I'd have to say Cain Velasquez is the UFC fighter most guilty of overtraining. His litany of injuries from his overtrained muscles, tendons and joints which apparently never get ample time for recuperation and growth are the most obvious sign he displays of overtraining. Have you ever seen how hard he works out in the gym? Anyone who works out that hard and has that type of body to show for it doesn't grasp the concept that training only stimulates muscular growth to occur. The actual growth only can take place during an ample period of rest.