Day 1: Double up with two-a-days.
Doubling up on workouts isn’t a good long-term plan — pushing your body non-stop week after week can increase your risk for injury — but it can get you faster results if you do it for the next 14 days. “Crush one part of your body with strength training during one session and do cardio the second session,” says Eric Ridings, a tier four coach at Equinox in Chicago. Make your second session a long, slower cardio workout. During shorter sessions (like HIIT), your body turns to carb-burning because they're readily available. “But when you do a longer cardio session, like 45 minutes to an hour, your body has the time to start breaking down body fat and using that for fuel,” says Ridings. Another bonus to two-a-days: Research shows combining strength-training workouts with cardio workouts results to bigger muscle growth.