title: Vertical stiffness asymmetries during drop jumping are related to ankle stiffness asymmetries.
abstract: Asymmetry in vertical stiffness has been associated with increased injury incidence and impaired performance. The determinants of vertical stiffness asymmetry have not been previously investigated. Eighteen healthy men performed three unilateral drop jumps during which vertical stiffness and joint stiffness of the ankle and knee were calculated. Reactive strength index was also determined during the jumps using the ratio of flight time to ground contact time. "Moderate" differences in vertical stiffness (t17= 5.49; P < 0.001), "small" differences in center of mass displacement (t17= -2.19; P = 0.043), and "trivial" differences in ankle stiffness (t17= 2.68; P = 0.016) were observed between stiff and compliant limbs. A model including ankle stiffness and reactive strength index symmetry angles explained 79% of the variance in vertical stiffness asymmetry (R2= 0.79; P < 0.001). None of the symmetry angles were correlated to jump height or reactive strength index. Results suggest that asymmetries in ankle stiffness may play an important role in modulating vertical stiffness asymmetry in recreationally trained men.
authors.affiliation: Institute of Sports Science and Physical Activity Research, University of Bedfordshire, Bedford, UK.
authors.forename: S J
authors.identifier: http://orcid.org/0000-0002-6637-5310
authors.initials: SJ
authors.lastname: Maloney
authors.affiliation: Institute of Sports Science and Physical Activity Research, University of Bedfordshire, Bedford, UK.
authors.forename: J
authors.initials: J
authors.lastname: Richards
authors.affiliation: Institute of Sports Science and Physical Activity Research, University of Bedfordshire, Bedford, UK.
authors.forename: D G D
authors.initials: DGD
authors.lastname: Nixon
authors.affiliation: Institute of Sports Science and Physical Activity Research, University of Bedfordshire, Bedford, UK.
authors.forename: L J
authors.initials: LJ
authors.lastname: Harvey
authors.affiliation: Institute of Sports Science and Physical Activity Research, University of Bedfordshire, Bedford, UK.
authors.forename: I M
authors.initials: IM
authors.lastname: Fletcher
mesh_terms: D000293:Adolescent; D000328:Adult; D000843:Ankle Joint / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D005080:Exercise Test; D006801:Humans; D007592:Joint Diseases / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D016059:Range of Motion, Articular; D063996:Warm-Up Exercise; D055815:Young Adult
keywords: Leg-spring behavior; center of mass displacement; spring-mass model; torsional spring model