One well known trial put ashwagandha next to a placebo in men who were lifting weights. Here is what that study found, what it did not, and how to read a label if strength is the reason you are buying.
Ownership disclosure: Optibio makes and sells one of the products discussed on this page, a KSM-66® ashwagandha supplement. We earn money if you buy from us, so please read this with that in mind. Competitor details come from what those brands published at the time of writing. Formulas, servings and prices change, so check the current label and the brand's own product page before you buy. We do not test competitor products in our own lab.
Quick answer: In one 8 week trial of resistance trained men, the group taking KSM-66® ashwagandha showed larger gains in bench and leg press strength and more muscle size than the placebo group. That is a single study in a specific group over 8 weeks, not a guarantee of what will happen for you, and individual results vary. Ashwagandha is a support tool next to the training that does the real work, not a shortcut. Shop Optibio™ →†
If you searched for what the research shows on ashwagandha and strength, you have probably seen the headlines. Bigger bench, more muscle, faster recovery. Most of those headlines trace back to one study, and most of them leave out the parts that would help you set honest expectations. So let us do the opposite. Below is what that study measured, in plain terms, with the limits stated up front rather than buried.
What did the strength study actually find?
The study people point to is Wankhede 2015. Researchers took a group of healthy young men who were new to resistance training, split them into two groups, and had everyone follow the same 8 week lifting program. One group took KSM-66® ashwagandha, the other took a placebo, and nobody knew which they were on.
By the end of the 8 weeks, the ashwagandha group showed larger gains than the placebo group on several measures the researchers tracked: bench press and leg extension strength, muscle size in the arms and chest, and a smaller rise in a marker of exercise related muscle damage.† It is a genuinely interesting result, and it is one of the reasons ashwagandha keeps coming up in strength conversations.
Here is the honest limitation, and it matters. This is one trial. It ran for 8 weeks in one specific group, younger men who were relatively new to lifting, and both groups were training hard the whole time. A group average from a study like this does not promise the same outcome for you, and results vary from person to person. Newer lifters also tend to gain quickly no matter what, which makes any single starting group harder to read. Treat this as a reason ashwagandha is worth a look next to your training, not as a switch that adds weight to the bar on its own.
Where a supplement fits, and where it does not
The most useful way to think about this is order of operations. Strength gains come from the training, the food, and the sleep. Those three do the heavy lifting, every time. A supplement sits on top of that foundation and, at best, supports the work you are already putting in. It does not replace any of it.
Ashwagandha is an adaptogen, and the mechanisms people study most are around recovery and the body's stress response rather than muscle fibers directly. That fits the way the Wankhede result read: the training built the strength, and the supplement group happened to show more of it alongside better recovery markers. So if your program is inconsistent, or you are undereating, or you are sleeping five hours a night, no capsule fixes that. Get the foundation steady first. Then a well made ashwagandha is a reasonable thing to add.
What to look for on a label if strength is your goal
If you want the version of ashwagandha that was actually used in the strength research, the label needs to tell you three things. Most of the shelf fails on at least one.
- A named, standardized extract. The strength study used KSM-66®, a branded root extract standardized to a set percentage of withanolides. A bottle that just says "ashwagandha extract" with no branded name and no standardization percentage is a generic, and you cannot line it up against the research on this page.
- The plant part. KSM-66® is root only. Some other extracts use root and leaf, which changes the compound profile. Traditional preparations use the root, and the strength trial used a root only extract.
- The serving size. A branded extract at too small a serving is not the same as the amount used in the studies. Check the milligrams per day, not just the milligrams per capsule.
For the full walkthrough of why a named extract beats a generic powder, our guide on KSM-66 versus regular ashwagandha covers the gap in detail.
How do the popular strength picks compare on label facts?
