Endurance
Endurance performance is bounded by oxygen delivery, fuel, and the acidity that builds when efforts go hard — plus how hard the effort feels. The supplements that matter here work on the last two levers: buffering the acid load of one-to-four-minute efforts, and lowering perceived exertion so the same output feels cheaper.
Duration decides everything in this category. Caffeine’s effect shows up across time-trial lengths; beta-alanine pays off only in the 60-to-240-second window; citrulline’s data sit in high-intensity work. Match the supplement to the length of your event before buying anything — the list below says which window each one owns.
Ranked by evidence
- Caffeine 3–6 mg/kg, 30–60 minutes before longer efforts; trial your gut response in training first
- Beta-alanine 3.2–6.4 g daily in split doses for 4+ weeks; pays off only in the 1–4 minute effort window
- Citrulline malate 6–8 g, 45–60 minutes before sessions
- Creatine monohydrate 3–5 g daily; helps repeated high-intensity surges more than steady-state pace
- Rhodiola rosea 200–400 mg extract in the morning; acute endurance data are small and mixed
Grades are per goal–ingredient pairing, hand-assigned from the evidence records linked on each monograph. Ingredients without a link have a monograph on the way.
What does not work (yet)
- Beta-alanine outside the 1–4 minute window. Pooled trials show no effect on shorter maximal efforts, and the benefit fades as events stretch past roughly ten minutes.
- A single pre-race citrulline dose. The endurance trial that moved a time-trial used a week of daily dosing; one-off acute data are thinner.
The list above is the general case. Your medications, current stack, budget, and other goals change it — sometimes a lot.