Analysis of center of gravity velocity using estimated lower limb muscle forces during squatting

Abstract

This study proposes a squatting model that describes the relation between the center of gravity velocity and lower limb muscle forces that contribute to hip and knee flexion-extension and ankle dorsi-plantar flexion during squatting. Squatting exercises are experimentally monitored using a 3D motion analysis system and two force plates. Participants perform a squatting exercise with their feet shoulder-width apart without using a weight such as a barbell. Simulations using the musculoskeletal model calculate the lower limb muscle forces based on measured marker positions and floor reaction forces. The squatting model parameters are determined by a Kalman filter using the experimentally obtained center of gravity velocity, and lower limb muscle forces estimated by the simulations. The analysis results quantitatively demonstrate the contribution of each muscle to the center of gravity velocity during squatting. To verify the model accuracy, the root mean squared errors are calculated by using the center of gravity velocity that is obtained by the squatting model and the 3D motion analysis system. The root mean squared errors indicate that the contribution of each muscle to the center of gravity velocity may have differed between participants and between trials. The proposed method is expected to be utilized to evaluate the relation between the exercise velocity and muscle forces that is different among individual.