DC2

DC2

Dual Core 2
chart link Legend   Sleep   Dark period   Flexible sleep window
Total sleep	5 hours 10 minutes
Proposed by	Polyphasic Society
Difficulty	Moderate
Specification	1 dusk core, 1 dawn core, 2 daytime naps

Mechanism

Dual Core 2, or DC2, is the second dual core schedule, a logical upgrade from DC1 with the addition of 1 nap and some sleep reduction from the core sleeps. The total sleep of DC2 hovers around the hospitable zone for long-term sustenance, approximately ~5-5.5h of total sleep each day. With 2 core sleeps placed around the sleep peaks and 2 supplemental naps in the day, DC2 is similar to 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.

The first core sleep is typically longer than the second core sleep to obtain an ideally sufficient amount of SWS, while the second core has a lot of room for REM sleep. With a 3h 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.

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.

Adaptation

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.

Alternatively, a gradual adaptation method from DC1 is also 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.

Alternate 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.

Slightly modified core duration

A DC2 variant proposed by Polyphasic Society

This scheduling variant was proposed by Polyphasic Society 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.

A DC2 variant with extra sleep compression

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.

A DC2-modified variant with the same sleep duration for both cores

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.

Early rotation/Pronap

A DC2 variant with the first nap around dawn

This interesting DC2 variant rotates the whole schedule backward, to earlier hours. The premise behind this distribution of sleeps is to place most sleep blocks to night hours, and only have one nap in the day. As a result, the wake gap between each core is possibly smaller than on the standard version. The first nap is placed at the usual position of the second core, and as a result, it is very similar to an Everyman schedule. The first core likely will contain most SWS needs, while the second core may be a mixed core (containing both SWS and REM, but likely more REM sleep). Both naps may contain REM sleep, which can boost the chance to recall dreams.

Alternatively, the first nap can be extended to become a Pronap (e.g, 30m) to better sustain wakefulness and provide more REM sleep for individuals with somewhat higher REM requirements, because the first nap is located in REM peak. The reason a Pronap can be used is that both core sleeps mostly cover all SWS needs, leaving basically no room for SWS to occur in this hypothetical Pronap. The Pronap can then yield better wakefulness sustaining, and can become flexible after adaptation. However, it is important to note that this is a new proposal for an alternate DC2 variation, and has not been tested. There is also little incentive to try out this early rotation/Pronap variant, because the first core is too early in the evening, and becomes a liability for social time for a lot of people.

Extended variant

DC2-extended simply extends the second core sleep by a full cycle, making it 3h total. This variant shares the same total sleep as E2-extended, with the exception of having 2 core sleeps. People with high sleep requirements (especially in both REM and SWS) can make use of the sleep frequency and the assistance from naps to meet the necessary vital sleep requirements. The only advantage of this version is that the first core can be delayed to the last hours of SWS peak - meaning it is possible to schedule this core at 11 PM or later. However, while looking realistic on paper, DC2-extended has never really reported any successes. It is also outclassed by E2-extended, which is more convenient in scheduling, more success and an allegedly easier adaptation. While it is possible to schedule the first core to be 4.5h long and the second core to be 1.5h long (for more SWS recovery from intense exercising or high SWS requirement), DC2-extended is also shadowed by DC1-extended, which has the same total sleep for both cores combined while only requiring 1 daytime nap (more comfortable to keep up long-term).

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.

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.

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.