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(4) Sleep Banking Before a 100-Miler — What the Evidence Actually Supports

/8 min read

You can't fill a tank that's already full

The glycogen analogy dominates ultra coaching: bank sleep the way you bank carbohydrates, top up your reserves, arrive with a full tank. Intuitive — and wrong in one critical way. Glycogen is stored fuel with a ceiling you can work toward; sleep is governed by a homeostatic pressure system — Process S — that rises with wakefulness and dissipates during sleep, regulated around biological need rather than a reservoir you can overfill. Borbély's two-process model (1982) pairs Process S with Process C, the circadian rhythm that modulates alertness across the 24-hour cycle. Banking acts on Process S alone — reducing the homeostatic debt you carry at the start line. The correct mental model is arriving debt-free, not overfull.

The lab findings — and their limits

The foundational evidence is robust. Rupp et al. (2009, n=24) and Arnal et al. (2015, n=14) independently showed that six to seven nights of 10-hour time-in-bed before sleep deprivation significantly reduces psychomotor vigilance task lapses and microsleep intrusions. Both used small, male-dominated laboratory samples, so transfer to recreational ultrarunners carries uncertainty. Clark et al. (2022) drew the ceiling: participants assigned eight hours per night showed no cognitive gain from six additional extended nights — the benefit is debt correction, not surplus accumulation. The most important finding comes from Rabat et al. (2019), who used the same banking protocol as Arnal but measured executive function — inhibition and working memory. The result: zero banking benefit under 38 hours of total sleep deprivation. Banking protects alertness and reaction speed; it does not protect the cognitive machinery needed to read a map or judge a DNF at mile 75.

1,154 runners can't be ignored — but the finding isn't what you expect

Kishi et al. (2024) provide the largest real-world dataset on pre-race sleep: 1,154 finishers across two mountain ultramarathons. Runners who increased pre-race sleep had significantly lower fall prevalence — 12.3% versus 17.3% (p = 0.02) — with no significant finish-time benefit. Banking is a risk management strategy, not a pace strategy. In a small cohort (n=11), Benchetrit et al. (2024) found a 17% increase in reaction time (Cohen's d = 1.09) at the Suffolk Back Yard Ultra-marathon, with seven-day pre-race sleep quality correlating with post-race degradation (r = −0.64). Brager et al. (2019), studying 257 runners across 50- and 100-mile events, found pace slowest around the circadian nadir (approximately ZT 20, corresponding to early-morning hours depending on race start), with peak dropout of 57% at mile 75. That window is where banking's attentional protection matters most.

Most of you are the target population

Martin et al. (2018) surveyed 636 ultramarathon runners and found habitual weekday sleep modal at six to seven hours, with a mean Epworth Sleepiness Scale of 8.9 and 37.6% scoring above the clinical threshold of 10 for excessive daytime sleepiness. Most mid-pack 100-milers are chronically under-slept — precisely the population banking evidence describes. Elite sub-twenty-hour finishers face a different calculus: they never encounter a second circadian night, so start timing matters more than extension. For runners spending 36 or more hours on course, in-race napping becomes equally important — Martin et al. (2018) found cumulative in-race sleep correlates with finish time for races lasting 36–60 hours (r = 0.48) and over 60 hours (r = 0.44).

What to actually do

Start 10 to 14 days before race day, not race week. Kishi (2024) found that 38.2% of runners who intended to bank still accumulated net sleep debt in the final seven days — pre-race anxiety and taper disruption are reliable saboteurs. Target 60 to 90 additional minutes per night for at least six nights (a practical adaptation; the RCT protocols used larger extensions of 96 to 173 minutes); keep your wake time fixed and shift bedtime earlier rather than sleeping later. Preliminary data from Lack et al. (2025) suggest the circadian component explains more variance in attentional lapses under deprivation than the homeostatic component alone — misaligning your clock while reducing Process S may be a net harm. If you already sleep eight or more hours, prioritise consistency over extension. For in-race sleep, target the first circadian nadir (broadly 0100–0400, later for evening chronotypes) and budget at least 90 to 120 minutes total: Boukhris et al. (2025) found 60 minutes minimum for sleep inertia to clear after a nap, so that window sits on top of the nap itself. A caffeine nap — 100 to 200 mg ingested immediately before sleep onset — is effective; avoid caffeine within six hours of a planned nap. Banking delays the point at which your footing becomes dangerous and appears to reduce your risk of falling. It does not make you a sound decision-maker at hour 28 — plan your nap strategy accordingly.

Sources

Core Banking RCTs

  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

  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., "Circadian phenotype and temporal patterning of performance during US Army 100-mile ultramarathons" https://doi.org/10.5935/1984-0063.20190132

  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 — General

  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