How long you can go without working out before you lose muscle and start gaining fat?
If the closest thing to a workout you've done recently is wine glass bicep curls, chances are you've been giving the gym the swerve.
The good news is that a week without flexing your muscles won't do too much damage.
The bad news is that any longer and the pounds creep on.
A Skidmore College study found that your metabolism could slow by 4% if you rest for just over a week. That's a two-pound gain in a fortnight.
'Muscle strength is preserved initially, but after two to four weeks, you'll see losses in strength and muscle size,' says Dr Graeme Close, reader in Sports Nutrition and Exercise Metabolism at Liverpool St John Moores University.
Luckily, it's pretty easy to get back on track. If you're returning to the gym after more than a week, focus on working large muscle groups with squats and lunges. It gets you back into a high calorie-burning mode.
Also, try interval training like in UpFit Classes - it helps your heart retrain faster than if you were keeping a steady pace.
Still lacking exercise inspiration? Make a goal and pin it somewhere visible. Focus on the feeling of achieving that goal and go smash your workout.