Öйú365betÖÐÎĹÙÍø

WASHINGTON, Nov. 3, 2016 � Marathons are tough. Athletes push their bodies for miles and deal with cramping, dehydration and every runner’s worst fear: that extreme form of fatigue called “hitting the wall.� Why is distance running so difficult? With the New York City Marathon kicking off this Sunday, Reactions runs through the science of distance running: why muscles burn, how sweat cools the body and the chemistry of runner’s high. Watch the video here:  .

Subscribe to our weekly series at and follow us on Twitter .