Power napping is undoubtedly a skill. Not all of us are able to drop off for 30 minutes in the middle of the day, even when we’re exhausted. But those of us who can nap reap considerable benefits to their health, productivity and brain power. And it turns out there’s actually a perfect time of day to grab some quick shut-eye: 3pm. The reason for this comes down to our circadian rhythm, which dips around 3pm. Many people also experience post-lunch sleepiness or a lack of alertness, making it the perfect time to nap. You should aim to nap for 20 to 30 minutes - any longer and you risk falling into a deep sleep which could actually leave you feeling groggy for an hour after waking up. This is known as sleep inertia. And although a nap can be particularly valuable if you didn’t get enough sleep the night before, napping for too long could make it harder to sleep that night. According to the latest report by the Sleep Council, almost three-quarters of Brits get less than seve...