, knee, and hip angles that feasibly achieve three depths (25%, 50%, and 75% of the model’s leg length) were determined, and solutions that did not satisfy the constraints to create a realistic flexion pattern were removed. Results: There were a large number of solutions at each depth, but the number of solutions decreased with increasing depth. For a given depth, increasing DFROM required an increase in knee flexion and a decrease in hip flexion. Increasing depth required an increase in all three flexion angles. The relationships between joint angles and depth and between joint angles for a given depth were significant, but the standard errors of the estimate and the coefficients of variation were large. Conclusions: The relationship between DFROM and lower extremity flexion depth is obscured by the multiple combinations of ankle, knee, and hip angles that can achieve a particular depth and their interdependencies.