title: A Comparison of Vertical Stiffness Values Calculated from Different Measures of Center of Mass Displacement in Single-Leg Hopping.
abstract: This study assessed the agreement between Kvertcalculated from 4 different methods of estimating vertical displacement of the center of mass (COM) during single-leg hopping. Healthy participants (N = 38) completed a 10-s single-leg hopping effort on a force plate, with 3D motion of the lower limb, pelvis, and trunk captured. Derived variables were calculated for a total of 753 hop cycles using 4 methods, including: double integration of the vertical ground reaction force, law of falling bodies, a marker cluster on the sacrum, and a segmental analysis method. Bland-Altman plots demonstrated that Kvertcalculated using segmental analysis and double integration methods have a relatively small bias (0.93 kN⋅m-1) and 95% limits of agreement (-1.89 to 3.75 kN⋅m-1). In contrast, a greater bias was revealed between sacral marker cluster and segmental analysis (-2.32 kN⋅m-1), sacral marker cluster and double integration (-3.25 kN⋅m-1), and the law of falling bodies compared with all methods (17.26-20.52 kN⋅m-1). These findings suggest the segmental analysis and double integration methods can be used interchangeably for the calculation of Kvertduring single-leg hopping. The authors propose the segmental analysis method to be considered the gold standard for the calculation of Kvertduring single-leg, on-the-spot hopping.
authors.affiliation: 1 Western Sydney University.
authors.forename: Kurt L
authors.initials: KL
authors.lastname: Mudie
authors.affiliation: 1 Western Sydney University.
authors.forename: Amitabh
authors.initials: A
authors.lastname: Gupta
authors.affiliation: 1 Western Sydney University.
authors.forename: Simon
authors.initials: S
authors.lastname: Green
authors.affiliation: 2 National Institute of Advanced Industrial Science and Technology.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hobara
authors.affiliation: 1 Western Sydney University.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Clothier
mesh_terms: D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis
keywords: agreement; kinematics; kinetic; lower limb; spring-mass model