Here’s a scenario: you’re tired and run down from a week of work and parenting and thinking about the world and find yourself with an oh-so-rare spare chunk of time. Should you be using it to swing kettlebells or snooze on the sofa? That is, which will do more for your well-being, exercise or sleep? Chances are, this is a choice you’ve faced. Who isn’t a little sleep-deprived? Who doesn’t need more exercise? If someone can create some sort of workout-while-you-sleep system, they’ll make a gazillion dollars from parents alone.

So, which should it be? Does the sofa bed win out? The answer is, well, a bit complicated. But understanding it can tell you a lot about your priorities.