Taking a midday snooze has been shown to increase alertness, focus and concentration. But just how long should your power nap be?

After studying a group of young adults who napped for five, 10, 20, and 30 minutes, Australian researchers assessed the participants for a range of benefits over the next three hours.

The results? Ten minutes seems to be the sweet spot.

According to the published study results, it produced “immediate improvements in all outcome measures (including sleep latency, subjective sleepiness, fatigue, vigor, and cognitive performance), with some of these benefits maintained for as long as 155 minutes.”

Longer naps either didn’t produce immediate results, or the results didn’t last as long. And a previous study done at UCLA found that the longer you nap, the more likely you are to awaken “confused and groggy.”

The timing matters, too. If you nap too late in the day, your body might think you’re down for the night and enter into “deep sleep,” which lessens the benefits and could mess up your body clock. So for the best results, experts recommend getting your 10 minutes of shuteye sometime between the hours of 1:00 and 3:00 p.m.

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