Is a treadmill incline just a marketing gimmick?

[LAP3141]

Makers of fitness treadmills usually include an adjustment for the treadmill surface incline. This allows the running surface to be tilted upward by a maximum of 10-15 degrees and it is supposed to simulate a more strenuous run up a hill.

But how can this be more strenuous? The runner is stationary and remains at the same height as the treadmill track moves under him. No work is being done against gravity. It is like climbing up on a down escalator. As the foot is placed up on the step the step then moves downward.

Is a treadmill incline just a marketing ruse that actually has no effect?

 

[anorlunda]

It just so happens that I got off one of those treadmills an hour ago.

As I plant one foot, I lift my body up in the air. As the other foot is coming forward, the other foot is moving back bringing my body down with is. So the answer is that your body does not stay at the same height, it moves up and down, averaging the same height.

 

[russ_watters]

Have you ever run on an inclined treadmill...?

The answer is that you aren't doing work against gravity, you are doing work against the treadmill. If you compare to the scenario where you are standing on the treadmill and it is moving back and down, you apply a force over a distance to counteract that.

For more depth, please check the related threads below; we've had exactly this question, recently.

 

[The Grassy Knoll]

You are actually raising your body, it just sinks back down as the planted foot rides the treadmill backwards which allows you to do the same motion with the other foot when it gets planted.

 

[PeroK]

Makers of fitness treadmills usually include an adjustment for the treadmill surface incline. This allows the running surface to be tilted upward by a maximum of 10-15 degrees and it is supposed to simulate a more strenuous run up a hill.

But how can this be more strenuous? The runner is stationary and remains at the same height as the treadmill track moves under him. No work is being done against gravity. It is like climbing up on a down escalator. As the foot is placed up on the step the step then moves downward.

Is a treadmill incline just a marketing ruse that actually has no effect?

There was a thread about this a while ago. I must confess, initially I thought you aren't doing as much work as moving uphill, but I was wrong. And, if you look online a lot of people get this wrong. It's the same on a down escalator.

One way to look at it is that if you don't move at all, then you will lose height. Imagine two down escalators, with one person going down one and another person walking against the other one. After a short time, one person will be higher than the other. They must have done work against gravity to achieve that.

However, if you hold on to the bar or otherwise make use of something that is not being pulled down, then that changes everything. Then, it's like being pulled uphill on a ski-tow.

 

[Orodruin]

Just to add to what has already been said, running up the hill is just a simple Galilei transform away from being a run on a treadmill.

Consider the case of running up an actual hill. Assuming that you run upwards at a constant speed and at a constant slope. You can make a Galilean transformation that makes you stationary and the ground move. Since it is a transformation with constant velocity, it is a transformation between inertial frames. The result is exactly equivalent to the case of running on an inclined treadmill since no additional inertial forces arise in transforming between two inertial frames.

The above argumentation shows that there cannot be any difference between running up the hill and running on the treadmill (of course idealising the situations to only cover the incline and gravitational field). The treadmill therefore in some sense creates a perfect constant incline slope for you to run in.

 

[sophiecentaur]

You are actually raising your body, it just sinks back down as the planted foot rides the treadmill backwards which allows you to do the same motion with the other foot when it gets planted.

With no braking, it's virtually the same as running on the spot, except that it 'feels' more like real running. If, instead of running, you were to sit on an exercise bike with no braking you wouldn't be able to do as much wasted work without turning the pedals at a ridiculous rate. Introducing some braking makes all these activities more realistic. Even more realistic is a motorised belt which makes you run uphill in order to keep up with the belt.

 

[A.T.]

Makers of fitness treadmills usually include an adjustment for the treadmill surface incline. This allows the running surface to be tilted upward by a maximum of 10-15 degrees and it is supposed to simulate a more strenuous run up a hill.

But how can this be more strenuous? The runner is stationary and remains at the same height as the treadmill track moves under him. No work is being done against gravity. It is like climbing up on a down escalator. As the foot is placed up on the step the step then moves downward.

Is a treadmill incline just a marketing ruse that actually has no effect?

Just analyse the inclined treadmill from the inertial frame, where the upper belt surface is at rest. Here you continuously move upwards, just as you would on a real hill. You have to look at both scenarios from the rest frame of the support surface. Here the work done on the surface is zero, so all the gain in potential energy comes from muscles.

 

[lekh2003]

Is a treadmill incline just a marketing ruse that actually has no effect?

Let's not jump to conclusions.

You need to think about what the treadmill is doing. It is essentially moving you backwards when not at an incline. This is perfectly normal, and the work you are doing is opposite the work the treadmill is doing so that you can stay still. At an incline, you are simply adding another axis to work with.

 

[A.T.]

You need to think about what the treadmill is doing. It is essentially moving you backwards when not at an incline. This is perfectly normal, and the work you are doing is opposite the work the treadmill is doing so that you can stay still.

On a level treadmill you are not doing any net work on the treadmill, and the treadmill is not doing any net work on you (over a whole gait cycle).

 

[lekh2003]

On a level treadmill you are not doing any net work on the treadmill, and the treadmill is not doing any net work on you.

Yes there is no net work. You are doing work, the treadmill is doing work in the opposite direction, having a zero total net work.

 

[A.T.]

