Ashwagandha and Exercise Performance: The Research

Ashwagandha has jumped from a niche Ayurvedic herb to a mainstream sports supplement in about a decade. Walk into any supplement store and you'll find it in half the "recovery" and "adaptogen" formulas on the shelf. The question is whether the research supports the marketing.

The short answer: partly. The evidence base is much bigger than most single-supplement stories, and the direction of the findings is consistent. Ashwagandha slightly improves strength, aerobic capacity, and recovery in most randomized trials. But the effect sizes are modest, and the marketing gets ahead of the data on things like testosterone, body composition, and "energy." This article walks through the actual studies. What they measured, who they used, how big the effect really is, and how to think about whether it's worth the money.

Along the way, I'll flag where the evidence is strong, where it's mixed, and where you should be skeptical. If you're deciding whether to try it, or whether to keep taking it, this is the read.

The Research: What Studies Show

Wankhede 2015: The Strength and Recovery Trial

The paper that put ashwagandha on the sports-nutrition map is Wankhede and colleagues (2015), published in the Journal of the International Society of Sports Nutrition. Fifty-seven young men (18-50, previously untrained) started an 8-week resistance training program and were randomized to 300 mg of a standardized root extract twice daily or a matched placebo.

The gap between groups was substantial. Bench press one-rep max went up by 46.0 kg in the ashwagandha group versus 26.4 kg in placebo (p = 0.001). Leg extension strength followed the same pattern. Arm muscle cross-sectional area grew more in the ashwagandha group, body fat dropped more (3.5% versus 1.5%), and creatine kinase (a marker of muscle damage from training) rose less after workouts in the ashwagandha group than in placebo (p = 0.03), consistent with faster recovery. Serum testosterone rose by about 96 ng/dL in the ashwagandha group versus 18 ng/dL in placebo, a finding the marketing has heavily leaned on.

Two caveats matter. The subjects were previously untrained, which is the population where any intervention layered on top of resistance training tends to look great (novices adapt fast). And the effect sizes on strength are unusually large for a supplement; subsequent trials have not matched them. Still, this is the paper that anchored the entire ashwagandha-for-lifting literature.

Ziegenfuss 2018: The STAR Trial

Three years later, Ziegenfuss and colleagues (2018) ran a more rigorous test. The Strength Training Adaptations and Recovery (STAR) trial recruited 38 recreationally active men (average age 26.5, training 2 to 3 days per week for 6 to 12 months at baseline) into a 12-week protocol combining a 4-day per week upper/lower split with either 500 mg per day of a standardized aqueous root and leaf extract (Sensoril) or placebo.

Results were smaller than Wankhede's but consistent in direction. The ashwagandha group showed significantly greater between-group gains in squat one-rep max (+19.1 kg versus +10.0 kg placebo, p = 0.009) and bench press one-rep max (+12.8 kg versus +8.0 kg placebo, p = 0.048), plus a favorable shift in the android-to-gynoid body composition ratio. Peak bench press power, average squat power, 7.5 km cycling time trial performance, and perceived recovery improved significantly within the ashwagandha group but not the placebo group, though the between-group differences on those measures did not reach significance. Blood chemistry stayed within normal limits across the board, and no adverse events were reported.

The STAR trial is important because it corrected the two biggest weaknesses in Wankhede's paper. Participants were already active (so the "novice bump" was smaller) and the training program was more standardized. The strength effect held up in a more experienced population, though the additional power and endurance signals were weaker.

Choudhary 2015: The Endurance Signal

Choudhary, Shetty, and Langade (2015), publishing in Ayu, took a different angle. They gave 50 healthy athletic adults 300 mg twice daily of a standardized root extract or placebo for 8 weeks and measured VO2max via the Queen's College Step Test. The ashwagandha group saw a 13% increase in VO2max versus a smaller change in placebo, with statistically significant differences at both 8 and 12 weeks.

