Open Access

After complete Achilles tendon rupture (ATR), long-term deficits in force generation of the triceps surae muscle-tendon-unit (MTU) and functional limitations have been described. Surgical reconstruction and early functional treatment of Achilles tendon rupture can lead to a lengthened Achilles tendon causing a lack of tension in the triceps surae MTU. As a consequence, an excessive sarcomere overlap forces the muscle fascicles to operate in a disadvantage length for force generation. In order to restore function, we hypothesize that a re-organization of in-series sarcomeres may compensate for changes in work constraints imposed by the longer tendon. Tendon stiffness has already been described to increase after ATR, which might also be an actuator to compensate for tendon lengthening. To clarify the mentioned deficits, this study investigates the mechanical and morphological properties of the triceps surae MTU post rupture and their effect on force generation.

The purpose of this study was to analyse stiffness in the mechanical system of the world’s elite high jumpers. Seven male elite high jump athletes (personal best 2.24 m ± 0.06 m) were filmed with 19 Infrared-High-Speed-Cameras during jumping. Kinetics were captured with a force plate. It was found that a different leg and joint stiffness during takeoff enables nearly the same jumping height. For example, a typical power jumper with a leg stiffness of 543.6 N m-1 kg-1 reached 2.13 m, while a typical speed jumper with a leg stiffness of 1133.5 N m-1 kg-1 reached a comparable height of 2.12 m. Therefore, it seems that sports performance in single leg jumping is not limited by athlete’s leg and joint stiffness in a small group of male elite high jumpers.