Ashwagandha Benefits: What the Research Says for Gym-Goers and Athletes

Ashwagandha (Withania somnifera) is an adaptogen with centuries of use in Ayurvedic medicine and, more recently, a growing body of clinical research. For gym-goers and athletes, the evidence is clearest in four areas: cortisol reduction, modest improvements in muscle strength, better endurance capacity, and improved sleep quality. The research is not miraculous — but it is real and replicable.

What Is Ashwagandha?

Ashwagandha is a shrub native to India and North Africa. Its root contains the primary active compounds, called withanolides, which are believed to drive most of the adaptogenic effects. 'Adaptogen' means a substance that helps the body manage stressors — physical, mental, or biological — without overstimulating any one system.

The most studied commercial forms are KSM-66 and Sensoril, both standardised extracts with published clinical trials. Most research uses 300–600 mg of root extract per day, typically standardised to 1.5–5% withanolides.

Ashwagandha Benefits Backed by Research

1. Cortisol Reduction

The most consistent finding across trials is that ashwagandha lowers serum cortisol. A 2025 systematic review and meta-analysis (Albalawi et al., Nutr Health) analysed 7 randomised controlled trials — 488 participants total — and found a statistically significant cortisol reduction of -1.16 µg/dL (95% CI: -1.64 to -0.69, P < 0.001) in ashwagandha groups versus placebo. Interestingly, the same analysis found no significant effect on perceived stress scores. This suggests ashwagandha may reduce the biological stress signal without necessarily changing how stressed you feel — relevant for athletes in heavy training blocks where cortisol is chronically elevated.

For gym-goers, lower cortisol during recovery windows means less muscle breakdown, faster glycogen replenishment, and a better anabolic environment — especially after hard sessions or during a deload week.

2. Muscle Strength and Body Composition

The most cited trial on ashwagandha and muscle is Wankhede et al. (2015, Journal of the International Society of Sports Nutrition), a double-blind RCT of 50 healthy untrained males taking 600 mg/day KSM-66 for 8 weeks alongside a resistance training programme. Both groups were training — ashwagandha appeared to amplify the gains:

• Bench press 1RM: +46.0 kg in ashwagandha vs. +26.4 kg in placebo (p=0.001)
• Leg extension 1RM: +14.5 kg vs. +9.8 kg (p=0.04)
• Body fat percentage: -3.5% vs. -1.5% (p=0.03)
• Serum testosterone: +96.2 ng/dL vs. +18.0 ng/dL (p=0.004)

The testosterone increase is clinically modest but statistically significant. Ashwagandha did not create these results on its own — this is why progressive overload training remains the irreplaceable foundation: ashwagandha works by amplifying what you are already doing.

3. Endurance and Physical Performance

A 2024 RCT (Raut et al., Cureus; PMC11460434) enrolled 51 healthy volunteers taking 500 mg/day of ashwagandha root extract for 60 days. The ashwagandha group covered significantly more distance in a standardised effort test: 2.85 ± 0.54 km vs. 2.16 ± 0.62 km in placebo (p=0.001), and moved at higher average speed (25.6 vs. 22.2 km/h, p<0.05).

The study also tracked inflammatory biomarkers. In the ashwagandha group, IL-6 dropped from 14.98 to 7.2 pg/mL, TNF-α from 12.43 to 8.05 pg/mL, and myostatin from 6.5 to 5.9 ng/mL — all consistent with reduced exercise-induced inflammation and a more favourable environment for muscle protein synthesis.

4. Sleep Quality

Ashwagandha may also improve sleep. A 2020 randomised, double-blind, placebo-controlled trial (Kelgane et al., Cureus; PMC7096075) found significant improvements in sleep quality (P<0.0001) and mental alertness on rising (P=0.034) in participants taking 600 mg/day for 12 weeks. For training, sleep is when most muscle repair and hormonal recovery occurs. A supplement that modestly improves sleep quality compounds well with the other steps you can take to optimise sleep for muscle growth.

