In this lecture you will learn how tendons adapt to load, what drives changes in stiffness, why strain thresholds are important, and how muscle–tendon unit properties influence performance and injury risk. We will cover the latest research on viscoelastic mechanisms, loading variables, and the time course of adaptation, and how these principles can be applied in clinical and performance settings. A key takeaway will be how to identify and use the optimal strain range (around 4.5–6.5 percent for Achilles) to design loading programs that build tendon capacity while minimising the risk of overload.

Learning outcomes

1. 1. Describe the key factors that influence tendon stiffness and strain, and their implications for injury and performance.

2. 2. Interpret current evidence on viscoelastic mechanisms and time course of tendon adaptation.

3. 3. Apply optimal strain range principles to design safe and effective tendon loading strategies.