47. Genzebe Dibaba / TRACK AND FIELD, DISTANCE
At 25, the latest Ethiopian star has emerged as the most dominant middle-distance runner in the world. The 5’6”, 115-lb. Dibaba—who last summer broke Yunxia Qu’s seemingly untouchable 16-year-old 1,500-meter world record and then took gold in the event at the world champs—combines off-the-charts aerobic capacity with flawless form and flowing speed.