The key to rocking shoulder-baring sweaters and blouses this season is pairing them with a strong, toned upper body. Contrary to popular belief, you don’t need to speed hours in the gym to achieve an eye-catching upper body. What you need is a challenging workout—one that cranks up the intensity on your muscles and eliminates every last ounce of flab. Enter Tabata training, also known as the 4-minute fat-burning workout.