B Is the Stairmaster a Valuable Exercise Tool Despite Physics Misconceptions?

[berkeman]

If you disagree with me, don't bet your 401K on being right

Thread closed temporarily for Moderation...

 

[berkeman]

I'm going to try 1 more time. This is about effort required of the climber.

Stairmaster: the 'F' in 'FdotdS' is body weight (max). station-keeping.

Stairs: the F is body weight plus the force required to produce a net upward velocity. If the force were only body weight (or less), no 'climb' could occur. The add'l force is not trivial.

I don't know another way to explain it. If you disagree with me, don't bet your 401K on being right (you aren't) You might go to the mall, or talk to someone who has actually walked on a treadmill/stairmaster and compared.

@Dullard -- Please lose the attitude, and please try to learn from the very valuable PF resource.

Thread reopened for now. Please respond in a substantive way to the helpful responses you have been provided so far. Thank you.

 

[OldYat47]

Walking up the down escalator at a pace that leaves you in the same vertical location is identical to the mechanics of a stairmaster-type machine.
Referencing the original question, I stand by my previous post (#10). Any one user may get more or less benefit than any other user based on the way they use the machine. If a user boosts themselves up quickly at each step they will be doing more work because their center of mass will be moving up and down more (force X distance). Quickly extend the leg while the step is high, stand on step as it lowers until the next upper step is in place, quickly step and extend, etc. A user pacing at the same rate as the machine will do less work (center of mass in the same vertical location), but their legs are still moving so some work is being done. And for exercise "value", no motion is necessary at all (isometrics, yoga as examples).

 

[PeroK]

Walking up the down escalator at a pace that leaves you in the same vertical location is identical to the mechanics of a stairmaster-type machine.
Referencing the original question, I stand by my previous post (#10). Any one user may get more or less benefit than any other user based on the way they use the machine. If a user boosts themselves up quickly at each step they will be doing more work because their center of mass will be moving up and down more (force X distance). Quickly extend the leg while the step is high, stand on step as it lowers until the next upper step is in place, quickly step and extend, etc. A user pacing at the same rate as the machine will do less work (center of mass in the same vertical location), but their legs are still moving so some work is being done. And for exercise "value", no motion is necessary at all (isometrics, yoga as examples).

... which is false. It doesn't matter whether you employ a funny walk, you cannot cheat gravity.

 

[jbriggs444]

If a user boosts themselves up quickly at each step they will be doing more work because their center of mass will be moving up and down more (force X distance).

This is not correct.

 

[A.T.]

I never claimed that my speed 'relative to the ground' mattered.

Then how do you define the following?

... actually elevating...

Elevating in what frame of reference? Movement is frame dependent, and so is work.

Please read the other threads, before you keep repeating more wrong stuff that was already debunked there:
https://www.physicsforums.com/threads/fitness-treadmill-incline.937725/
https://www.physicsforums.com/threads/work-done-running-on-an-inclined-treadmill.927825/

 

[A.T.]

...will do less work

See post above.

 

[russ_watters]

Referencing the original question, I stand by my previous post (#10). Any one user may get more or less benefit than any other user based on the way they use the machine.

In other words, if you change your gait it might get more or less efficient. This is both obvious and pointless as pertains to this thread.

 

[russ_watters]

This is not correct.

Actually, it is true - with the caveat that it isn't very helpful to the thread, per my previous post...

Please note: the OP and the post quoted were about "exercise value", which is different than mechanical work. We've for the most part been assuming the motion is identical in the various cases, making the "exercise value" the same because the mechanical work done is the same.

But energy is *not* conserved in human motion. That means that smoother motions are more efficient than jerky motions because the extra acceleration energy of a jerky motion is not recovered when you decelerate again. So if you change your gait when using a machine you may expend more or less energy to do the same amount of mechanical work.

 

[Dullard]

I've pondered some more. I apologize for getting the thread locked - I was smiling when I typed the offending words, but that apparently didn't come across.Is a treadmill/stairmaster as much ‘exercise’ as an equivalent ramp/stairs? I still don’t think so.

Case 1 (Treadmill)

Imagine a wheeled cart on an inclined (moving) treadmill. Neglect friction, etc. The cart is attached to the uphill end of the treadmill structure with a fixed rope – the rope is parallel to the deck of the treadmill. The tension (T) in that rope is a function of the incline angle and the weight of the cart; it is (exactly)the force required to maintain the cart position. The force does not change if the treadmill is stopped. It doesn’t change if the treadmill is reversed.

