title: Determinant of leg stiffness during hopping is frequency-dependent.
abstract: Identifying the major determinant of leg stiffness during hopping would be helpful in the development of more effective training methods. Despite the fact that overall leg stiffness depends on a combination of the joint stiffness, it is unclear how the major determinants of leg stiffness are influenced by hopping frequency. The purpose of this study was to identify the major determinant of leg stiffness over a wide range of hopping frequencies. Fourteen well-trained male athletes performed in a place hopping on two legs, at three frequencies (1.5, 2.2 and 3.0 Hz). We determined leg and joint stiffness of the hip, knee and ankle from kinetic and kinematic data. Multiple linear regression analysis revealed that knee stiffness could explain more of the variance of leg stiffness than could ankle or hip stiffness at 1.5 Hz hopping. Further, only ankle stiffness was significantly correlated with leg stiffness at both 2.2 and 3.0 Hz, and the standardized regression coefficient of ankle stiffness was higher than that of knee and hip stiffness. The results of the present study suggest that the major determinant of leg stiffness during hopping switches from knee stiffness to ankle stiffness when the hopping frequency is increased.
authors.affiliation: Graduate School of Human Sciences, Waseda University, Tokorozawa, Saitama, Japan. h.hobara@gmail.com
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hobara
authors.forename: Koh
authors.initials: K
authors.lastname: Inoue
authors.forename: Kohei
authors.initials: K
authors.lastname: Omuro
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Muraoka
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kanosue
mesh_terms: D000054:Acceleration; D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena / Q000502:physiology*; D004548:Elasticity / Q000502:physiology; D005080:Exercise Test; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000502:physiology; D007866:Leg / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult