The support shouldn’t stop at the start line.

Knowing a pacing strategy beforehand is a different thing from making the right call while you are in it. During a session you are constantly deciding whether you are going too hard, whether the effort is sustainable, when to fuel and when to back off — and that is exactly the moment the advice runs out.

Elite athletes have coaches and performance staff for those decisions. Almost nobody else does. Backd exists to make that kind of support available to a person running on their own, in their own session, from a phone already in their pocket.

We have tried to build it the unglamorous way. The fuelling engine takes its numbers from a qualified sports nutritionist and records which version of his guidance produced each plan. Where he has not given us an answer, the app says so rather than inventing one — and where the evidence does not support a decision, it refuses to make it.

Backd is made by Surgent Tech Ltd, a small company in the UK. It is in pre-release testing on TestFlight, with a handful of runners at a time.