Quality-of-life scores on the WHO questionnaire also improved more in the supplemented group. The 13% VO2max bump is larger than what you'd expect from 8 weeks of unstructured training alone, and larger than the effect from most other supplements. Replication attempts have shown smaller effects, but the direction is consistent: ashwagandha modestly increases aerobic capacity when paired with regular exercise.

Bonilla 2021: The First Meta-Analysis

By 2021, there was enough literature to pool. Bonilla and colleagues (2021), publishing in the Journal of Functional Morphology and Kinesiology, ran a PRISMA-based systematic review and Bayesian meta-analysis of 13 studies. They separately modeled strength/power, cardiorespiratory fitness, and fatigue/recovery outcomes.

The conclusion: ashwagandha showed a positive effect on all three domains, with the strongest evidence for strength and VO2max in healthy adults performing resistance or aerobic training. Risk of bias across the included trials was rated low to moderate. It's a well-executed review, and it's the paper reviewers most often cite for "ashwagandha probably works" when a topic comes up.

Li 2026: The Most Recent Word

The current best summary is Li and colleagues (2026), publishing in Nutrients. Their three-level meta-analysis pooled 13 trials involving 599 participants and 79 effect sizes, using restricted-maximum-likelihood random-effects models with GRADE certainty ratings and dose/duration meta-regressions. It's the most methodologically sophisticated analysis to date.

They confirmed positive effects on VO2max, muscle strength, and recovery markers. Effect sizes were small to moderate. Formulation (standardized root extract worked better than whole herb powder), dose (roughly 500 to 600 mg per day was the effective range), and duration (at least 8 weeks) were the biggest moderators. Elite athletes showed smaller responses than recreational or untrained participants, mirroring what's been observed with beetroot juice and other legal ergogenic aids.

The GRADE certainty was moderate for strength and endurance outcomes and low for recovery, meaning the strength and cardio signals are on firmer ground than the "faster recovery" marketing claims.

How Ashwagandha Actually Works

The active compounds are called withanolides, a family of steroidal lactones. The most-studied are withaferin A and withanolide A. They're concentrated in the roots (and, in some formulations, the leaves) and are the reason standardized root extracts consistently outperform whole herb powders in trials.

The mechanism story is still being assembled. The best-supported piece is stress modulation. Multiple trials show that ashwagandha lowers salivary and serum cortisol at rest and blunts the cortisol spike from acute stress. That matters for training because chronically elevated cortisol interferes with recovery, sleep, and muscle protein synthesis. If ashwagandha shifts the stress/recovery balance, downstream training adaptations improve without any direct effect on muscle contraction.

A second mechanism is anti-inflammatory and antioxidant activity. Withanolides scavenge free radicals and dampen inflammatory signaling. That plausibly explains the recovery findings (lower creatine kinase, faster perceived recovery) but is harder to link to peak strength or VO2max directly.

A third proposed mechanism is on skeletal muscle itself: some in-vitro and animal work shows withanolides affect satellite-cell activation and muscle protein synthesis. The human evidence for this is thin. Treat "ashwagandha directly builds muscle" as speculative until larger mechanistic trials land.

None of these mechanisms is a stimulant pathway. Ashwagandha is not a pre-workout. You will not feel a kick 45 minutes after a dose. The whole model is that daily exposure over weeks shifts the biological environment inside which training happens, and the accumulated effect shows up on the test-day measurements at week 8 or week 12.

Why This Matters for Your Fitness

The realistic upside for a recreational lifter or runner is a small performance edge over 8 to 12 weeks of consistent training. Small is the key word. Meta-analytic effect sizes for ashwagandha on strength and VO2max sit in the roughly 0.3 to 0.5 standardized-mean-difference range, which is meaningful but not transformative. You are not going to accidentally beat your training partner's numbers because you added a capsule.

What ashwagandha will not do is fix the actual bottleneck for most people. The biggest predictor of fitness outcomes is whether you keep stringing workouts together week after week. If you're doing 2 workouts per week when you'd planned 4, no supplement closes that gap. The reason ashwagandha shows up in the data at all is that the trials enforce daily supplementation on top of a real training program. That combination is what moved the numbers.

