Physiology Friday #138: Can a "Caffeine Nap" Enhance Your Exercise Performance?
Sip some coffee, take a siesta, and you might just have the best workout ever.
Hello friend.
Welcome to Physiology Friday.
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Quick finding of the week: How does a “nightcap” affect your sleep? In a randomized controlled study in young adults, drinking alcohol before sleep impaired mental function, reduced total sleep time, decreased sleep efficiency, lessened REM sleep time, and increased overnight heart rate by almost 10 beats per minute.
Leveraging the “caffeine nap” for physical performance
Caffeine is ergogenic.
Think of any mental or physical performance outcome — reaction time, executive function, sprinting ability, endurance, or muscle strength — and caffeine has probably been shown to improve it.
Caffeine is likely the most used performance-enhancing substance in the world. And it’s among the top, if not the top, in terms of its effectiveness.
That is…next to sleep.
Adequate sleep is a necessity if we want to perform at our mental and physical best, and a lack of it wreaks havoc on our mind and body. For athletes especially, sleep needs to be made a priority along with the other pillars of performance: proper training and nutrition. Sleep allows rest for the nervous and cardiovascular systems, and it’s the time when learning, muscle repair, and growth occur.
Naps are a form of sleep, but they’ve taken on somewhat of a stigma as a “luxury” afforded only to those with an extra 20–30 minutes to spare in the mid-afternoon. Naps may also be seen as a weakness — a sign that someone didn’t get enough sleep the previous night or that they’re unable to make it through the day without a quick siesta.
However, the power of napping has long been recognized among athletes and high performers as an extra opportunity for sleep and adaptation. In fact, if you’re like me, the occasional nap can contribute to productivity rather than detract from it. It’s not something to be ashamed of or avoided.
Napping during the day can also help to improve performance during a workout in the afternoon. But as we all have likely experienced, waking up from an extended nap leaves us feeling groggy, sluggish, or lost in a mental fog — something known as “sleep inertia.”
Enter the “caffeine nap” — the proposed solution to combat sleep inertia.
“How do I take a caffeine nap?” you might ask. Allow me to explain.
Consume caffeine (in your preferred potation) in about a 5–10 minute timespan. Next, find a comfy location, lie down, and drift off into a 20–30 minute nap. The pharmacokinetics of caffeine is such that peak levels in the blood occur about 60 minutes after ingestion. This means that, right around the time your nap is ending, the caffeine starts “kicking in.” With caffeine flowing through your system, you can hop up from your nap, sleep inertia nowhere to be found, and get on with your day.
You may even have the workout of your life.
If caffeine and napping can improve physical performance independently, could their combination — the caffeine nap — be even more effective? That’s what a recent study published in the journal Biology of Sport investigated.
14 young men were randomized to complete four different experimental conditions: a control condition, a nap-only condition, a caffeine-only condition, and a caffeine + nap condition.
In the nap-only and caffeine + nap conditions, participants took a 20-minute afternoon nap.
In the caffeine-only and caffeine + nap conditions, participants ingested pills containing 5 milligrams of caffeine per kilogram of body weight — an average of about 365 mg in this study (about 3 cups of strong coffee).
30 minutes after waking up from the nap, the participants performed an anaerobic sprint test, during which they completed six 35-meter all-out sprints.
Maximum power during the sprints increased when participants took a nap, ingested caffeine, and when they combined caffeine and a nap. Though not significant, maximum power output was higher in the caffeine + nap condition (+135 watts above placebo) compared to the other two conditions.
Average power also increased when participants took a nap, ingested caffeine, and when they combined caffeine and a nap. Average power was 70 watts higher in the caffeine + nap condition compared to the nap-only condition (a significant difference) but was not different than the caffeine-only condition.
Biomarkers of metabolism, muscle damage, and recovery were also assessed in the study.
Blood glucose after exercise was higher in both of the caffeine conditions compared to the nap-only condition. Markers of muscle damage increased in the caffeine-only and caffeine + nap conditions, but not the nap-only condition. On the other hand, plasma antioxidants increased in both of the nap conditions.
This study reinforces the idea that napping and caffeine ingestion improves performance. Though only one performance outcome (average power) was slightly higher when caffeine and napping were combined, the other outcomes didn’t seem to benefit from the nap + caffeine synergy.
The increase in antioxidants after exercise when participants napped is a neat finding. Muscle damage markers were also lower in the nap-only condition after exercise compared to both of the caffeine conditions. This might suggest that going into a workout well-rested might expedite recovery.
One interesting finding was that participants' ratings of perceived exertion during exercise were not different among any of the conditions. Since participants completed more overall work during the caffeine + nap condition, this would imply that the caffeine nap may allow you to work harder or do more work with less effort.
The finding that muscle damage markers were higher in both of the caffeine conditions compared to the placebo and nap-only conditions could be a function of participants performing more overall work — since muscle damage is related to the intensity of exercise.
It should be noted that the performance-boosting effects of caffeine, napping, and their combination were observed in well-rested individuals. Before each test day, participants were allowed a full night of sleep. So, the nap and caffeine weren’t just bringing them back to baseline.
However, this same group of researchers has shown that a 20- or 90-minute caffeine nap can improve sprint performance and reaction time after partial sleep deprivation. So, if you’re running on little sleep and in need of a major boost, call on the caffeine nap (though 90 minutes seems a bit long in my opinion).
There were only 14 participants in this study, all of whom were young males performing a single test of anaerobic performance. There’s much to be learned about how the caffeine nap may impact other types of performance (i.e., strength, endurance, or cognitive) in different study populations. There’s also the question of whether people with different versions of the gene that affects caffeine metabolism (making them a “faster” or “slower” metabolizer) would respond similarly to a caffeine nap. But that’s a topic for another post.
In the meantime, you can experiment with the caffeine nap starting today. And if you’ve already been taking advantage of this “hack”, I’d love to hear about it in the comments below or on social media.
As always, thanks for reading. See you next Friday.
~Brady~