"We are all special and unique," says the energetic instructor of my weekly early-morning cardio kickboxing class. She then reminds the 16 or so participants "to go at your own pace, take a break, get a drink, jump back in when you're ready.
"This is your workout," she reminds everyone.
Although we are in the class together, we are not the same: different ages, body types, physical and mental characteristics and abilities.
Among those abilities, one that comes in handy after the early class is the super-power of napping. I'm lucky to be among the third of Americans who possesses it; I can crawl under my desk in my office or dismount my bicycle, sprawl on a park bench and snooze for 15-20 minutes at any time, waking up refreshed.
Others find naps disruptive, resulting in foggy brains upon awakening, or tossing, turning, and not being able to get to sleep at all. A reason for that, suggests The Washington Post, is some adults are genetically predisposed to need more hours of continuous sleep than others.
Naps are helpful for all sorts of situations, such as when flying to London and arriving at, say, 6:30 a.m. after leaving the U.S. the evening before. It's difficult to catch a good night's sleep on such a flight, but nappers can get by. Travelers who can't shouldn't be responsible for sorting out ground transportation upon arrival. Airline coffee isn't stout enough to stave off jet lag.
And journalists in pursuit of a story are often faced with weird work hours that can keep them up late and back on the beat early if circumstances require. Writing a recent review of a lengthy production at Arkansas Repertory Theatre got me home at 12:15 a.m., followed by about 45 minutes of scuttling around preparing for the next morning, which started at 5:15 a.m.
An afternoon nap got me through that next day; I was working from home and didn't have to resort to crawling under my desk.
According to Sleepfoundation.org, naps can be categorized by function:
Recovery nap: If you are up late or have interrupted sleep one night, you might take a recovery nap the next day to compensate (see above).
Prophylactic nap: Night shift workers might schedule naps before and during their work hours in order to prevent sleepiness and to stay alert while working; I knew emergency room physicians who would do this.
Essential nap: When you are sick, you have a greater need for sleep.
Researchers found that five-minute naps are too short to produce a notable benefit. Sleeping for 30 minutes or longer gives the body enough time to enter deep (slow-wave) sleep. Napping for too long can cause grogginess (called sleep inertia) for up to an hour.
Naps lasting 10 to 20 minutes are sometimes referred to as "power naps" because they provide recovery benefits without leaving the napper feeling sleepy afterward. President John F. Kennedy was a renowned napper; after a mid-morning swim, he would lunch in bed and then settle in for a nap.
Other nap enthusiasts, according to sleepadvisor.org, include Margaret Thatcher, Winston Churchill, Eleanor Roosevelt, Lyndon B. Johnson, Albert Einstein, Salvador Dali, Gwyneth Paltrow, Lady Gaga, Bill Clinton and Benedict Cumberbatch.
Napping can be helpful or harmful depending on factors, such as your age, what time and how long you nap, and the reason for your nap.
We all have had that bleary sensation of feeling drowsy while driving. That's dangerous. The National Highway Traffic Safety Administration recommends that before a long journey, get a decent night's sleep. If you start to feel sleepy while driving, a short-term fix is to drink caffeine and pull over safely for a 20-minute nap. Then use your temporarily alert state to get off the road.
As with everything in life now, there are ways to do better when it comes to naps:
Set an alarm to go off in 15-20 minutes to counter sleep inertia.
Napping late in the day can affect your ability to fall asleep at bedtime. Try napping around the halfway point between the time you wake up and the time you plan to go to bed.
Find a comfortable napping space that is dark, cool, and quiet. Hey, that sounds like the space under the desk in my office!
If you're having trouble with racing-brain concerns, commitments and to-do lists, try practicing relaxation exercises (deep breathing, stretching, meditation, guided imagery). These can help you fall asleep and wake feeling recharged.
Think about what you hope to gain from your nap. When you set intentions, you can plan your nap around those goals. An example of this is what author Colson Whitehead, in his novel "Harlem Shuffle," calls dorvay, which comes from the French dorveille. It's when his character Raymond Carney keeps crooked hours, sleeping in two shifts; the first starts soon after dusk, then he awakens around midnight for a few hours of mischief-making before the second phase of sleep, which lasts through the morning. Not for everybody, but it works for Raymond. "This was the body's natural rhythm, before Thomas Edison let us make our own schedule," he says.
And here's a nap-inducing suggestion that works for me: Surround yourself with gently snoring dogs. It will likely result in what "Seinfeld's" George Costanza learned from a self-help recording: "Serenity now!"
Karen Martin is senior editor of Perspective.