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Dual Core 2, or DC2, is the second [[Dual core|dual core schedule]], a logical upgrade from DC1 with the addition of 1 nap and some sleep reduction from the core sleeps.<ref name="polysoc" /> The total sleep of DC2 hovers around the hospitable zone for long-term sustenance, approximately ~5-5.5h of total sleep each day. {{TNT|DC2}}

== Mechanism ==

Dual Core 2, or DC2, is the second [[Dual core|Dual core schedule]], with two cores and two naps.<ref name="polysoc" /> The total sleep of DC2 is around 5 to 5.5 hours.  

With 2 core sleeps placed around the sleep peaks and 2 supplemental naps in the day, DC2 is similar to [[E3|E3-extended]] in sleep distribution and offers a decent napping frequency to learn the napping behavior. '''DC2 in a way resembles E3''', except that the first nap of E3 is now the second core in DC2.  

==Mechanism==

With 2 core sleeps placed around the [[Circadian sleep peaks|peaks]] and 2 naps in the day, DC2 is similar to [[E3#Extended|E3-extended]] in timings, except that the first nap of E3 is replaced with a core.  

The first core sleep is typically longer than the second core sleep to obtain an ideally sufficient amount of [[wikipedia:Slow-wave_sleep|SWS]], while the second core has a lot of room for [[wikipedia:Rapid_eye_movement_sleep|REM]] sleep. With a 3h [[Cores|core]] (2 full cycles) in SWS peak hours, SWS is likely preserved after repartitioning is completed, and SWS deprivation symptoms on DC2 are overall a lot milder than schedules with only 1-cycle core sleeps around SWS peak/night hours. The naps provide more alertness boost to sustain the long wake gap in the day as the core duration becomes shorter, and meet the remaining REM sleep requirements. The second nap on DC2 may not give any REM sleep, and just [[NREM2]] or trace SWS instead if it is placed in mid/late afternoon (e.g, after ~4 PM). Because of the reduced total core duration compared to that of [[DC1]], an extra nap has to be added to compensate for the reduced amount of REM sleep in the second core of DC2.  

The first core should ideally contain nearly all the required [[wikipedia:Slow-wave_sleep|SWS]], while the second core should contain primarily [[wikipedia:Rapid_eye_movement_sleep|REM]] sleep. The naps help [[Wake time reduction|sustain wakefulness]] with reduced total sleep time, and may or may not contain REM sleep.  

In addition, DC2 is also a middle ground between the easier DC1 and the advanced [[DC3]]. The total sleep is not as high as DC1-extended and not as low as DC3, which is '''a favorable zone of total sleep for flexing sleep after adaptation'''. The total sleep is equivalent to [[E2]], but the splitting of core sleeps will provide a deeper core experience for the first core, and high likelihood for vivid/lucid dreaming in the second core as SWS is met in the first core. The wake gap between 2 cores is also large enough for certain favorite nighttime activities, including certain brainstorming or somewhat mentally taxing duties without having to worry about cooling down for the second core around sunrise hours too soon. It is also possible to have a 5-6h wake gap from the morning core to the first nap, and another ~4-5h to the second nap. 4 sleeps per day also renders the wake gap between each sleep more manageable than on E2 for instance. Skipping one nap as a result may be tolerable during adaptation, as long as this does not happen too often.  

The total sleep is relatively high, and may allow for [[flexing]] after adaptation. Compared to [[E2]], which has a similar total sleep, the split cores may allow for more efficient sleep. Four sleeps per day keeps sleep pressure relatively low, and skipping naps would be more tolerable compared to schedules like E2, as long as this does not happen often.  

== Difficulty ==

==Difficulty==

It is generally considered that adapting to '''multi-core schedules''' (more than 1 core sleep) is harder than to schedules with only 1 core sleep (e.g, Everyman), except in the case of naturally segmented sleepers who are used to sleeping in more than one core sleep. This is believed to be the case because repartitioning of vital sleep stages into both core sleeps becomes more complicated, and this '''doubles''' the chance for SWS wakes from both cores during adaptation. Thus, adaptation to DC2 in general is at least as difficult as that to E2, or possibly as challenging as to E3 (3.5h core) for non-natural Segmented sleepers. Initially, splitting the monophasic core sleep into 2 smaller cores can result in a much rougher wake from the first core, if the '''cold turkey adaptation method''' is chosen.  

For non-naturally segmented sleepers, adapting to Dual core schedules generally more difficult compared to [[Everyman]], because splitting of vital sleep stages into two cores may induce difficult wakes. In that case, adapting to DC2 is slightly more difficult compared to E2, but may be easier for naturally segmented sleepers.

