Few pleasures in life are as decadent as a nap. Today, I really enjoy a nap after dinner, my belly full and head swimming with the tastes and smells of a good meal. I’ll grab 40 winks on the couch whenever I can. Back in my days behind the wheel, however, napping
wasn’t a luxury, it was an integral part of my survival strategy, a fatigue countermeasure.

Naps are a preventive measure in dealing with short-term sleep deprivation. Sleep researchers say strategic napping can enhance your alertness provided the nap is taken before the effects of acute fatigue make a temporary recovery impossible.

There’s where my strategy always went awry. Not knowing how to manage my naps properly back then, I frequently overslept and missed more than a few delivery appointments.

I’ve since learned more about sleep and the way my sleep patterns affect my ability to awaken following a nap. Sleep consists of cycles, like the crests and troughs of a wave. Each cycle begins with light sleep, called phase-one sleep, progressing in depth to phase-four sleep, then back up to phase-one sleep.

An average eight-hours-a-night sleeper will experience three or four sleep cycles after he hits the hay, with a full cycle lasting about 90 minutes. The first transition from phase one to phase four takes about an hour. It then takes about 30 minutes to get back to phase one, completing the first full cycle. The second cycle is similar, but the third and fourth involve shallower sleep over a longer period, say two hours.

If you’re sleep-deprived, the time between the initial transition from phase one to phase four is shortened from an hour to only 15 or 20 minutes. When you’re really tired, you dive rather than drift into a deep sleep. On the first two cycles, you sleep more deeply for longer periods than a well-rested person, but still follow the typical pattern of cycles becoming shallower and longer as the night progresses.

The key to a restful nap is to know the best time to wake up. In phase-four sleep, a bomb blast might work. In phase-one sleep, a light disturbance could do the trick.

Working with the theory that sleep becomes lighter as time passes in the first cycle, I’d set an alarm clock for about an hour and then observe how I felt upon waking. If I was really groggy and lethargic, I concluded I had set the alarm for too short an interval, likely awakening somewhere in or near the deepest phase of sleep. The next time, I’d set the alarm again, using a slightly longer interval, perhaps an hour and 15 minutes.

I wanted to discover the approximate time my body took to complete a full sleep cycle, from phase one through phase four and back to one again.

Similarly, I experimented with how long it took me to reach a point where I couldn’t awaken following a short nap (trying to avoid slipping into phase-four sleep). My target was the end of my phase-two sleep, which usually worked out to between 15 and 20 minutes when I was really tired, or about 45 minutes otherwise.

On the long side, I found I could set the alarm for either 90 minutes or three hours and wake refreshed. There was no room for negotiating with my body on this one. If I tried to nap for two hours, I’d sleep through the alarm (being in the second cycle of phase-four sleep) and wake up when I had had my fill — nine hours later.

I learned my limits. I could safely manage a 20-minute nap if I was really tired when I lay down, or a 40-minute nap if I wasn’t too tired. I could also take a longer nap of either 90 minutes or three hours. I found that if I planned a nap early into the evening, before I was really tired, I responded better to the benefits of the brief snooze. It may surprise you, but these patterns are the same today, three years after I stopped driving.

Napping is no substitute for a full night’s sleep. But if you know how to snooze, you can bed down with little fear of oversleeping, a fear that prevents many drivers from taking a chance on a nap.