Even if you’re well-rested, naps can improve your performance in a variety of ways. Napping can boost your reaction time, attention, and alertness. When you’re on patrol, outside the wire, or on staff duty, getting the optimal amount of sleep might not be possible. In those scenarios, naps are a critical recovery tool that can be leveraged to help you be at your best mentally, physically, and emotionally. While your brain will always perform better with more sleep, being strategic with your naps also can help combat sleep loss when conditions aren’t ideal.
When you get less sleep than your body needs, you acquire “sleep debt.” Most adults need about 7–8 (or more) hours of sleep each night in order to stay healthy and perform their best. If you get less, then you need extra sleep to make up for whatever was lost. There are times when sleep deprivation is unavoidable (for example, a new baby, studying for a test, a night training mission, or night ops), but you can engage in strategic napping before and after sleep loss to ensure that you don’t suffer the consequences of a big sleep debt.
How long should I nap?
For most people the “ideal” nap length to make up for lost night sleep is the longest one you can get! It’s true that waking up before you go into deeper sleep (such as napping for only 20–30 minutes) or at the end of a sleep cycle (every 90–120 minutes) might help you avoid grogginess or “sleep inertia.” The issue is it’s usually impractical to time your nap duration to complete one or more "sleep cycles," and there’s little reason even to try because cycling through various stages of sleep in a predictable way happens only under perfect lab conditions.
In most cases, "sleep inertia" isn't the problem it's built up to be. It usually lasts only a few minutes before things return to normal. You can help shake off any grogginess by standing upright and spending time in light—ideally daylight. The long-term benefits of sleep generally far outweigh the temporary risk of feeling dazed or making an error due to “sleep inertia.”
Can I nap too much?
If you are tired and have the opportunity to sleep, the short answer is “No”—the more sleep, the better. The only way to “repay” a sleep debt is to secure extra sleep strategically beyond your daily requirement. For example, if you stay up all night and lose 8 hours of sleep, an extra hour or two of sleep per night for the next several nights can help you recover. If you no longer have a sleep debt and feel energized, you don’t need to nap. If you nap too much, you risk having trouble falling or staying asleep that night.
Make sleep-bank “deposits” to prepare for future sleep loss
Plan ahead. If you know you’re going to go without sleep in the future, “banking” extra sleep can improve your performance. It’s unclear how much extra sleep you need to bank. But some evidence suggests those who sleep approximately 9–10 hours nightly for one week—before any situation involving performance or sleep deprivation—perform well. And those who bank extra sleep before a sleep-deprivation event tend to bounce back quicker during recovery time.