==Adaptation==

==Adaptation==

A gradual adaptation method from DC1 is viable, but it also has more limited success than the cold turkey method. It is also worth noting that after the adaptation to DC2 is completed, one can proceed to flexing the naps and the core(s) and adapt to [[DUCAMAYL]], or transition to DC3. The first core sleep on DC2 can naturally shorten by 30m (becoming 2.5h core instead) as a result of compressed repartitioning and high frequency of sleep, but this is not guaranteed for everyone.  

Either cold turkey or gradual adaptation to DC2 is possible. After adapting to DC2, one can start flexing the naps and possibly core(s) and adapt to [[DUCAMAYL]], or transition to DC3. The first core sleep may also naturally shorten to about 2.5h as a result of compressed repartitioning and high frequency of sleep.  

==Lifestyle Considerations==

==Lifestyle Considerations==

In spite of the seemingly unnecessary sleep distribution across the day on DC2, it is actually viable to attempt this schedule, because of its ability to become flexible after adaptation, and even scheduling viability. For the most part, the first nap can be taken during a noon or lunch break (which is allowed in many workplaces) and the second nap can be taken after work (~4:30-5:30 PM). It is then possible to sustain 2 naps per day, with a consistent work schedules on weekdays for example.  

In spite of the four scheduled sleeps, DC2 can be a viable schedule for many, because of its ability to become flexible after adaptation. The first nap can be taken during a noon or lunch break and the second nap can be taken after work (16-17:30). It is then possible to sustain 2 naps per day, with a consistent work schedules on weekdays for example.  

Both core sleeps total '''at least 3 full sleep cycles''', and with the more efficient use of sleep peaks, DC2 is an underrated option to pick for some physical exercises. The second core, being safe from virtually any real-life interruptions at late hours, acts as a storage for REM sleep, which can in return boost alertness and performance before heading out to work or school. The second core, once adapted, can create a strong impression of a long, restful night sleep that is compacted down to only 90m sleep. Not only is REM sleep safer to be maintained on DC2 (compared to regular E3) but also the DC2 naps can sustain alertness after only a couple hours staying awake, replenishing the energy budget after a long morning at work/school and then another nap after work/school for extra recovery. This also indicates that DC2 is one of the few polyphasic schedules that can go well with mainstream 9-to-5 jobs '''as long as it is possible to take one nap in the middle of this work gap'''.  

DC2 also allows for some physical exercise since it has a relatively high total time in cores. Both cores may feel long and restful after adaptation, despite the relatively short durations compared to monophasic sleep. DC2 provides many alertness boosts, replenishing energy in the morning, at noon, and in the afternoon.

However, to ensure the naps have good quality, it can be tricky to plan the nap before lunch when the noon break window is too short to take both the nap and have lunch. In addition, many people can also sustain 1 daytime nap in the long run, so 2 naps may prove to be an arduous choice for long-term practice. This also calls for the viability of the '''early rotation/[[Pronap]]''' scheduling choice, at the cost of a complete sacrifice of social time in the evening. In the end, though, the first core sleep of DC2 (which is usually taken around ~9-10 PM, or at worst, 11 PM in rare cases) poses more hindrance for social life around these hours; this weakness is only mitigated on extended version, which is also outperformed by other extended schedules with the better niches they offer. Non-natural Segmented sleep habits or poor planning during the wake gap at night can quickly lead to boredom and boost the difficulty of the adaptation. Overall, even though DC2 possesses the flaws of a typical Dual Core schedule, it does offer decent variability and diversity in its scheduling potential.

However, it may be difficult to both take a nap and have lunch with a relatively short lunch break. As with other Dual core schedules, the first core starts relatively early, and may pose difficulties with social life. Non-natural segmented sleepers may experience boredom during the night gap, which can make adaptation more difficult.

==Variants==

==Variants==

Over the years, there have been a lot of changes in DC2 scheduling. A lot of principles and bases discovered throughout these years have opened up multiple possibilities for a DC2 setup, making DC2 a very underrated schedule.  

Over the years, many variants of this schedule has been proposed following a range of scheduling principles. This opens up a wide range of scheduling options for DC2, which may suit different people.