Case 2 (Ramp)

Move this rig to a stationary ramp of the same incline (or stay on the stopped treadmill). Note that the tension in the rope is exactly the same as in Case 1. The cart isn’t going up the ramp. You’ll need to ‘tug’ on the rope to get the cart moving and reel in the rope to maintain motion. The tension in the rope will (initially) be higher than ‘T’ while the cart accelerates from rest to climbing velocity; call that difference ‘F’. Once at climbing velocity, you’re back to ‘T.’ The application of the additional force (F) over the distance where velocity is changing is work that is not required in Case 1.

It is tempting to say that this is not steady-state behavior, and should be neglected for this and any similar analysis. In the example of the cart, I agree – there is no steady-state difference between a treadmill and a ramp. In the case of human locomotion, I have an apparently irreconcilable problem:

Any actual experiment comparing the amount of exertion required to walk on a treadmill/stairmaster with the effort required on their geometrically equivalent low-tech counterparts empirically demonstrates that they are not equivalent in terms of effort (it isn’t even very close). I’ve done it, and don’t know of anyone (who actually did an experiment) who disagrees.

Unless my understanding of the experimental data is wrong, I can only conclude:

The nature of human locomotion (the complexity of many parts moving different directions) requires that the penalty (‘F,’ above) is paid (at least in part) at every new step.

I suspect that the reason that the simple models don’t accurately answer the basic question is the inability of a human to ‘benefit’ from negative work. ‘Effort’ isn’t paid back on the other side of the hill. Work which would sum to zero in an over-simple model leaves a user sweating.

 

[jbriggs444]

The nature of human locomotion (the complexity of many parts moving different directions) requires that the penalty (‘F,’ above) is paid (at least in part) at every new step.

You have not identified any difference in gait on the moving treadmill versus a stationary ramp that would be required to make F (the initial acceleration penalty) applicable.

 

[Dullard]

I don't believe that a difference in observable gait is required. The forces are different in the 2 cases, not (necessarily) the gait.

 

[A.T.]

In the example of the cart, I agree – there is no steady-state difference between a treadmill and a ramp.

So we agree that there is no mechanical reason for the work to be different?

I suspect that the reason that the simple models don’t accurately answer the basic question is the inability of a human to ‘benefit’ from negative work.

No, that is not the reason far any differences, because that inability exists in both cases.

What is different between treadmill and ground, are the visual cues (fixed vs moving surrounding) and the spatial limitations due to the size of the belt surface (no tolerance for variable walk speed). These can lead to a different gait pattern and muscle activation.

The forces are different in the 2 cases, not (necessarily) the gait.

What forces are different despite same gait pattern and why?

 

[jbriggs444]

I don't believe that a difference in observable gait is required. The forces are different in the 2 cases, not (necessarily) the gait.

Given identical gait, the forces are identical in the two cases.

 

[anorlunda]

I think the posters are ignoring the very clear way @russ_watters delineated the problem in #39.

Please note: the OP and the post quoted were about "exercise value", which is different than mechanical work. We've for the most part been assuming the motion is identical in the various cases, making the "exercise value" the same because the mechanical work done is the same.

The question is not mechanical work, force*distance. It is human biological work, which obey the mechanical laws of physics but it also much more. Standing still consumes work in the body. We could say that mechanical work establishes the floor of biological work, but the average and peak values of biological work (exercise) are necessarily higher.

If everyone continues debating while thinking of differing definitions of work, the debate is endless. So please, let's stick to the OP's question about "exercise value" or biological work.

 

[Dullard]

anorlunda:
I agree. That's really at the heart of what I'm arguing. The 'net' work for the 2 cases is the same, but the ''peak-to-peak' is larger for actual climbing. My example with the cart was an attempt to illustrate that there are real differences in the forces.

 

[A.T.]

The 'net' work for the 2 cases is the same, but the ''peak-to-peak' is larger for actual climbing.

Do you mean that there is more antagonist muscle co-contraction, which uses more energy, despite the same external work? This is theoretically possible, but why would it be more on ground?

