Bad Night's Sleep? Move the Session, Don't Skip It: What the Research Says About Training on Short Sleep
In short: Do not skip the session, move it. A review pooling 69 publications found sleep loss cut performance by 7.56% on average. Evening tasks were consistently impaired while morning tasks largely held up, with roughly a 0.4% drop for every hour spent awake. Train early and lighten the heavy compound lifts.
There is one training slot almost every professional in Riyadh defaults to, and after a short night it is the single most expensive one on the clock. Not because evening training is weak. Because the cost of a short night is not a flat charge you pay on waking. It accumulates through the day, and by the time you walk into the gym at eight in the evening you have been carrying it for fourteen hours.
The useful half of that finding is what it implies. If the cost grows with hours awake, it is at its smallest first thing in the morning. Which means a short night rarely has to cost you the session at all. Most of the time it just means moving it.
The Kingdom is training. The open question is when.
Start with the good news, because it is genuinely good. GASTAT's Physical Activity Statistics Publication (GASTAT, 2024) put the share of adults aged 18 and above doing 150 minutes or more of physical activity per week at 58.5%, with men at 64% and women at 46.3%. A clear majority of the adult population now clears the international weekly threshold. That is a remarkable thing to be able to write about Saudi Arabia, and it reframes the coaching problem entirely: the question is no longer how to get people training. It is how to protect the training they are already doing.
The same publication records an average of 5.9 sedentary hours a day for adults, excluding sleep. So the picture is not a population that refuses to move. It is a population that moves, sits a good deal around it, and has to fit the moving into a day shaped by work, traffic, family and prayer times. Where that lands, almost universally in this city, is after 20:00.
Riyadh does not sleep short. It sleeps split.
Before we get to the training, it is worth being accurate about how people here actually sleep, because the received wisdom is wrong in an interesting way.
Bamagoos and colleagues surveyed 1,200 Saudi adults and found workday night sleep averaging 7.1 hours, which is unremarkable. What is remarkable is everything around it. Fifty-one percent took a regular nap on workdays, averaging 2.1 hours, pushing total 24-hour sleep to 8.7 hours. At weekends the whole clock slides: median sleep onset moved to 5am and median wake time to noon, for 9.7 hours in total (Bamagoos et al., 2025). Separately, (Ahmed et al., 2017) found 33.8% of Saudi adults reporting short sleep of under seven hours a night, more common in women (37.3%) than men (31.4%).
Read those together and the shape is clear. The combination of a compressed night, a long afternoon nap and a weekend that shifts the whole clock by seven hours make the Saudi sleep week something other than simple deprivation. Total volume is decent. The architecture is split and mobile. That is not a deficiency to be corrected, and I would be wary of any coach who tells a client to adopt a Northern European sleep schedule in a city that runs on a different clock. But it does interact with training time in a way that most people, and most trainers, have backwards.
Why the evening slot earned its reputation
The evening preference is not just convenience. It has real physiology behind it. Chtourou and Souissi reviewed the time-of-day literature and found the pattern well established for anaerobic work: an early-morning trough and a peak in the late afternoon and early evening, tracking the core temperature rhythm (Chtourou & Souissi, 2012). Sprint outputs, jump heights and maximal strength all tend to sit higher when the sun is going down than when it is coming up.
So the 20:00 session is a defensible choice. You are training near your daily peak. That holds beautifully, right up until the night before goes wrong.
After a short night, the rhythm inverts
This is the part I did not expect when I first read it properly, and it is the reason this article exists.
Craven and colleagues pooled 227 outcome measures from 69 publications covering anaerobic power, speed and power endurance, high-intensity intervals, strength, endurance, strength-endurance and skill. The headline is what you would guess: sleep loss produced a mean change in performance of -7.56%, and the effect was significant across every exercise category (Craven et al., 2022).
The subgroup analyses are where it gets interesting. In their words, the negative effects on tasks performed in the PM were consistent, while tasks performed in the AM were largely unaffected. They also found a dose relationship with time awake: roughly a 0.4% decrease in performance for every hour spent awake before the task.
Sit with that for a second, because it runs directly against the chronobiology above. The normal expectation is that you are at your worst in the morning and best in the evening. After a short night, that ordering flips. The morning session is the protected one. The evening session is where the damage shows up, because you have had all day to accumulate it. Ask most experienced coaches which session to save after a bad night and they will say the evening, on the grounds that you have had more time to recover and your body temperature has come up. The pooled data says the opposite.
