Mark Fainaru-Wada and Lance Williams, authors of Game of Shadows, make a compelling case concerning the use of performance enhancing substances in sport. Designer steroids (such as the Clear and the Cream) or Human Growth Hormone have powered numerous athletic achievements, from baseball’s home run chases to the 2000 Olympics. After reading the book, it is difficult to take any sporting record seriously. Where is the line? Where do vitamins or natural products like flaxseed oil end and controlled substances like steroids or H.G.H. begin? Lance Armstrong’s decision to devote his entire career to train for the Tour de France …