He Ran a 1:36 Half. Six Weeks Later: 2:57 Marathon

He ran a 1:36 half marathon. Six weeks later: a 2:57 marathon — double the distance, nearly forty seconds per mile faster. Every race calculator says that cannot happen. It predicted 3:22. Here is why it was wrong, and why it might be wrong about your autumn marathon too. Race predictors assume two things: that your half was a maximal, tapered effort, and that the runner on marathon day is the same runner who raced it. Neither was true. His half was a checkpoint — placed mid-block, run cont...