In vivo passive mechanical properties estimation of Achilles tendon using ultrasound

Erect Position as the Alternative Technique in Achilles Tendon US: Comparison with Prone Position

“…The normal retrocalcaneal caudex should produce a radiolucent anterior to the distal fibers of insertion of the Achilles tendon which extends at least 2 mm below the superior surface of the calcaneus [3,4,10].…”

Effect of a 10-Week Stretching Program of the Triceps Surae Muscle Architecture and Tendon Mechanical Properties

“…The calculation of the tangent modulus (E t ) is detailed in Oliveira et al [27] and is defined as the local derivative of the true axial stress (σ true ) relative to the true axial strain (ε true ) [28,30]. This approach is more appropriate to describe large deformations and non-linear mechanical behavior typically observed in axial tendon experiments [32].…”

“…3. The subsequent methodology used to estimate L T and L M as a function of ankle angle was described in Oliveira et al [27]. The curves were divided into 100 equally spaced strain intervals for normalization purposes.…”

“…Regarding the triceps surae muscle-tendon unit, ultrasound (US) imaging allows investigating the gastrocnemius muscles architecture, such as the fascicle length (FL) and pennation angle (PA), in response to stretching programs [13,25]. In conjunction with dynamometry, US can be applied to assess the tendon stiffness [15,16] and material properties such as the modulus of elasticity [2,33] and tangent modulus [27], which is the derivative of the stress curve relative to strain. For muscle architecture, some studies showed no changes of the gastrocnemius FL [3,13,25] and pennation angle [13] after a stretching program up to 6 weeks, suggesting that muscle structure was not changed.…”

“…It is suggested that the tendon mechanical adaptations occur after a threshold of cumulative strain [1]. Tendon mechanical properties, as the modulus of elasticity [1,33] and tangent modulus [27] are more conceptually robust approaches to study tendon material adaptation to mechanical stimuli, since the intrinsic material properties are isolated from the variations of the tendon and joint geometry. Remains the question if tendon adaptations could be observable after a longer term static stretching program.…”