Changes

Before the advent of electrical lighting in modern times, humans historically had a stable period of time during the night in which there was little light. This kept their circadian rhythms stable and synchronized to the natural day/night cycle.

Before the advent of electrical lighting in modern times, humans historically had a stable period of time during the night in which there was little light. This kept their circadian rhythms stable and synchronized to the natural day/night cycle.

Modern humans often use electric lighting during the night. This can cause difficulty as the body thinks it is still daytime even if it is already midnight, and is part of the reason why people often experience the desire to sleep later and later each day. For monophasic sleepers, a somewhat short dark period can be maintained during their long sleep hours, which keeps their circadian rhythms relatively stable.

Modern humans often use electric lighting during the night. This can cause difficulty as the body thinks it is still daytime even if it is already midnight, and is part of the reason why people often experience the desire to sleep later and later each day.<ref>Eun Yeon Joo, Sabra M Abbott, Kathryn J Reid, Donghong Wu, Joseph Kang, John Wilson, Phyllis C Zee (April 2017). ''[https://www.sciencedirect.com/science/article/abs/pii/S1389945716302295 Timing of light exposure and activity in adults with delayed sleep-wake phase disorder]''. Sleep Medicine, Volume 32, April 2017, Pages 259-265, https://doi.org/10.1016/j.sleep.2016.09.009</ref> For monophasic sleepers, a somewhat short dark period can be maintained during their long sleep hours, which keeps their circadian rhythms relatively stable.

However, for polyphasic sleepers who might not have such long sleep blocks, this poses an issue. As artificial light is present around the clock, [[Wikipedia:melatonin]] production is suppressed and the quality of SWS is compromised. This causes extra difficulty in adaptation and is also unhealthy, as circadian disruption is linked to various health issues.<ref>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632990/</ref> To avoid this, polyphasic sleepers (and monophasic sleepers too) should practice a dark period, during which no blue, green or white (as this contains both blue and green) light should enter the eye.

However, for polyphasic sleepers who might not have such long sleep blocks, this poses an issue. As artificial light is present around the clock, [[wikipedia:Melatonin|melatonin]] production is suppressed and the quality of SWS is compromised. This causes extra difficulty in adaptation and is also unhealthy, as circadian disruption is linked to various health issues.<ref>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632990/</ref> To avoid this, polyphasic sleepers (and monophasic sleepers too) should practice a dark period, during which no blue, green or white (as this contains both blue and green) light should enter the eye.

== Timing ==

== Timing ==

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Notes:

Notes:

* The dark red goggles may be too dark and reduce vision, but this would useful for use during daylight hours or in bright environments.

* The dark red goggles may be too dark and reduce vision, but this would be useful during daylight hours or in bright environments.

* The light red goggles let in substantially more red and green light than the orange one, but less yellow. The overall brightness appears to be slightly higher for the orange one, but the orange one allows for more colour perception. Based on the melanopic sensitivity function, both should provide similar levels of protection against melatonin suppression.

* The light red goggles let in substantially more red and green light than the orange one, but less yellow. The overall brightness appears to be slightly higher for the orange one, but the orange one allows for more colour perception. Based on the melanopic sensitivity function, both should provide similar levels of protection against melatonin suppression.

* There is a significant price difference between the first two and the third and the fourth one. However, the third and fourth ones have better quality (fewer rough edges on the plastic, more uniform transparency, and provides more options).

* There is a significant price difference between the first two and the third and the fourth one. However, the third and fourth ones have better quality (fewer rough edges on the plastic, more uniform transparency, and provide more options).

=== Red interior lighting ===

=== Red interior lighting ===

=== Exercise ===

=== Exercise ===

Intense exercise such as strenuous weight lifting and long-distance running should be avoided during dark period, as they might disrupt the circadian rhythm.<ref>Christopher A Wolff, Karyn A Esser, Exercise timing and circadian rhythms, Current Opinion in Physiology, Volume 10, 2019, Pages 64-69, ISSN 2468-8673, <nowiki>https://doi.org/10.1016/j.cophys.2019.04.020</nowiki>.</ref> In addition, exercise may also disrupt sleep and/or increase sleep onset as a result of increased heart rate. However, during adaptation, it might be desirable to use exercise as a means to stay awake. Choose mild exercise routines and do not exercise for an extended period of time to avoid circadian disruption or sleep onset issues; both of which may hinder your sleep quality and harm your adaptation.

Intense exercise such as strenuous weight lifting and long-distance running should be avoided during dark period, as this might disrupt the circadian rhythm.<ref>Christopher A Wolff, Karyn A Esser, Exercise timing and circadian rhythms, Current Opinion in Physiology, Volume 10, 2019, Pages 64-69, ISSN 2468-8673, <nowiki>https://doi.org/10.1016/j.cophys.2019.04.020</nowiki>.</ref> In addition, exercise may also disrupt sleep and/or increase sleep onset as a result of increased heart rate. However, during adaptation, it might be desirable to use exercise as a means to stay awake. Choose mild exercise routines and do not exercise for an extended period of time to avoid circadian disruption or sleep onset issues; both of which may hinder your sleep quality and harm your adaptation.

== See also ==

== See also ==

* [[Crimsonflwr]]'s free and comprehensive dark period [https://www.polyphasic.net/courses/dark-period-course/ course] (registration to polyphasic.net required).

* [[Crimsonflwr]]'s free and comprehensive dark period [https://www.polyphasic.net/courses/dark-period-course/ course] (registration to polyphasic.net required).

* [[Crimsonflwr]]'s dark period [https://docs.google.com/spreadsheets/d/10dAiiTWo4V6Fq2P0b4_xjSyvdydOHcz68BLxWGyFlSw/edit?usp=sharing calculator]. Refer to the above course for instructions regarding useage.

* [[Crimsonflwr]]'s dark period [https://docs.google.com/spreadsheets/d/10dAiiTWo4V6Fq2P0b4_xjSyvdydOHcz68BLxWGyFlSw/edit?usp=sharing calculator]. Refer to the above course for instructions regarding usage.

== References ==

== References ==