Evidence Level
Moderate
Eleuthero was the foundational adaptogen studied by Soviet scientists Brekhman and Dardymov, who coined the term "adaptogen" in the 1960s. Their extensive research on athletes, soldiers, and cosmonauts documented improved stress tolerance, though much of this work was published in Russian and not always to Western peer-review standards. Modern research has been more modest. Kuo et al. (2010) published a well-designed crossover study showing improved cycling endurance. A 2014 Cochrane-style review found some evidence for physical performance benefits but noted most studies had small sample sizes and moderate quality.