Flexibility & Flexing

Flexing refers to the act of exercising flexibility:
Flexibility, in the context of sleep, refers to the ability for a sleep to be had at a different time on one day than the one before it, while maintaining the schedule and causing no or no relevant increase in sleep pressure.

Flexing is the core concept behind schedules with a "-flex" modifier, and AMAYL schedules. Schedules with the modifier are ones where one or more sleeps (almost always naps) is flexible, reached through adapting the base schedule first and then performing a flexing adaptation as described below the section on difficulty (which you should read before attempting such a flexing adaptation).

Difficulty

Flexing is fundamentally more straining on the body than consistent sleep:

In the case that a flexing adaptation has not been done, the body is not particularly used to the different time. As a result, sleep quality (Vitals percentage) is lost or even an oversleep-equivalent reaction is induced (causing issues adapting and potentially undoing some progress even post-adaptation). (See alignment for more info.)

In the case that a flexing adaptation is complete, no more oversleep-equivalent reaction is caused, but the nap is just not as efficient - so even here, a slight amount of sleep quality is lost. Together with that, a sleep that is flexible may spread a slight tiredness throughout its whole flex range. This should go away over time, but often won't stop entirely.

However, flexing is still worth it if you fall into one of the categories mentioned later.

Seizing up

Flexible schedules have the unfortunate potential to seize up and become inflexible again given poor care. As such, flexible schedules demand that naps are actually flexed in practice. A nap that isn't flexed in a week or two will eventually become less flexible, and at some point even completely rigid. This is also dependent on the sleep pressure in the schedule (with higher pressure meaning more potential to freeze) and the skill (both general and in flexing specifically) of the sleeper - a very skilled napper who has been following flexible schedules for a long time is almost inevitably going to have an easier time keeping up with the demands of a flexible schedule, including having a lower potential to have it seize up. This is simply due to the body and mind learning to see flexible sleep as more natural.

When and when not to go for flexing

Flexing is a good idea if:

• Your daily schedule (as in, what each day is built like) is unreliable
• You have enough time around each nap to consistently exercise the flex range
• You want to be able to go events or activities that you cannot control much or at all and thus cannot be sure you can sleep during
• You are seeking a challenge or want to flex (pun intended) on your friends (but make sure its not just sleep greed)

Do not flex if:

• You are on a fixed schedule that keeps all your naps consistent most days
• You are especially greedy and may skip sleep if you allow yourself more freedom
• You have no actual use for flexing
• You have not been on the schedule for a particularly long time (about a month post-adaptation is the minimum recommended)
• You are very new to polyphasic sleeping - though if you are careful, it can still be fine: Maybe talk to some others and get their feedback :)
• The schedule is very reducing and you are either already close to your limit or don't know the limit (though if you deliberately want to test your limits, this doesn't need to stop you)

Adaptation

And now to the thing you have been waiting for: The flexing adaptation.

The flexing adaptation is as banal as it is risky: It simply involves moving an existing, adapted sleep back and forth more and more. Over time, both the jump distance ("yesterday to today") and the schedule deviation ("schedule to today") can increase. It's best to start very small here, on the order of around 10 minutes. Unfortunately, there is no one-size-fits-all guide on this however, and it involves a careful balance between causing sleep debt that is big enough to break the schedule and never getting anywhere.

It is common to feel mildly tired throughout the whole process - this is a sign that it is working. The issue is: If this tiredness gets too big, it can result in an oversleep and completely mess you up. So the key is to keep it at a level where it never increases, but is high enough to get the body and mind to broaden the timespan the sleep is expected.

Too little of this tiredness means no progress is going to be made, similar to base adaptation's stage 1. On the other hand, too much means you're going too far in too little time - in which case it is likely that the nap is nearly useless and thus you are missing a lot of sleep each day, finally resulting in a rebound and thus oversleep.