100 Miles In 100 Degrees: Western States Endurance Run Will Test Runners' Resolve

SQUAW VALLEY (CBS13) — A 100-mile endurance run kicks off this weekend, right in the middle of sizzling triple-digit heat.

The run from Squaw Valley to Auburn will likely be the fourth-hottest Western States Endurance Run in the event's 40-year history.

Jonathan Heinz doesn't sweat the mileage, but training in Calgary, Canada, hasn't prepared him for the heat.

"I haven't done a race in this temperature before," he said. "50 to 100 [degrees] is a huge difference, so we'll see."

He's done hot yoga to help prepare for this weekend's heat.

"That's one to two hours a week, and this is 10, 20, 30 hours," he said.

Runners had their vital signs checked today, along with being weighed in.

"The weight is important so runners know their hydration status," said Dr. Marty Hoffman.

Along the course, runners will monitor their weight change.

Dr. Hoffman says it's possible for runners to overhydrate as well.

"That actually puts them at risk for hyponatremia, which can cause death," he said. The condition is caused by a lack of sodium in the body fluids outside of cells.

To avoid the heat, most will wear light colors. Sun protection for their head may not be such a good choice.

Runners know there's no avoiding the heat and hope to prepare their body as best they can.

Runners will be adjusting their goals because of the heat.