Does More Sleep Make You Faster? What Sleep-Extension Studies Show

Most triathletes know they should sleep more. Fewer actually do. Early swim sessions, long commutes, work, family and evening training squeeze sleep from both ends of the day, and sleep is usually the first thing to give when the week gets busy. It doesn't feel like training, so it's easy to treat as optional.

The question this article tries to answer is narrower than "is sleep important?" (it is). It's whether deliberately sleeping more than you usually do, a strategy researchers call sleep extension, makes you faster. The answer is: possibly, but the evidence is thinner than the confident claims you'll often see. It comes from small studies, mostly in men, mostly in team sports, and it rarely includes anyone who looks like an age-group triathlete.

This article covers what sleep extension is, the key studies and their sample sizes, what happens when sleep is cut short, the evidence on naps, how this applies to early race starts and travel, and what we still don't know.

What sleep extension means

Sleep extension is a simple intervention: increase the time you spend in bed, and ideally asleep, above your usual amount. Studies have done this in different ways:

• Setting a target time in bed, such as at least 10 hours a night.
• Increasing time in bed by a percentage, such as 30% more than usual.
• Adding daytime naps on top of night-time sleep.
• Sleep hygiene education, which advises athletes on habits such as consistent bedtimes and a dark, cool bedroom, without setting a target.

It's worth separating two ideas. One is that athletes who are chronically short of sleep would benefit from getting enough. The other is that already well-rested athletes can gain an extra edge by sleeping even longer. The studies below don't always distinguish between these, and most participants were probably sleeping less than they needed at the start.

How much sleep do athletes get?

A 2021 expert consensus statement in the British Journal of Sports Medicine, led by Neil Walsh with 18 co-authors including Shona Halson and Charli Sargent, summarised what is known about sleep in athletes. Key points:

• Elite athletes are particularly prone to inadequate sleep, often under 7 hours a night, and poor sleep quality.
• Between 50% and 78% of elite athletes report sleep disturbance across studies, and 22% to 26% report highly disturbed sleep.
• Sport-specific risk factors include high training loads, short- and long-haul travel, the night before competition, evening competition, and early morning training before 8:00.
• Non-sport risk factors include female sex, age, poor mental health, stress and anxiety.
• General guidance for adults is 7 to 9 hours a night. Experts speculate that athletes may need more, but the consensus recommends an individualised approach based on the athlete's perceived sleep need.

The panel also described much of the research as weak, citing few control groups, few female athletes and questionable sleep measurement tools. That caveat applies to everything that follows.

Inference: early-morning swim sessions are one of the risk factors listed, and they are a regular feature of many triathletes' weeks. Age-group triathletes weren't studied, but there's no obvious reason to expect them to sleep better than the elite athletes who were.

The systematic review

The most direct summary is a 2021 systematic review by Aldo Silva and colleagues in Sleep Medicine. They searched five databases in November 2020 for controlled trials of sleep extension in athletes with at least one performance outcome. According to the published abstract:

• The search found 74 records.
• Sleep extension added between 26 and 106 minutes of time in bed or total sleep per night.
• Of 15 performance measures, 6 showed large effects, and the rest ranged from trivial to medium.
• Risk of bias was high in the randomised trial and low in the non-randomised trial.
• The authors concluded the evidence is limited and that sleep extension may improve performance, with effects that depend on the measure. They called their conclusions tentative.

The abstract reports that 2 studies were included, while the tables in the accepted manuscript list 7 trials, including the basketball and cycling studies described below. Either way, the evidence base is small. In the manuscript the authors also noted that all of the large effects came from studies with methodological weaknesses, that samples were mostly male, and that few sports were represented.

The basketball study

The study most often quoted is by Cheri Mah and colleagues at Stanford, published in Sleep in 2011. It involved 11 healthy male varsity basketball players with a mean age of 19.

• Baseline: players kept their usual sleep schedule for 2 to 4 weeks.
• Extension: for 5 to 7 weeks, they aimed for as much sleep as possible, with a minimum of 10 hours in bed each night.
• Sleep increased by 110.9 minutes per night on average, measured objectively.
• Sprint times improved from 16.2 to 15.5 seconds.
• Free-throw and three-point shooting percentages each improved by about 9%, as reported in the abstract.
• Reaction time, daytime sleepiness and mood (more vigour, less fatigue) also improved.

These are striking results, but the design has clear limits. There was no control group: every player did the baseline phase and then the extension phase, so improvements could partly reflect ongoing training, growing familiarity with the tests, or the players' expectations. It was 11 young men in one team sport. None of the outcomes were endurance measures.

The cycling and triathlon study

For triathletes, the most relevant trial is by Spencer Roberts and colleagues at Deakin University, published in Medicine & Science in Sports & Exercise in 2019. It involved nine endurance-trained cyclists and triathletes (all men, according to the Silva review's tables).

