Its actually not a joke. It is a little thing called EPOC.
EPOC or excess post-exercise oxygen consumption, is the amount of energy your body continues to burn after a workout. This is through fuel replenishment, repairing muscle tissue, returning the blood and oxygen back to the organs (they were being sent to the muscles while in use), recovering heart rate, etc.
We often over-estimate the amount of energy (calories) we burn post workout so what types of workouts will guarantee a greater EPOC? It isn’t the length of time you spend working out, it is what you do in the workout.
Cardio: Without going into a long boring explanation I will tell you that according to recent studies, short bursts of higher intensity cardio exercises produce a greater post workout energy burn than steady state exercise such as walking, running or biking on a flat road at a consistent speed. Don’t panic if you cannot sprint or run up and down stairs due to physical limitations. Simply changing your pace while you walk or jog by walking faster for short intervals can produce some increase in EPOC.
Weight lifting: You must challenge and fatigue the muscles in order to produce desirable EPOC results. Lifting weights is a great way to boost your post workout energy burn so make sure you are lifting weights that are a challenge to lift no more than 12- 15 reps if this is your goal. You will also need to minimize your rest in between sets so no 5 minute flexing in the mirror break people. Keep it down to 1 min if you can.
HIIT: (High Intensity Interval Training) This is a big trend right now and for a good reason. You perform high intensity exercise for short intervals with brief intervals of rest. An example would be sprint for 30 seconds, rest for 30 seconds, run up and down stairs for 30 seconds, rest for 30 seconds, etc.
So go out there and try to gear your workout toward burning more calories while you sleep!