We Run Ultras

(4) Sleep Extension Before a 100-Miler Protects Alertness, Not Judgement

By Francesco//8 min read/Race execution & strategy

Sleep debt, not a larger tank

Pre-race "sleep banking" is usually described as storing sleep like glycogen. Sleep is instead regulated partly by homeostatic pressure — Process S — which rises during wakefulness and dissipates during sleep. Borbély's two-process model pairs it with Process C, the circadian rhythm that modulates alertness across 24 hours. Extending sleep before a 100-miler can reduce accumulated debt and improve sustained attention during later sleep loss. It cannot overfill a reservoir or guarantee sound judgement through the night.

Laboratory findings and their limits

Rupp et al. (2009, n=24) and Arnal et al. (2015, n=14) showed that six or seven nights with a 10-hour sleep opportunity before deprivation reduced psychomotor-vigilance lapses and microsleep intrusions. Both used small, male laboratory samples, so transfer to recreational ultrarunners remains uncertain. Clark et al. (2022) found no cognitive gain when adults already assigned eight hours in bed extended sleep for another six nights, suggesting a ceiling in sleep-replete people. Rabat et al. (2019) tested 14 healthy men and found no significant protection for inhibition or working memory during 38 hours awake. That single study does not prove that extension never helps executive function; it shows that alertness evidence cannot be casually extended to complex decisions.

The counterargument is that better sleep can improve performance before deprivation as well. Small athlete studies report benefits to mood, reaction time and some sport-specific outcomes after extension. One nine-person crossover study in endurance cyclists and triathletes found better time-trial maintenance after three extended nights. Those results support adequate sleep as preparation, but they do not identify a stored reserve that can be spent without consequence during a 30-hour race. The benefit still depends on baseline sleep and the outcome measured.

What 1,154 ultrarunners showed

Kishi et al. (2024) surveyed 1,154 finishers from two mountain ultramarathons. Runners who reported increasing sleep before the race also reported fewer falls — 12.3% versus 17.3% — with no significant finish-time difference. Because sleep strategy and falls were self-reported in a cross-sectional survey, the association is useful but not causal. In 11 backyard-ultra runners, Benchetrit et al. found reaction time slowed by 17%, while better sleep quality in the preceding week correlated with less deterioration. Brager et al., studying 257 runners, found that pace slowed around the circadian low. Field evidence therefore matches the laboratory mechanism more clearly for vigilance than for speed.

The runners most likely to benefit

Martin et al. (2018) surveyed 636 ultramarathon runners and found weekday sleep most commonly reported in the six-to-seven or seven-to-eight-hour bands; 37.6% scored above 10 on the Epworth Sleepiness Scale. Kishi's later cohort began race week with an average sleep debt of about 50 minutes. These data do not show that every mid-pack runner is chronically under-slept, but they make pre-race measurement worthwhile. Runners already obtaining roughly eight hours consistently have less room to benefit. Those expecting a second night also need an in-race sleep plan rather than assuming pre-race extension will carry them indefinitely.

Race duration changes the decision. A runner finishing before the first full night has limited opportunity to nap and may gain more from protecting the final pre-race nights. A runner expecting 36–60 hours must decide where sleep is possible, how an aid crew will recognise deterioration and how much time to allow after waking before technical ground. Martin's survey found that longer-race participants commonly used in-race sleep, but correlations between sleep duration and finish time are confounded because slower runners have more time and greater need to sleep.

A practical sleep-banking protocol

The trials support six or seven extended nights; beginning 10 to 14 days out is a coaching inference that leaves room for a poor night during the taper. Offer 60–90 extra minutes in bed, keep wake time stable and record actual sleep rather than intended sleep. If baseline sleep is already about eight hours and daytime alertness is good, protect consistency rather than forcing more. For races extending into a second night, rehearse short naps and allow for sleep inertia before technical terrain; athlete studies support naps but do not establish one universal ultra dose. Place extension inside a wider race-execution strategy. If navigation, balance or judgement deteriorates, extra sleep obtained a week earlier is not evidence that continuing is safe.

The rehearsal should include the environment, not only the nap length. Test whether you can sleep in race clothing, which alarm or crew cue wakes you, what food and fluid you tolerate on waking, and how long coordination feels impaired. Caffeine can delay sleep and complicate the plan, so schedule it around intended naps rather than consuming it automatically through the night. The goal is a protocol an impaired runner can follow, with a crew empowered to override it when safety changes.

Sources

Core banking trials

  1. Rupp TL, Wesensten NJ, Bliese PD, Balkin TJ, "Sleep Banking: Realization of Benefits During Subsequent Sleep Restriction and Recovery" https://doi.org/10.1093/SLEEP/32.3.311

  2. Arnal PJ, Sauvet F, Léger D, et al., "Benefits of Sleep Extension on Sustained Attention and Sleep Pressure Before and During Total Sleep Deprivation and Recovery" https://doi.org/10.5665/sleep.5244

  3. Rabat A, Arnal PJ, Monnard H, et al., "Benefit of Sleep Extension on Sustained Attention and Vigilance Despite No Improvement of Executive Function During Total Sleep Deprivation and Recovery" https://doi.org/10.3389/fnins.2019.00591

Banking in athletes

  1. Mah CD, Mah KE, Kezirian EJ, Dement WC, "The Effects of Sleep Extension on the Athletic Performance of Collegiate Basketball Players" https://doi.org/10.5665/SLEEP.1132

