Ashwagandha vs Caffeine
for strength
Stronger evidence: tie
Stronger effect: Caffeine
Safety: Ashwagandha has the more serious interaction profile (moderate vs minor).
For strength, the two are evidence-matched; the difference is in effect and safety.
Ashwagandha
grade B moderate certainty
Ashwagandha supplementation was more efficacious than placebo for improving strength/power variables in healthy individuals.
Caffeine
grade B high certainty
reliable ergogenic effect on power and endurance performance
3–6 mg/kg pre-exercise, exercising adults
sources: PMID:33670194 · PMID:20000114