Squat thrusts are a killer cardio exercise, and this single-arm version really kicks up the intensity and core-conditioning capacity of every rep.
How to do it: Start standing with your feet slightly wider than hip width. Squat down to the floor and press your right hand into ground just below the center of your chest (left arm reaches behind your body). Brace your abs in tight and jump both feet back, landing in a full plank position. Quickly jump feet back in towards your hands, landing in a squat, and stand up. Repeat using your left arm. That's one rep. Try up to 3 sets of 10 repetitions as quickly as you can, taking a brief break in between sets to recover.