How to Use Ashwagandha

Dose: 300–600 mg/day of a standardised root extract (KSM-66 or Sensoril). Lower doses (250–300 mg) are effective for stress and sleep; higher doses (600 mg) are used in strength trials. Take with food to minimise mild nausea — a common side effect when taken on an empty stomach.

Timing: you can split the dose (morning and evening) or take the full dose in the evening. The sleep benefit may be slightly enhanced by evening dosing; the performance and cortisol benefits are not time-sensitive.

If you are already taking magnesium for sleep, ashwagandha can be taken alongside it — the two work through different mechanisms (GABA/melatonin pathway for magnesium; HPA axis regulation for ashwagandha).

Duration: clinical trials showing strength and performance effects run 8–12 weeks. Cortisol reduction is measurable within 4 weeks. There is no clear evidence on optimal long-term cycling; most people take it continuously with no published safety concern at standard doses for up to 90 days.

Ashwagandha Side Effects and Safety

Ashwagandha is generally well-tolerated in clinical trials at doses up to 600 mg/day for up to 12 weeks. The most common side effects are mild gastrointestinal upset (nausea, loose stools) — usually resolved by taking it with food.

Liver: there are rare case reports of drug-induced liver injury (DILI) associated with ashwagandha supplements, primarily with unregulated products or high doses. The European Food Safety Authority (EFSA) reviewed these reports in 2023. If you have existing liver conditions or take hepatotoxic medications, consult a healthcare provider before use.

Contraindications: avoid during pregnancy (uterotonic effects in animal studies), breastfeeding, and if taking immunosuppressants or thyroid medications — ashwagandha may modestly stimulate thyroid hormone production.

What Ashwagandha Won't Do

It is not a primary driver of muscle growth. In every trial, ashwagandha was taken alongside a structured training programme. Without consistent resistance training, the strength and body composition effects disappear.

It will not replace sleep hygiene. The sleep improvements observed are modest and most relevant for people with elevated stress or poor sleep quality. Prioritise 7–9 hours in a dark, cool room first.

It is not fast-acting. Most studies see meaningful changes at 4–8 weeks of consistent use. Pairing it with exercise for mental health and stress management compounds the effect — ashwagandha addresses the biochemical side while training addresses the behavioural side of stress.

FAQ

What does ashwagandha do to your body?

Ashwagandha works primarily as an adaptogen: it helps regulate the hypothalamic-pituitary-adrenal (HPA) axis, which controls cortisol release. The result is lower average cortisol, reduced exercise-induced inflammation, and — in people under stress or in heavy training — modest improvements in sleep quality and recovery capacity.

Can ashwagandha cause high AST (liver enzymes)?

There are rare reports of elevated liver enzymes in people using ashwagandha, mostly linked to unregulated supplements at high doses. Clinically tested standardised extracts (KSM-66, Sensoril) at doses of 300–600 mg/day show no hepatotoxicity in published trials. If you have liver disease or take hepatotoxic medications, speak to a doctor before use.

How long does ashwagandha take to work?

For cortisol and general wellbeing, most trials show measurable effects at 4 weeks. For muscle strength and body composition changes, 8–12 weeks of consistent use alongside resistance training is needed.

Is ashwagandha better in the morning or at night?

There is no definitive timing rule. The sleep benefit is theoretically amplified by evening dosing; the performance and cortisol benefits are not time-sensitive. Take it with your largest meal to reduce nausea risk.

Can women take ashwagandha?

Yes. The cortisol and performance benefits have been replicated in female athlete populations. The testosterone increase seen in male trials is not relevant for women in the same way. Avoid during pregnancy due to uterotonic risk.

Bottom Line

Ashwagandha has a credible evidence base for reducing cortisol during high-stress training phases, amplifying strength gains from resistance training, modestly improving endurance performance, and improving sleep quality in stressed or overtrained individuals. At 300–600 mg/day of a standardised extract, the risk profile is low and the evidence-to-hype ratio is better than most supplements on the market. It works best layered on top of solid sleep habits and consistent progressive training — not as a standalone fix.