How the negative split calculator works
The banking myth, priced
Running 2% faster than goal early "banks" seconds that cost 4%+ extra pace later — glycogen drains non-linearly with intensity, and the debt collector arrives around mile 18–20 with compound interest. The fade that follows banked starts is not weakness; it is arithmetic.
Why negative splits win
Races decided in the last third reward the runner with glycogen left — which is exactly what conservative first halves preserve. Negative splits also produce better finishing experiences (passing people, strong photos, wanting to race again), which is not in the math but is in the training consistency that follows good race memories.
Executing the plan
Program the watch with the cumulative splits (from the pace calculator), run the first third by feel-plus-check (honest effort 4/10), and let the race decide when to spend. The most common execution error is the disciplined-looking "I felt so good" surge at mile 10 — the plan exists precisely to veto that feeling with numbers.