Ashwagandha for Athletic Performance and Testosterone: What the Evidence Actually Shows
Ashwagandha (Withania somnifera) has been used in Ayurvedic medicine for centuries as a rasayana — a class of preparations intended to promote vitality and longevity. In the contemporary supplement market, it has been repositioned primarily as a sports performance and testosterone-support ingredient, appearing in pre-workout formulas, testosterone boosters, and recovery products. The global ashwagandha supplement market exceeded $800 million in 2024, with sports nutrition representing the fastest-growing segment.
The marketing claims cluster around three areas: increased testosterone and anabolic hormone levels, improved muscle strength and body composition, and enhanced recovery from exercise. These claims are supported by a genuine, if limited, clinical trial literature — primarily using two proprietary standardized extracts, KSM-66 (Ixoreal Biomed) and Sensoril (Natreon), which account for the majority of published human RCTs. The evidence is real but narrower and more conditional than the category marketing implies, and the testosterone claim in particular requires careful interpretation.
This analysis examines the athletic performance and testosterone evidence in detail, then addresses the stress and cortisol data that provides the most plausible mechanistic explanation for the observed effects.
The Testosterone Claim: What the Trials Actually Measured
The most-cited testosterone trial is Wankhede and colleagues (2015), published in the Journal of the International Society of Sports Nutrition. The study randomized 57 young men (18–50 years) with limited resistance training experience to KSM-66 ashwagandha (300 mg twice daily) or placebo for 8 weeks, combined with a standardized resistance training program. The ashwagandha group showed statistically significant increases in serum testosterone (mean increase approximately 96 ng/dL, or roughly 15% from a baseline of ~630 ng/dL), along with improvements in muscle strength (1-RM bench press and leg extension) and reductions in exercise-induced muscle damage markers (creatine kinase).
A second frequently cited trial is Lopresti and colleagues (2019), published in Medicine, which examined KSM-66 (240 mg/day) in 43 overweight men aged 40–70 with self-reported fatigue and suboptimal testosterone. After 8 weeks, the ashwagandha group showed a statistically significant increase in DHEA-S (approximately 18%) and a trend toward increased testosterone that did not reach statistical significance in the full sample, though a subgroup analysis of men with lower baseline testosterone showed a significant increase.
The testosterone findings are real, but several contextual factors limit how broadly they apply. First, the effect sizes are modest: a 15% increase from a baseline of 630 ng/dL produces a final value of approximately 726 ng/dL — still within the normal adult male range (300–1,000 ng/dL), not a supraphysiological elevation. Second, the trials enrolled men who were either untrained, overweight, or had self-reported fatigue — populations where baseline testosterone may be suppressed by stress, poor sleep, or suboptimal body composition. The effect in eugonadal, well-trained men with normal testosterone is less well-established. Third, the mechanism is almost certainly indirect: ashwagandha's withanolide constituents do not appear to be direct androgen receptor agonists; the more plausible pathway is cortisol suppression, which reduces the inhibitory effect of elevated glucocorticoids on the hypothalamic-pituitary-gonadal (HPG) axis.
The Claim
"Clinically proven to boost testosterone by up to 17%, increase muscle strength, and accelerate recovery. Our KSM-66 ashwagandha formula is the natural testosterone support backed by real science — not just marketing. Maximize your gains and dominate your training."
(Composite representative claim; reflects language used across multiple sports nutrition and testosterone-support supplement brands featuring ashwagandha.)
What the Evidence Actually Shows
The testosterone increase in the Wankhede 2015 trial was approximately 15%, not "up to 17%" — a minor distinction, but the rounding up is characteristic of how these results are presented. More importantly, the trial enrolled untrained men with a mean baseline testosterone of ~630 ng/dL. The absolute increase (~96 ng/dL) is statistically significant but clinically modest, and the final testosterone level remains well within the normal range. The claim that this constitutes "boosting testosterone" in the sense that performance-enhancing drugs do is not supported.
The muscle strength improvements in Wankhede 2015 are real: the ashwagandha group showed significantly greater increases in bench press 1-RM (+46 kg vs. +26 kg) and leg extension 1-RM (+14 kg vs. +8 kg) compared to placebo over 8 weeks of resistance training. These are meaningful effect sizes in an untrained population, though the absolute gains are partly attributable to the large novice adaptation effect in untrained subjects. Whether the same effect size would be observed in trained athletes is not established.
A 2021 meta-analysis by Pérez-Gómez and colleagues (Nutrients) pooled five RCTs on ashwagandha and muscle strength/body composition and found significant improvements in muscle strength and lean mass versus placebo, with moderate heterogeneity. The pooled evidence is directionally consistent but limited by small trial sizes and the predominance of industry-affiliated studies.
