Evidence grade: A
Dozens of trials and meta-analyses show caffeine improves endurance and many strength and power measures. Responses vary from person to person.
What it is
A natural stimulant found in coffee, tea and cacao. It blocks adenosine, the signal that builds tiredness.
What people claim
- Better endurance
- Slightly more strength and power
- Lower perceived effort
- Sharper focus and reaction time
Doses used in studies
Studies commonly use about 3–6 mg per kg of body weight, taken about 60 minutes before exercise. Lower doses of around 2 mg per kg also show effects in some studies.
These are amounts researchers tested, not a recommendation for you.
Who should be cautious
- Pregnant people (guidance generally caps intake around 200 mg a day)
- People with heart rhythm problems, high blood pressure or anxiety
- Anyone with sleep problems; caffeine lasts for hours
- Avoid concentrated powders, which make overdose easy
- Anyone taking prescription medication: check with a doctor or pharmacist for interactions
- Under 18: talk to a doctor or parent before using any supplement
Holistic and Eastern context
Green tea and matcha pair caffeine with L-theanine. In Chinese and Japanese tea traditions they are valued for calm alertness rather than a jolt.
Sources
- ISSN position stand: caffeine and exercise performance Guest et al., J Int Soc Sports Nutr, 2021
- Caffeine and exercise performance: an umbrella review of 21 meta-analyses Grgic et al., Br J Sports Med, 2020
← All supplements · Laws & Research
Education only, not medical advice. Supplements are not reviewed by the FDA for safety or effectiveness before sale, and nothing here is meant to diagnose, treat, cure or prevent any condition. Talk to your doctor or pharmacist before starting any supplement, especially if you are pregnant, nursing, take medication or have a health condition.