Training · Running
Pacing: why going out fast fails
The commonest reason a target time is missed is not fitness. It is that the runner covered the first part of the race faster than they could sustain, and paid for it with a much larger loss later. This is why that trade is so bad, and what to do about it.
Running the first half of a race faster than target does not buy you time you get to keep. The seconds gained early are repaid later with interest, and the exchange rate is poor: a modest overspend in the opening kilometres commonly costs several times as much over the closing ones.
The reason is that the cost of going too hard is not a fixed debt but a change in state. Once you are past what you can sustain, the pace does not merely become uncomfortable — it becomes unavailable, and no amount of resolve returns it. A runner who has gone out too fast is not choosing to slow down.
Everybody, every time, finds correct race pace unreasonably comfortable for the first few minutes. You are rested, the field is moving, and adrenaline is doing a great deal of work. The feeling that you could go faster is accurate — you could, for a while.
So the discipline is to run the opening at a pace that feels wrong, and to trust the plan rather than the sensation. Being passed early by people you will pass later is the normal experience of a well-paced race, and it is worth deciding in advance that you will let it happen, because deciding in the moment does not work.
A target pace has to come from evidence rather than ambition, and the only good evidence is what you have actually run recently — a recent race, a time trial, or a sustained training effort. A pace derived from what you would like to run is a wish with a decimal point on it.
Once you have a target, the useful preparation is converting it into the splits you will actually see, at whatever intervals the event marks. Doing that arithmetic in advance means the only decision left on the day is whether you are on the number, which is a much easier question than working out a pace while running.
What to settle before the start:
- The target, and where it came from — If you cannot name the run it is based on, it is not a target.
- Your splits, written down — The pace calculator here will produce them from a target time and distance.
- A plan for the first kilometre — The one part of the race where the correct decision is the counterintuitive one.
- What you will do if you are ahead of schedule — The answer is nearly always to slow down, and it is much easier to have decided that beforehand.
Even pacing assumes an even course. On anything hilly, holding a constant pace means running the climbs far too hard and the descents too easily, which is the opposite of what you want. On undulating and off-road courses runners hold a constant effort instead and let the pace vary, which is why trail and fell runners talk about effort where road runners talk about splits.
Wind does the same thing to a flat course. A strong headwind on an out-and-back makes the outward leg slower at identical effort, and a split-based plan run into one will wreck the return.
Questions this guide answers
Listed so you can tell at a glance whether this is the page you wanted. HobbyHQ keeps one guide per question family rather than a page per phrasing.
- why do I slow down at the end of a race
- how should I pace a 5k
- what is an even split
- should I start fast or slow in a race
- how do I work out my race pace
- why does the first mile feel easy
Sources for this section
- Half marathon (opens in a new tab) — World Athletics · Governing body · read — supports the claim
Part of Running. Last reviewed 2026-08-30.