 

[anorlunda]

This is PF. We can do still better in making this a quality debate.

V02 https://en.wikipedia.org/wiki/VO2_max is a qualitative metric of exercise used by doctors. Rather than personal opinions, let's see some peer reviewed studies citing V02 for running, stairmasters, and treadmills. Or any other objective measures. But please let's stop with personal opinions unsubstantiated by references.

I would prefer to see this thread become better quality than to close it.

 

[russ_watters]

I don't believe that a difference in observable gait is required. The forces are different in the 2 cases, not (necessarily) the gait.

This is quite simply false. The force in both cases is exactly your weight.

 

[russ_watters]

anorlunda:
I agree. That's really at the heart of what I'm arguing. The 'net' work for the 2 cases is the same, but the ''peak-to-peak' is larger for actual climbing. My example with the cart was an attempt to illustrate that there are real differences in the forces.

Except that the cart example doesn't actually match the exercises. The cart example you gave is what happens if you hold on to the handlebars. We all agree that if you do that, it reduces or eliminates the exercise value.

Please: apply some numbers: A person weighs 170lb and walks smoothly up the stairs or stairmaster. What is the force applied?

Any actual experiment comparing the amount of exertion required to walk on a treadmill/stairmaster with the effort required on their geometrically equivalent low-tech counterparts empirically demonstrates that they are not equivalent in terms of effort (it isn’t even very close). I’ve done it, and don’t know of anyone (who actually did an experiment) who disagrees.

That is shocking to me. If there wasn't a significant exercise value, there would be no point to the exercise! Maybe you are using it wrong; are you holding on to the handlebars? I've seen people at the gym leaning hard on the Stairmaster handlebars.

 

[russ_watters]

Climbing stairs is a great exercise to raise the heart rate and sculpt a strong, lean lower body... if you're doing it right.

"I see many people placing close to half of their body weight leaning on the rails that they give you as just protection so you won't fall," Mark Hendricks, Group Fitness Manager at Greenwich Avenue Equinox says. "It's a safety issue not to place your hands on the handrail. That being said, there should never be pressing/pushing down on them."

When you push down on the rails, it decreases the load on your legs and glutes. "The heavier you load your muscle, the more muscle fiber you activate and essentially the more change you make in your muscle,"

https://www.self.com/story/the-mistake-youre-making-at-the-gym-stairmaster

So are you using it wrong?

 

[Dullard]

The cart example just provides a simple way (the tension in the rope) to illustrate the forces. The wheels eliminate any 'gait' questions.

I never claimed that a treadmill/stepper was 'no exercise' - just not as much. I only did that after others claimed that the required effort was identical. An open-minded reading of post #40 should be sufficient to make my point about the 'difference in forces' to any who are likely to grasp it. I won't be posting in this thread any more.

 

[russ_watters]

The cart example just provides a simple way (the tension in the rope) to illustrate the forces. The wheels eliminate any 'gait' questions.

I never claimed that a treadmill/stepper was 'no exercise' - just not as much. I only did that after others claimed that the required effort was identical. An open-minded reading of post #40 should be sufficient to make my point about the 'difference in forces' to any who are likely to grasp it. I won't be posting in this thread any more.

Sorry, but it isn't. You are really just handwaving and saying irrelevant things (a person on a stairmaster is not supported by a rope hanging from the ceiling). If you do choose to return to the thread, I must insist you start using numbers: A person weighs 170 lbs. What force does he apply to the stairs/stairmaster in a smooth/steady state climb?

 

[Tom.G]

Here is a start on using numbers. (looks like they may just give more to argue about!)

The formatting was not maintained but this was found as Category 02 at:
https://sites.google.com/site/compendiumofphysicalactivities/references

It shows that walking up a down escalator at 70 steps per minute uses 7% more energy than a StairMaster at 77 steps per minute.

From pg 7 of 17: https://632e345c-a-62cb3a1a-s-sites.../02-ConditioningExercise-2011CompendiumPA.pdf

02065 Stair treadmill ergometer, general 9.0
Average of 5 measures below

(Device)              (Speed)               (Energy?)          (Reference)
 StairMaster® , 60 steps/minute, level 5      6.51         (Butts, Dodge et al. 1993)

 StairMaster® , 77 steps/minute, level 7      7.99         (Butts, Dodge et al. 1993)

 StairMaster® , 95 steps/minute, level 9      9.48         (Butts, Dodge et al. 1993)

 StairMaster® , 112 steps/minute, level 11   10.98         (Butts, Dodge et al. 1993)walking up a descending escalator,
,                70 steps/minute,              8.56        (Bassett, Vachon et al. 1997)

 

[russ_watters]

Here is a start on using numbers. (looks like they may just give more to argue about!)

