Siesta sleep schedules are the most common of the polyphasic schedules, involving sleeping in two separate segments throughout the day – once at night, and a nap in the middle of the day. There are three distinct biphasic schedules, the ‘power siesta’ schedule which involves sleeping for 20 minutes in the middle of the day and between 5-6 hours at night (varies between invididuals), and the more common ‘long siest’ involving 4.5-5.5 hours at night and a 60-90 minute sleep during the day, and of course segmented sleep (which we won’t talk about in this article).
Both siesta schedules are commonly called a siesta. Both of these schedules can be seen in various cultures throughout the world – taking a siesta is a cultural right of the latinos and other tropical populations, is important to middle easteners, and is even a favorite of the Europeans (England, Germany, and Spain specifically). Romans had a regular siesta;
“it was considered to be a physical necessity rather than a luxury, but it is unlikely that they had a health policy that included this, as was the case in Islam.”
In regards to health, there is enough scientific data to say that this method of sleeping is better for your health, and leads to improved mood, decreased stress, increased alertness and productivity over a typical monophasic schedule. Likewise, both biphasic schedules have been shown in scientific studies to significantly aid in learning and cognitive functions. As an added bonus, in terms of the most waking time gained per nap taken, biphasic schedules are the most efficient.
There is nothing saying a 20 minute nap is better than a 90 minute sleep in the middle of the day. Napping for around 20 minutes is healthy. And sleeping for 90 minutes has lots of benefits, and are especially great for athletes. But also napping for 90 minutes, too late in the afternoon, can impact on night time sleep. So this is why we sleep within 7 hours of starting our day!
Scientists have long wondered if this sleepiness was caused by the midday meal, but although insulin change does seem to play a role in sleepiness, there is a large amount of evidence that biphasic sleep is much more natural than sleeping monophasically, and the midday energy drop is driven by our circadian rhythm far more than our eating habits. There are natural core temperature changes that are controlled by our circadian clocks which prepare our bodies for a sleep-like state.
A nap exaptation can be beneficial for a 20 minute power-siesta schedule, to regulate one’s ultradian rhythm, training oneself to nap efficiently. The 90 minute sleep schedule can take a few days or a week or two to get used to if you have no napping experience, but can be easier for some people. The longer you try to nap in the middle of the day (and if you do not drink caffeine) the easier it becomes to nap and the better quality it will become.
Naps early in the day do not negatively impact on night time sleep.