Achilles tendon stiffness


Accurate measurements of tendon mechanics are necessary for biomechanists when trying to identify injury risk factors, optimise athletic performance and develop musculoskeletal models. Measuring Achilles tendon (AT) mechanics dynamically is now possible by combining motion capture and ultrasound (US). The aim of this study was to quantify sources of error when measuring AT length using motion capture and US, and establish their effect on calculated strain values. Errors in AT insertion tracking and data synchronisation caused differences in AT length and moment arm of 5.3 ± 1.1 mm and 11.2 ± 0.9 mm, respectively; this decreased calculated AT peak strain from 11.6 ± 3.5% to 5.4 ± 2.5%. These differences could significantly impact a researcher‘s interpretation of the effects of footwear, technique, and specific kinematics on AT loading.
Listed In: Biomechanics, Sports Science

Muscle and tendon adaptation in young and older adult athletes: A combined longitudinal and cross sectional investigation

This study examined triceps surae muscle strength and tendon stiffness in young adult elite sprinters and jumpers over one season, in order to detect potential discordance between muscle and tendon adaptation due to training. Furthermore, we examined the effect of habitual training on triceps surae muscle-tendon unit (MTU) mechanical properties in young and older athletes, using a cross-sectional design. Eleven healthy younger elite sprinters and jumpers, 12 master athletes, 12 recreationally active young controls and one young elite athlete, 10 months after unilateral Achilles tendon reconstruction participated. All young athletes underwent regular measurements over one season. Triceps surae muscle strength and tendon stiffness of both legs were analysed using dynamometry and ultrasonography synchronously. Within one season, similar patterns of relative changes in muscle strength and tendon stiffness were seen in the young elite athletes. For the tendon reconstruction athlete, the affected leg showed no increases in muscle strength or tendon stiffness over one season, and remarkably lower muscle strength but similar tendon stiffness compared to the non-affected leg. Healthy young elite athletes showed higher muscle strength and tendon stiffness than both other subject groups, with no differences between young controls and master athletes. Our results provide evidence for training-induced concordant adaptation of muscle and tendon over one season within healthy young elite athletes. Achilles tendon rupture and reconstruction may be a major risk factor for irreversible discordance within the triceps surae MTU. Finally, habitual athletics training over the lifespan may effectively counteract age-related decreases in muscle strength and tendon stiffness.
Listed In: Biomechanics, Sports Science