Roughly three quarters of athletes use caffeine before training. Done well, it's worth a 2 to 4 per cent improvement on most endurance and strength tasks, which over a 5K is worth about 30 seconds, and over a HYROX run is worth a couple of minutes. Done badly, it spikes your heart rate, sends you to the toilet on the start line, and tanks your sleep.

This is the beginner's guide to using caffeine for training: how much, when, what form, and the times you're better off skipping it.

Why Caffeine Works

Caffeine blocks adenosine receptors in your brain, which is a fancy way of saying it stops you noticing how tired you are. The effect is bigger than it sounds. The same effort genuinely feels easier, which lets you push closer to your true limit. It also slightly increases fat burning at low intensities and improves muscle contraction speed, which is why it helps both long runs and heavy lifts.

The interesting part is that the benefit is almost entirely a perceived effort effect. The numbers on the watch get faster because your brain lets your body work harder, not because your body is suddenly able to work more. That's still a real performance gain, just one with a clear ceiling.

How Much, In Real Numbers

The research range is 3 to 6 mg per kg of bodyweight. For a 70 kg person that's 210 to 420 mg of caffeine. For a 60 kg person it's 180 to 360 mg. Higher than 6 mg/kg gives no extra benefit and a lot more side effects.

What that looks like in actual drinks:

• Filter coffee, large mug: 90 to 120 mg
• Espresso shot: 60 to 75 mg
• Standard energy gel with caffeine: 25 to 75 mg per gel
• Pre-workout scoop: 150 to 300 mg, but check the label, the range is huge
• Energy drink (250 ml): 80 to 160 mg
• Caffeine pill: 100 or 200 mg, very precise

Most beginners overshoot. If you're new to using caffeine for performance, start at the bottom of the range. 3 mg/kg is plenty.

When to Take It

Caffeine peaks in your blood about 45 to 60 minutes after drinking it, and the effect lasts roughly 4 to 6 hours. So for a single hard session, take it 45 to 60 minutes before you start.

For long events (a marathon, a half ironman, a HYROX) the strategy is different. Take a smaller dose 45 minutes before, then top up with a caffeinated gel about halfway through. The total stays within range, but the boost is fresh when you need it.

The Three Times to Skip It

Should You Cycle Off?

The classic advice is to "cycle off" caffeine for two weeks before a big race so you can re-sensitise to it. The newer evidence says you don't need to. Regular users still see most of the performance benefit on race day. The only real reason to cut back is if you've stacked your daily intake so high (multiple coffees, pre-workout, gels) that you've become genuinely dependent and the headaches when you stop are getting in the way.

A simpler rule: keep daily background intake to 2 to 3 cups of coffee, save anything above that for training and races, and you'll get the benefit without the rebound.

The Bottom Line

Caffeine works, but only at the right dose, the right time, and on the right sessions. Aim for 3 to 6 mg per kg of bodyweight, take it 45 to 60 minutes before a hard workout, skip it on easy runs and after lunch. Test what you'll use on race day in training first.

Used like that, caffeine is the simplest, cheapest performance edge you have. Used badly, it's a sleep killer with stomach issues. Pick the first one.