Research · 3 min read · 2026-10-12
Treadmill or outside?
A 1 percent incline makes treadmill running cost the same energy as running outside. How to use your pace targets indoors.
Is running on a treadmill easier than running outside? Without wind resistance it costs a little less energy at the same speed. A study from 1996 measured how much incline it takes to make up for it.
What the researchers did
Nine trained male runners ran six-minute efforts at six speeds, from 10.5 to 18 km/h, which is from about 5:42 to 3:20 per km. They did this on a treadmill set at 0, 1, 2 and 3 percent incline, and once on a flat road. The researchers measured their oxygen uptake at each speed.
What they found
With the treadmill at 1 percent incline, the energy cost matched running outside at all speeds tested. At the two slowest speeds, 5:42 and 5:00 per km, running on the flat treadmill also matched running outside. At faster speeds, the flat treadmill was easier.
What it means for you
Set the treadmill to 1 percent incline, and your pace targets work indoors too. If you run slower than about 5:00 per km, the difference is small, and a flat treadmill is close enough.
Treadmills are not always accurately calibrated, and watches often estimate pace poorly indoors. Use the speed on the treadmill, and check your effort and breathing. If a pace feels much harder or easier than outside, trust the effort.
What the study can't tell you
The runners were well trained and used to treadmills, and the efforts lasted about five minutes. Long runs on a treadmill can feel different, for example because of heat indoors.
How we use it
Pace targets in PX7 Training are made for running outside on flat ground. On a treadmill, use 1 percent incline and the same targets.
Source
- Jones & Doust (1996), A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. Journal of Sports Sciences.
Written by Jørgen Larsen for PX7 Training.