This chapter describes David Behm’s history as a Canadian football player who sought to reach the professional level. However, he lacked the essential running speed of a professional football running back. Based on the literature from the 1970s, he trained his flexibility aggressively, in order to increase his running speed (improve sprint performance by increasing stride length and decreasing resistance to limb movement), and decrease injuries. His extensive flexibility training did not seem to positively impact either variable. Was the research or common knowledge about stretching and flexibility incorrect?