How the Hydration Test Is Supposed to Work
Athletes now go through a combined hydration test and weigh-in 24 to 48 hours before an event. A medical technician collects a urine sample and measures its specific gravity, a proxy for hydration level. ONE Championship sets the cutoff at 1.025; a fighter above that threshold is considered too dehydrated and is not permitted to weigh in until a second sample comes back under the limit. Only after passing the hydration check does the athlete step on the scale for the actual weight reading.
The stated goal, according to ONE officials including former executive and ex-fighter Rich Franklin, is fighters entering the cage closer to their fight-night weight rather than rehydrating 10 to 15 pounds between a same-day weigh-in and the bout, a gap that produces the size mismatches many fans associate with extreme cutting.
