Caffeine and Training: How Much Helps and When It Hurts

Caffeine is probably the most widely used performance enhancer in the world, and it actually works. It can make hard efforts feel easier, improve endurance and help with strength and power output. But more is not better, and the costs show up at night.

How It Works

Caffeine blocks adenosine, a molecule that builds up during the day and makes you feel tired. With less adenosine signalling, you feel more alert and effort feels lower. That is why the same workout can feel easier after a coffee.

How Much?

Research on performance typically uses around 3 to 6 milligrams per kilogram of body weight, taken 30 to 60 minutes before exercise. For a 70 kg person, that is roughly 200 to 400 mg. Many people get noticeable benefits from lower doses, around 2 to 3 mg per kilogram, with fewer side effects.

For reference, a typical cup of brewed coffee contains roughly 80 to 120 mg, and an espresso around 60 to 80 mg, though it varies a lot.

Safety Limits

Health authorities generally consider up to about 400 mg per day safe for most healthy adults, and lower amounts during pregnancy. Pre-workout supplements can contain 200 to 300 mg or more in one scoop, so read labels — it is easy to stack coffee, pre-workout and energy drinks into an uncomfortable total.

The Sleep Problem

Caffeine has a half-life of around five hours, and it can be longer for some people. A strong dose in the late afternoon may still affect your sleep at midnight, even if you fall asleep fine. Poor sleep then undermines the recovery you trained for. A good rule: avoid caffeine within about eight hours of bedtime.

Tolerance

Regular use reduces the effect. Some people save caffeine for their hardest sessions or reduce intake for a week or so before an important event to restore sensitivity.