The formatting was not maintained but this was found as Category 02 at:
https://sites.google.com/site/compendiumofphysicalactivities/references

It shows that walking up a down escalator at 70 steps per minute uses 7% more energy than a StairMaster at 77 steps per minute.

From pg 7 of 17: https://632e345c-a-62cb3a1a-s-sites.../02-ConditioningExercise-2011CompendiumPA.pdf

I've requested a copy of the full paper to check the methodology.

...And tonight at the gym I'll count how many people on the stairmaster are holding on to the handlebars...

 

[jbriggs444]

In a stairmaster, as distinct from an escalator, I believe[d and was incorrect] that the idle leg is not lifted completely by the user but gets a "free ride" up on the ascending pedal. This amounts to positive work being done by the ascending pedal on the user. Although external work done on the user cannot normally be recovered as available energy, in this case it serves to elevate the leg. That is a task that the user would otherwise need to call on his hip flexors to perform.

In addition to recovering the energy needed to lift the idle leg back into position for another power stroke, the force applied by the power leg on its downstroke is reduced by whatever fraction of the user's weight is on the rising pedal. In effect, the work recovered from the rising pedal is doubled -- the same figure appears twice in the energy budget.

Edit: Thank you, @russ_watters. I stand corrected.

 

[russ_watters]

In a stairmaster, as distinct from an escalator, I believe that the idle leg is not lifted completely by the user but gets a "free ride" up on the ascending pedal.

Please note: "Stairmaster" is a brand name, not a type of machine. I think the assumption here needs to be that we are talking about the type that uses actual steps, not the type that uses pedals:

Not:

 

[.Scott]

Stairmaster: the 'F' in 'FdotdS' is body weight (max). station-keeping.

Stairs: the F is body weight plus the force required to produce a net upward velocity. If the force were only body weight (or less), no 'climb' could occur. The add'l force is not trivial.

Let me take a shot at this.
I believe what @Dullard is saying is that as a person walks up stairs they effectively pause at each step. Then they need to reaccelerate to move to the next step.

The key is this: When they pause, they pause relative to the steps. And when they accelerate, they accelerate relative to the steps. If a person pauses on an escalator, they don't stop gaining altitude. And when they resume their climb, they only need to increase their vertical velocity by as much as they would if the steps were not moving.

Bottom line is: There are difference in the forces during the transitions from a stationary floor to moving step or vice versa. But once you are on the steps (and presuming you are not holding onto the bar), you will exert the same amount of energy per step whether the steps are in motion or not.

 

[russ_watters]

Let me take a shot at this.
I believe what @Dullard is saying is that as a person walks up stairs they effectively pause at each step. Then they need to reaccelerate to move to the next step.

Agreed, though there are two ways around this:
1. We've specified and he's accepted that the gaits for each will be the same.
2. To make the analysis easier, we've tried to specify uniform motion, but it isn't clear if he's accepted. Perhaps he (and you)think it matters, but it doesn't:

The key is this: When they pause, they pause relative to the steps. And when they accelerate, they accelerate relative to the steps. If a person pauses on an escalator, they don't stop gaining altitude.

*Losing* altitude. They are going up the down escalator.

And when they resume their climb, they only need to increase their vertical velocity by as much as they would if the steps were not moving.

Which is exactly the same velocity as would be on stationary steps. Otherwise they are just plain walking slower on the escalator.

...once you are on the steps (and presuming you are not holding onto the bar), you will exert the same amount of energy per step whether the steps are in motion or not.

Given what you said above, it surprises me you still agree the energy is the seame, but I'm glad you do! ...maybe it was just a typo?

 

[.Scott]

*Losing* altitude. They are going up the down escalator.

I was taking the more normal scenario of going up the up escalator. So whe the pedestrian pauses on the escalator, they are still going up. And when the resume, they are restarting from upward vertical velocity - not from stationary.