The most used substance in the world to improve performance really works, but it has a hidden “cost” on recovery if you mistime it: here is how to manage it.
- What it does: Masks fatigue by blocking adenosine; it doesn’t “give” energy.
- The dose: 3-6 mg/kg is the scientific standard, but often less is enough.
- The timing: Peaks at 45-60 minutes, but stays in your system for hours.
- The danger: Sleeping doesn’t mean resting. Caffeine worsens the quality of deep sleep.
- The golden rule: Stop caffeine at least 8-10 hours before sleeping.
If there is one supplement that unites the Sunday amateur and the Olympic champion, it is caffeine. It is legal, accessible, and, above all, it works.
But there is a problem. We often use it “randomly”: to wake up, to survive the 2:00 PM meeting, to get pumped before the evening run.
The result? Maybe the workout goes well, but at night we toss and turn, or worse, we sleep but wake up tired.
Caffeine is a useful tool, and like all effective tools, you need to know how to handle it. Obviously, we aren’t moralizing (we like coffee as much as you do, we’ve talked about it often), but it helps to line up all the information to help you understand.
What Caffeine Really Does (and What It DOES NOT Do)
Let’s clear up a misunderstanding: caffeine doesn’t give you energy. It contains no calories usable as fuel (unless you put three packets of sugar in it).
Caffeine acts on the central nervous system as a “deceiver.” It binds to adenosine receptors (the molecule that tells the brain “you are tired, rest”) blocking them. Basically, it takes off the fatigue handbrake and increases the release of neurotransmitters like dopamine and adrenaline.
The result is a reduction in Rate of Perceived Exertion (RPE). At the same speed, you feel less fatigue.
A recent meta-analysis published in PubMed confirms that caffeine intake significantly improves endurance performance and time to exhaustion. You run longer or harder simply because your brain “feels” the pain of fatigue less.
Dose: How Much You Need for Effect (Without Overdoing It)
“The more I take, the faster I go.” False. There is an inverted U-curve: beyond a certain threshold, benefits disappear and tremors, tachycardia, and anxiety arrive.
Scientific literature indicates an effective dose between 3 and 6 mg per kg of body weight.
For a 70 kg runner, that means between 210 and 420 mg.
However, for many unaccustomed amateurs, even lower doses (1-3 mg/kg) offer tangible benefits without heavy side effects.
Starting with the bare minimum is always the best strategy.
Quick Table – Caffeine in Common Drinks
Values are approximate and vary based on blend and preparation.
- Espresso (bar): 60-80 mg
- Moka (homemade cup): 80-120 mg (often more concentrated than espresso!)
- American/Filter Coffee (large cup): 100-150 mg
- Tea (cup): 30-50 mg
- Energy Drink (standard can): 80-160 mg
- Energy Gels with caffeine: 25-100 mg (but always read the label)
Timing: When to Take It and When to Stop to Protect Sleep
And here is the catch.
Caffeine reaches its peak in the blood after about 45-60 minutes. So taking it while tying your shoes makes sense.
The problem is the half-life, i.e., the time the body takes to eliminate half of it. The average half-life is 5-6 hours, but can reach 9-10 hours in slow metabolizers.
If you take a double coffee at 6:00 PM to train, at midnight you still have the caffeine of a whole cup in your system.
Even if you are one of those who says “I sleep anyway,” science proves you wrong: epidemiological studies and controlled trials show that evening caffeine reduces total sleep duration and suppresses deep sleep, the regenerative kind.
You wake up, but you haven’t recovered. And recovery is part of training.
Three Practical Scenarios (Morning / Lunch Break / After Work)
How to behave in real life?
- Early Morning Workout (06:00 – 09:00):
- Green Light. Pre-run coffee is great. It helps wake you up, activates the gut, and improves performance. You have all day to clear it.
- Lunch Break Workout (12:00 – 14:00):
- Yellow/Green Light. A coffee around 11:30-12:00 is fine. However, be careful not to overdo post-lunch coffee if you suffer from insomnia.
- Late Afternoon/Evening Workout (after 17:30):
- Red Light. Avoid caffeine. If you are mentally tired from work, use other strategies: rhythmic music, hydration (often we are just dehydrated), a light snack with carbs, or, if you have time before, a strategic Power Nap (but without coffee if it’s too late). The priority here is sleeping well afterwards.
If You Are Sensitive – 3 Signs Caffeine Is Screwing You Over
We are not all genetically equal in metabolizing caffeine. Be careful if:
- “Tired but Wired”: You are dead tired but your brain won’t shut off when you go to bed.
- High Resting Heart Rate: If the next morning your heart rate is 5-10 beats above average, you might not have recovered (or be overstimulated).
- Excessive Pre-Race Anxiety: If before an important workout you have tremors or nausea, caffeine is worsening stress instead of helping you.
When to Avoid It or Talk to a Doctor
Caffeine is safe for most people, but there are cases where it should be drastically limited or avoided:
- Gastroesophageal Reflux: Coffee relaxes the stomach valve and increases acidity. Running with reflux is hell.
- Uncontrolled Hypertension: Caffeine temporarily raises blood pressure.
- Anxiety Disorders: If you suffer from anxiety or panic attacks, caffeine is gasoline on the fire.
- Chronic Insomnia: If you sleep poorly, cutting caffeine after 12:00 PM is the first test to do, before any melatonin or supplement, perhaps trying relaxation techniques like NSDR.
Use it like a turbo: press the button when you really need it, don’t hold it down all day.