It’s not quite winter yet but the weather is getting hairy. In the Rocky Mountains, fall days run from scorching heat, pleasantly crisp mornings, blustery 30 mph sustained winds and the occasional snowstorm. The unpredictable conditions often drive athletes indoors for workouts.
The treadmill has a place in every runner’s repertoire. But debate rages over whether indoor miles stack up the same as outdoor miles. Runners are uncertain if they should you your workouts for the treadmill and don’t know if the treadmill is harder or easier than running outside.
As a coach, I’ve dished out plenty of treadmill advice. Unfortunately, recent research has cast doubt on the value of that advice. So my new advice is don’t listen to me, listen to science. Here’s the latest on treadmill training.
Incline and Effort
A study released in 1996 recommended setting the incline of the treadmill at 1% to replicate outdoor running. Coaches high and low, including myself, prescribed the 1% rule to athletes.
However, new research has cast doubt on the recommendations of the original study. A 2019 meta-analysis of 34 studies found that oxygen consumption was equal between treadmill running and outdoor running, even at no incline and even at speeds as fast as six minutes per mile.
Sorry team. I was wrong about the incline. But, to my credit, the meta-analysis did uncover a few unexpected physiological differences between treadmill running and outdoor running. Heart rate and perceived effort were about equal between treadmill and outdoor running at moderate speeds. Nonetheless, compared to running outside at the same speed, running slowly on a treadmill feels easier with a corresponding lower heart rate. Unsurprisingly, running at fast speeds on a treadmill generates higher heart rates and a harder perceived effort.
The researchers conclude that the increased effort and heart rate at high speeds might be coming from a few different factors. Running on a treadmill at a high speed makes people afraid they’ll fall off, and the fear might result in a spike in heart rate. Secondly, at high speeds, heat builds up on a treadmill. Outside, you’ve got more air flowing over your body to cool you off but that’s not the case in a sweaty gym.
Finally, most runners aren’t used to running fast on a treadmill. Even if they do their easy runs on the treadmill, most of their race-specific work is likely to be on the roads or on a track. Adding an unfamiliar element to an already difficult run can make the run feel much harder.
Treadmills And Workout Performance
Speed workouts and harder training days should be spent outside, especially if you’re trying to improve performance. When the researchers pooled the results, they found that running performance was consistently worse on the treadmill, whether it was a performance test over a set distance or a set time.
Does The Treadmill Matter?
When choosing a treadmill pay attention to how much resistance it offers. While softer treadmills might feel better, their bounce might be cheating your training. One study found that just like a track, the stiffer the treadmill the better. A firm platform means more energy return, whereas a spongier treadmill platform means less energy return.