Each athlete completed three conditions in a crossover design, each lasting four consecutive days with a time trial on each day:

• Normal sleep: usual time in bed.
• Sleep restriction: time in bed cut by 30% for three nights, giving about 4.7 to 4.9 hours of sleep.
• Sleep extension: time in bed increased by 30% for three nights, giving about 8.2 to 8.6 hours of sleep, compared with roughly 6.5 to 7.1 hours in the normal condition.

The results:

• Extension improved performance. On day four, after three extended nights, the time trial took 56.8 minutes on average, compared with 58.7 minutes after normal sleep.
• Restriction impaired performance. On day three, the time trial took 60.4 minutes, compared with 58.8 minutes after normal sleep.
• Mood and attention improved with more sleep and worsened with less.

Inference: those differences are roughly 3% faster with extension and 3% slower with restriction, calculated from the reported means. That's a meaningful effect for a time trial, but it comes from nine men tested over a few days, so the true effect could be considerably smaller or larger.

Note too that "normal" sleep in this study was under 7 hours on some nights. The extension condition may have been correcting a modest sleep shortfall rather than adding sleep on top of an already adequate amount. That fits the idea that the biggest gains go to athletes who are under-slept to start with.

Other trials in the review

The Silva review's tables describe several other small studies. A tennis study of 12 players (5 men, 7 women) found that sleeping more than 9 hours, including naps, was followed by better serving accuracy. A football (soccer) study of 20 men used sleep hygiene education and found mostly trivial to small changes. A shooting study of 24 athletes (12 men, 12 women) added only about 26 minutes of sleep. Two studies tested naps rather than night-time sleep.

The pattern is a lot of young, male, team-sport athletes, with small samples and a wide mix of methods. The cycling study is the only one involving endurance athletes, and none involved age-group triathletes or masters athletes.

What sleep loss does

The evidence that losing sleep hurts performance is considerably stronger than the evidence that extra sleep helps. A 2022 systematic review and meta-analysis by Jonathan Craven and colleagues in Sports Medicine pooled 69 publications, 227 performance outcomes and 959 participants, about 89% of them men. Sleep loss was defined as 6 hours or less in 24 hours, compared with more than 6 hours.

• Sleep loss reduced exercise performance by 7.56% on average. Results varied widely between studies.
• Effects were seen in every exercise category, including endurance, strength, high-intensity intervals and skill.
• Total sleep deprivation and "late restriction" (waking earlier than usual) consistently hurt performance. "Early restriction" (going to bed later than usual) did not show consistent effects.
• For each extra hour awake before exercise, performance fell by about 0.4%.
• Afternoon and evening performance was consistently impaired, but morning performance was largely unaffected.

That last finding is relevant to triathlon, which usually starts early. Inference: a short night caused by a pre-dawn alarm before a morning race may cost less than many athletes fear, because you've been awake for only a few hours when you start. A long-course race that runs into the afternoon is a different matter, and no study has tested sleep loss over an Ironman.

Naps

Naps are the most practical form of sleep extension for many athletes, and they have a better evidence base than night-time extension. A 2023 systematic review and meta-analysis by Arthur Mesas and colleagues in the British Journal of Sports Medicine pooled 22 randomised controlled trials in 291 men aged 18 to 35, of whom 164 were trained athletes and 127 physically active adults.

• After a normal night's sleep, naps taken between 12:30 and 16:50 (most often at 14:00) improved physical performance (SMD 0.99), cognitive performance (SMD 0.69) and perceived fatigue (SMD −0.76).
• Naps also helped after partial sleep deprivation.
• The largest benefits came from naps of 30 to under 60 minutes, and when more than an hour passed between waking and testing.

There were no women in the included trials, and the results varied a lot between studies. The Walsh consensus suggests naps under 30 minutes for alertness and mood with less grogginess, timed for roughly 13:00 to 16:00, and advises avoiding naps if you struggle to fall asleep at night. The two pieces of guidance aren't contradictory: shorter naps limit grogginess, while the meta-analysis found slightly longer naps gave more benefit when there was time to wake up properly before training.

Early starts, the night before and travel

The night before a race

Many athletes sleep badly before a race because of nerves, an unfamiliar bed and an early alarm. The Walsh consensus lists the night before competition as a risk factor for poor sleep. The Craven meta-analysis suggests morning performance is less affected by sleep loss than afternoon performance.

Inference: rather than worrying about the last night, aim to sleep well in the week before. That is also the period when the cycling study's extension effect appeared, after three nights.

