Air Resistance, Glutes, and Why You Shouldn’t Keep Your Treadmill on an Incline

In the last post I explained why treadmill running can feel so unnatural and what good treadmill running form looks like. But there’s more you need to know! So let’s dive deep into the biggest difference between the treadmill and solid ground: the lack of air resistance. The standard advice about it is bad for you; I’ll tell you what to do instead.

When you run on the ground you have to push the air aside. Unless you’re running into a stiff wind you’re unlikely to notice the air resistance, but it’s a big enough deal that elite runners draft behind others in races, just as cyclists do. The most famous recent example was the “flying wedge” of pacers in the Breaking 2 Project.

If you don’t have your own flying wedge to move the air out of the way for you, it helps to lean forward because a runner who stays upright, with torso perpendicular to the ground, catches more wind. On a gusty day you’ll feel this when you’re running into the wind, and you’ll probably notice you lean forward to resist it better.

Try walking in chest-high water and you’ll feel the same thing. You simply have to lean forward to get anywhere.

When there’s no wind you don’t notice the effort because you’re used to feeling this slight resistance every single time you move through space. But subconsciously it’s perceptible, and it still helps to lean forward.

However on a treadmill you’re not running through space and thus don’t need to push through the air in front of you. So leaning forward doesn’t give you that particular benefit of making running easier.

Notice my careful wording—there’s still a benefit and we’re about to talk about it.

Experts often recommend setting your treadmill at an incline of anywhere from 1-6% all the time. This increases two things: your effort level and your glute/hamstring activation. Both are too low because you’re not pushing through the air and the incline helps correct that.

However the effect of logging a lot of miles on a treadmill that’s always set to a slight incline isn’t good. You become accustomed to having each footstrike slightly higher than the last, and when you do go outside to run on level ground you’ll feel the pounding of each foot dropping that extra fraction of an inch you aren’t used to—a bit like stepping off a curb you didn’t realize was there and getting a jolt.

Downhill running will feel even worse because it magnifies this effect and you haven’t been practicing it at all. Your movement habits and your muscle development are now mismatched to level and downhill running. You’ll pay the price in your feet, hamstrings, and low back. That may drive you back to the treadmill, thinking it’s safer and better for you. It isn’t—it’s just more familiar.

There are two better ways to activate your glutes and hamstrings properly on a treadmill than keeping a continual incline.

The first is to lean forward. To understand why this works we have to go back to what the job of the glutes and hamstrings is when you run. It is not primarily to push you forward; it is primarily to keep you from collapsing forward in midstance. EMG data shows the hams and glutes don’t work much at the point you’re pushing off the ground. Instead, their maximum activation is at midstance when you have 2.5 times your body weight compressing you. They act to resist that. You can (and should!) read much more about that here.

The other job of the hamstrings is to decelerate the forward-swinging leg so it comes to the ground in time for you to land on it rather than flying into the air like a dancer’s high kick. As far as I can tell, that role stays the same regardless of whether you’re on a treadmill or solid ground, so we’ll set it aside.

What this means is that the glutes and hamstrings work more—work properly, in fact—when you lean forward. Your spine is relatively straight, not bent forward in a slouch, and you’re tipped forward from your hip joints. Your standing hip joint is over your standing foot in midstance, not back behind it in a sitting action. And, optimally, your skull has slid forward on your top vertebra in an action I call face forward. If you’re not familiar with these elements of healthy running form, definitely click through and read about them.

All of that is too much to think about when you’re running. My free one-week Mind Your Running Challenge will help you feel how to do it without having to think so much.

It’s actually a little easier to tell whether you’re leaning forward on a treadmill than on solid ground because you can see the relationship between your upper body and the console. But if you’re still not sure whether you’re doing it right, think about what muscles get sore from running extra fast or long. If it’s your glutes and hams, you’re doing it right. If it’s your quads, you’re not.

On a treadmill you won’t feel the need to lean forward because you don’t feel any air resistance—so there’s a good chance you won’t do it. That is a clear-cut reason for lower glute/ham activation in treadmill running!

But there’s nothing stopping you from leaning forward either. So give yourself the space you need between your body and the console and do it anyway so you can get your glutes and hamstrings working right.

Better yet, why not give yourself that missing air resistance by putting a fan right in front of you? That’s the second way to increase your glute/ham activation and overall effort to something like normal. A treadmill is really an incomplete facsimilie of solid-ground running because the ground moves but the air doesn’t move with it. A fan would fix that.

It would have to be right in front of you, blowing straight into your body, and not above you where most gyms put them. It would also have to be positioned to catch your whole body, not just your face and upper body. The built-in fans some treadmills have would probably not do the job because they’re too close to you.

There’s definitely the potential here for someone with technical know-how to calibrate the fan speed to the treadmill speed, and it would be even fancier if you could control the fan speed as another variable of the treadmill, so you could set it faster to make it feel like you’ve got a headwind or slow it down to make it feel like a tailwind (which is in fact what the lack of air resistance truly resembles).

You could even set it to change randomly and change direction, like real wind, to give you a little more of that variety that’s sorely lacking on a treadmill.

And as a bonus, you won’t get so sweaty.

So to summarize this long blog post: leaning forward correctly when you run on a treadmill is the best way to get your glutes and hamstrings working properly, and it avoids the problems created by keeping the machine at a constant incline. You might not naturally do this because there’s no air resistance to fight, but you still can choose to do it. Adding a fan in front of the treadmill would be a way to create air resistance and increase your effort level comparable to what it would be at that speed outdoors—and also give you a natural reason to lean forward.

In the next post we’ll tackle the problem of confused sensory signals, including what to do about that TV that so many gym treadmills have. Trust me, this is also a big deal.

2 thoughts on “Air Resistance, Glutes, and Why You Shouldn’t Keep Your Treadmill on an Incline”

  1. I believe it is the fact that the treadmill carries the legs back that causes the glutes, hamstrings, and even the gastroc soleus to get lazy. Once you begin to really sense this happening in your body it’s easy to accommodate it, on a treadmill even with a nice big front facing fan is blowing. I think the wind(big fan) resistance can help trick the brain. But, it’s not as strong a stimulus as the feeling of the belt carrying the legs back. Treadmills still have a long way to go!!

    • I agree that the legs being drawn back is a big sensory difference from solid ground, and the nervous system responds to that. But again, the glutes and hamstrings don’t play a big role in propulsion, their main job is to control the torso, so leaning forward properly on a treadmill will noticeably activate them, and wind helps provide the impetus to lean. I agree, though–treadmill running leaves a lot to be desired, and it’s always better to run outside on terra firma if possible.


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