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- Tabata Timer8 × 0:20 / 0:10Seven to eight sets of twenty seconds with ten of rest between them, handed over whole by the 1996 paper.Medicine & Science in Sports & Exercise
- Norwegian 4x4 Timer4 × 4:00 / 3:00LoadedFour intervals of four minutes at 90 to 95% of maximum heart rate with three minutes of active rest, the 2007 Trondheim protocol.Medicine & Science in Sports & Exercise
- HIIT Timer8 × 0:40 / 0:20Forty hard and twenty easy, eight times over: a gym circuit format for near-maximal work, with time to reach the next station.
- EMOM Timer10 × 1:00A cue once a minute and no scheduled recovery, so you earn your rest by finishing the repetitions early.CrossFit
- Rest Timer1 × 2:00Two minutes of rest, started as you rack the bar: the top of the ACSM range for muscle growth and the NSCA floor for big lifts.American College of Sports Medicine · National Strength and Conditioning Association
- Plank Timer3 × 0:30 / 0:30Three holds of thirty seconds with thirty between them, the front plank in the USA Gymnastics exercise progression sheet.USA Gymnastics
- CrossFit Timer1 × 20:00One twenty minute clock with no rounds and no rest inside it, the length the published benchmark Cindy is scored over.CrossFit
- Stretching Timer10 × 0:30 / 0:10Thirty second holds taken twice a muscle group, which is the sixty seconds the ACSM position stand asks for.American College of Sports Medicine
What eight weeks of 4x4 did for VO2max in the 2007 study
Researchers at the Norwegian University of Science and Technology (NTNU) in Trondheim use and recommend the 4x4. In a 2007 study there, 40 healthy, moderately trained men trained three days a week for eight weeks, on four programmes matched for total work. The 4x4 group ran four 4-minute intervals at 90 to 95% of maximum heart rate with 3 minutes of active rest at 70%. Their VO2max, the most oxygen the body can use, rose by 7.2%; 15 seconds hard and 15 easy raised it by 5.5%. Both interval groups improved significantly more than the groups that ran steadily at 70% or 85%.
Norwegian University of Science and TechnologyExercise advice, Cardiac Exercise Research Group (CERG)Medicine & Science in Sports & ExerciseHelgerud et al., 2007, Med Sci Sports Exerc 39(4):665 to 671, PMID 17414804
A 2019 meta-analysis of 53 randomised trials looked at interval training one part at a time. Against steady training, VO2max rose significantly more only with intervals of 2 minutes or longer, with at least 15 minutes of hard work in a session, and with programmes of 4 to 12 weeks or more. Shorter formats still beat doing nothing. The 4x4 has the first two built in: 4-minute intervals, 16 minutes of hard work.
The 2007 results come from healthy, moderately trained men. Anyone with a heart condition, or new to hard training, should check with a doctor first. NTNU’s own seven-week programme starts with a single 4-minute interval and works up to all four within those weeks.
Medicine & Science in Sports & ExerciseHelgerud et al., 2007, Med Sci Sports Exerc 39(4):665 to 671, PMID 17414804Norwegian University of Science and Technology7 week fitness program, Cardiac Exercise Research Group (CERG)
The protocol
4 intervals of 4 minutes with 3 minutes of active rest between them: 25 minutes from the first interval to the end of the last. The shape is the 2007 study’s.
How hard: 90 to 95% of your maximum heart rate in each interval, about 70% in the rest. Without a monitor, breathe so hard you cannot hold a conversation.
Medicine & Science in Sports & ExerciseHelgerud et al., 2007, Med Sci Sports Exerc 39(4):665 to 671, PMID 17414804Norwegian University of Science and Technology7 week fitness program, Cardiac Exercise Research Group (CERG)
It takes time to get there. NTNU is happy if you reach 90% during the first interval, and expects each later one to take 1 to 2 minutes to climb back up.
Keep moving through the 3 minutes: walk or jog slowly. NTNU sets the rest near 70% of maximum heart rate because lactate is cleared most efficiently there.
Warm up for 10 minutes until you sweat a little, and cool down for 5 after, as NTNU’s programme does. Set Get ready to 10:00 if you want the warm-up counted too.
