Caffeine capsules and chewing gum for leg strength in trained men
What it found
Both caffeine capsules and caffeinated chewing gum improved leg strength, power and jump height compared to a placebo in 15 trained men.
More than half of the participants saw meaningful gains with either form.
What they found
Studies in people
Leg strength improvements
Average knee extension strength rose by 11.2% with capsules and 7.3% with gum compared to the dummy pill. Knee flexor force development also went up by 24.1% with capsules and 20.6% with gum.
Higher jumps
Vertical jump height was 5.5% higher after capsules and 6.0% higher after gum compared to the dummy pill. About 73% of men jumped higher with capsules and 66% with gum beyond normal day-to-day variation.
Capsules versus gum
Capsules led to slightly more men improving their strength measures. Gum worked better for speed-related measures, like how fast muscles reached peak force.
Not everyone responded
Individual results varied widely. For most tests, between 46% and 80% of the men showed a meaningful improvement, meaning some got no clear benefit at all.
What the authors conclude
- They conclude that both caffeine capsules and caffeinated chewing gum improve lower-body strength and power in trained men.
- They note that capsules may suit tasks needing sustained strength, while gum may be better when speed matters.
- They suggest future research should look at how individual genes change the way people respond to caffeine.
How it was done
People take caffeine to boost exercise performance, but scientists wanted to know if different forms work differently. Chewing gum is thought to enter the bloodstream faster than swallowed capsules, so the authors compared the two.
Fifteen strength-trained men each tried three things on separate days: caffeinated chewing gum, a caffeine capsule, or a starch capsule as a dummy pill. They took about 3 to 4.5 mg per kg of body weight, then did jumping and leg strength tests after waiting up to 60 minutes.
What it can’t tell you
- This trial only included young, strength-trained men who usually consume little caffeine. It cannot show whether women, older adults or heavy caffeine users would see the same results.
- The researchers could not fully hide which form the men were taking because gum and capsules feel different. This might have influenced effort during the tests.
Who paid
- Conflicts
- No potential conflict of interest was reported by the author(s).
- Authors work at
- Shahid Beheshti University, Iran; Shiraz University, Iran; University of Chichester, UK
The paper
- Title
- Individual responses to encapsulated caffeine and caffeine chewing gum on strength and power in strength-trained males
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Teimouri-Korani H, Hemmatinafar M, Willems ME, Rezaei R, Imanian B (2025). Individual responses to encapsulated caffeine and caffeine chewing gum on strength and power in strength-trained males. Journal of the International Society of Sports Nutrition. doi:10.1080/15502783.2025.2495228Free full textPubMed 40249126DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error