Yes there is no net work. You are doing work, the treadmill is doing work in the opposite direction, having a zero total net work.

No, that is not what I mean. On a level treadmill you are not doing any net work on the treadmill over a whole gait cycle. And the treadmill is not doing any net work on you over a whole gait cycle. These both quantities are zero, not just their sum.

 

[lekh2003]

No, that is not what I mean. On a level treadmill you are not doing any net work on the treadmill over a whole gait cycle. And the treadmill is not doing any net work on you over a whole gait cycle. These both quantities are zero, not just their sum.

Ahh, yes, on a level treadmill, apologies.

 

[sophiecentaur]

No, that is not what I mean. On a level treadmill you are not doing any net work on the treadmill over a whole gait cycle. And the treadmill is not doing any net work on you over a whole gait cycle. These both quantities are zero, not just their sum.

Yes. It's the same for all sport (all human activity, in fact). We do no net work 'on' the Earth or ourselves during our lives as we end up at more of less the same altitude. Sport just exercises our muscles to make them and our CV system stronger. "Work On" is a bit of a red herring here - as it is in most cases - because it doesn't address the real question which is to do with Energy Dissipated.

 

[A.T.]

We do no net work 'on' the Earth or ourselves during our lives as we end up at more of less the same altitude.

In the rest frame of the Earth, we do no work on the Earth, regardless if we end up at the same altitude. But I wasn't talking about the rest frame of the belt in post #12.

 

[Mathew]

Just analyse the inclined treadmill from the inertial frame, where the upper belt surface is at rest. Here you continuously move upwards, just as you would on a real hill. You have to look at both scenarios from the rest frame of the support surface. Here the work done on the surface is zero, so all the gain in potential energy comes from muscles.

Sorry to resurrect this thread as my first post, but I’ve been thinking about this specific question and came across this thread in a search, and I’m still not convinced. Perhaps I don’t understand the physics well enough, but from the reference point of the top surface of the inclined treadmill is the entire Earth and its gravitational field not moving up at the same speed as the runner? Surly that’s a major difference from running up a real hill?

Also, I don’t think the comparison earlier in the thread to walking up a down escalator is accurate enough.

I think of running on a treadmill as a bit like having sea legs on a boat. You can let the inertia of the majority of your mass keep you mostly stationary while just moving your legs to meet the movement of the boat below you. It’s harder work that standing still on the ground, but it’s not as hard as doing squats.

Equally, if you’re walking up an escalator in a stop-start motion, moving your entire mass the distance of the step before waiting to be lowered, that will be like walking up real stairs. But running on an inclined treadmill isn’t as simple as that. As people have mentioned when running your centre of mass does go up and down with your gait. The question is, to what extent does the incline of the treadmill increase the up and down motion of the running, and to what extent is that mitigated by a change in your gait that keeps the majority of your body’s mass comparatively level? Certainty your feet have to go further up and down by the entire height of the incline over the distance of each pace. But does your torso do the same?

I would guess that the incline of the treadmill does increase the effort needed to run on it, but I don’t think it’s clear that it does so to the same level as running up a similarly inclined hill, and I think it depends on the specific mechanics of your running gait.

 

[jbriggs444]

Perhaps I don’t understand the physics well enough, but from the reference point of the top surface of the inclined treadmill is the entire Earth and its gravitational field not moving up at the same speed as the runner? Surly that’s a major difference from running up a real hill?

The movement or not of the entire Earth is irrelevant to the runner. The movement of the gravitational field is similarly irrelevant. It is a [nearly] uniform field. Its force is what it is regardless of whether the pattern of forces is moving up or down.

The stationary climber has to exert a force while extending his legs repeatedly. That is all his muscles care about.

 

[Mathew]

The movement or not of the entire Earth is irrelevant to the runner. The movement of the gravitational field is similarly irrelevant. It is a [nearly] uniform field. Its force is what it is regardless of whether the pattern of forces is moving up or down.

The stationary climber has to exert a force while extending his legs repeatedly. That is all his muscles care about.

So does that mean gravitational potential and the up and down motion of the body while running, effectively have no impact on this?

I really need to re-study physics.

 

[anorlunda]

I would guess that the incline of the treadmill does increase the effort needed to run on it, but I don’t think it’s clear that it does so to the same level as running up a similarly inclined hill, and I think it depends on the specific mechanics of your running gait.

Why don't you try the experiment yourself? That's the scientific method.

When I use the treadmill at the gym, I find it easy to track how my heart rate changes in response to changes in the incline. You could do that on a treadmills, then go outside and do the same thing on a real hill. If you do that, feel free to post here again and tell us your results.

 

[Orodruin]

One point is that the gravitational potential is irrelevant for the physics as the approximation of a constant gravitational field holds to large accuracy. You could add an arbitrary time dependent function to the gravitational potential and it would still lead to the same gravitational force.

 

[A.T.]

So does that mean gravitational potential and the up and down motion of the body while running, effectively have no impact on this?.

As already explained in post #8, you have the same gain in potential energy in both scenarios, when you analyze both scenarios from the rest frame of the support surface (where no work is done on the surface). As others noted, we assume a uniform gravitational field here.

I really need to re-study physics.

See here:
https://en.wikipedia.org/wiki/Galilean_invariance