Athletic Performance: VO2 Max and Endurance
Beyond strength, ashwagandha has been studied for cardiorespiratory endurance. Choudhary and colleagues (2015, AYU) examined KSM-66 (300 mg twice daily) in 50 healthy adults over 8 weeks and reported significant improvements in VO2 max and time to exhaustion on a treadmill test versus placebo. Slaght and colleagues (2021, Journal of Functional Morphology and Kinesiology) found similar VO2 max improvements with KSM-66 in recreational cyclists. The endurance evidence is less developed than the strength evidence but points in a consistent direction.
The proposed mechanism for endurance effects involves improved mitochondrial function and reduced exercise-induced oxidative stress, mediated by withanolides' antioxidant properties. This is mechanistically plausible but has not been directly validated in human tissue studies.
The Stress and Cortisol Evidence: The More Reliable Story
The most consistent and best-replicated finding in the ashwagandha literature is not testosterone or strength — it is stress reduction and cortisol suppression. Chandrasekhar and colleagues (2012, Indian Journal of Psychological Medicine) randomized 64 adults with chronic stress to KSM-66 (300 mg twice daily) or placebo for 60 days. The ashwagandha group showed statistically significant reductions in serum cortisol (approximately 28% reduction from baseline), along with improvements on validated stress scales (PSS, GHQ-28) and self-reported quality of life. This trial is methodologically among the stronger in the ashwagandha literature: adequate sample size, validated outcome measures, and a 60-day duration sufficient to observe chronic adaptogenic effects.
The cortisol-suppression finding has been replicated across multiple trials and is the most plausible mechanistic explanation for the testosterone, strength, and recovery effects observed in the sports performance literature. Chronically elevated cortisol suppresses the HPG axis (reducing testosterone), impairs muscle protein synthesis, and delays recovery from exercise-induced damage. An ingredient that reliably reduces cortisol in stressed individuals would be expected to produce secondary improvements in testosterone, body composition, and recovery — which is precisely the pattern observed in the ashwagandha trials.
This mechanistic framing has an important implication for who is likely to benefit. Athletes and individuals with elevated baseline stress and cortisol — overtrained athletes, individuals with high occupational stress, those with poor sleep — are the population most likely to see meaningful effects. Well-rested, low-stress individuals with normal cortisol and testosterone are less likely to see the same magnitude of benefit.
Key Trials in the Ashwagandha Literature
| Study | Extract / Dose | Duration | Population | Key Finding | Funding |
|---|---|---|---|---|---|
| Wankhede et al., J Int Soc Sports Nutr 2015 | KSM-66, 300 mg × 2/day | 8 weeks | 57 untrained men, 18–50 yr | +15% testosterone; significant strength gains (bench, leg ext); reduced CK | Industry-affiliated (Ixoreal) |
| Chandrasekhar et al., Indian J Psychol Med 2012 | KSM-66, 300 mg × 2/day | 60 days | 64 adults with chronic stress | −28% serum cortisol; significant PSS and GHQ-28 improvement | Industry-affiliated (Ixoreal) |
| Lopresti et al., Medicine 2019 | KSM-66, 240 mg/day | 8 weeks | 43 overweight men, 40–70 yr, fatigue | +18% DHEA-S; testosterone trend (NS overall; significant in low-T subgroup) | Industry-affiliated |
| Choudhary et al., AYU 2015 | KSM-66, 300 mg × 2/day | 8 weeks | 50 healthy adults | Significant VO2 max improvement; improved time to exhaustion | Industry-affiliated |
| Pérez-Gómez et al., Nutrients 2021 (meta-analysis) | Mixed extracts, 5 RCTs pooled | Mixed | Mixed | Significant pooled effect on muscle strength and lean mass vs. placebo | Academic; no industry funding declared |
Verdict & Clinical Implications
Verdict: Partially Supported
Ashwagandha has a genuine evidence base for stress reduction and cortisol suppression, supported by multiple RCTs with validated outcome measures. The athletic performance and testosterone findings are real but more conditional: effect sizes are modest, most trials enrolled untrained or stressed populations, and the mechanism is most plausibly cortisol-mediated rather than directly androgenic. The claim that ashwagandha "boosts testosterone" in the sense of producing meaningful supraphysiological or clinically significant androgen elevation in healthy, well-trained men is not well-supported. The claim that it supports recovery, reduces exercise-induced stress, and may modestly improve strength outcomes in stressed or untrained individuals is reasonably supported. Nearly all published trials use industry-affiliated extracts (KSM-66, Sensoril) and have industry-affiliated investigators, which is a meaningful limitation on the independence of the evidence base. Evidence rating: 3/5.
For athletes and active individuals, the practical implication is that ashwagandha is most likely to produce meaningful benefit in those with elevated baseline stress, poor recovery, or overtrained states — where cortisol suppression has the most to offer. For well-rested, low-stress individuals with normal testosterone, the expected benefit is smaller. The standardized extracts (KSM-66, Sensoril) at doses of 300–600 mg/day are the forms with the most clinical support; unstandardized root powder products at unspecified withanolide content have a much thinner evidence base. Ashwagandha is generally well-tolerated at studied doses; rare cases of hepatotoxicity have been reported and warrant caution in patients with liver disease or on hepatotoxic medications.