Tissue adaptation timelines to mechanical loading

Connective tissues adapt to loading more slowly than the cardiovascular system and muscle. Tendon shows initial stiffness and collagen-synthesis changes over a few weeks, with substantial remodelling over 3 to 6 months and full turnover far longer; bone remodels over weeks to months. Because the cardiovascular system improves fastest, runners can outrun the readiness of their tendons and bones, and a rapid rise in load is the classic precursor to stress fractures and tendon overuse injury in distance runners. Moderate (synthesis of loading and stress-fracture literature).