Japanese interval walking: does it work?

image credit: Unsplash

On 18 May 2004, 246 people in Matsumoto, a city in the mountains of central Japan, set out on a five-month walking experiment. Some were told to walk steadily and clock up 8,000 steps a day. Others carried a small accelerometer and did something odder: three minutes fast, three minutes slow, over and over. By October, the stop-start walkers had stronger legs, fitter hearts and lower blood pressure than the steady walkers. Same city, same months, both groups asked to walk at least four days a week: the big difference was the rhythm.

Twenty years later, that routine has a new name, "Japanese walking", and it went viral in 2025. Most of the videos skip the interesting part: what the studies found, where the evidence runs thin, and why the slow minutes matter less than you'd think.

What is Japanese interval walking?

Researchers call it interval walking training, or IWT. It was developed by Hiroshi Nose and Shizue Masuki, exercise physiologists at Shinshu University, and the recipe has barely changed since the first trial:

• 3 minutes slow, at about 40% of your peak aerobic capacity: an easy stroll you could chat through.
• 3 minutes fast, at 70% or more of your peak: hard enough that you can only get a few words out.
• Five rounds of each, so 30 minutes.
• Four or more days a week.

Here's the whole session on one clock:

The percentages sound technical, but they're relative to you. The researchers measured each walker's own fitness first, so "fast" for a fit 40-year-old and "fast" for a 70-year-old are very different speeds that feel equally hard. There's nothing especially Japanese about it, either: it's interval training, the same idea runners have used for a century, slowed down to a walk. What was new was making it work for people who would never run, outdoors, on their own, without a coach.

What did the studies find?

The first trial, 2007. The 246 volunteers, average age 63, were split into three groups: no training, steady walking at about 50% of their peak, or intervals. After five months, the interval walkers' thigh strength was up 13% (straightening the knee) and 17% (bending it), and their aerobic fitness was up 8–9%. All of those gains were significantly bigger than the steady walkers', and the interval walkers' systolic blood pressure fell more too.

The big follow-up, 2019. The team then put 679 people, average age 65, through the same five-month programme. Fitness rose by 14% on average, and a combined risk score for conditions like high blood pressure and type 2 diabetes fell by 17%. The most useful finding was about dose: the gains grew with every extra minute of fast walking each week, up to about 50 minutes, then levelled off. The slow minutes and the total minutes didn't predict anything.

The long run, 2015. Among 696 people followed for 22 months, walkers managed about 70% of their target training days on average, and the more days they managed, the more they improved. Fitness rose by about 12%, and the risk score fell by about 13%.

Outside Japan, 2013. A Danish team tried it on 32 people with type 2 diabetes for four months, matching the interval and steady walkers for the energy they burned. Only the interval walkers got fitter (by 16%), lost weight and body fat, and brought their blood sugar down. The steady walkers held steady, which still beat the group that didn't train at all: their blood sugar got worse.

Which of the viral claims hold up?

How strong is the evidence, really?

Better than most fitness trends get, and narrower than the headlines suggest. Four things to keep in mind:

1. Most of it comes from one team in one city. The people who invented the method ran most of the studies. That's normal for a young idea, but independent repeats are few: the Danish trial is the main one.
2. The volunteers were a particular group. Mostly middle-aged and older Japanese adults who signed up for a walking programme, and three in four of the first trial's were women. Results may differ for younger people, or for people who wouldn't volunteer.
3. The biggest studies had no comparison group. The 679- and 696-person studies show people improving, not that they improved more than they would have doing something else. Only the smaller trials can show that.
4. Nobody has counted heart attacks, strokes or years of life. The studies measured fitness, strength and risk factors, which predict those things, but aren't them. A 2024 review by both the Japanese and Danish teams says so plainly: long-term studies in the real world are still needed, and sticking with it over years is the hard part.

So, does it work? For getting fitter and stronger in the legs over a few months, yes, and it beat steady walking in the trials that compared them. For the bigger promises, it's too early to say.

How do you try a session tonight?

