title: Influence of elastic properties of tendon structures on jump performance in humans.
abstract: The purpose of this study was to quantify the elastic properties of tendon structures in vivo and to investigate the influence of the tendon properties on jump performance with and without countermovement. Elongation of the tendon and aponeurosis of vastus lateralis muscle (dL) was directly measured by ultrasonography while subjects (n = 31) performed ramp isometric knee extension up to the voluntary maximum (MVC). The relationship between muscle force and dL was fitted to a linear regression above 50% MVC, the slope of which was defined as stiffness of the tendon structures. Statistical analysis revealed no significant difference between duplicated measurements of stiffness, with an interday reliability of r = 0.88 and a coefficient of variance of 6.1%. Although the stiffness was not significantly related to absolute jump height in either vertical jump, it was inversely correlated with the difference in jump height between the vertical jumps performed with and without countermovement. The results suggested that the stiffness of tendon structures has a favorable effect on stretch-shortening cycle exercise, possibly due to adequate storage and recoil of elastic energy.
authors.affiliation: Department of Life Science (Sports Sciences), University of Tokyo, Tokyo 153, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kubo
authors.forename: Y
authors.initials: Y
authors.lastname: Kawakami
authors.forename: T
authors.initials: T
authors.lastname: Fukunaga
mesh_terms: D000328:Adult; D004548:Elasticity; D006801:Humans; D007537:Isometric Contraction; D007717:Knee; D008297:Male; D008954:Models, Biological; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology; D013710:Tendons / Q000502:physiology*; D013718:Tensile Strength; D014463:Ultrasonography