Where ashwagandha is more interesting is the recovery and stress side. If you are chronically under-sleeping, work-stressed, and finding that your workouts feel harder than they should, the anti-cortisol effect may take the edge off. Multiple non-exercise trials have shown improvements in perceived stress and sleep quality with 300 to 600 mg per day. That's not "performance" in the strictest sense, but it's the state under which performance actually happens. If you're already sleeping 8 hours and managing stress well, this angle offers less.

How to Use Ashwagandha in Practice

Translating the evidence into a workable protocol:

• Target 500 to 600 mg per day of a standardized root extract. That's the effective range from the positive trials. Wankhede split 600 mg into two doses; Ziegenfuss used 500 mg once daily. Both worked. Whole herb powders at the same nominal weight are weaker because they contain less withanolide per gram.
• Look for a standardized extract with a stated withanolide content. The two most-studied branded extracts are KSM-66 (root-only, roughly 5% withanolides) and Sensoril (root and leaf, roughly 10% withanolides, used in the STAR trial). Generic "ashwagandha root powder" without a standardization number is a coin flip on potency.
• Take it daily for at least 8 weeks before judging. The trials that showed benefits ran for 8 to 12 weeks of continuous supplementation. If you take it for 3 weeks and quit because "nothing happened," you never entered the window where the effect shows up.
• Timing does not need to be exact. Because the mechanism is not stimulant, you are not looking for a pre-workout window. Most trials dosed morning and evening (300 mg twice) or with breakfast (500 mg once). Pick a time you'll actually stick to.
• Pair it with real training and adequate sleep. The signal in the trials came from ashwagandha layered on top of a structured resistance or aerobic program, in participants sleeping normally. It is not a compensator for a bad program or 5 hours of sleep.
• Cycle it or take it continuously? The trials don't answer this cleanly. Most studies ran 8 to 12 weeks straight without evidence of tolerance. Longer-term safety data in humans is thinner, so many practitioners cycle 8 to 12 weeks on, 4 weeks off. This is convention, not RCT-supported.

Individual Variation: Who Responds Most

Training Status

The clearest moderator is fitness level. Untrained and recreationally trained adults show the largest effect sizes across strength, endurance, and recovery outcomes. Elite athletes show smaller and less consistent responses. The Li 2026 meta-analysis flagged this directly, and it mirrors the pattern seen with other legal ergogenic aids. Systems that are already highly optimized have less headroom for a small pharmacological nudge.

Sex and Age

Most of the trials to date have been in young to middle-aged men. Trials in women are fewer but generally directionally consistent for strength and recovery. Data in adults over 60 is thinner. Given that older adults tend to have higher baseline cortisol, poorer sleep, and slower recovery, the theoretical case for ashwagandha in this group is strong, but it isn't yet backed by large trials.

Baseline Stress and Sleep

People who start with elevated cortisol, poor sleep, or high perceived stress tend to see larger benefits, presumably because they have more room for the adaptogenic effect to work. Recreational lifters who are already well-recovered may notice less. This is the reason ashwagandha's "recovery aid" reputation among busy professionals holds up better than its "performance enhancer" reputation among competitive athletes.

Common Misconceptions

Misconception 1: "Ashwagandha is a testosterone booster."

The Wankhede 2015 paper reported a testosterone jump, and the marketing ran with it. But subsequent trials have shown smaller or absent testosterone effects, and the Li 2026 meta-analysis did not identify testosterone as a robust outcome. What ashwagandha does more reliably is lower cortisol. If you're a stressed, under-recovered lifter, a lower cortisol level can indirectly support the anabolic environment, but that is not the same as pharmacologically raising testosterone. Do not use ashwagandha as an alternative to actual testosterone-replacement therapy for anyone who clinically needs it.

Misconception 2: "Ashwagandha is a natural pre-workout."

It isn't. The mechanism is not stimulant, and no acute-dose trial has shown a same-session performance boost the way a caffeine dose does. Taking a capsule 45 minutes before the gym expecting a kick will produce nothing. The molecule works over weeks, not minutes. If you want an acute performance nudge, caffeine is the evidence-based choice.

