Does a StairMaster actually simulate climbing stairs?

Factual Questions
21

The problem with a “single step” stop/start mechanism is that 1) if it is at a set pace, then the user could simply get “out of synch” and you’d be back to the stairmaster as it is, or 2) if the pace (the stop start) is dictated by the user moving, then the user could also just pause and take a break whenever too easily. That is, if the “start” doesn’t occur until the user has stepped up, the user can simply not just step when they are tired.

This is why the (regularly paced) big escalator approach would work (although I guess they could just pause there too, now that I think about it).

22

They may have improved StairMasters since I used them. When I used them, no force was required to push the pedals. They moved on their own. I lifted my foot, then put it down after the pedal finished moving down. I never pushed on it at all.

23

If you were not pushing down on the pedals at all, then your arms were carrying all of your weight.

If your arms were not carrying your weight, then your feet were, and you were pushing down on the pedals with a force equal to your weight. This is a non-negotiable consequence of the laws of physics.

The pedals move upward on their own when you step off of the machine (or when you lift one foot while using the machine), but they will not move downward unless you are pushing down on them. Your weight, in combination with the speed setting of the machine, determines how quickly they move down when you step on them - but they will not move down unless you are stepping on them (i.e. pushing down on them).

Mechanical work is mechanical work, regardless of your frame of reference. If you weigh 160 pounds, your muscles don’t know whether they are lifting your body upward 12 inches from a stationary step, or pushing a step downward 12 inches while your body remains stationary. In each case, your muscles have done 160 lbf-ft of mechanical work.

If the machine didn’t resist the downward movement of the pedal/step with a force equal to your weight, then it would slam to the floor as soon as you tried to step on it.

24

Quite the contrary: You are lifting your body weight, since the steps descend below you. Walking “in place” on a down escalator (of any size) is precisely the same as walking up a flight of stairs with the same pitch.

25

That’s right. If you didn’t walk then your body would have descended with the stairs. Preventing your body descending with the stairs is the same as lifting your body up stationary stairs.

26

Chronos, I agree with you from a physics standpoint, you have to exert an equivalent force downwards to stay in the same place. But then how do we explain anecdotes like this:

27

They let you climb the stairs in the CN Tower? (Note to self: Climb Tower if ever in Toronto.)

I tried to use one of those once. I couldn’t get the stairs to go anywhere near as fast as I wanted them to. Obviously I didn’t understand the controls. So I gave up on them and just use stationary bikes or sometimes treadmills.

Any exercise machine is not going to be the same work as doing the same exercise without the machine. For one thing, there’s no air resistance when on the machine since your body isn’t moving through air. This is a very significant factor for a stationary bike, less so but still non-negligible for other machines.

There may be other factors we aren’t considering.

28

I disagree. You are “holding” your body weight, but not “displacing it”. It would be similar to when you stand up off the seat when you are riding a bicycle. Your legs are “descending” below you as you push, but you are not “lifting” your body - not displacing your weight. You are only “holding” it -maintaining it’s position.
This does require effort, but it is not the same amount of work that would be required to “lift” your body up each step.

I do not “race” up the Stairmaster. I keep a reasonably slow pace - but one that I can maintain for the full 20 minutes. But I KNOW, if I were to maintain that same pace on real steps/stairs, I’d never last for 20 minutes ! Either I would need to take breaks, or my pace would slow. It is NOT the same amount of “work”.

29

Invalid analogy. On a bike you are turning the pedals underneath you yourself and they rotate so they go up and down, on a moving set of stairs the stairs are being moved away from you by an outside force and they don’t come back up again. If you don’t do anything your body ends up lower than what it was previously, you are literally climbing. Note this refers only to a set of escalators or an escalator type device, I’m not entirely sure how the stairmaster fits in to that.

30

I’m still not seeing it. I can’t see the sense in these responses:

Let’s try this again with a much-simplified situation. Let’s consider a rolling vehicle (a) traveling on level ground; (b) traveling up-hill; (c) traveling on a level treadmill; (d) traveling on an inclined treadmill. And let’s ignore air resistance, okay?

(a) Traveling on level ground, once it gets up to speed, a vehicle must overcome various kinds of friction to keep moving at a constant speed. This is the exercise you must do if you attempt to push the vehicle.

(b) Pushing the vehicle up-hill, you must do all the work in (a) PLUS raising the altitude of the vehicle against gravity. This is much more work. Just try pushing a car up-hill, even up a hardly-steep driveway.

(c) Pushing a vehicle on a level treadmill: Suppose we coordinate the forward speed of the vehicle with the backward speed of the treadmill. Thus, the vehicle remains stationary w/ respect to the surrounding landscape. Yet, pushing this car takes the same effort as (a), no? (At least, we know the car won’t take off.)

