Phase One: Acclimation
“These workouts are designed to get you used to being uncomfortable, increasing your capacity for work and prepping your heart, lungs, and large muscle groups for the demands of the coming weeks,” says DeGood. The routines for this phase are simple circuits, alternating between strength and conditioning. Before each workout, do a five- to 10-minute warm-up like a light jog, jumping jacks, or burpees. Then do one set of each exercise, in order, with very little rest between exercises. Rest two to three minutes, then start back at the top for the next set. Do at least two full sets of the circuit, but up to four sets if you’re able. If you feel comfortable doing these moves the first week, move on to phase two immediately. If they’re still a little challenging, repeat these workouts again for a second week.