Ashwagandha for Athletes: The 13.6% VO2max Trial — And What 2025’s Meta-Analysis Confirms
The headline number on ashwagandha and endurance comes from one trial. A 2025 meta-analysis pooling six RCTs across athletic populations adds the context most articles skip: who responds, how much, and what the dose-response curve looks like.
Quick answer: The most-cited piece of athletic-performance evidence on ashwagandha is Choudhary 2015 — 600mg/day KSM-66® for 8 weeks produced a 13.6% VO2max increase in 50 athletic adults. A 2025 meta-analysis published in the Turkish Journal of Sports Medicine pooled six RCTs and confirmed an average +4.09 mL/kg/min VO2max improvement across athletic populations. Optibio® Ashwagandha KSM-66® uses the same protocol.†
If you train seriously, you’ve probably hit the wall where stacking more volume just produces more fatigue, not more fitness. Recovery is the limiter. The supplement category that addresses recovery without resorting to over-the-counter caffeine megadoses is short, and ashwagandha sits at the top of it on evidence depth.
Here’s the 2026 read on what the research actually says, with the new meta-analysis context layered in.
The flagship trial: Choudhary 2015
- Subjects: 50 healthy athletic adults (cyclists)
- Protocol: 600mg/day KSM-66® (300mg twice daily) vs placebo, 8 weeks
- Test: Cycle ergometer VO2max
- Result: Treatment group from 45.0 → 51.1 mL/kg/min (+13.6%). Placebo: +4.4%. P<0.0001.
That effect size, in trained athletes over 8 weeks, is comparable to a structured aerobic-base block in someone who’s already fit. Layered on top of normal training, it compounds.
What the 2025 meta-analysis adds
The 2025 Turkish Journal of Sports Medicine systematic review and meta-analysis pooled data across six RCTs and reported an average VO2max increase of +4.09 mL/kg/min versus placebo. Other outcomes in the pooled data: improvements in core strength, muscle recovery, and reductions in resting heart rate.
A separate 2025 review in Nutrition & Metabolism argues that part of the VO2max effect runs through hemoglobin and red-blood-cell concentration improvements — ashwagandha appears to support oxygen-carrying capacity, not just fatigue tolerance. That’s a mechanistically different lever than caffeine or beta-alanine, which is why it stacks cleanly with both.
How to actually use this if you train
Match the trial dose
600mg/day KSM-66®. Below 300mg, the published effect sizes don’t reliably apply.
Give it 8 weeks
VO2max gains were measured at week 8. Don’t evaluate at week 3.
Stack honestly
Creatine and caffeine work on different mechanisms. Ashwagandha is a recovery and oxygen-delivery tool, not a pre-workout stimulant. Run all three if you want.
Pick a third-party-tested product
If you compete in sanctioned sport, third-party batch testing matters more than brand. Ashwagandha is not on the WADA prohibited list.
Frequently asked questions
Is the 13.6% VO2max number realistic for me?
Trial averages aren’t individual outcomes. The 2025 meta-analysis pooled +4.09 mL/kg/min across six trials — a more representative expectation for the average athlete than the headline 13.6%. Both are real numbers from real research; the meta-analysis is the better personal benchmark.
Will it work if I’m not currently training?
Ashwagandha’s VO2max effect was measured in athletic adults already training. If you’re sedentary, the trial conditions don’t map cleanly. The recovery and cortisol effects still apply, but VO2max gains require an exercise stimulus.
Should I cycle ashwagandha if I’m using it for performance?
The trials don’t cycle. The 2025 12-month safety study (191 adults) found no significant adverse events at sustained dosing. Some athletes cycle 8 weeks on / 2 weeks off as a precaution, though the literature doesn’t require it.
Will ashwagandha test positive on a sport drug screen?
It’s not on the WADA prohibited list. Standard panels don’t flag KSM-66®. If you compete in a sanctioned context, choose a third-party-tested product.
What about ashwagandha for strength athletes specifically?
Different trial dataset. Wankhede 2015 measured strength gains in young men starting resistance training, same 600mg/day KSM-66® dose. Read our deep dive on ashwagandha strength gains →
The bottom line
The Choudhary 2015 13.6% VO2max trial is real and the protocol is replicable. The 2025 meta-analysis confirms a more conservative average effect of +4.09 mL/kg/min across athletic populations. Either way, the dose anchor is 600mg/day KSM-66® for 8–12 weeks. Optibio® Ashwagandha KSM-66® matches the protocol exactly.†
Related: best ashwagandha for endurance, ashwagandha muscle recovery, our science page.
Shop Optibio Ashwagandha KSM-66® →
†These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.