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6 min readfocus / endurance

6 hours a night for 2 weeks equals a night without sleep

I run about 5,000 km a year, race 100 km, and spend training days on my feet in front of a room. The hour I used to cut first was the last one in bed, and I read the bill off how I felt at 10 a.m. Hans Van Dongen's laboratory held that reading against a stopwatch for 14 nights and the two came apart: people restricted to 6 hours in bed stopped feeling worse after a few days while their scores kept falling 1.

What the research shows.

Van Dongen's group kept healthy adults at 4, 6 or 8 hours in bed for 14 consecutive nights, alongside a group held awake for 3 nights 1. The 8-hour group stayed flat. Lapses on a vigilance task climbed through all 14 nights in the 4-hour and 6-hour groups, and by the end the 6-hour group performed on vigilance and digit symbol substitution at the level one night of total sleep deprivation produces, with the working memory deficit drifting toward the 2-night mark. Subjective sleepiness in those groups rose for the first few days and then leveled off, so the gap between what participants reported and what they scored widened every night 1.

Physical output responds within a single night. Jonathan Craven's team pooled 227 performance outcomes from 69 publications comparing exercise after 6 hours of sleep or less against exercise after a normal night 2. Performance came out 7.56% lower on average (95% CI 3.13% to 11.9% lower). Two details in that pooling change how you arrange a short night: afternoon and evening sessions suffered more than morning ones, and losing sleep at the end of the night through an early alarm cost more than going to bed late 2.

Thiago Lopes's meta-analysis of 31 studies, 478 participants and 38 effect sizes put the effect of sleep deprivation on endurance performance at a standardized mean difference of -0.52 (95% CI -0.67 to -0.38), with efforts over 30 minutes hit harder than shorter ones 3.

Extra sleep moves the same measures upward. Cheri Mah followed 11 players on the Stanford men's basketball team through 2 to 4 weeks of their habitual schedule, then 5 to 7 weeks with a 10-hour minimum in bed 4. They gained 110.9 minutes of sleep per night. Their 282-foot sprint fell from 16.2 to 15.5 seconds, free throws went from 7.9 to 8.8 out of 10, and 3-point shooting from 10.2 to 11.6 out of 15 4.

Sleep can be stored before you need it. Pierrick Arnal's team gave subjects 6 nights at 9.8 hours in bed or 6 nights at their habitual 8.2, then took both groups through a night of total sleep deprivation followed by 10 hours of recovery sleep. The extended group made fewer vigilance lapses before the deprivation, held that margin during it, and kept part of it after recovery 5.

Injury and illness follow the same dose. Matthew Milewski surveyed 112 school athletes and matched their answers to injury records: sleeping under 8 hours a night went with 1.7 times the injury rate of athletes at 8 hours or more 6. Aric Prather tracked 164 adults with wrist actigraphy for a week, then administered nasal drops containing rhinovirus. Sleepers under 5 hours developed a clinical cold at 4.50 times the odds of those above 7 hours (95% CI 1.08 to 18.69), and the 5-to-6-hour band at 4.24 times 7.

Daniel Windred's group scored more than 10 million hours of accelerometer data from 60,977 UK Biobank participants on night-to-night consistency of sleep and wake times. The four most regular quintiles carried 20% to 48% lower all-cause mortality risk than the least regular quintile, and that index predicted mortality better than sleep duration did 8.

The sharpest numbers sit in the smallest samples.

Mah's study has 11 players and no control group, and a team improving across 9 weeks of a season has practice working for it as well as sleep 4. Milewski's sleep hours and injuries come from a school survey, which gives an association, not a cause 6. Prather's odds ratios have lower bounds at 1.08, so the direction of the cold effect is firmer than its size 7. Craven's pooling reports an I² of 98.1%, meaning the studies inside it disagree widely about magnitude 2. The result I plan around is Van Dongen's dissociation, because it recurs across the restriction literature: after roughly 3 days, your rating of your own alertness stops tracking your performance, which makes "I feel fine" useless as a stopping rule.

The protocol.

  1. Fix one wake time for all 7 days and let bedtime absorb the variation. Weekend catch-up sleep moves your wake time, and the night-to-night consistency it costs you predicted mortality better than duration in 60,977 people 8.
  2. Book 8.5 hours in bed rather than 8 hours of sleep. Time in bed is the number you control; sleep is the fraction you get. Mah's players needed a 10-hour floor in bed to add 111 minutes of sleep 4.
  3. Move the loss to bedtime rather than the alarm. On a long day, go to bed an hour late instead of setting the alarm an hour early. Early awakening cost more performance than delayed bedtime across Craven's 227 outcomes 2.
  4. Move the hard session to the morning after a short night. A 6 p.m. interval workout becomes 7 a.m., or becomes easy running with the intervals pushed 24 hours. Afternoon and evening work took the larger hit, and efforts over 30 minutes the larger still 23.
  5. Extend for the 6 nights before the day that matters. Add 60 to 90 minutes in bed before a race, a launch or a long-haul flight. Arnal's group reached 9.8 hours in bed and kept the advantage through a night without sleep 5.
  6. Count vigilance lapses 3 mornings a week. Run a 3-minute reaction time test and log the number of responses over 500 ms next to your 7-day sleep average. Watch the lapse count, since the feeling flattens by day 3 while the count keeps rising 1.
  7. Treat a short night in race week as a training decision. One night under 6 hours in the 10 days before a race moves the quality session back a day; 3 in a row cancels it, then rebuild the week from the fixed wake time in step 1.

Sources.

  1. Van Dongen, H. P. A., Maislin, G., Mullington, J. M., & Dinges, D. F. (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep, 26(2), 117-126. link
  2. Craven, J., McCartney, D., Desbrow, B., Sabapathy, S., Bellinger, P., Roberts, L., & Irwin, C. (2022). Effects of acute sleep loss on physical performance: a systematic and meta-analytical review. Sports Medicine, 52(11), 2669-2690. link
  3. Lopes, T. R., Pereira, H. M., Bittencourt, L. R. A., & Silva, B. M. (2023). How much does sleep deprivation impair endurance performance? A systematic review and meta-analysis. European Journal of Sport Science, 23(7), 1279-1292. link
  4. Mah, C. D., Mah, K. E., Kezirian, E. J., & Dement, W. C. (2011). The effects of sleep extension on the athletic performance of collegiate basketball players. Sleep, 34(7), 943-950. link
  5. Arnal, P. J., Sauvet, F., Leger, D., van Beers, P., Bayon, V., Bougard, C., Rabat, A., Millet, G. Y., & Chennaoui, M. (2015). Benefits of sleep extension on sustained attention and sleep pressure before and during total sleep deprivation and recovery. Sleep, 38(12), 1935-1943. link
  6. Milewski, M. D., Skaggs, D. L., Bishop, G. A., Pace, J. L., Ibrahim, D. A., Wren, T. A. L. (2014). Chronic lack of sleep is associated with increased sports injuries in adolescent athletes. Journal of Pediatric Orthopaedics, 34(2), 129-133. link
  7. Prather, A. A., Janicki-Deverts, D., Hall, M. H., & Cohen, S. (2015). Behaviorally assessed sleep and susceptibility to the common cold. Sleep, 38(9), 1353-1359. link
  8. Windred, D. P., Burns, A. C., Lane, J. M., Saxena, R., Rutter, M. K., Cain, S. W., & Phillips, A. J. K. (2024). Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. Sleep, 47(1), zsad253. link

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