Justin Gatlin signaled his victory in the 100-meter final at the U.S. Olympic trials in June, covering the distance in 9.80 seconds. Gatlin, 30, is competing again after serving a four-year suspension from the U.S. Anti-Doping Agency for testing positive for steroids. (Associated Press)

Justin Gatlin signaled his victory in the 100-meter final at the U.S. Olympic trials in June, covering the distance in 9.80 seconds. Gatlin, 30, is competing again after serving a four-year suspension from the U.S. Anti-Doping Agency for testing positive for steroids. (Associated Press)