Guides · Is treadmill running easier
Is treadmill running easier? It depends on your pace, and on your belt
Outside, a 7:48 mile feels like honest work. On the treadmill you set 7.7, the display shows 7:48, and the miles slide past. Your training partner swears the treadmill is the harder of the two. So which of you is right, and did you even run 7:48?
At easy paces, it tends to feel easier. At faster steady paces, a review of 34 studies found runners rated the treadmill harder, and in time trials, runners did worse on it. Either way, the speed you compare is the setting you pressed, and a belt a few percent off changes the pace you really ran.
On paper, the belt saves you a little
With no air to push out of your way, a flat belt costs a little less energy than the road at quicker paces. That is where the habit of setting a 1 percent incline comes from, and the guide to the 1 percent incline rule sorts out when the grade matters. A 2019 review found that at the steady speeds it tested, oxygen cost on the belt came out close to the road's whether it ran flat or at 1 percent.
How it feels flips with your pace
That same review pooled 34 studies where the same people ran on a treadmill and on the ground. At slower speeds, they rated the treadmill easier. At faster speeds, they rated it harder. When the studies timed hard efforts such as time trials, runners did worse on the treadmill.
A separate test found 17 trained men rated a treadmill at a 1 percent grade harder than an indoor track at every speed tried, from about 8:47 down to 6:26 a mile. Heat may be part of it, since on a treadmill you lose the breeze your own running makes. The guide on how treadmill pace compares with road pace explains that cooling.
The review's summary gives no pace where easier turns into harder, so it cannot tell you which of your own runs count as slow and which count as fast. An easy jog that feels easier indoors fits the research. A hard session that feels easier indoors is not what the review found on average. One run's feel is not a study, but it is a reason to look at the belt. The same review also measured heart rate on a treadmill, if that is the gap you notice.
Every verdict assumes the speed is real
Those studies compared the same speeds indoors and out, as the researchers set them. You are comparing something else: the speed on the display against the pace your watch logged on the road. What the display shows is the speed you requested, and the belt can run a little off it. When a lab checked four treadmills while people walked and ran on them, each belt averaged between 98 and 103 percent of its target.
You make more free throws in the gym than at the park, so the gym feels easier. Now suppose the gym rim hangs a few inches low. Your shot stayed the same, and the target moved. The display is the rim height you were told, and nobody checked it with a tape measure.
At one setting, the math looks like this. Both belts below are made up, and both sit inside that lab range.
Two verdicts on one 7:48 setting
You set 7.7 both times and the display reads 7:48.
| Your verdict | What the belt did | What you really ran | The belt's share |
|---|---|---|---|
| Easier than the road | Ran 1.5 percent slower than the display | 7:55 a mile | 7 seconds a mile slower than you logged |
| Harder than the road | Ran 2.5 percent faster than the display | 7:36 a mile | 12 seconds a mile faster than you logged |
I picked these two misses and worked out the paces myself.
Take the slow belt. The run that convinced you the treadmill is easy was a 7:55 run filed as 7:48. Plan a road race from it and your goal pace is 7 seconds a mile faster than anything you have actually held.
Your watch cannot settle it
Indoors your watch has no satellite signal to go on, so it judges pace from motion sensors on your wrist. Some watches ask you to type in the distance the machine shows when you save the run. A watch that matches the display may simply be repeating it. Read why your watch cannot tell you whether the belt ran slow before you lean on it as a referee.
How to judge it for your own runs
Compare like with like: an easy treadmill run next to an easy road run, a hard session next to a hard one, because the research answer changes with the pace. If your hard sessions are the ones that feel easier indoors, measure the belt at the setting you compare. If the reading lands far from the setting, leave the fix to your manual or a technician.
Put a true pace behind your verdict
Pick the setting you have in mind when you say the treadmill feels easier. Treadwell reads the real belt speed at that setting, using the camera and LiDAR together on an iPhone Pro. You do it standing on the floor next to the treadmill, with nobody on the belt. Then your treadmill pace is a measured number, not just a setting.
Check the belt behind the easy feeling
Read your usual setting before you decide which surface is easier. Treadwell runs on iPhone Pro models, because it needs the LiDAR sensor.
Scan with your iPhone Pro to get the appTested: in our tachometer tests the app read within about 2 percent of true belt speed.
Quick answers
Is treadmill running easier than road running? At easy paces, it tends to feel easier. At faster steady paces, a review of 34 studies found runners rated the treadmill harder, and in time trials, runners did worse on it. Either way, the speed you compare is the setting you pressed, and a belt a few percent off changes the pace you really ran.
Why does treadmill running feel harder? At faster paces, a review of 34 studies found it does. Losing the breeze you make outside may be part of the reason. A belt that runs faster than its display adds work you never see, and that part you can measure.
Is a 5K easier on a treadmill? In the lab, runners did worse in time trials on a treadmill than on the ground. That is a finding about groups of runners, so it cannot promise anything about your own 5K. If your treadmill 5K comes out well ahead of your road 5K, look at the belt before you trust the time. The guide to virtual races on a treadmill explains how to make that result count.
Is treadmill running as good as road running? For how you move, mostly yes. A 2020 review of 33 studies found running mechanics on a motorized treadmill largely comparable to running on the ground, with some differences at footstrike. The guide on whether treadmill running carries over to the road covers the training side, and the pace is the part you still have to check.
Sources.
- Effort and performance indoors versus out: a 2019 meta-analysis by Miller, Van Hooren, Bishop and colleagues in Sports Medicine (volume 49, pages 763 to 782, PMID 30847825) pooled 34 crossover studies. Effort ratings came out lower on a motorized treadmill at slower submaximal speeds and higher at faster ones. Endurance performance, judged by time trials, was poorer on the treadmill, and oxygen uptake at a steady pace was similar to overground running at both 0 and 1 percent grade.
- Treadmill versus indoor track: Pind and colleagues, 2019, in Research Quarterly for Exercise and Sport (volume 90, pages 470 to 478, PMID 31282820). With the treadmill set to a 1 percent grade, their 17 male endurance athletes rated it substantially harder than the track at each of 11, 13 and 15 km/h. I converted those speeds to per-mile paces.
- Why runners set 1 percent: Jones and Doust, 1996, in the Journal of Sports Sciences (volume 14, pages 321 to 327, PMID 8887211), who found a 1 percent grade evened out treadmill and outdoor energy cost for runs of about five minutes between 2.92 and 5.0 m/s.
- The breeze you make outdoors: Yamashita and colleagues, 2024, in the Journal of Applied Physiology (volume 137, pages 554 to 568, PMID 38867667), on cooling from self-generated wind.
- Belts versus their settings: Willwacher and colleagues, 2021, in Scientific Reports (article 2244 in volume 11, PMID 33500528). Four lab treadmills were tested with seven people walking and running, and the average belt speed sat around 98 to 103 percent of the target.
- How you move on a belt: Van Hooren and colleagues, 2020, in Sports Medicine (volume 50, pages 785 to 813, PMID 31802395), a review of 33 studies with 494 participants that rated mechanics largely comparable between motorized treadmill and overground running.
- Watches indoors: Apple Support article 105002, which describes the accelerometer standing in when GPS is unavailable, and the Garmin Forerunner 165 owner's manual, which asks you to enter the distance the machine shows when you save a treadmill run.
- The 7.7 setting, both belts and the free throw comparison are illustrations I made up for this page. I measured none of them.