Newton Running athletes Brenda Guajardo and Harvey Lewis will compete in two of the most extreme endurance races on the planet this week.

Guajardo is racing in the Spartathlon, a 153-mile road race from Athens to Sparta, beginning September 30. The Spartathlon runs over rough roads and muddy paths, crosses vineyards and olive groves, climbs steep hillsides and takes runners on the nearly 4,000-foot ascent and descent of Mount Parthenio. There is less than a 50% finish rate with more than 70 time cutoffs. Learn more about Spartathlon at spartathlon.gr/en/home.html.

In 2016, Guajardo recorded a win at Nove Colli, a 125-mile race in Cesenatico, Italy, with a new women’s course record and first place overall male/female, and a second place female finish at Badwater 135 in Death Valley, CA. In addition to Nove Colli, Brenda previously won fist overall male/female at the Graveyard 100 mile, Keys 100 mile, and Palm 100km.

Lewis is taking on the Gobi Trail Ultra, which begins September 28. This 248-mile race across the Gobi Desert is China’s first super ultra-distance event. It doesn’t have course markings, so runners are required to self-navigate through one of the most arid and uninhabited regions in the world. Temperatures can swing more than 80 degrees Fahrenheit in a single 24-hour period. Runners also pass through historic sites including ancient ruins from the Great Silk Road, two UNESCO World Heritage sites and six national protected areas. Read more about the Gobi Ultra at utgchina.com.

Lewis has more than 20 years of ultra-running experience. In 2014, he won the Badwater 135, listed by National Geographic as the world’s toughest race. He has represented Team USA at the 24 Hour World Championships on three consecutive teams with a new PR of 158.7 miles in Torino, Italy in 2015. In 2015, he won the 24 Hour National Championship in the USA. He has run ultras ranging from the cold of Arrowhead 135 to the heat of Marathon Des Sables. In addition to racing, Harvey has run numerous historic routes including Gandhi’s 240-mile salt March and the Selma Civil Rights March.

Newton Running, based in Boulder, CO, is a manufacturer and marketer of performance running shoes.