Woman's challenge: 7 marathons, 7 days, 7 continents _ again

FILE - In this Jan. 30, 2016 file photo, Becca Pizzi of the United States, holds an American flag after winning the seventh and final leg of the World

FILE - In this Jan. 30, 2016 file photo, Becca Pizzi of the United States, holds an American flag after winning the seventh and final leg of the World

FILE - In this Feb. 27, 2015, file photo, Becca Pizzi poses in Newton, Mass., wearing some of her medals from the 15 Boston Marathons she has complete

FILE - In this Feb. 27, 2015, file photo, Becca Pizzi poses in Newton, Mass., wearing some of her medals from the 15 Boston Marathons she has complete

BOSTON (AP) — A Massachusetts marathoner is racing to become the only person on the planet to have run seven marathons in seven days on all seven continents — twice.

Becca Pizzi (PEE'-zee) won the World Marathon Challenge in her first attempt in 2016.

Now, the Belmont woman is preparing to tackle the odyssey again. If she completes it, she'll become the first to repeat the feat.

The 37-year-old single mother starts the challenge on Jan. 30 by running the full 26.2-mile (42.2-kilometer) marathon distance in Antarctica. She'll then run back-to-back marathons on successive days in South Africa, Australia, the United Arab Emirates, Portugal and Colombia, finishing in Miami on Feb. 5.

Pizzi and 54 other competitors will cross 16 time zones and endure wildly disparate temperatures and terrain.