You need 30 minutes and some way of knowing when three minutes is up.

1. Start slow. The first three minutes are your warm-up: an easy stroll, shoulders loose.
2. Go fast. Lengthen your stride, swing your arms and pick up the pace until talking in full sentences gets hard. You should be breathing hard, but not desperate for the three minutes to end.
3. Slow down, don't stop. Ease back to the stroll and let your breathing settle. If it hasn't settled by the end of the slow three minutes, your fast was too fast.
4. Repeat until you've done five of each.

Set a timer you can't miss. On Apple Watch, open the Workout app, scroll to Outdoor Walk, tap the ⋯ button and choose Create Workout, then Custom. Add a 3-minute Work interval and a 3-minute Recovery interval, five of each, and the watch taps your wrist every time the pace changes.

Or let the music do it. A lot of pop songs run about three minutes. Make a playlist that swaps between slow songs and fast ones, ten songs long, and the playlist becomes your timer: change pace when the song changes. For the fast songs, pick something with a beat you can step to; a song around 120–130 beats a minute pulls your cadence up without you thinking about it. It won't be exact to the second, and it doesn't need to be.

If five rounds is too many, start with two or three and add one a week. And notice the arithmetic in your favour: five rounds on four days is 60 minutes of fast walking a week, already past the 50 minutes where the 2019 study's gains levelled off. You don't need to do more than the recipe.

How do you know your fast is fast enough?

The research teams measured each walker's capacity in a lab. You can get close with what's on your wrist:

• The talk test. On the fast stretch you can manage a few words, not a conversation. On the slow stretch you could chat easily.
• Your cadence. Brisk walking starts at about 100 steps a minute, and the fast stretch should be well above that: for many adults, somewhere around 120 to 130, often lower if you're older or just starting out. It's the effort that counts, not the number. StepUp's Tempo shows your cadence for every walk, so you can see the fast and slow stretches as two different rhythms.
• Your heart rate. The fast stretch should take you to the top of the brisk zone or past it. Walking heart rate: what's normal? explains the zones, and the walking heart rate calculator works out yours. StepUp's Effort shows how hard each walk was for your heart.
• Your speed. The walking pace calculator turns your fast stretch into a pace you can aim for next time.

Then give it a few weeks. Fitness is the gain these studies found most consistently, and StepUp's Fitness metric is built to show that change: as you get fitter, the same pace takes a lower heart rate.

Who should be careful?

Talk to your doctor before you start if you have a heart condition, high blood pressure that isn't under control, diabetes treated with insulin, or joint problems, or if you haven't been active for a long time. The fast stretches are meant to be hard, and that's what makes them worth a check.

Watch the weather, too. When the Shinshu team tried interval walking with sedentary college students, summer heat cut how often they walked, and the summer group ended the study less fit than they started, while the winter group got fitter. On hot days, walk early or late: the Golden Hour walk planner shows when the sun is low where you are, just after sunrise and before sunset. And if you're new to walking for exercise at all, a walking plan for beginners builds the base first.

Does it replace the rest of your walking?

No, it sits on top of it. Your everyday steps still count for your health, whatever their pace, and how many steps a day covers what the research says about those. Interval walking is a way to make some of your walks work harder, much like adding a hill.

It also doesn't replace strength training. The 2007 trial's thigh gains are real, but they're one muscle group, and the guidelines ask for strength work for the whole body on two days a week. Is walking enough exercise? has a simple routine that fits after a walk.

The short version

• Japanese interval walking is three minutes slow, three minutes fast, five times, four or more days a week.
• In trials, it improved fitness, thigh strength and blood pressure more than steady walking did.
• The fast minutes do the work: gains levelled off at about 50 minutes of fast walking a week, and the recipe already gives you 60.
• The evidence is good but narrow: mostly one research team, older volunteers, and months rather than years.
• Time it with an Apple Watch custom workout, or a playlist of three-minute songs.

Written by Dheeraj Kumar Sharma, who makes StepUp. How the guides are written.