title: Muscle performance during maximal isometric and dynamic contractions is influenced by the stiffness of the tendinous structures.
abstract: Contractile force is transmitted to the skeleton through tendons and aponeuroses, and, although it is appreciated that the mechanocharacteristics of these tissues play an important role for movement performance with respect to energy storage, the association between tendon mechanical properties and the contractile muscle output during high-force movement tasks remains elusive. The purpose of the study was to investigate the relation between the mechanical properties of the connective tissue and muscle performance in maximal isometric and dynamic muscle actions. Sixteen trained men participated in the study. The mechanical properties of the vastus lateralis tendon-aponeurosis complex were assessed by ultrasonography. Maximal isometric knee extensor force and rate of torque development (RTD) were determined. Dynamic performance was assessed by maximal squat jumps and countermovement jumps on a force plate. From the vertical ground reaction force, maximal jump height, jump power, and force-/velocity-related determinants of jump performance were obtained. RTD was positively related to the stiffness of the tendinous structures (r = 0.55, P < 0.05), indicating that tendon mechanical properties may account for up to 30% of the variance in RTD. A correlation was observed between stiffness and maximal jump height in squat jumps and countermovement jumps (r = 0.64, P < 0.05 and r = 0.55, P < 0.05). Power, force, and velocity parameters obtained during the jumps were significantly correlated to tendon stiffness. These data indicate that muscle output in high-force isometric and dynamic muscle actions is positively related to the stiffness of the tendinous structures, possibly by means of a more effective force transmission from the contractile elements to the bone.
authors.affiliation: Institute of Sports Medicine Copenhagen/Team Danmark Test Center, Bispebjerg bakke, 23, bygn 8, Bispebjerg Hospital, 2400 Copenhagen NV, Denmark. jbm01@bbh.hosp.dk
authors.forename: Jens
authors.initials: J
authors.lastname: Bojsen-Møller
authors.forename: S Peter
authors.initials: SP
authors.lastname: Magnusson
authors.forename: Lars Raundahl
authors.initials: LR
authors.lastname: Rasmussen
authors.forename: Michael
authors.initials: M
authors.lastname: Kjaer
authors.forename: Per
authors.initials: P
authors.lastname: Aagaard
mesh_terms: D000328:Adult; D004548:Elasticity; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D013314:Stress, Mechanical; D013710:Tendons / Q000000981:diagnostic imaging / Q000502:physiology*; D019415:Torque; D014463:Ultrasonography