Benefits
Better oxygen uptake (VO2 max) after three weeks
In the single cited study, 28 young adults (average age about 23) took a mushroom blend containing Cordyceps militaris at 4 g/day. After three weeks, VO2 max improved by about 4.8 ml/kg/min (p=0.042) and the ventilatory threshold rose by about 0.7 l/min. After one week there were no significant improvements. The paper does not name PeakO2 or any brand, so this is evidence for the mushroom blend that was tested rather than proof for this specific product, and 28 people is a small group.
No measurable benefit in the first week
No published study on this page supports a fast power boost. The one study cited here states plainly that one week of supplementation showed no significant improvements, and it did not measure peak power output at all. The 17.6% figure and the comparison with creatine and beta-alanine come from material that is not published or cited, so treat them as marketing rather than as results.
Time to exhaustion and endurance extension
In the same 28-person study, time to exhaustion increased by about 69.8 seconds after three weeks at 4 g/day. That is the most concrete finding on this page, but it comes from one small short study of a mushroom blend that the paper does not identify by brand, and the same study found no significant change after one week. Explanations involving lactate clearance or multiple mechanisms are speculation, not measured outcomes reported here.
Immune and stress claims have no cited study behind them
No study is cited on this page for immune or stress effects, either for the blend as a whole or for Turkey Tail, Reishi or Lion's Mane individually. The only reference here looked at exercise capacity in 28 young adults. Statements about immune modulation, NK cell activation and stress resilience are untested for this product and should not be treated as established.
Mechanism of action
Proposed mechanism: oxygen use and cellular energy
Cordyceps militaris contains cordycepin, adenosine and beta-glucans, and researchers have suggested these may help the body use oxygen more efficiently during hard exercise. This is a proposed explanation, not a measured one. The single human study cited here recorded exercise outcomes such as VO2 max and time to exhaustion; it did not measure mitochondrial function, ATP yield, oxidative damage or ergothioneine, and it did not test the other five mushrooms separately.
Clinical trials
Randomized study of a mushroom blend containing Cordyceps militaris at 4 g/day in 28 young adults, average age about 23, with outcomes measured after one week and after three weeks. Outcomes included VO2 max, time to exhaustion and ventilatory threshold. (Hirsch KR et al., J Diet Suppl 2017; PMID 27408987)
28 healthy young adults, average age about 23.
One week showed no significant improvements. After three weeks at 4 g/day, VO2 max rose about 4.8 ml/kg/min (p=0.042), time to exhaustion rose about 69.8 seconds, and the ventilatory threshold rose about 0.7 l/min. Limitations: only 28 participants, all young adults, a short study, a single study, and the paper does not name PeakO2 or any brand, so the results belong to the Cordyceps militaris blend that was tested rather than to this product. Independent replication is needed.