While tendinopathy is common and increases with age, current treatments are limited and ineffective. Development of new treatment strategies is challenging, as the factors predisposing specific tendons to tendinopathy are poorly understood. However, we have evidence suggesting that the interfascicular matrix (IFM) is critical for facilitating tendon extension and recoil, and thus maintaining tendon fatigue resistance and health. This is particularly important in energy storing tendons, which experience high strains during use and are prone to tendinopathy. Further, we have evidence that IFM properties are altered in aged individuals, a group in which tendinopathy is widespread. We therefore hypothesise that energy storing tendons have a specialised IFM, enabling them to sustain large repetitive strains without damage. A less specialised IFM or age-related deterioration reduces IFM extensibility and elasticity, predisposing certain tendons to chronic tendinopathy. We will investigate IFM structure in different tendon types from different aged individuals, and correlate this with IFM and tendon fatigue and failure properties. This will allow us to identify the IFM components key in maintaining tendon function and preventing tendinopathy, and determine why specific tendons and individuals are prone to injury. This understanding will aid the development of novel repair and rehabilitation strategies for tendinopathy.