Smart Stopwatch
EN Interval Timer: Programmes That Run Themselves
How to build and run an interval training programme: writing steps as work and rest, setting rounds, training hands-free, and what the saved session really records.
Interval training is defined by its structure: a fixed effort, a fixed recovery, repeated a fixed number of times. The structure is the training stimulus — change the rest period and you have changed the workout, even if every other number stays the same. Which means the timing is not administrative overhead around the session. It is the session.
The problem is that you cannot run it and read it at once. Forty seconds into a hard interval, nobody is doing arithmetic about when to stop. This guide covers building a programme that runs itself, so the only thing you have to do during a workout is the workout.
Why a countdown timer is not enough
A single countdown handles one interval. A workout is a sequence, and the gap between those two things is where every improvised timing method falls apart.
Reset a countdown between every step and you introduce an unmeasured pause at each transition — the seconds spent reaching for the phone, finding the button, restarting. Twelve steps in, your forty-second rests have quietly become fifty-five, and the interval ratio that defined the workout is gone. You did not do the session you designed; you did an easier one.
A programme removes the transitions entirely. Steps follow each other automatically, so the timing is the same on your last round as your first — which is precisely when fatigue would otherwise make you slower at everything, including pressing buttons.
Writing a programme
A programme is a list of exercises, and the form gives each one a row: a name, a phase, a duration in hours, minutes and seconds, and a photo if you want one. So a simple pair of steps is entered like this:
Squats · Work · 00 h 00 min 45 s
Rest · Rest · 00 h 00 min 30 s
The name is what appears on screen while the step runs, so write it for someone glancing up mid-effort: short, and unambiguous. The phase is a label picked from a list — typically Work or Rest. The shortest an exercise can be is five seconds.
The total appears as you type and is recalculated on every keystroke. It is the length of one round: multiplied by the number of rounds it gives you the whole session, which saves you keeping a total up to date by hand.
Photos are optional, both for the programme as a whole and for each exercise. They earn their place on movements whose name says nothing about the position: an image read at a glance lands faster than a sentence read mid-effort.
Rest is a step, not a gap
The most common mistake in a first programme is listing only the exercises. Rest periods have to be written in as steps of their own, because the timer runs exactly what you gave it and nothing in between.
This is a feature rather than an inconvenience, and it is worth understanding why. Writing rest explicitly forces you to decide how long it is — which is the decision that determines what kind of training this is. The same eight exercises with fifteen seconds of rest and with sixty seconds of rest are not two versions of one workout; they are conditioning and strength work respectively.
It also means the recovery is protected. A rest you have to remember to take is a rest that shrinks as the session gets harder, exactly when you need it most.
Rounds and how programmes get long
A programme repeats for the number of rounds you set, so the list you write is one circuit rather than the whole session. Eight steps at four rounds is thirty-two steps performed, from eight lines written.
Do the arithmetic before your first attempt, because it escapes people. A circuit of six exercises at forty seconds with twenty seconds of rest is six minutes; at five rounds that is a thirty-minute session, which is a different proposition from what six short lines on screen suggests.
Build a short version first and run it once. A programme that looked sensible while typing and turns out to be brutal in round three is the normal outcome, and finding out on a two-round test costs you five minutes instead of a wasted session.
Running it hands-free
Once started, the programme advances on its own: each step announces itself, counts down, and hands over to the next. There is nothing to press between exercises, which is the entire point — a timer you have to touch during a set is a timer that changes your set.
Set the device up before you begin, not during. Screen where you can see it from the floor, volume up, and the phone plugged in if the session is long. A screen that sleeps in the middle of round two will not stop the programme, but it will stop you knowing where you are, and nothing breaks a circuit faster than crouching over a dark phone.
Keep the tab in front. Browsers throttle hidden tabs, and while the elapsed time stays correct, an audible cue for a step change can arrive late if the page is buried behind something else — which for a workout means you find out about the transition after it happened.
What the saved session records
A finished session records the programme used, the total duration, how many exercises you completed and any notes you add. Completed steps are worth recording honestly: a session you cut short at round three is useful data about that day, and a record that claims five rounds is not.
A calorie figure is also stored, and it deserves a caveat rather than trust. If you do not supply one, it is estimated at roughly eight kilocalories per minute of session — a generic average that knows nothing about your body mass, your effort, or whether the step was burpees or a plank. Treat it as a rough index for comparing your own sessions with each other, and not as a measurement. If you have a better number from a heart-rate monitor, enter that instead.
The workout tools need an account, unlike the stopwatch and countdown, because a programme is something you build once and reuse rather than a single measurement. That is also what makes it worth building carefully: a good programme is used fifty times.
For work blocks rather than exercise, the Pomodoro timer has the same shape with different defaults, and for kitchen steps that overlap rather than follow one another, the cooking timers are the better fit.
Frequently asked questions
How do I write a programme?
One row per exercise, in the form on the interval timer page: a name, a phase (Work, Rest and so on), and a duration entered as hours, minutes and seconds. The round total adds up as you go. The minimum duration is five seconds, and you can attach a photo to each exercise.
Do I have to write the rest periods?
Yes. Rest is a step like any other, and the timer runs only what you listed. Writing it explicitly is what forces you to decide how long the recovery is, which is the number that determines what kind of training the session actually is.
Can I do a Tabata protocol with it?
Yes — two lines, twenty seconds of work and ten of rest, run for eight rounds. Any interval structure that repeats a fixed circuit can be written the same way.
How accurate is the calorie estimate?
It is not a measurement. Without a figure of your own it assumes roughly eight kilocalories per minute, which ignores your body mass, your effort and the exercise itself. Use it to compare your own sessions, or enter a better number from a heart-rate monitor.
Do I need an account?
Yes, for the workout tools. Programmes are built once and reused, so they need somewhere permanent to live. The stopwatch, countdown, multi-timer, chess clock, breathing and Pomodoro all work without one.