Misconception 3: "If some is good, more is better."

The positive-outcome trials clustered around 500 to 600 mg per day of standardized extract. A few smaller trials have used higher doses (up to 1,200 mg) with no clear additional benefit and slightly more reports of gastrointestinal upset. The dose-response curve appears to flatten in the 600 mg range. Chasing higher doses looks like a waste of money and increases the risk of side effects.

Misconception 4: "Ashwagandha replaces sleep, food, or a program."

No supplement does. Every positive trial in the sports literature layered ashwagandha on top of a real training program in reasonably-fed, reasonably-rested participants. Read the methods of any of these papers and the training protocol is doing most of the work. The supplement is a small addition, not a substitute for the fundamentals.

What the Research Suggests Going Forward

The ashwagandha and exercise literature is in solid but not final shape. The direction of effects (positive for strength, VO2max, and recovery) is consistent across trials and confirmed by two independent meta-analyses. The effect sizes are modest and clearest in recreational adults on standardized root extract at roughly 500 to 600 mg per day for 8 to 12 weeks. That's the confident core.

What's still open:

• Longer-term safety and efficacy data past 12 weeks in humans. Most trials are short.
• Whether the testosterone signal from Wankhede replicates in bigger trials with more experienced lifters. Current data is mixed.
• Whether ashwagandha adds anything to well-recovered, well-fed elite athletes, or whether the ceiling is already hit. Current data leans toward "smaller effect at the elite end."
• Whether the effect on older adults (60+, postmenopausal, or with high baseline stress) is larger than in young athletes. The mechanism suggests yes, the data isn't there yet.
• Whether liver-injury reports in the pharmacovigilance database reflect specific formulations, contaminants, or dose thresholds, or whether they warrant caution across the class.

The takeaway for someone deciding whether to try it: ashwagandha is one of the few supplements outside the caffeine/creatine/beetroot trio where the evidence is strong enough to make a defensible case. The upside is small and the mechanism is real. If you're a recreational trainee running a structured program, sleeping reasonably, and looking for one modest edge to layer on top, this is the right shape of supplement for the job. Take a standardized root extract at 500 to 600 mg per day, give it 8 weeks, and decide from your own numbers whether it earned its spot. If you're already recovering well and hitting your workouts, the marginal benefit may not be worth the cost.

And if you're skipping workouts, no capsule will fix that. Building the habit is a bigger lever than any supplement, and it costs nothing.

References

1. Wankhede S, Langade D, Joshi K, Sinha SR, Bhattacharyya S. "Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial." J Int Soc Sports Nutr. 2015;12:43. doi:10.1186/s12970-015-0104-9
2. Ziegenfuss TN, Kedia AW, Sandrock JE, Raub BJ, Kerksick CM, Lopez HL. "Effects of an Aqueous Extract of Withania somnifera on Strength Training Adaptations and Recovery: The STAR Trial." Nutrients. 2018;10(11):1807. doi:10.3390/nu10111807
3. Choudhary B, Shetty A, Langade DG. "Efficacy of Ashwagandha (Withania somnifera [L.] Dunal) in improving cardiorespiratory endurance in healthy athletic adults." Ayu. 2015;36(1):63-68. doi:10.4103/0974-8520.169002
4. Bonilla DA, Moreno Y, Gho C, Petro JL, Odriozola-Martínez A, Kreider RB. "Effects of Ashwagandha (Withania somnifera) on Physical Performance: Systematic Review and Bayesian Meta-Analysis." J Funct Morphol Kinesiol. 2021;6(1):20. doi:10.3390/jfmk6010020
5. Li X, Li H, Yao S, Hou Y, Chi A. "Effects of Withania somnifera (Ashwagandha) Supplementation on Exercise Performance: A Systematic Review and Three-Level Meta-Analysis." Nutrients. 2026;18(12):1915. doi:10.3390/nu18121915