After-burn refers to the bodies continued calorie burn at an elevated rate for 24 hours after the completion of your workout. The scientific term for after-burn is excess post-exercise oxygen consumption (EPEOC). This refers to the oxygen that your body needs to restore after a heart pounding workout. A good example of this type of workout would be HIIT (High Intensity Interval Training).
So the after-burn effect is real.
While you exercise your body needs fuel to keep your muscles firing, and this requires oxygen to transport the fuel into the muscles. This causes your metabolism to rev up to an elevated state during and after exercise.
To get the most after-burn effect, avoid single joint movements that isolate body parts and instead focus on compound, full body movements. For example, squats, lunges and deadlifts work multiple joints and muscles that will increase the intensity of your workout.