NOW, Case (d): Pushing a car “up” an inclined treadmill. Suppose, as in (c), the speed of the car and the treadmill are kept constant (ETA: and equal) and in opposite direction. So the wheels turn, but the car stays stationary over the surrounding ground, vertically as well as horizontally. I am arguing that this must be similar to cases (a) or (c), and NOT the extra effort of case (b) because you are not raising the vehicle to a higher altitude against gravity. I can’t see an argument that this takes the same effort as (b) because the treadmill is constantly lowering the car and you are pushing it “up” just to keep it in the same place.

Let’s work with that. When I think I understand that, then let’s talk about walking (a) on level ground; (b) up-hill; (c) on a level treadmill; and (d) on an inclined treadmill. And when I think I understand THAT, then let’s add the additional complication of doing all this on something like a stair-master.

31

Consider the extreme case of a vertical treadmill and assume the car has enough friction on the tyres so it doesn’t just slip away. Holding the car on a vertical treadmill you have to do all the work of holding the car against gravity as well as fighting the treadmill which is trying to drag the car down. Smaller values of incline have exactly the same effect.

32

Lemme clarify this a bit: We established, somewhere in some thread recently, that walking is a much more complex kinetic activity than rolling. So I’m using a rolling vehicle here, in order to give us a much-simplified scenario to begin with. But, confusingly, I also talked about the effort of pushing the vehicle. I wrote that simply to emphasize the human effort required with these various exercises.

But I did intend to leave the complexity of human walking out of it, for now. So I don’t want to analyze the kinetics of that, yet. Just the work required to move a rolling vehicle in the various scenarios (a) through (d) described.

33

Okay, I think I’m getting an inkling of what you’re on about here. But I still don’t think I buy it.

My case (a), rolling on level ground, entails continual friction in the bearings and the friction of the tires against the ground, which must be continuously overcome.

My case (b), rolling up-hill, entails all the same friction and thus the same effort as (a) but in addition requires lifting the car vertically. I believe the lifting effort entails substantial more work than the effort of overcoming friction. This is why, for example, walking uphill is so much more effort than walking on level ground.

You suggest that simply holding the car up at a constant altitude against gravity is just as much work as raising it to a higher altitude, PLUS the effort of overcoming the friction against the treadmill. But overcoming the friction of the treadmill dragging the car down is just the (a) effort, and not the (b) effort. And the part I’m not seeing that that holding the car at constant altitude is equal work to raising it to higher altitude.

So, holding the car still on your vertical treadmill requires the effort of overcoming the downward tug of the treadmill (which I think is just the effort of overcoming friction, and not and effort to continually “raise” the car against gravity), PLUS the effort of holding it up where it already is – which I can’t see as being an effort equal to raising the car to a still-higher altitude.

34

Ah, the person holding the car up against gravity is pushing on the treadmill*, NOT some stationary piece of ground. From the point of view of the car and the person pushing, the ground outside of the treadmill may as well not exist.

What I mean is their feet are moving with the treadmill so they are not just holding the car they moving themselves and the car vertically with reference to the treadmill.

35

It’s late at night where I am (1:40 a.m.), so I’ll be back on the morrow . . .

36

Yes, in April (well May this year) & October. Lots of buildings/towers have charity climbs that allow you in one (or two) days a year.

What city are you near?

37

Notice I said “similar to”. I do understand about the pedal rotation, and the one “pushing you up” as you also push down. I was trying use (just) the pushing down motion as similar to the steps descending away.
A better analogy would be comparing squats and a leg press machine. With squats (without additional weight) you are displacing your body weight as you extend your legs. With a leg press machine, you are displacing “weight”, but how much depends on how much you have loaded. Just because you are making the same motion/exertion with your legs doesn’t mean you are doing the same amount of work. This is what is happening on the stairmaster - your legs are going through the same motions as climbing stairs, but you are not (see below) exerting the same amount of work.

Upon further thought, there is one factor with the stairmaster discussion that may be causing this debate: the rate that you have the machine running.
It would be possible to run the stairmaster machine slow enough so that on each step, you actually DO displace your entire body weight - step fully up. But to run the machine this slow would cause you to pause on each step, while the machine rotates the steps “enough” to be able to make the next step. That is, you would have enough time to even match both feet on the same step before proceeding.
So I’ll rephrase my previous statement: When operating the stairmaster at a rate which requires “continuous motion” (immediately going from one step to the next), you are 1) not displacing your (full) body weight, and therefore 2) not simulating actual stair climbing.

So you have two options on the stairmaster:

  1. run at a pace for “continuous motion” for an aerobic workout (what most people do).
  2. run at a slow pace to simulate actual stair climbing, but in an unrealistic (compared to climbing actual stairs) stepping pace.
38

I’d rather not get into multiple types of examples and analogies. I think the analysis of a single step is probably the simplest, most universally accessible/understandable thing we can deal with, so I’m gonna stick with that.

I think this is more difficult for people who don’t have a physics or engineering background because they haven’t been formally taught what mechanical work is. So let me start with that.

Mechanical work (hereafter referred to as work) is the transfer of energy from one physical entity to another via the exertion of force over a distance. It’s a calculable quantity:

W = F * d

When you are standing on the ground, you are exerting a force against the ground equal to your weight (let’s say 160 pounds). But since you are standing still, d=0, and you are not doing any work.