The kind of short night matters more than the length
The same review separated the ways a night can go short, and the results were not symmetrical. Consistent negative effects appeared only with total deprivation and with late restriction, meaning waking earlier than normal. Early restriction, meaning a delayed bedtime with a normal wake time, did not produce consistent decrements.
Translate that into Riyadh terms and it is almost a licence. The 1am bedtime after a long dinner, with your usual 7am alarm, is the survivable version of a short night. The 4:30 alarm for a flight to Jeddah on top of an already-short night is the expensive one. Same hours lost, very different cost.
Two caveats, because this is a heterogeneous body of work and pretending otherwise would be dishonest. The pooled inconsistency was high (I² = 98.1%), and 89% of participants across the included trials were male. Treat the AM-versus-PM finding as a strong planning heuristic rather than a law of nature.
Which lifts actually take the hit
Knowing the session is compromised is only useful if you know what to change in it. Knowles and colleagues reviewed sleep and resistance exercise specifically, and their finding is sharper than the general one: across consecutive nights of reduced sleep, restriction reduced the force output of multi-joint movements but not single-joint movements (Knowles et al., 2018). Total deprivation, oddly, had minimal effect on strength measures overall.
So the vulnerable item in your session is not the session. It is the top set of the squat, the deadlift, and the heavy press. Your accessory work, the rows and curls and lateral raises, is essentially intact.
There is a second detail in that review worth more than it first appears. The compound-lift impairment showed up in trials run without specific interventions designed to increase motivation. Where encouragement was applied, the decrement largely went away. That is not a soft observation. It means the drop is partly a central drive problem rather than a pure tissue problem, and it means training with a coach or a decent partner on a bad-sleep day is doing measurable physical work, not just keeping you company.
Practically, this is what training by reps in reserve is for. Hold the effort constant and let the load float down to meet it. A useful benchmark: if your normal working weight feels roughly two reps harder than usual, take about 10% off the bar and keep the prescribed reps. You will finish having trained rather than having tested.
The nap is not a workaround. It is the local advantage.
Here is where the Saudi sleep pattern stops being a complication and starts being an asset. Half the country already naps on workdays. The qailulah is not a habit anyone here needs to build, only one to point at the right target.
Boukhris and colleagues had seventeen physically active men perform a 5-metre shuttle run test after nap opportunities of 25, 35 and 45 minutes, and after no nap at all. Best distance rose by 6% after the 25-minute nap and 9% after the 45-minute nap compared with no nap. Total distance improved after all three durations, with the 45-minute condition producing an 8% gain against 3% for the shorter two. Perceived exertion told the same story from the other side: mean RPE was around 20% higher after the 25-minute nap and 19% higher with no nap than after the 45-minute one (Boukhris et al., 2019). The same work, done better, and it felt easier.
One correction to the local default, though. The 2.1-hour average nap that Bamagoos recorded is far longer than anything tested here, and long afternoon sleeps carry a real cost in grogginess on waking and in pushing the night later still. Trim it to 25–45 minutes, take it early in the afternoon, and finish at least 90 minutes before you train.
How to plan the week around this
None of this is complicated, which is rather the point. Five decisions cover almost every case:
- Slept normally? Keep the evening slot. That is where your peak lives, and Chtourou and Souissi's data says you should use it.
- Late bedtime, normal wake time? Train as planned. This was the pattern that held up. Expect the heavy top set to feel weighty and autoregulate the load.
- Early alarm, or a genuinely broken night? Move the session to the morning, within a few hours of waking. At roughly 0.4% per hour awake, a 07:00 session and a 20:00 session are not the same session.
- Cannot move it? Nap 25–45 minutes in the early afternoon, then train. And book the session with someone.
- Consistently a morning trainer? The morning trough is trainable. Chtourou and Souissi found that regular training at a set time of day raises performance at that time, in some cases up to the level of the usual evening peak.
That last one matters more than it looks for anyone whose life keeps producing short nights: a fixed early slot is not a compromise you settle for, it is an adaptation you earn. The same logic applies to training through a Riyadh summer, where the early hours are the comfortable ones anyway, and to anyone building a week around two well-placed sessions rather than five scattered ones. Fewer sessions raise the value of protecting each one.
What I would not do is chase sleep hygiene advice that fights the city you live in. Blackout blinds and a cooler bedroom are fine. Telling a Riyadh executive to be asleep by 22:00 is a plan that will be abandoned inside a fortnight. Work with the clock you have: protect the wake time, use the nap, and put the hard training closer to it.
