400m Track Interval Timer

400m repeats are the most versatile session on a track, because the same distance trains completely different qualities depending on the rest. Short rest makes it a lactate tolerance session; long rest makes it a speed session; equal rest sits near VO2max work. The distance is fixed and the recovery is the variable that decides what you are actually doing.

That is why prescribing 400s without a rest ratio is meaningless. Eight 400s with 90 seconds recovery and eight with three minutes are different sessions with different purposes, and running the second when you intended the first produces a comfortable workout that develops nothing in particular.

Set the pace from a race, not from a goal

Target splits should come from a recent race result rather than the time you want to run. A runner training at goal pace they cannot yet hold trains at the wrong intensity, accumulates more fatigue than the session was designed to produce, and often gets slower.

Recalculate from a new race when you have one. Chasing splits that were appropriate three months ago is the other half of the same error.

The rest decides the session

With full recovery — three minutes or more — you can run genuinely fast and the session develops speed and running economy. With equal or shorter recovery you cannot fully clear between reps, which is the stimulus for lactate tolerance and for VO2max work.

Neither is better. What matters is deciding which you are doing before you start, because the temptation mid-session is always to extend the rest, which quietly converts one session into the other.

Consistency across the set is the measure

A set where the last repeat matches the first is a session run at the right pace. A set that fades by five seconds was run too fast, whatever the average says.

If you cannot hold the pace, stop the session rather than completing it slower. Finishing a set at a pace that trains nothing is worse than a shorter set run correctly.

The same 400m repeats train different qualities depending on recovery. Decide which session you are running before you start.

What the rest ratio makes the session
Rest	Ratio	Trains	Typical set
30–45 s	under 1:1	Lactate tolerance	6–10 reps
60–90 s	about 1:1	VO2max, race-specific	8–12 reps
2 min	about 1.5:1	Mixed aerobic and speed	8–12 reps
3 min	about 2.5:1	Speed, running economy	6–8 reps
4–5 min	over 3:1	Pure speed, near-full recovery	4–6 reps

Set target splits from a recent race result rather than from a goal time you cannot yet hold.
If the set fades, the pace was wrong. Stop rather than finishing slower — a fading set trains fatigue, not speed.

Source: Widely used track training structure. Rest ratios and their training effects are coaching convention supported by exercise physiology literature rather than a single published standard

Sources

Widely used track training structure. Rest ratios and their training effects are coaching convention supported by exercise physiology literature rather than a single published standard , TheTimerLab — accessed 2026-07-28

🔗 Related Timers

800m Repeat Timer

Hill Repeat Timer

Tempo Run Timer

Cooper 12 Minute Run Timer

Fartlek Interval Timer

Yo-Yo Intermittent Recovery Timer

❓ Frequently Asked Questions

How much rest between 400m repeats?

It depends entirely on what you are training. Thirty to forty-five seconds makes it a lactate tolerance session, about a minute to ninety seconds sits near VO2max work, and three minutes or more makes it a speed session.

Why does the rest matter more than the distance?

Because the same 400m repeats train completely different qualities depending on recovery. Prescribing 400s without a rest ratio is meaningless — eight with 90 seconds and eight with three minutes are different sessions.

How do I set my target splits?

From a recent race result, not from the time you want to run. Training at a goal pace you cannot yet hold means training at the wrong intensity and accumulating more fatigue than the session was designed to produce.

What if I cannot hold the pace?

Stop the session rather than completing it slower. A set finished at a pace that trains nothing is worse than a shorter set run correctly, and a fading set tells you the pace was wrong rather than that you tried hard.

Is a fading set a sign of a good workout?

No — it is a sign of a mis-prescribed one. A set where the last repeat matches the first was run at the right pace. Fading by five seconds means you started too fast, whatever the average looks like.

Should I extend the rest if I am struggling?

Be aware that it quietly converts one session into another. Extending recovery turns a VO2max session into a speed session, which is a legitimate choice but should be a decision rather than a drift.