Each runner is a force-velocity sprinter with a limited anaerobic energy store, topped up by an aerobic supply. The force an athlete can produce falls as the store empties, which creates the slowdown in the home straight. Air drag, wind, air density, bends, lane geometry and a wet track are all included.

Accuracy on unseen races: profiles fitted to 50 athletes' semi-finals predicted their final within 0.29 s on average when the semi was a full effort, against 0.33 s for an "average fade" rule. Athletes who eased off in their semi were about 1 s out. The full method is in the guide.

Race data: official World Athletics results and race analysis sheets (Seiko timing), the World Athletics biomechanical report for London 2017, and the Athlete First split compilation. Real athletes' top speed and anaerobic capacity are model estimates fitted to their splits.