The obvious catch is that moving a session to 06:30 only works if there is somewhere to move it to, and a commute to a gym at that hour undoes the whole advantage. This is the part RWC was built around: our coaches come to you, at home or at the office, so the early slot costs you the length of the session and nothing else. Get in touch and we will build a week that fits the clock you actually keep.
Sleep decides a great deal about how strong you are at eight in the evening. It has far less to say about how strong you are at seven in the morning. That is a scheduling decision, and it is entirely yours.
Frequently Asked Questions
Should I skip the gym after a bad night's sleep?
Usually no. Craven et al. (2022) found that after sleep loss, exercise tasks performed in the morning were largely unaffected, while afternoon and evening tasks were consistently impaired. Moving the session earlier is a better response than cancelling it.
Is it better to train in the morning or the evening?
After normal sleep, the evening. Chtourou and Souissi (2012) describe a well-established early-morning trough and a late-afternoon peak for anaerobic performance. After a short night that ordering reverses, because performance falls by roughly 0.4% for every hour you have been awake.
How long should a nap be before training?
Boukhris et al. (2019) compared 25, 35 and 45 minute nap opportunities and found 45 minutes produced the largest gains, with best distance up 9% and lower perceived exertion. Take it in the early afternoon and finish at least 90 minutes before you train.
Does poor sleep affect all exercises equally?
No. Knowles et al. (2018) found sleep restriction reduced force output in multi-joint movements such as squats and presses, but not in single-joint movements. Reduce the load on your heavy compound lifts and leave your accessory work as planned.
Does a late bedtime matter if I still wake at my usual time?
Less than you might think. Craven et al. (2022) found consistent performance decrements only with total sleep deprivation and with waking earlier than normal. A delayed bedtime followed by a normal wake time did not produce consistent impairment.
References
- Craven J, McCartney D, Desbrow B, Sabapathy S, Bellinger P, Roberts L, Irwin C. 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
- Knowles OE, Drinkwater EJ, Urwin CS, Lamon S, Aisbett B. Inadequate sleep and muscle strength: Implications for resistance training. Journal of Science and Medicine in Sport. 2018;21(9):959-968. doi:10.1016/j.jsams.2018.01.012
- Chtourou H, Souissi N. The effect of training at a specific time of day: a review. Journal of Strength and Conditioning Research. 2012;26(7):1984-2005. PMID:22531613
- Boukhris O, Abdessalem R, Ammar A, Hsouna H, Trabelsi K, Engel FA, Sperlich B, Hill DW, Chtourou H. Nap Opportunity During the Daytime Affects Performance and Perceived Exertion in 5-m Shuttle Run Test. Frontiers in Physiology. 2019;10:779. doi:10.3389/fphys.2019.00779
- Bamagoos AA, Altayeb AA, Rawas HF, Alsulaimani SS, Basurrah MA, Aleissi SA, Wali SO. Patterns of Sleep and Napping in Saudi Arabia: A Cross-sectional Evaluation. Saudi Journal of Medicine & Medical Sciences. 2025;13(2):124-132. doi:10.4103/sjmms.sjmms_679_24
- Ahmed AE, Al-Jahdali F, AlALwan A, Abuabat F, Salih SB, Al-Harbi A, Baharoon S, Khan M, Ali YZ, Al-Jahdali H. Prevalence of sleep duration among Saudi adults. Saudi Medical Journal. 2017;38(3):276-283. doi:10.15537/smj.2017.3.17101
- General Authority for Statistics. Physical Activity Statistics Publication 2024. GASTAT, Kingdom of Saudi Arabia. 2024. stats.gov.sa
Questions people ask
Why does training in the evening feel worse after a short night?
Because the cost of a short night accumulates with time awake. Craven et al. (2022) found roughly a 0.4% fall in performance for every hour spent awake before the task, so a 20:00 session carries fourteen hours of it while a session within a few hours of waking carries barely any.
How should I change my workout after a poor night's sleep?
Keep the effort, not the weight. If your usual working load feels about two reps harder, take roughly 10% off the bar and keep the prescribed reps. Knowles et al. (2018) found sleep restriction reduced force only in multi-joint lifts, so leave rows, curls and lateral raises as planned.
How can I train early if getting to a gym at 06:30 is impossible?
That commute is exactly what undoes the advantage of an early slot. RWC coaches come to you, at home or at the office, so the session costs you its own length and nothing else. If you cannot move the session at all, nap 25 to 45 minutes in the early afternoon first.