If sleepy in the afternoon, try a ten-minute nap rather than thirty minutes
A ten-minute nap improved alertness immediately, with some effects lasting two and a half hours. Five minutes did little. Twenty minutes took over half an hour to help. Thirty minutes initially produced grogginess and worse performance than not napping.
What it takes
Free. Find somewhere to recline or rest your head and allow ten minutes.
What you may gain
After restricted nighttime sleep, a 10-minute nap immediately improved sleepiness, fatigue, vigor and cognitive performance, with some benefits persisting beyond 155 minutes. Five minutes offered little benefit; 20-minute naps helped only after 35 minutes. Thirty-minute naps initially caused sleep inertia, worsening performance before later improvement.
Context & considerations
One laboratory study in healthy young adults. Do not force sleep if it will not come. This source provides no evidence that merely lying with closed eyes for ten minutes has the same effect. Longer naps exceeding an hour are associated with higher mortality and coronary risk; see nap duration.
Research & references
Brooks & Lack (2006). A brief afternoon nap following nocturnal sleep restriction: Which nap duration is most recuperative? Sleep. https://doi.org/10.1093/sleep/29.6.831