and maintain a reasonable pace, you still only have about 2,000 calories worth of glycogen stored in your muscles – enough to get most runners to about mile 18 or 20," he says. "As glycogen reserves are used up and fatty acid metabolism increases, your heart
GETTY IMAGES Better sleep. That's all that could be standing between you and a new PB. Too good to be true? Not according to Mara Yamauchi, who set a new marathon PB (2:25:03) at the International Women's Marathon in Tokyo in November. "Sleep is one
