| Sleep needs can be increased temporarily, usually as an effect of needed physical recovery. Such cases include increased [[Special:MyLanguage/Exercise|physical activity]]<ref>Erik Naylor, MS, Plamen D. Penev, MD, PhD, Larry Orbeta, BA, Imke Janssen, PhD, Rosemary Ortiz, Egidio F. Colecchia, MS, Moses Keng, MS, Sanford Finkel, MD, Phyllis C. Zee, MD, PhD (January 2000). ''[https://academic.oup.com/sleep/article/23/1/1/2749954 Daily Social and Physical Activity Increases Slow-Wave Sleep and Daytime Neuropsychological Performance in the Elderly.]'' Sleep, Volume 23, Issue 1, January 2000, Pages 1–9, <nowiki>https://doi.org/10.1093/sleep/23.1.1f</nowiki></ref><ref>Markus Dworak, Alfred Wiater, Dirk Alfer, Egon Stephan, Wildor Hollmann, Heiko K. Strüder (March 2008). ''[https://www.sciencedirect.com/science/article/abs/pii/S1389945707001815 Increased slow wave sleep and reduced stage 2 sleep in children depending on exercise intensity]''. Sleep Medicine, Volume 9, Issue 3, March 2008, Pages 266-272, https://doi.org/10.1016/j.sleep.2007.04.017</ref> and some substances such as [[Special:MyLanguage/cannabis|cannabis]]<ref>Barratt, E. S., Beaver, W., & White, R. (1974). ''[https://psycnet.apa.org/record/1974-24717-001 The effects of marijuana on human sleep patterns]''. Biological Psychiatry, 8(1), 47–54.</ref> or [[Special:MyLanguage/alcohol|alcohol]]<ref>Irshaad O. Ebrahim, Colin M. Shapiro, Adrian J. Williams, Peter B. Fenwick (January 2013). ''[https://onlinelibrary.wiley.com/doi/abs/10.1111/acer.12006 Alcohol and Sleep I: Effects on Normal Sleep]''. Alcoholism: Clinical & Experimental Research, Volume 37, Issue 4, April 2013, Pages 539-708, https://doi.org/10.1111/acer.12006</ref>. External events such as these sometimes may significantly increase sleep needed (mostly [[wikipedia:Slow-wave_sleep|SWS]]) which can shake the adapted state with increasing intensity inversely proportional to the total sleep time of the schedule. This is the main reason why schedules with at least 3 sleep cycles are commonly recommended<ref>[https://www.polyphasic.net polyphasic.net]. Retrieved 07-12-2020.</ref> in the polyphasic community for those with intense physical activity, as they more likely guarantee the possibility to accommodate enough SWS in core(s). | | Sleep needs can be increased temporarily, usually as an effect of needed physical recovery. Such cases include increased [[Special:MyLanguage/Exercise|physical activity]]<ref>Erik Naylor, MS, Plamen D. Penev, MD, PhD, Larry Orbeta, BA, Imke Janssen, PhD, Rosemary Ortiz, Egidio F. Colecchia, MS, Moses Keng, MS, Sanford Finkel, MD, Phyllis C. Zee, MD, PhD (January 2000). ''[https://academic.oup.com/sleep/article/23/1/1/2749954 Daily Social and Physical Activity Increases Slow-Wave Sleep and Daytime Neuropsychological Performance in the Elderly.]'' Sleep, Volume 23, Issue 1, January 2000, Pages 1–9, <nowiki>https://doi.org/10.1093/sleep/23.1.1f</nowiki></ref><ref>Markus Dworak, Alfred Wiater, Dirk Alfer, Egon Stephan, Wildor Hollmann, Heiko K. Strüder (March 2008). ''[https://www.sciencedirect.com/science/article/abs/pii/S1389945707001815 Increased slow wave sleep and reduced stage 2 sleep in children depending on exercise intensity]''. Sleep Medicine, Volume 9, Issue 3, March 2008, Pages 266-272, https://doi.org/10.1016/j.sleep.2007.04.017</ref> and some substances such as [[Special:MyLanguage/cannabis|cannabis]]<ref>Barratt, E. S., Beaver, W., & White, R. (1974). ''[https://psycnet.apa.org/record/1974-24717-001 The effects of marijuana on human sleep patterns]''. Biological Psychiatry, 8(1), 47–54.</ref> or [[Special:MyLanguage/alcohol|alcohol]]<ref>Irshaad O. Ebrahim, Colin M. Shapiro, Adrian J. Williams, Peter B. Fenwick (January 2013). ''[https://onlinelibrary.wiley.com/doi/abs/10.1111/acer.12006 Alcohol and Sleep I: Effects on Normal Sleep]''. Alcoholism: Clinical & Experimental Research, Volume 37, Issue 4, April 2013, Pages 539-708, https://doi.org/10.1111/acer.12006</ref>. External events such as these sometimes may significantly increase sleep needed (mostly [[wikipedia:Slow-wave_sleep|SWS]]) which can shake the adapted state with increasing intensity inversely proportional to the total sleep time of the schedule. This is the main reason why schedules with at least 3 sleep cycles are commonly recommended<ref>[https://www.polyphasic.net polyphasic.net]. Retrieved 07-12-2020.</ref> in the polyphasic community for those with intense physical activity, as they more likely guarantee the possibility to accommodate enough SWS in core(s). |
