Think a double scoop of pre-workout means double the performance? A new trial in competitive boxers suggests that may not be true. Researchers compared 3 mg/kg and 6 mg/kg of caffeine against placebo. Both doses improved jump performance, and the bigger dose was not consistently better.
What the Researchers Actually Did
The study, published in the Journal of the International Society of Sports Nutrition (2026) by Tuerhongjiang and colleagues, used a randomized, double-blind, placebo-controlled crossover design. Fifteen male boxers, all at the Chinese national second-class athlete standard or higher, took part.
Each boxer completed three conditions in random order, separated by a one-week washout:
- Placebo
- 3 mg/kg caffeine (CAF3)
- 6 mg/kg caffeine (CAF6)
The team measured countermovement jump (CMJ), ballistic push-up (BPU) and isokinetic peak torque (PT) of the dominant shoulder and knee. Testing took place at baseline and in blocks starting 30 and 60 minutes after ingestion. The statistics used Holm adjustment across 10 planned interaction tests, which guards against false positives.
The Headline Finding: Both Doses Worked at 60 Minutes
At the scheduled 60-minute assessment, both 3 and 6 mg/kg beat placebo for CMJ jump height, peak power and relative peak power. There was no significant difference between the two caffeine doses.
For lower-body explosiveness, the lower dose captured the measured benefit. Doubling the dose added nothing detectable on this test.
Where 6 mg/kg Pulled Ahead
The higher dose did win on a few outcomes:
- Ballistic push-up: CAF6 produced higher concentric impulse, mean power and peak power than placebo at 60 minutes. CAF3 did not differ from placebo on these measures.
- Knee extension torque: This was the clearest dose-specific result. CAF6 beat both placebo and CAF3 at 60 minutes.
- Shoulder torque: Flexion and extension PT rose under caffeine at selected time points, but with no consistent dose advantage.
The authors concluded that the response pattern varied by dose and task, and that 6 mg/kg was not consistently superior to 3 mg/kg. A bigger dose bought a few extra wins, not across-the-board gains.
Mg-per-Kg Cheat Sheet
Here is what these doses look like in milligrams of caffeine:
| Body weight | 3 mg/kg | 6 mg/kg |
|---|---|---|
| 60 kg (132 lb) | 180 mg | 360 mg |
| 70 kg (154 lb) | 210 mg | 420 mg |
| 80 kg (176 lb) | 240 mg | 480 mg |
| 90 kg (198 lb) | 270 mg | 540 mg |
| 100 kg (220 lb) | 300 mg | 600 mg |
Check your pre-workout label. Many products list 200–400 mg per serving, and some stack caffeine with other stimulants. If you take two scoops, a coffee and an energy drink, you may be well past 6 mg/kg without realizing it.
Timing: Aim for About 60 Minutes
The significant effects were reported during the scheduled 60-minute assessment. That is the best-supported window from this study, so taking caffeine roughly an hour before a session lines up with the data. The abstract highlights the 60-minute block rather than 30 minutes, so don't count on peak benefits from a dose taken right before you start.
The Overdosing Angle: Why More May Not Be Better
This study did not report side effects in its abstract, so the following is general background, not a finding from this paper. Higher caffeine doses are commonly linked to jitters, anxiety, elevated heart rate, stomach upset and disrupted sleep. For a boxer, being too wired could hurt focus and recovery, and late-day dosing can wreck the night's sleep.
If 3 mg/kg gives you most of the measurable benefit, going to 6 mg/kg adds side-effect risk for a limited extra return. The trade-off may be worth it for some outcomes, such as knee extension torque, but it is not a free upgrade.
Who This Is For
- Strength-power and combat athletes looking for a sensible starting dose.
- Lifters and gym-goers who suspect their pre-workout is stronger than they need.
- Caffeine-sensitive people, who have good reason to start at the lower end.
A practical approach is to start near 3 mg/kg, take it about an hour before training, and move up only if you have a clear reason and tolerate it well. Caffeine response varies between individuals, so test any dose in training, never for the first time on competition day.
Limitations You Should Know About
- Punching was not tested. The authors say the results are evidence for selected neuromuscular outcomes, not direct evidence of improved punching or competitive boxing performance.
- Small sample. Fifteen male boxers is a modest group, and the results may not apply to women or to other levels of athlete.
- Laboratory tests. Jumps, push-ups and isokinetic torque are controlled measures, not a fight.
- Mixed dose pattern. The differences between doses depended on the task, and the abstract notes that individual-response classifications were exploratory.
- Habitual intake. The abstract does not address how usual caffeine consumption might shape responses, so treat personal tolerance as an open question.
Bottom Line
In trained boxers, 3 mg/kg of caffeine improved jump performance about as much as 6 mg/kg did at the 60-minute mark. The higher dose showed advantages only for some outcomes, notably ballistic push-up power and knee extension torque. Before you scoop more, work out your mg/kg, time it about an hour before training, and remember that nobody has yet shown this translates to a better punch.
Source: Tuerhongjiang et al. Acute effects of 3 and 6 mg·kg-1 caffeine on strength-power performance and isokinetic peak torque in competitive male boxers: a randomized, double-blind, placebo-controlled crossover trial. J Int Soc Sports Nutr. 2026. DOI: 10.1080/15502783.2026.2743368 | PubMed
