Cordyceps and Stamina: What the Exercise Trials Actually Measured

Four small controlled trials have tested Cordyceps products on exercise, with mixed results. A Cordyceps militaris blend raised VO2max in a three-week subgroup of just 10 young adults. Cs-4 raised breathing and lactate thresholds in older adults. In two trials in cyclists, Cordyceps products changed nothing. A reliable stamina effect is not established.

This article looks only at those exercise trials: what they measured, who took part and how to read the results.

What Do Exercise Trials Actually Measure?

"Stamina" is not a lab measurement. Trials use more specific markers:

• VO2max: the most oxygen your body can use during all-out effort.
• Ventilatory and lactate thresholds: the intensity at which breathing and blood lactate start to rise steeply. A higher threshold means you can work harder before fatigue builds quickly.
• Time to exhaustion: how long you last at a set, rising workload.
• Time trials and power output: closer to real-world performance, but noisier to measure.

A change in one marker does not guarantee a change in the others, and lab markers do not always translate into faster races.

The Four Trials, One by One

Parcell et al. 2004 — trained cyclists, no effect. Twenty-two endurance-trained male cyclists took 3 g a day of Cs-4 tablets or placebo for five weeks. VO2peak, ventilatory threshold and a work-based time trial did not differ between groups (Parcell et al., International Journal of Sport Nutrition and Exercise Metabolism, 2004).

Colson et al. 2005 — cyclists, no effect. Eight male cyclists took a Cordyceps sinensis and Rhodiola rosea formula or placebo. Muscle oxygen saturation, VO2max, ventilatory threshold and time to exhaustion did not change significantly (Colson et al., Journal of Strength and Conditioning Research, 2005).

Chen et al. 2010 — older adults, thresholds improved. Twenty healthy adults aged 50–75 took 333 mg of Cs-4 or placebo three times a day for 12 weeks. In the Cs-4 group, the metabolic threshold rose by 10.5% and the ventilatory threshold by 8.5%. VO2max did not change in either group. The product was supplied by its manufacturer (Chen et al., Journal of Alternative and Complementary Medicine, 2010).

Hirsch et al. 2017 — young adults, mixed. Twenty-eight young adults took 4 g a day of a mushroom blend containing C. militaris mycelial biomass, or placebo. After one week there were no significant differences on the main analysis. Ten volunteers continued for three weeks, and in that small group VO2max rose by 4.8 ml/kg/min with the blend versus 0.9 with placebo. Time to exhaustion also improved on a secondary analysis (Hirsch et al., Journal of Dietary Supplements, 2017). The study was funded partly by a supplement company.

Why Do the Results Disagree?

• Who took part. The positive trials involved healthy older adults and a general group of young adults. The two cyclist trials, including one in endurance-trained men with less room to improve, showed nothing.
• Which product. Cs-4 is a fermented mycelium strain, not wild Cordyceps. The Hirsch blend contained several mushrooms, and its exact C. militaris content is not stated. None of these trials tested whole C. militaris fruiting bodies.
• Tiny samples. The three-week result in Hirsch rests on six people taking the blend and four on placebo.
• Many endpoints. When a trial measures many markers, one can turn positive by chance.
• Funding. Two of the four trials had product or funding support from industry.

What about the "mental edge" often attached to Cordyceps? None of these trials measured cognition, focus or mood. That claim is untested in exercise research. Our article on Cordyceps militaris and the inner athlete discusses the wider claims, and our overview of natural mushroom supplements compares Cordyceps with other species.

Safety, Interactions and Sport

The trials above reported few side effects, and the Chen trial reported none. Memorial Sloan Kettering's clinical herb database still lists important cautions (Memorial Sloan Kettering, About Herbs: Cordyceps, updated 2022):

• Blood thinners. Cordyceps inhibits platelet aggregation and may add to anticoagulant or antiplatelet drugs.
• Diabetes medication. Lab studies suggest additive blood-sugar lowering.
• Transplant and immunosuppressant drugs. Anecdotal reports link cordyceps to changes in cyclosporin-related kidney effects, so check with your transplant team first.
• Pregnancy and breastfeeding. No safety data exist. Avoid it.

Competitive athletes face one more risk. Supplements can be contaminated, so check with your sport's anti-doping body and prefer third-party tested products. Our mushroom product checklist lists what to ask a seller.

If you are curious about the mushroom itself, our Cordyceps militaris dried fruiting bodies are a whole-food form, not the products used in these trials, and we make no performance claim for them. If you take medication, talk to your doctor or pharmacist first.

Frequently Asked Questions

Does Cordyceps improve stamina?

The evidence is mixed. Small trials found improved thresholds in older adults and a VO2max gain in 10 young adults after three weeks, but two trials in cyclists found no effect.

Did Cordyceps help trained athletes?

No. In a 2004 trial, 22 trained male cyclists took 3 g of Cs-4 daily for five weeks with no change in aerobic capacity or time-trial performance.

What did the Hirsch 2017 trial find?

A mushroom blend containing Cordyceps militaris showed no significant effect after one week. After three weeks, VO2max improved in a subgroup of 10 volunteers.

Does Cordyceps sharpen mental focus during exercise?

This has not been tested. None of the controlled exercise trials of Cordyceps measured cognition, focus or mood.

Is Cordyceps safe to take with medication?

Ask your doctor first. Cordyceps may add to the effects of blood thinners and diabetes medication and may interact with immunosuppressants. There are no safety data for pregnancy.

This article is for educational purposes only and is not medical advice. It does not replace a consultation with a doctor or pharmacist, especially if you take medication, have a health condition, or are pregnant or breastfeeding.