Key Points

While not ideal, one night of bad sleep does not significantly impair muscle performance or workout quality.
Aerobic and explosive movements may be subtly affected, but strength metrics remain stable after a single night of sleep deprivation.
Hormonal fluctuations from sleep loss, such as increased cortisol, may not translate directly to noticeable performance changes.
Partial sleep deprivation has subtler impacts compared to complete sleep deprivation but may still affect morning workouts more than evening ones.

Introduction:

There are few things in life I love more than sleep, and for good reason. Sleep could easily be considered one of the "ultimate performance enhancers". It plays a critical role in recovery, muscle repair, and overall performance. Athletes and fitness enthusiasts should be constantly reminded about the importance of good sleep hygiene to optimize their results. But I think often we can take this line of thinking too far. For example, what happens when life gets in the way, and you find yourself tossing and turning all night before a workout? Should you use that as an excuse to skip the gym session? Or should you push yourself and get your body under the bar? Fortunately, science offers some reassuring answers.

The evidence suggests that while consistent, quality sleep is crucial, a single night of poor sleep may not have the devastating effects on performance that many fear. This post dives into the research on sleep deprivation—both partial and complete—to explore how it impacts various aspects of physical performance. We’ll break down the findings, provide actionable insights, and ultimately help you navigate those occasional rough nights without derailing your fitness goals.

Scientific Findings

One key study by Cullen et al. (2019) analyzed the effects of both complete and partial sleep deprivation on athletic performance, here’s what they found: Complete sleep deprivation, going an entire night without rest, resulted in significant declines in aerobic performance (11.4%), countermovement jump height (10.9%), and handgrip strength (6%). However, with partial sleep deprivation, where participants only slept for 4 hours, the impacts were more subtle. Aerobic performance dipped slightly by 4.1%, and jump height reduced by 5.2%, while handgrip strength remained largely unaffected (1).

Longer-term sleep restriction offers additional insights. Knowles et al. (2022) investigated nine consecutive nights of limited sleep (5 hours per night) and found that although total workout volume was maintained, the quality of resistance exercises declined. Bar velocity for lower-body exercises dropped by up to 15%, and perceived exertion increased by 11%. This indicates that chronic sleep restriction may affect how workouts feel more than what can actually be completed (2).

The research also explores how sleep deprivation affects specific muscle groups. Kujawa et al. (2020) studied the knee extensors and flexors under 24-hour sleep deprivation and found reduced strength in the extensor muscles, particularly among individuals with left-leg dominance. Flexor muscles, however, showed no significant changes (3).

Interestingly, hormonal responses to sleep deprivation may not directly correlate with performance outcomes. Goh et al. (2001) reported elevated cortisol and melatonin levels after a sleepless night but found no significant impairments in handgrip strength or psychomotor skills. This suggests that hormonal disruptions do not necessarily result in immediate performance deficits (4).

Finally, Bambaeichi et al. (2005) demonstrated the importance of timing. Their research revealed that muscle strength tends to peak in the evening, and partial sleep deprivation had a greater impact on morning performance. This highlights the potential for timing your workouts strategically to mitigate the effects of poor sleep (5).

Analysis of the Findings

Listen, I would never say that you shouldn’t worry about sleep, but the collective body of research paints a more nuanced picture of how sleep deprivation impacts performance than I think people realize. It’s clear that different types of activities—from aerobic tasks to strength exercises—respond differently to poor sleep. Explosive and endurance activities seem more susceptible to performance declines, while maximal strength tasks like handgrip tests are surprisingly resilient.

Hormonal fluctuations, such as elevated cortisol levels, often cited as markers of stress, do occur with sleep deprivation. However, their immediate impact on performance is not as dramatic as one might expect. This disconnect between physiological changes and practical performance outcomes suggests that the body has a remarkable capacity to adapt, at least in the short term.

Timing also plays a critical role. The observed diurnal variations, where performance peaks later in the day, offer a practical workaround for those struggling with morning workouts after a sleepless night. This highlights the importance of aligning workout schedules with natural energy peaks to optimize results.

Perhaps most importantly, the psychological effects of sleep deprivation deserve attention. Many studies report increased perceived exertion during workouts, which can deter individuals from pushing themselves. However, this is largely a perception issue rather than an actual limitation of physical capacity. Recognizing this distinction can empower individuals to still show up and perform, even when they feel off their game.

Practical Takeaways

If you’ve had a bad night of sleep, don’t despair, your body can deal with less than optimal conditions. Most of the time, you can still get a productive workout in—it just might look or feel a little different. Instead of skipping the gym entirely, try adapting your approach to suit your energy levels.

If you feel like you have to change your workouts based on a bad night’s sleep, consider first the timing of your workout. If possible, schedule your session for the late afternoon or evening, when strength and performance metrics are naturally higher. This can help counterbalance some of the negative effects of sleep deprivation. Second, adjust your expectations for the session. Focus on maintaining good form and technique rather than hitting personal records. Lowering the intensity slightly can still yield significant benefits while reducing the risk of injury.

Lastly, prioritize recovery. Use the following nights to catch up on sleep, ensuring your body can fully recuperate. While one bad night won’t derail your fitness journey, chronic sleep deprivation should be addressed to prevent cumulative effects on both health and performance.

Conclusion

In the grand scheme of your fitness journey, one bad night of sleep is not even a small bump in the road. The evidence shows that while complete and partial sleep deprivation can have subtle effects on performance, they are unlikely to ruin your workout. Strength metrics often hold steady, and even aerobic and explosive tasks are only moderately affected. By understanding how sleep impacts your performance and making small adjustments, you can navigate occasional sleep disruptions without losing momentum.

Most importantly, don’t let a poor night of sleep discourage you from showing up. The act of staying consistent, even when conditions aren’t perfect, is often more valuable than the session itself. With the right mindset and a strategic approach, you can keep moving forward, one workout at a time.

Sources:

Cullen, T., et al. “The Effects of a Single Night of Complete and Partial Sleep Deprivation on Physical and Cognitive Performance.” Journal of Sports Sciences, 2019.
Knowles, O. E., et al. “Sustained Sleep Restriction Reduces Resistance Exercise Quality and Quantity in Females.” Medicine & Science in Sports & Exercise, vol. 54, no. 12, 2022, pp. 2167-2177.
Kujawa, K., et al. “The Influence of 24-Hour Sleep Deprivation on the Strength of Lower Limb Muscles.” Sustainability, vol. 12, no. 7, 2020, pp. 2762.
Goh, V. H. H., et al. “Effects of One Night of Sleep Deprivation on Hormone Profiles and Performance Efficiency.” Military Medicine, vol. 166, no. 5, 2001, pp. 427-431.
Bambaeichi, E., et al. “The Influence of Time of Day and Partial Sleep Loss on Muscle Strength in Eumenorrheic Females.” Journal of Sports Sciences, 2005.

DISCLAIMER

The information in this article is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider or medical professional before beginning any new exercise, rehabilitation, or health program, especially if you have existing injuries or medical conditions. The assessments and training strategies discussed are general in nature and may not be appropriate for every individual. At Verro, we strive to provide personalized guidance based on each client’s unique needs and circumstances.