How is this different from just picking a cardio exercise?

The cardio exercise generator gives you a single movement; this builds the whole structure around it — how many repetitions, how long each effort and recovery lasts, and the running total including warm-up and cool-down. Use this when you want the session planned, not just the exercise named.

Can I use this for distance-based intervals rather than time-based ones?

Not directly — there's no distance mode, since the tool works in time throughout. Put the distance in the effort name (e.g. '400m') and set the work duration to roughly how long that takes you, and the structure still works even though the clock is timing rather than measuring distance.

Running Interval Generator

Generates a structured interval-running session — reps, distance or time, and recovery — for runners who want genuine session variety without planning the whole structure themselves.

Format

Effort

What you are doing in the work period — a distance, a pace, or just "hard effort".

1 entry

Rounds

How many work periods.

Work (seconds)

How long each work period lasts.

Rest (seconds)

Between work periods. Zero means continuous work.

Warm-up (seconds)

Optional. Zero leaves it out entirely.

Cool-down (seconds)

Optional. Zero leaves it out entirely.

Seed (optional)

A word that brings the same session order back.

Shuffle the order of the list

Your session will appear here.

How to use this tool

Press Build session.
Warm up first, then follow the structure shown.

Understanding the controls

Effort: What you are doing in the work period — a distance, a target pace, or simply hard effort. Several entries cycle round repetition by repetition.
Work and rest: The effort and the recovery. The ratio between them characterises a running session far more than the absolute lengths do.
Rounds: How many repetitions. The total updates as you change it, and that is the number deciding whether the session fits the time you have.
Warm-up and cool-down: Counted in the total but kept out of the work and recovery figures. Worth setting honestly, since together they are often a third of a running session.

Worked examples

6 x 3 minutes with 90 seconds recovery: 25 minutes 30 seconds of efforts and recoveries, before any warm-up.
With 10 minutes at each end: 45 minutes 30 seconds in total, which is the figure that matters for fitting the session in.
Mixed efforts: Enter several and the session cycles through them repetition by repetition.

Common use cases

Running-training variety
Structured cardio sessions
Breaking a single-pace running routine

How this generator works

Efforts and recoveries alternate, and the session ends on an effort rather than a recovery so the sheet finishes where the running does. The running clock down the side is the accumulated total, so you can see when each repetition starts, and the total includes any warm-up and cool-down — which is what makes it the figure to plan around rather than the sum of the efforts alone.

Randomness and fairness

Nothing is random unless several efforts are entered and shuffling is switched on, in which case the order they fall in is drawn at random. The structure and the total are pure arithmetic. A seed makes that order reproducible so a squad can be set the same session on different days. It is deterministic, not cryptographic: two runners with the word get the same session, and so would anybody else.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

The tool arranges time and knows nothing about pace, distance or your fitness. The efforts are yours to set, and it recommends nothing.
Every repetition is the same length, so a session that shortens the efforts or the recoveries as it progresses has to be built as two or three separate sessions.
There is no distance mode. If your session is measured in metres, put the distance in the effort name and set the work time to how long it takes you.
Warm-up and cool-down default to zero, which is almost never right for a running session — set them, or the total will understate the time you need.

Privacy and your data

The efforts you type stay in your browser and are never uploaded or stored — closing the tab discards them. What is measured is that a session was generated and how many blocks it has, never the effort list itself.

Not personalised advice — check with a medical professional before starting a new exercise routine, especially with an existing health condition.

Frequently asked questions

How is this different from just picking a cardio exercise?: The cardio exercise generator gives you a single movement; this builds the whole structure around it — how many repetitions, how long each effort and recovery lasts, and the running total including warm-up and cool-down. Use this when you want the session planned, not just the exercise named.
Can I use this for distance-based intervals rather than time-based ones?: Not directly — there's no distance mode, since the tool works in time throughout. Put the distance in the effort name (e.g. '400m') and set the work duration to roughly how long that takes you, and the structure still works even though the clock is timing rather than measuring distance.