===Slightly modified core duration===

===Shortened core(s)===

[[File:DC2-mod.png|thumb|A DC2 variant proposed by Polyphasic Society|alt=]]

[[File:DC2-mod.png|thumb|A DC2 variant proposed by Polyphasic Society|alt=]]

This scheduling variant was proposed by <u>'''[[Polyphasic Society]]'''</u> a long time ago, which gives an extra amount of sleep reduction compared to the standard variant. Totaling 4h40m of sleep, this version may be more appealing to adapt to than the standard version, as it also gives a similar amount of total sleep to E3 (3.5h core and 3 20m naps). The basis of this version was to induce a bit more sleep reduction in the first core sleep and add a second nap. However, it is not recommended to schedule a 2.5h core from the beginning, because it likely will result in heavy SWS wakes and increases the chance for oversleeping. As mentioned above, there is still some chance for the automatic reduction in the SWS core's length after adaptation, so it is not necessary to adapt to this variant. This total sleep may also contribute to the potential inflexibility of the schedule after adaptation, or make it a lot more difficult to flex each sleep block. Throughout the years, there were '''virtually no successful adaptations to this DC2 variant'''. It may benefit sleepers with lower SWS requirements or shorter overall sleep duration on monophasic sleep, though.  

The inner ring is the original variant of the schedule proposed by [[Polyphasic Society]], which cuts more sleep than the current standard variant. Totaling 4h40m of sleep, this version has a similar amount of total sleep to E3 (3.5-hour core). However, scheduling a 2.5h first core may result in heavy SWS wakes in the beginning and cause oversleeping. This reduced total sleep may also make this variant less flexible after adaptation. Throughout the years, this variant has seen little success, but those with slightly reduced monophasic sleep requirements may be able to adapt to it more easily.  

 

Similar to the Polyphasic Society's proposal of a possible DC2 variant, this DC2 variant stresses on the final goal once the adaptation is completed - to compress both core sleeps down to a '''multiple of 80m cycles''' (from 90m). The common approach would be to adapt to the original '''3-1.5''' standard combination, and then wait for the compression to occur, thanks to the frequency of sleep. It is not recommended to start an adaptation with this variant, however, because of the increased chance to run into SWS/REM wakes that give an excessive amount of sleep inertia that could be alleviated in the standard setup.  

It may also be possible to compress the cycle lengths down to 80 minutes. The common approach would be to adapt to the standard variant, and then wait for the compression to occur. It is not recommended to directly start an adaptation to variant.  

[[File:DC2-mod 3.png|thumb|A DC2-modified variant with the same sleep duration for both cores|alt=]]

[[File:DC2-mod 3.png|thumb|A DC2-modified variant with the same sleep duration for both cores|alt=]]

This DC2 variant offers a somewhat higher total sleep than usual (not high enough to be grouped into the extended category), and both core sleeps last for 2.5h each. So far there has only been one success with this variant, however. The premise behind this variant is to '''provide some buffer total sleep to advance to DUCAMAYL''' with both cores becoming flexible. This example sets the consideration for appropriate core durations to ensure that they can receive some flexibility after adaptation. Because of the highly uncommon and ill-advised 2.5h core duration, beginners and inexperienced polyphasic sleepers should avoid this variant.  

This DC2 variant offers a somewhat higher total sleep than usual (not high enough to be grouped into the extended category), and both core sleeps last for 2.5h each. So far there has only been one success with this variant, however. The premise behind this variant is to '''provide some buffer total sleep to advance to DUCAMAYL''' with both cores becoming flexible. This example sets the consideration for appropriate core durations to ensure that they can receive some flexibility after adaptation. Because of the highly uncommon and ill-advised 2.5h core duration, beginners and inexperienced polyphasic sleepers should avoid this variant.  

[[File:Dc2tc1.png|thumb|A DC2 variant with TC1 structure]]

[[File:Dc2tc1.png|thumb|A DC2 variant with TC1 structure]]

=== TC1 structure ===

===TC1 structure===

This is an experimental variant, proposed by [[User:Sekvanto|Sekvanto]]. Both cores have the same length of 2 hours. Three blocks of sleep are placed during the night hours: both cores and one of the naps. The second nap is placed midday. Such schedule resembles the structure of [[TC1]], replacing one of the cores with a nap and extending the remaining cores. This variant has fewer naps during the daytime, which potentially makes it more convenient socially for some. An early core may be an issue, on the other hand. Another benefit is a dawn nap, which may increase dream recall.

This is an experimental variant, proposed by [[User:Sekvanto|Sekvanto]]. Both cores have the same length of 2 hours. Three blocks of sleep are placed during the night hours: both cores and one of the naps. The second nap is placed midday. Such schedule resembles the structure of [[TC1]], replacing one of the cores with a nap and extending the remaining cores. This variant has fewer naps during the daytime, which potentially makes it more convenient socially for some. An early core may be an issue, on the other hand. Another benefit is a dawn nap, which may increase dream recall.