Short naps are well studied. In a NASA study of long-haul pilots, a planned cockpit nap (about 26 minutes on average) improved reaction-time performance by 34% and physiological alertness by 54% (Rosekind et al., 1994). However, if you nap for too long or at the wrong time, you can wake into "sleep inertia," a heavy grogginess that can drag on your afternoon.
The 20-Minute Power Window#
The key to a successful nap is staying in the light stages of sleep. If you sleep longer than about 30 minutes, you risk entering deep sleep. Waking up from deep sleep is disorienting and can take 30 minutes or more to clear. (More on shaking it off in the sleep inertia guide.)
The Nappuccino Technique#
The coffee nap has been tested on drivers: a cup of coffee followed by a nap of under 15 minutes cut sleepiness more than either alone (Reyner & Horne, 1997, Psychophysiology). Here's how it works:
- 1.Drink a cup of coffee quickly.
- 2.Immediately lie down for a nap of 15 to 20 minutes.
- 3.Set an alarm to wake up around the time the caffeine starts to kick in.
The idea: the short nap takes the edge off your sleep pressure while the caffeine is still being absorbed, so you wake up just as it starts working.
The best time for that nap is your real afternoon dip (why you crash at 2 PM explains where it comes from). ARC measures it from your energy check-ins after about ten days, and if you take a caffeine nap, the coffee counts toward tonight's cutoff like any other drink you log. Can't nap at work? A non-sleep deep rest session is the next best thing.