Eleuthero — Siberian ginseng, Eleutherococcus senticosus — is the root sold as a stimulant sports supplement claimed to increase metabolism and fight fatigue. Russian sports scientists popularised it as an “adaptogen,” a substance supposedly helping the body resist stress, and it entered Western supplement shelves for energy, endurance, and immune support. The root contains eleutherosides credited with the effects, but clinical evidence is thin — small, mixed trials rather than the robust data behind caffeine or creatine. Like many sports supplements it lives in the gap between tradition, marketing, and proof, and quality varies since regulation is light. Athletes subject to doping control should note that supplement contamination is a real risk. Eleuthero’s reputation outruns its evidence — a common story in the performance-supplement trade.