Let me get this out of the way: Treadmill running is better than sitting on the couch. If it’s your only option—or even just the way you prefer to exercise—then by all means use the treadmill. The best exercise is the one you’ll do.
But there are limitations, risks, and biomechanical changes that occur when treadmill running. It’s not the same as running outside, and there’s evidence to suggest it might be worse in some respects.
So let’s explore the potential problems associated with treadmill running:
1. Running outside is more enjoyable.
A 2004 study out of Duke University found that treadmill runners reported higher RPE (rates of perceived exertion) despite running more slowly. They also enjoyed themselves less and experienced less satisfaction than runners doing their thing outside.
If an exercise is so boring that it becomes work and you don’t feel like you accomplished much after doing it, you are less likely to do that exercise.
2. Treadmills are flat and linear and unchanging. The outside world is not.
Running outside across natural ground is characterized by thousands of subtle biomechanical reactions to every pebble, half-buried root, slight dip, furrow, bump, and elevation or incline change—and our bodies adapt to this nonlinear environment by becoming stronger and more balanced.
On a treadmill, every step you run is the same as the last one. Your foot lands in exactly the same place with exactly the same cushioning. Your joints receive the same stresses. This is a recipe for repetitive strain injuries.
3. Treadmills change the biomechanics of your run.
One study found that treadmill runners showed significantly greater peak eversion (rolling inward), eversion velocity, tibial internal rotation, and tibial internal rotation velocity than overground runners. Treadmill runners have also been shown to take longer strides, altering their gaits to spend more time in the air and allow more of the treadmill to pass under.
Another 2013 study found major differences between accelerating on the treadmill and accelerating on the ground. On the ground, the runner accelerates and modifies his or her biomechanics to accommodate the acceleration. On the treadmill, the belt accelerates, and “virtually no kinesiological adaptations to an accelerating belt are observed.”
I wouldn’t be surprised if novel biomechanics result in novel injuries.
4. Treadmills don’t engage the posterior chain as much as running outside.
Runners typically generate the majority of their power with their posterior chains: the glutes and the hamstrings. It’s the hip extension, powered by the glutes and hamstrings, that propels the runner across the terrain.
Since treadmill running cuts way back on peak hip extension the already sorely underdeveloped (from sitting and office work and generally sedentary living) posterior chain receives even less attention. Why engage the glute to bring your leg back and your body forward if the treadmill belt does it for you?
5. Treadmills are “easier” but harder.
Running at the same speed on the treadmill requires less energy expenditure than running at the same speed outside—yet treadmill running feels harder, so we think we’re working harder than we actually are.
Less work and fewer results despite greater perceived effort? No thanks.
6. Running outside checks multiple boxes.
When you run outside, you’re getting:
- Natural light for circadian entrainment.
- Sunlight for vitamin D and nitric oxide.
- Green space exposure for stress reduction, cortisol inhibition, and mood boosting.
- Where you need to go. You can actually use running outdoors as a mode of transportation.
I get that treadmills are more convenient for some people. My point is that running (or walking, or whatever you’d do on a treadmill) outside is far more efficient in every possible manner than running on a treadmill. If you have the choice, choose outdoors.
