VO₂ max usually stays flat until the final 20‑30 % of a 10 K. In most runners it peaks around the 70‑80 % speed mark, which translates to roughly the 6‑8 km mark for a 10 K. After that, with glycogen depletion and rising lactate, VO₂ falls off by about 5‑10 % per kilometer until the finish. To predict it, track real‑time VO₂ or heart‑rate data; a sharp rise above 90 % HRmax without a corresponding VO₂ spike is the early warning that fatigue is setting in. The key is to hit that 70‑80 % sweet spot, keep the pacing tight, and watch for the first drop in VO₂ as a sign to adjust intensity.