LEASHA WEST’S BODY HAS been through the wringer. As a U.S. Marine Corps veteran and former combat instructor, she hiked 15-plus miles several times a week with a 150-pound pack on her back. The bottoms of her feet turned raw and blistered, her toenails fell off, her legs went numb. “It’s not uncommon to have blood in your stool” from the training regimen, says West, who served from 1998 to 2002. “My body took a serious beating.”

But the 45-year-old – who lives in Kalamazoo, Michigan – hasn’t stopped. In addition to working toward her MBA while running her own financial services and insurance agency, she regularly lifts weights and swims.

And, for a few minutes almost every morning for the past three years, she’s stepped, nearly naked, into a negative 250 degree F (or colder) chamber. That’s more than twice as cold as dry ice.

“It’s the best way to start (the day)”