Marathoners are the NASCAR racers of running, trying to keep their radiators from boiling over during 42 kilometers and more than two hours on the road. Sprinters don¡¯t have the same worries about heat and humidity. They are dragsters, generating massive power and searing speed then pulling the parachute in seconds.

The men¡¯s and women¡¯s Olympic marathons will be held in Sapporo, some 800 kilometers north of Tokyo, to escape the smothering blanket that is Tokyo¡¯s average August weather: a high of 31 degrees Celsius, low of 25; humidity at 73%; a ¡°feels-like¡± temperature or heat index of 38.5 degrees.

But when the men¡¯s and women¡¯s sprints begin Friday, most competitors will embrace the hot weather, reveling in conditions that Carl Lewis, the nine-time Olympic champion sprinter and long jumper, calls ¡°the Caribbean without the breeze.¡±