Positron emission tomography (PET) represents the most advanced scintigraphic imaging technology in humans, which allows non-invasive studies of metabolism and perfusion in vivo. PET has been employed for research of skeletal muscle physiology and pathophysiology as well as for studies of effects of training and exercise. PET is a functional research method, being a powerful tool, especially in studies of skeletal muscle perfusion in humans. It also provides a potential tool for studies of tendon physiology. In this review examples of recent studies of skeletal muscle in athletes and during exercise are given and potential applications of PET in the field of tendon studies discussed.