Runner's Blood.

Magnus, a delusional athlete, is consumed with perfecting his physical performance. Every morning he endures a rigorous routine to enhance his endurance. While running in a park one morning Magnus is effortlessly outperformed by a runner, Ashton. Magnus is awestruck by Ashton's natural capabilities and hires Ashton to be his personal trainer. Ashton recommends Magnus vigorous workout and diet changes to amplify his performance. Despite Magnus matching Ashton's intense training, his endurance does not improve. Upon realizing Ashton is genetically gifted, Magnus implores disturbing methods to meet Ashton's perfection.