World Marathon Challenge by the numbers

U.S. marathoner Becca Pizzi is trying to become the first person to have twice completed the World Marathon Challenge — seven marathons in seven days on all seven continents.

That's already a lot of numbers. Here are more. (What's your excuse for not exercising? Yeah, we didn't think so.)

— All seven races are the classic marathon distance: 26.2 miles (42.2 kilometers)

— Fifty-five competitors will cross 16 time zones between the start in Antarctica and the finish in Miami

— Temperatures will fluctuate wildly: It'll be zero degrees Fahrenheit (minus 17 degrees Celsius) in Antarctica — maybe colder — and 80 degrees F (26 degrees C) the very next day in Cape Town, South Africa.