  2. Ritland BM, Simonelli G, Gentili RJ, et al., "Effects of sleep extension on cognitive/motor performance and motivation in military tactical athletes" https://doi.org/10.1016/J.SLEEP.2019.03.013

  3. Swinbourne R, Miller J, Smart D, Dulson DK, Gill N, "The Effects of Sleep Extension on Sleep, Performance, Immunity and Physical Stress in Rugby Players" https://doi.org/10.3390/sports6020042

  4. Bouzouraa E, Dhahbi W, Ferchichi A, et al., "Effects of One-Night Sleep Extension on Performance and Well-Being" https://doi.org/10.3390/life15081178

  5. Varesco G, Lavoie FA, Adoutoro J, et al., "Sleep extension before exercise in healthy adults" https://doi.org/10.1111/jsr.70269

Mechanism and theory

  1. Borbély AA, Daan S, Wirz-Justice A, Deboer T, "The two-process model of sleep regulation: a reappraisal" (reappraisal of the 1982 original) https://doi.org/10.1111/jsr.12371

  2. Axelsson J, Vyazovskiy VV, "Banking Sleep and Biological Sleep Need" https://doi.org/10.5665/sleep.5222

  3. Clark C, Rivas E, Gonzales J, "Effects of multi-night sleep extension on cognition in sleep-replete individuals" https://doi.org/10.1111/jsr.13582

  4. Lack L, Abeywickrama A, Vakulin A, Dunbar C, Guyett A, "Relative contributions of circadian and homeostatic processes to attentional lapses during prolonged wakefulness" https://doi.org/10.1093/sleep/zsaf090.0013

Sleep deprivation and cognition

  1. Van Dongen HPA, Maislin G, Mullington JM, Dinges DF, "The Cumulative Cost of Additional Wakefulness" https://doi.org/10.1093/sleep/26.2.117

  2. Killgore WDS, Balkin TJ, Wesensten NJ, "Impaired decision making following 49 h of sleep deprivation" https://doi.org/10.1111/j.1365-2869.2006.00487.x

  3. Venkatraman V, Chuah YML, Huettel SA, Chee MWL, "Sleep deprivation elevates expectation of gains and attenuates response to losses following risky decisions" https://doi.org/10.1093/sleep/30.5.603

  4. Yu B, Guan G, He H, Kong Y, Wang Y, "Effects of sleep deprivation on aerobic endurance performance in athletes: a meta-analysis" https://doi.org/10.3389/fphys.2025.1544286

  5. Schrimpf M, Liegl G, Boeckle M, et al., "The effect of sleep deprivation on pain perception in healthy subjects: a meta-analysis" https://doi.org/10.1016/j.sleep.2015.01.010

Ultramarathon-specific evidence

  1. Benchetrit S, Badariotti JI, Corbett J, Costello JT, "Sleep, cognitive function and performance at a multi-stage back-yard ultra-marathon" https://doi.org/10.1371/journal.pone.0299475

  2. Kishi A, Millet GY, Desplan M, Lemarchand B, Bouscaren N, "Pre-race sleep behaviors and in-race sleep strategies in mountain ultramarathon runners" https://doi.org/10.1186/s40798-024-00704-w

  3. Martin T, Arnal PJ, Hoffman MD, Millet GY, "Sleep habits and strategies of ultramarathon runners" https://doi.org/10.1371/journal.pone.0194705

  4. Brager AJ, Demiral S, Choynowski J, et al., "Earlier shift in race pacing can predict future performance during a single-effort ultramarathon under sleep deprivation" https://pmc.ncbi.nlm.nih.gov/articles/PMC7347363/

  5. Poussel M, Laroppe J, Hurdiel R, et al., "Sleep management strategy and performance in an extreme mountain ultra-marathon" https://doi.org/10.1080/15438627.2015.1040916

Napping

  1. Boukhris O, Suppiah H, Kerkeni M, et al., "How long does it take to fully recover from a nap? Performance and sleep inertia after 25- and 90-minute naps" https://doi.org/10.1080/07420528.2025.2597953

  2. Keramidas ME, Siebenmann C, Norrbrand L, Gadefors M, Eiken O, "Brief daytime naps to offset physical performance and perceptual impairments associated with short-term sleep deprivation" https://doi.org/10.1080/07420528.2018.1490316

  3. Lastella M, Halson SL, Vitale JA, et al., "To Nap or Not to Nap? A Systematic Review Evaluating Napping Behavior in Athletes" https://doi.org/10.2147/NSS.S315556

Caffeine

  1. Khcharem A, Souissi W, Masmoudi L, Sahnoun Z, "Repeated caffeine supplementation maintains endurance performance during prolonged sleep deprivation" https://doi.org/10.1080/07420528.2022.2097089

  2. Pauchon B, Drogou C, Gomez-Mérino D, et al., "Caffeine before a daytime nap: effects on sleep architecture and post-nap cognitive performance" https://doi.org/10.3390/nu16203442

Individual differences and chronotype

  1. Yamazaki E, Goel N, "Phenotypic Stability of Neurobehavioral Vulnerability to Sleep Loss" https://doi.org/10.1093/sleep/zsz292

  2. Clark C, Dellinger JR, Gonzales JU, "Chronotype moderates the relationship between sleep extension and cognitive performance" https://doi.org/10.1038/s41598-023-45238-5

Athletes and sleep

  1. Walsh NP, Halson SL, Sargent C, et al., "Sleep and the athlete: narrative review and 2021 expert consensus recommendations" https://doi.org/10.1136/bjsports-2020-102025

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