By Paul Kendrick, Cardio & Endurance Editor · Updated 27 September 2026
High-intensity interval training on a treadmill means short, hard efforts separated by easier recovery, repeated several times. It fits a lot of work into 20 to 30 minutes, and a treadmill makes it easy to control, because you set the exact speed and incline instead of guessing your effort on a road.
The catch is that treadmills are slow to change speed. Most home machines take several seconds to climb from 6km/h to 14km/h, which eats into a 30-second sprint. So the sessions below use longer intervals and lean on incline, which suits home treadmills far better than the sprint-and-rest routines you'll see copied from gym bikes.
Warm up for 5 minutes every time: 3 minutes of brisk walking, then 2 minutes building to a gentle jog. Finish with the same in reverse. Clip the safety key to your clothing, and stay off the side rails.
"Hard" in these workouts means an effort you could hold for the interval and no longer, roughly 8 or 9 out of 10. Speeds are suggestions; adjust them so the effort feels right. If you train with a chest strap, the hard efforts should push you into zones 4 and 5, which our heart rate zone training guide explains.
No running required. This is the one to start with if you're new to exercise or coming back after a break.
| Block | Time | Speed | Incline |
|---|---|---|---|
| Warm-up | 5 min | 4.5 to 5.5km/h | 1% |
| Hard | 1 min | 5.5 to 6km/h | 8 to 10% |
| Easy | 1 min 30 | 4.5km/h | 1% |
| Repeat hard and easy | 6 rounds total | ||
| Cool-down | 2 min | 4km/h | 0% |
You'll feel this in your calves and glutes. Incline is the best way to make walking hard, because the effort climbs steeply with gradient, far more than with a small bump in speed (Journal of Biomechanics, 2012). If you like this style, the 12-3-30 workout is its steady-state cousin.
For people who can jog for a few minutes but aren't regular runners.
When 6 rounds feel manageable, cut the walk to 90 seconds before you make the runs faster. Shorter recovery is a gentler progression than higher speed.
Hills give you a hard effort at a lower speed, which is easier on the joints and much safer on a home treadmill.
The key detail: drop the speed before the incline when you finish each effort, since most treadmills lower the incline slowly. Your legs will thank you for the extra walking time while the deck comes down.
This is the classic "Norwegian" format, and it's hard. Only try it once the other three feel comfortable.
Longer intervals like these seem to drive the biggest fitness gains. A meta-analysis of 37 interval training studies found VO2max rose by about 0.5 litres per minute on average over 6 to 13 weeks, and the subset using longer intervals saw larger rises of roughly 0.8 to 0.9 L/min (PLOS One, 2013).
Twice a week, with at least a day between. The NHS guidelines say 75 minutes of vigorous activity a week is a good target, or 150 minutes of moderate (NHS physical activity guidelines); two HIIT sessions plus a couple of easy walks gets most people there. More HIIT than that tends to backfire, because tired legs can't hit the intervals and the sessions turn into medium-hard slogs.
Going too hard on the first rep. If round one is flat out, rounds four to six fall apart. Aim to finish the last interval at the same speed as the first.
Holding the handrails. Gripping the rails, especially on incline, takes load off your legs and makes calorie and heart-rate readings meaningless. Let go, and lower the incline if you can't.
Jumping to the side rails. Straddling a moving belt to rest and then hopping back on is how people fall. Change the speed on the console instead.
Skipping the warm-up. Cold muscles and a fast belt don't mix, particularly for hamstrings and calves on hill sprints.
Any machine works for Workouts 1 and 2. Hill sprints need a powered incline of at least 8%, and 4 x 4s need a deck long enough to run on comfortably, ideally 130cm or more. Our best incline treadmill guide covers machines that do both, and the KITOPA treadmill review looks at an 18% incline model under £500. If you're choosing a first machine, read our 6 mistakes to avoid on a treadmill too.
Start with incline walking intervals rather than sprints. Warm up for 5 minutes, then alternate 1 minute of fast walking at 8% to 10% incline with 2 minutes at a flat, easy pace, 6 times. Cool down for 5 minutes. It gets your heart rate up without the impact or the risk of jumping on and off a moving belt.
Between 20 and 30 minutes including the warm-up and cool-down. The hard intervals themselves usually add up to 8 to 16 minutes. If you can keep going much longer than that, the intervals probably aren't hard enough.
Two sessions a week is plenty for most people, with at least a day between them. Fill the rest of your cardio with easier steady walking or jogging. Doing HIIT every day leaves you too tired to hit the intervals properly.
It helps, mainly because it burns a lot of energy in a short time and improves fitness quickly. But total weekly activity and diet matter more than the type of session. HIIT twice a week plus regular walking is a better plan than HIIT alone.
Only if you're experienced and the machine is fast to respond. Straddling the side rails while the belt runs and hopping back on is a common way to fall. Changing speed on the console, or using incline instead of speed, is safer for most people.
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