Let us suppose you climb up a 1-foot-tall step. in this case, you have moved upward 1 foot against the influence of gravity. You have been pushing downward on the ground and/or step with 160 pounds of force during the entire event; if you weren’t, you would have fallen in a heap. In the process of climbing up this one step, you have done some work:

W = 160 pounds * 1 foot

W = 160 pound-feet

From the definition above, this means that in climbing a step we have transferred some energy from somewhere to somewhere. In this case, the energy came from our muscles and went into increasing your gravitational potential energy by exactly that much.

Now, let us suppose you are standing on the pedals of a Stairmaster. The pedals are sinking, so you move your legs in order to keep your center of mass at a constant altitude. You are exerting a downward force on the pedal of the stairmaster for the entire time that it’s sinking; if you weren’t, you’d crumple in a heap. Because you are exerting a force of 160 pounds, and the pedal moves downward one foot, you have done 160 pound feet of work. Instead of increasing your gravitational potential energy as you did on the stationary step, the energy you have provided has gone into the Stairmaster. Inside the Stairmaster the pedals spin a flywheel that is connected to an eddy current brake; this brake is where all of your work goes (check page ten of this PDF parts manual for a Stairmaster; look for part #41). It manifests as heat in an aluminum rotor which experiences drag torque due to the influence of magnets. When you adjust the intensity of the workout on the control panel, the Stairmaster moves those magnets to change the drag behavior of that eddy current brake. The flywheel/brake may spin faster or slower, but the amount of force on those pedals will always be the same: your weight.

Bottom line? Your muscles have no idea whether they’re pushing your body up or pushing something else down. All they know is that they are pushing and covering some distance, and the only difference is where the energy goes, into gravitational potential, or into an eddy current brake (your muscles don’t care which).

39

Okay, now we’re making some progress. I’ve got a certain rudimentary understanding of the laws of physics and mechanics, such that your little lecture is helpful and informative at about the right level for me. So far so good.

And finally, we have some discussion of the internal mechanism of the Stairmaster, to the effect that there is some deliberate design work in there to make the user’s stepping motion take some work. Now I am partially seeing it. But still not quite.

First, a question: If the effort comes from pushing down on the steps and thus working against that internal resistance built into the machine with those brakes and magnets, then how does this correspond to the user’s weight? You say it’s done by adjusting knobs on the control panel? Does this mean I have to manually set some knob according to my weight? (Or, alternatively, set that knob to whatever resistance level I want, according to how hard a work-out I want?)

Okay, I can half-way see how that works, so far. (See below.) But then, this resistance is not a function of the user’s weight, it’s a function of the resistance in the device which is not directly dependent on the user’s weight.

Does the Stairmaster (or any similar device) have some kind of computer-controlled workout paradigm that will automatically sense the user’s weight and maybe even track the user’s movements through the stepping cycle, and automatically make all the right adjustments in real-time?

Now, the part I don’t see yet. Suppose you are laying horizontally on your back in a canoe-like exercise machine, with foot pedals that you alternately push against. These foot pedals are built with resistance in them, so you get a work-out pushing on them. But there’s no lifting anything against gravity, nor even any simulation of that. It sounds to me like the Stairmaster, as you’ve described it, is similar to that, rather than a simulation of walking up steps. But wait, there’s still a bit I don’t get . . .

Suppose I use this Stairmaster in a room with a low ceiling, such that I can reach up overhead and press the palms of my hands flat against the ceiling. Now, if I step up and straighten my leg, and press hard against the ceiling, then I can’t go up, so straightening my leg presses down harder on the step. This pushes the step down against the built-in resistance. What happens if that ceiling isn’t there? What keeps me from just going up while the step stays still?

Okay, I’m getting a bit of a picture here, but still a little foggy. Suppose I weigh 160 lb. Suppose I set the machine to 160 lb. of resistance. I straighten my leg, pushing down on the step with 160 lb. and the step goes down while I stay put. What is happening here different from what happens if I just stand motionlessly on the step, not bending or straightening my leg at all? I’m still pushing down on it with 160 lb. of my weight. What happens differently when I put my foot on the next step up and straighten my leg? If the step stays still (as a stationary staircase would), I go up, lifting my 160 lb. a few inches. And if I push upward on that hypothetical ceiling while straightening my leg, that exerts extra downward force on the step – but that is in proportion to the strength of my muscle, not a function of my 160 lb. weight. And if the step descends under my weight as I straighten my leg (without pushing on any hypothetical ceiling), (a) how is that different from just taking a step forward on level ground, and (b) why didn’t the step descend when I just stood still on the step?

40

Even if all of the physics arguments are correct a Stairmaster workout still wouldn’t be equivalent to walking up actual stairs unless the range of motion was identical for both.

I believe that the Stairmaster requires a larger range of motion than climbing up stairs one step at a time, which requires more effort for the same amount of physical work.