Biomechanical Comparison of Warm-Up Strategies for Preventing Achilles Tendon Injury

Achilles tendon (AT) is the biggest and strongest tendon in human body. It connects with Gastrocnemius, soles muscles and calcaneus bone. The elastic properties of the human Achilles tendon are crucial for locomotion; however, in vitro tests suggest that repeated cyclic contractions lead to tendon fatigue and increase risk of rupture. Despite many risk factors being identified for Achilles injuries, understanding of the causation of the injury and the best strategy of its injury prevention remains unclear. The purpose of this study is to determine the influences of different warm-up methods and evaluate biomechanical risk factors associated with Achilles tendon injuries in landing. This study plans to use freehand ultrasound scan to determine whether the free Achilles tendon (calcaneus to soleus) or the gastrocnemius tendon (calcaneus to gastrocnemius) demonstrated tendon fatigue after running exercise or heated by a warm pad. Participants underwent ultrasound scans of the Achilles tendon during isometric contractions at various ankle torque levels before and after running or heating warm-up only. The length, cross-sectional area and blood flow of the free Achilles tendon will be compared among groups with control, running and warmed. While the tendon was shown to lengthen, the lack of change in stiffness suggests the tendon exhibited mechanical creep rather than fatigue. In addition, finite element analyses of human ankle will be used to evaluate the risk of rupture during jump landing after warm-up treatment.