Soft skeletal tissue such as tendons adapt to their local mechanical environment. Mechanical loading has therefore been shown to yield positive results during the repair phase of ruptured tendons. Previous studies in our group have shown that in rats during Achilles tendon healing (after a complete tendon transaction) in vivo unloading resulted in higher collagen content, but a less organized and oriented structure, compared to normally loaded tendons. From clinical studies, intriguing new evidence was found that shows mineral fragments forming within the healing and intact tendons. The process through which these mineral fragments form is not yet well understood, and neither is their effect on mechanical loading. The research primarily involves the characterization of tissue composition, structure, and mechanical function at the different length scales, ranging from nano-scale up to the organ level.