NASM-certified personal trainer Sydney Cummings is bringing you this half-hour Tabata sweat session with bodyweight circuits. The first circuit, which is more of a warmup to get your abs engaged and body moving, features jumping jacks and planks that you'll alternate doing four times 20 seconds on, 10 seconds off. The next circuit targets your lower-body and core (jumping lunges and V-sits). The circuits that follow have the same format but different moves.