Achilles Tendon Properties in Minimalist and Traditionally Shod Runners.

Context:Tendon adapts to load through alterations in its composition and mechanical properties. Mechanical adaptation to increased load often involves increases in cross-sectional area (CSA), stiffness, and modulus. Runners exhibit these adaptations. Objective:To determine if runners wearing minimalist shoes had larger and stiffer Achilles tendons (AT) than traditionally shod runners. Design:Cross-sectional study of well-trained, traditionally and minimally shod runners. Setting:Laboratory assessment of trained runners. Participants: 23 men (11 traditional, 12 minimalist) and 8 women (6 traditional, 2 minimalist). Runners wearing minimalist shoes had 4.2 ± 1.6 y of training experience in minimalist shoes. Main Outcome Measures:The authors used diagnostic ultrasound and isokinetic dynamometry to generate a force-elongation curve and its derivatives. Results: Minimalist runners had a greater CSA: mean difference (MD) = 9.2 mm2, stiffness (MD = 268.1 N/mm), and modulus (MD = 202.9 MPa). ATs of minimalist run...