title: Dynamically adjustable foot-ground contact model to estimate ground reaction force during walking and running.
abstract: Human dynamic models have been used to estimate joint kinetics during various activities. Kinetics estimation is in demand in sports and clinical applications where data on external forces, such as the ground reaction force (GRF), are not available. The purpose of this study was to estimate the GRF during gait by utilizing distance- and velocity-dependent force models between the foot and ground in an inverse-dynamics-based optimization. Ten males were tested as they walked at four different speeds on a force plate-embedded treadmill system. The full-GRF model whose foot-ground reaction elements were dynamically adjusted according to vertical displacement and anterior-posterior speed between the foot and ground was implemented in a full-body skeletal model. The model estimated the vertical and shear forces of the GRF from body kinematics. The shear-GRF model with dynamically adjustable shear reaction elements according to the input vertical force was also implemented in the foot of a full-body skeletal model. Shear forces of the GRF were estimated from body kinematics, vertical GRF, and center of pressure. The estimated full GRF had the lowest root mean square (RMS) errors at the slow walking speed (1.0m/s) with 4.2, 1.3, and 5.7% BW for anterior-posterior, medial-lateral, and vertical forces, respectively. The estimated shear forces were not significantly different between the full-GRF and shear-GRF models, but the RMS errors of the estimated knee joint kinetics were significantly lower for the shear-GRF model. Providing COP and vertical GRF with sensors, such as an insole-type pressure mat, can help estimate shear forces of the GRF and increase accuracy for estimation of joint kinetics.
authors.affiliation: School of Mechanical Engineering, Chung-Ang University, Seoul, Republic of Korea.
authors.forename: Yihwan
authors.initials: Y
authors.lastname: Jung
authors.affiliation: AnyBody Technology A/S, Aalborg, Denmark.
authors.forename: Moonki
authors.initials: M
authors.lastname: Jung
authors.affiliation: Korea National Sport University, Seoul, Republic of Korea.
authors.forename: Jiseon
authors.initials: J
authors.lastname: Ryu
authors.affiliation: Korea National Sport University, Seoul, Republic of Korea.
authors.forename: Sukhoon
authors.initials: S
authors.lastname: Yoon
authors.affiliation: Korea National Sport University, Seoul, Republic of Korea.
authors.forename: Sang-Kyoon
authors.initials: SK
authors.lastname: Park
authors.affiliation: School of Mechanical Engineering, Chung-Ang University, Seoul, Republic of Korea. Electronic address: skoo@cau.ac.kr.
authors.forename: Seungbum
authors.initials: S
authors.lastname: Koo
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D001696:Biomechanical Phenomena; D005080:Exercise Test; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008297:Male; D008954:Models, Biological; D011312:Pressure; D011930:Reaction Time / Q000502:physiology*; D012420:Running / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Contact model; Dynamic adjustment; Gait; Ground reaction force; Skeletal simulation