This timer rings a bell as each interval starts and ends, warns ten seconds before each interval ends, has a fullscreen key, and keeps the screen awake where the browser allows; it is free and needs no account. Keep this tab in front, because a browser may pause the sound of a tab you cannot see.
Sessions to try
These are our suggestions. Where one follows a published source, that source is cited under it.
- Kick-start
One 4-minute interval, the session NTNU’s seven-week programme opens with. Set Rounds to 1.
- Build up
Two, then three intervals with 3 minutes of relaxed walking between them, before the full four. Set Rounds to 2, then 3.
- The 2007 study
4 × 4:00 with 3:00 of active rest at about 70%, three days a week for eight weeks, which is where the timer starts.
- Uphill
Walk or run the intervals up a hill or on a treadmill with some incline, as NTNU recommends. It says a high heart rate is easier to reach uphill.
Norwegian University of Science and Technology7 week fitness program, Cardiac Exercise Research Group (CERG)Norwegian University of Science and TechnologyExercise advice, Cardiac Exercise Research Group (CERG)
- Bike or row
Any activity that works large muscle groups dynamically will do: NTNU names swimming, cycling and rowing beside running and walking.
Common mistakes
Emptying the tank in the first interval. You should be about as tired after each one, and feel you could manage a fifth once the four are done.
Taking it easy because 4 minutes sounds long. If you can still hold a conversation near the end of an interval, you are going too easy.
Standing still in the rest. The 3 minutes are active: walk or jog slowly.
Medicine & Science in Sports & ExerciseHelgerud et al., 2007, Med Sci Sports Exerc 39(4):665 to 671, PMID 17414804Norwegian University of Science and TechnologyExercise advice, Cardiac Exercise Research Group (CERG)
Going all out in the last interval. NTNU says the gain over staying at 90% is practically negligible, and that it can be discouraging enough to make it harder to keep training.
Questions
What is the Norwegian 4x4 workout?
Four intervals of 4 minutes at 90 to 95% of maximum heart rate, with 3 minutes of active rest at about 70% between them. Researchers at NTNU in Trondheim use and recommend it, and their 2007 study found it raised VO2max more than steady running for the same total work.
Medicine & Science in Sports & ExerciseHelgerud et al., 2007, Med Sci Sports Exerc 39(4):665 to 671, PMID 17414804Norwegian University of Science and TechnologyExercise advice, Cardiac Exercise Research Group (CERG)
How do I find my maximum heart rate?
NTNU’s test: warm up until you sweat, run two 4-minute intervals with 3 minutes of slow walking between, then two minutes into a third, go as fast as you can until you cannot continue. The highest heart rate you reach is your maximum. With a heart condition, ask a doctor before an all-out test.
How often should I do 4x4 intervals?
Three sessions a week for eight weeks is what the 2007 study used. To improve fitness, NTNU recommends 2 to 3 interval sessions a week, and that nobody yet knows the ideal number.
Medicine & Science in Sports & ExerciseHelgerud et al., 2007, Med Sci Sports Exerc 39(4):665 to 671, PMID 17414804Norwegian University of Science and TechnologyExercise advice, Cardiac Exercise Research Group (CERG)
Six palettes, and a phase keeps its meaning in all of them
The same four grounds, drawn six ways. Each is solved so that get ready, work, rest and done stay apart, and so the clock stays readable from across a gym. Pick one and the whole page turns with it; this browser remembers the choice.
The app
The same clock, in your pocket
Bursta is being finished for phones. Android comes first and iPhone after it. It is the timer you have above, built as an app: the same reading of the wall clock every frame, so a locked screen, a phone call or a backgrounded app does not make it drift.
It keeps sounding with the screen off
The bell lands with the phone locked in your bag and your music still playing. A page in a tab cannot do that.
Your own workouts, and a record of them
A builder, a library you name and reorder, a history that fills itself in, and a calendar with repeats and reminders.
Made to be read while you are breathing hard
Six palettes, five text sizes, and the phase in the colour of the whole screen. English and Ukrainian.
Soon on Google PlaySoon on the App Store