Early training

The Walsh consensus lists training before 8:00 as a risk factor for sleep loss. If you swim at 6:00 three days a week, you are effectively doing "late restriction" on those nights unless you go to bed earlier. The Craven meta-analysis found late restriction was one of the types of sleep loss that consistently hurt performance.

Travel

Long-haul travel to a race also disrupts sleep. The Walsh consensus notes that jet lag typically resolves at about one day per time zone crossed. For a race in a distant time zone, that suggests arriving early enough to adapt, or adjusting your sleep schedule before you leave.

A triathlon scenario

The following example is illustrative, not drawn from a study. An age-group athlete targets a 70.3 with an 07:00 start. Their usual week includes two 06:00 swims, a long ride at the weekend, and around 6.5 hours of sleep on weeknights. Race morning means a 04:30 alarm.

Based on the evidence above, a sensible approach would be:

1. In the final two weeks, move bedtime 30 to 60 minutes earlier on most nights, especially before early swims. This is the kind of extension the cycling study used, though in an athlete who may well be under-slept to start with.
2. On the weekend before the race, add a 30 to 60 minute nap after the long session if time allows, finishing at least an hour before any training.
3. During race week, don't introduce sleep medication or new supplements to "make sure" of sleep.
4. The night before, accept that sleep may be short and broken. Get to bed early, but don't panic if you lie awake.

This is inference, not a tested protocol. It combines the extension studies with the sleep-loss meta-analysis. No study has tested it in triathletes.

Common mistakes

• Treating sleep as optional when training load rises. The Walsh consensus lists high training loads as a risk factor.
• Expecting one long night to fix a sleep deficit. The positive studies extended sleep over several nights or weeks.
• Panicking about the night before a race. Sleep in the preceding days probably matters more.
• Napping too long, too late and then sleeping poorly at night.
• Ignoring signs of a sleep disorder, such as loud snoring, gasping at night or excessive daytime sleepiness despite enough time in bed.
• Relying on a wearable alone. Consumer devices estimate sleep with varying accuracy. TriForward's "Reading the Trend, Not the Number" covers the related problem of over-reading single HRV readings.

Who benefits most?

The positive studies mostly involved young athletes who were probably not sleeping enough at baseline. Inference: if you're already sleeping 8 hours a night and wake without an alarm, extra sleep may add little. If you're regularly on 6 hours with an alarm and an early swim, you're more likely to resemble the athletes who improved.

The Walsh consensus suggests using validated questionnaires, such as the Athlete Sleep Screening Questionnaire, to identify athletes who need help. They recommend referring athletes with moderate to severe problems to a sleep professional.

What we don't know

• Whether sleep extension improves long-course triathlon performance. No study has tested it in triathletes over race distances.
• Whether the effects apply to women. The cycling study, the basketball study and every trial in the nap meta-analysis included only men.
• Whether well-rested athletes benefit. Most participants were probably under-slept.
• How much of the effect is expectation. You can't blind someone to sleeping longer.
• The effect in older athletes. Participants were mostly in their late teens or twenties.
• How long the benefits last. Most studies lasted days or weeks.

References

• Silva AC, Silva A, Edwards BJ, Tod D, Amaral AS, de Alcântara Borba D, et al. Sleep extension in athletes: what we know so far – a systematic review. Sleep Medicine, 2021;77:128–135. doi:10.1016/j.sleep.2020.11.028
• Mah CD, Mah KE, Kezirian EJ, Dement WC. The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep, 2011;34(7):943–950. doi:10.5665/SLEEP.1132
• Roberts SSH, Teo WP, Aisbett B, Warmington SA. Extended sleep maintains endurance performance better than normal or restricted sleep. Medicine & Science in Sports & Exercise, 2019;51(12):2516–2523. doi:10.1249/MSS.0000000000002071
• Craven J, McCartney D, Desbrow B, Sabapathy S, Bellinger P, Roberts L, et al. Effects of acute sleep loss on physical performance: a systematic and meta-analytical review. Sports Medicine, 2022;52(11):2669–2690. doi:10.1007/s40279-022-01706-y
• Mesas AE, Núñez de Arenas-Arroyo S, Martinez-Vizcaino V, Garrido-Miguel M, Fernández-Rodríguez R, Bizzozero-Peroni B, et al. Is daytime napping an effective strategy to improve sport-related cognitive and physical performance and reduce fatigue? A systematic review and meta-analysis of randomised controlled trials. British Journal of Sports Medicine, 2023;57(7):417–426. doi:10.1136/bjsports-2022-106355
• Walsh NP, Halson SL, Sargent C, Roach GD, Nédélec M, Gupta L, et al. Sleep and the athlete: narrative review and 2021 expert consensus recommendations. British Journal of Sports Medicine, 2021;55(7):356–368. doi:10.1136/bjsports-2020-102025