An exaptation is simply a pre-adaptation, a way to prepare yourself for adapting to your goal schedule. Often people will simply jump into their goal schedule and suffer deep sleep deprivation spread out over a long period of time, and this is not ideal.
You can shorten your adaptation time by inducing sleep deprivation early so that your body goes into a GAS.
Think about what intervals you need to sleep in, and expand or divide from there. The further you expand, though, the less predictable your doze/wake cycle will be.
You can begin to plan an exaptation by deciding on a larger interval that fits your timetable such as napping 3, 4, 5, 6h.
Start an exaptation plan by setting your BRAC length (between 1-2h) which might be half your larger interval. From there you can then expand that BRAC out into the more useful ultradian rhythm by napping half as often (your larger interval).
Not only will a nap exaptation help set ultradian rhythm, but secondly, napping so often will give the oppertunity for the body to practice napping as a practised skill, and thirdly it will allow for more sleep (and faster sleep rebound from initial sleep deprivation) without disrupting the schedule.
For example if you want to follow a classic Uberman schedule, your set BRAC would be 2h. You would nap once every 2h for 2-4 days. Expand your BRAC into a 2x2h rhythm, nap every 4h for 2-4 days.
Lets say you wanted to shift from Uberman to E3, you would expand your 4h rhythm into a 4h and 6h rhythm. This means that you can now sleep in 4 and 6h intervals, and probably 2h intervals too, if you wanted. Of course the more chaotic you let your schedule become, the less you will recover.
You can see you are setting a starting point, and a pattern for your body to follow, then you are expanding that pattern until you get to your goal schedule, but every nap is placed so that your body is ready to sleep at those times.
Because the gut clock is able to communicate with the brain, eating helps signal that it is circadian ‘day’ time.
It has often been a strategy to reset the circadian rhythm to a new time by fasting, to fight jet lag. Adapting to polyphasic sleep can be equated to jet lag, but on a much greater scale. This strategy is implemented by fasting for at least 24 hours, and then breaking the fast when you want the new ‘circadian morning’ to be. You can also perform some exercise and then feast on a large high fat/protein meal at the times you need to become more active.
For example if you are starting a schedule with a 3.5h core from 9pm-12.30 and you think you will struggle to stay awake at 3am, then you may want to reset your circadian morning to 3am. Fast for 24h and then break the fast with a feast at 3am.
The guts are tricked into thinking that when you fast there is no chance of catching prey so you should sleep, but when you feast you have the most chance of catching prey so you should then be awake.