The one number every session hangs off.
Threshold pace is the pace you could hold for about an hour flat out. Enter a recent race or a hard effort and this works out yours.
Get it wrong and every zone, every prescribed session and every race prediction is aimed at a runner who is not you.
Threshold sessions should sit within a few seconds either side of that — comfortably hard, controlled, not a race.
How it works
Your effort is converted to a VDOT using Daniels' equations, then we ask that model how far you would cover in an hour. The pace over that distance is your threshold pace. It is the same method Structur uses on real training data, where it reads your fastest continuous 5k or 10k inside any run from the last 120 days, plus any race results you have logged.
A 21:40 5k gives a threshold pace of 4:34 per kilometre. So a threshold session of 5 × 1km sits at 4:31–4:37, and anything run at 4:20 is a race, not a session.
Questions
What is threshold pace?
The pace you could hold for roughly an hour at maximum effort. It is the anchor every other training pace is set from.
How accurate is it?
As accurate as the effort you put in. A recent, genuinely maximal race gives a good answer; a steady long run does not.
How often should I update it?
Every four to six weeks, or after any race. Structur does it automatically from your training.
This number is where Structur starts.
Coaches prescribe against it. Self-coached runners build a block around it. Either way it stays current on its own.