If you're inclined toward a siesta, science offers some pointers for timing it right.
Go short. Naps of about 20 minutes are great for getting a boost. "If you're seeking alertness, clarity of the mind, pushing the reset button, that can all happen with a 20-minute nap," Mednick says.
Go big. During sleep, adults cycle through a series of sleep stages, with a single cycle lasting about 90 minutes. If you can spare an hour and a half, that's a great length for a nap that confers all the benefits of each sleep stage, Mednick says.
Don't split the difference. In the middle of a sleep cycle, we sink into a deep, heavy stage of sleep that's hard to wake from. If you try to rise from a nap after 40 to 60 minutes, you're more likely to be stuck with a groggy feeling that lingers all afternoon.