Most of the ashwagandha supplements people buy for training use KSM-66®, so the differences are less about the extract and more about serving size, testing, and the guarantee. Here is how a few common options line up on the facts they publish.
| Brand | Extract | Withanolides | Daily serving | Testing & guarantee |
|---|---|---|---|---|
| Optibio™ | KSM-66® root only | ~5% | 600 mg (2 caps); 90 caps per bottle | Third party tested, every batch; 90 day money back; rated 4.75 out of 148 reviews |
| Transparent Labs | KSM-66® | 5% | 60 servings (check current label) | Publishes a COA; 45 day guarantee |
| Physician's Choice | KSM-66® root extract | KSM-66® spec | 1,000 mg (2 caps) | 60 day guarantee |
| Nutricost | KSM-66® | 5% | 600 mg (also adds BioPerine) | Third party tested; 60 day money back |
| Sports Research | KSM-66® (organic) | KSM-66® spec | 600 mg; 90 caps | Third party tested |
Details reflect what each brand published at the time of writing. Prices, servings and formulas change, so check the current label before you buy.
On the active extract, several of these are close. Optibio's case is plain and does not need dressing up: root only KSM-66® standardized to about 5% withanolides, a full 600 mg daily serving from a 90 capsule bottle, third party tested every batch, a 90 day money back guarantee, and a real 4.75 out of 148 rating. It is made in the USA in a GMP certified facility in New York with globally sourced ingredients. That is the whole pitch.
What dose did the research use?
In the strength study, the ashwagandha was KSM-66® taken as 300 mg twice a day, which is 600 mg total, alongside the 8 week lifting program. That full 600 mg daily serving is the amount you will see referenced across most of the KSM-66® research, which is why a genuine 600 mg per day is a reasonable target if you want to match what was studied.
Two practical notes. First, more is not automatically better, the studies used specific servings, so there is no reason to double up hoping for a bigger effect. Second, adaptogens are usually judged over weeks, not days. People commonly give ashwagandha a full 8 to 12 week run before deciding whether it fits, which is one reason a longer guarantee window is worth having. A 90 day window covers that whole evaluation period.
Is it safe to take while training?
Ashwagandha is well tolerated by most healthy adults, and the strength trial reported it was well tolerated over the 8 weeks. Even so, it is not right for everyone, and a supplement should fit the rest of what you are doing.
Talk with a qualified healthcare professional before you start if you are pregnant or nursing, if you take any medication, or if you have a thyroid or autoimmune condition. This is the general guidance from the National Center for Complementary and Integrative Health (NCCIH). If you are a competitive or tested athlete, check that any supplement fits your sport's rules before you add it. For a fuller walkthrough of daily use and cautions, see our endurance and training guide.
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Frequently asked questions
Does ashwagandha build muscle on its own?
No. The training, the food and the sleep build muscle and strength. In one 8 week trial of men who were lifting weights, the group taking KSM-66® ashwagandha showed larger strength and muscle size gains than the placebo group, but that was alongside a training program, not instead of one, and results vary from person to person.†
How much ashwagandha did the strength study use?
The strength study used KSM-66® at 300 mg twice a day, which is 600 mg total per day, over 8 weeks alongside resistance training. That full 600 mg daily serving is the amount referenced across most of the KSM-66® research.
How long before I would know if it fits me?
People commonly give an adaptogen a full 8 to 12 week run before deciding whether it fits, and the strength trial ran for 8 weeks. That is one reason a longer money back window matters. Optibio's is 90 days, which covers the whole evaluation period.
Does the type of ashwagandha extract matter for strength?
Yes. The strength research used KSM-66®, a root only extract standardized to about 5% withanolides at a 600 mg daily serving. A generic bottle that just says "ashwagandha extract" with no branded name and no standardization percentage cannot be lined up against that research.
Is it safe to take ashwagandha while lifting?
Ashwagandha is well tolerated by most healthy adults, and the strength trial reported it was well tolerated over 8 weeks. Talk with a qualified healthcare professional first if you are pregnant or nursing, take medication, or have a thyroid or autoimmune condition, and if you are a tested athlete, check your sport's rules.
References
- 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. Journal of the International Society of Sports Nutrition. 2015;12:43. PMID 26609282. (One 8 week trial of resistance trained young men; a group average, not a personal promise, and individual results vary.)
- National Center for Complementary and Integrative Health (NCCIH). Ashwagandha: What You Need To Know. U.S. Department of Health and Human Services. (General safety context only, not evidence for any Optibio product claim.)
† 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. This page is for informational purposes only and does not constitute medical advice.