| In some cases, [[wikipedia:Rapid_eye_movement_sleep|REM]] sleep can be increased as well. Causes may include depression<ref>Mathias Berger, Dieter Riemann (December 1993). ''[https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2869.1993.tb00092.x REM sleep in depression—an overview]''. Journal of Sleep Research, Volume 2, Issue 4, December 1993, Pages 211-223, https://doi.org/10.1111/j.1365-2869.1993.tb00092.x</ref> or intense mental activity<ref>J. De Koninck, D. Lorrain, G. Christ, G. Proulx, D.Coulombe (September 1989). ''[https://www.sciencedirect.com/science/article/abs/pii/0167876089900184 Intensive language learning and increases in rapid eye movement sleep: evidence of a performance factor]''. International Journal of Psychophysiology, Volume 8, Issue 1, September 1989, Pages 43-47, https://doi.org/10.1016/0167-8760(89)90018-4</ref>. The latter is still controversial, because other studies<ref>J. M. Siegel (November 2001). ''[https://pubmed.ncbi.nlm.nih.gov/11691984/ The REM sleep-memory consolidation hypothesis]''. doi:10.1126/science.1063049</ref> have shown no connection between REM duration and mental activity such as studying intensity. | | In some cases, [[wikipedia:Rapid_eye_movement_sleep|REM]] sleep can be increased as well. Causes may include depression<ref>Mathias Berger, Dieter Riemann (December 1993). ''[https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2869.1993.tb00092.x REM sleep in depression—an overview]''. Journal of Sleep Research, Volume 2, Issue 4, December 1993, Pages 211-223, https://doi.org/10.1111/j.1365-2869.1993.tb00092.x</ref> or intense mental activity<ref>J. De Koninck, D. Lorrain, G. Christ, G. Proulx, D.Coulombe (September 1989). ''[https://www.sciencedirect.com/science/article/abs/pii/0167876089900184 Intensive language learning and increases in rapid eye movement sleep: evidence of a performance factor]''. International Journal of Psychophysiology, Volume 8, Issue 1, September 1989, Pages 43-47, https://doi.org/10.1016/0167-8760(89)90018-4</ref>. The latter is still controversial, because other studies<ref>J. M. Siegel (November 2001). ''[https://pubmed.ncbi.nlm.nih.gov/11691984/ The REM sleep-memory consolidation hypothesis]''. doi:10.1126/science.1063049</ref> have shown no connection between REM duration and mental activity such as studying intensity. |
| In a similar vein to flexing, a schedule may be destabilized due to sleep time changes. Examples include the time shift that occurs as a result of Daylight Savings Time, time zone changes as a result of travel, or changing sleep times without a proper flexing adaptation first. These shifts can cause a desynchronization between a sleeper's circadian rhythm and their schedule, which cause similar changes to sleep quality that flexing may have, but often on a greater scale. The farther one shifts a sleep, and the more sleeps they shift at once, the higher their chances of schedule destabilization are. | | In a similar vein to flexing, a schedule may be destabilized due to sleep time changes. Examples include the time shift that occurs as a result of Daylight Savings Time, time zone changes as a result of travel, or changing sleep times without a proper flexing adaptation first. These shifts can cause a desynchronization between a sleeper's circadian rhythm and their schedule, which cause similar changes to sleep quality that flexing may have, but often on a greater scale. The farther one shifts a sleep, and the more sleeps they shift at once, the higher their chances of schedule destabilization are. |