What's the reason that it requires less effort to walk against an escalator (to stay stationary) than walking up stairs? I had this discussion with my relatives about the reason why it feels like you spend less energy on a step machine in the gym (basically an escalator that goes down), than it is to move up some stairs. They agreed that the former takes less energy than the latter, but we had different reasons for why.
My reasoning was that on real stairs you walk up against gravity. This means that you have to convert kinetic energy from your moving legs into potential energy ($m\cdot g \cdot h$). While on step machine (or downwards escalator) you only have to keep yourself in one place, so $h = 0$.
However my relatives argued that it had nothing to do with physical laws, but rather a combination of these factors:

*

*The handles on the step machine allow you to carry less weight.

*I move at an irregular pace up actual stairs.

*I don't walk with the same velocity up the stairs as the step machine goes down.

*Air resistance.

While I agree that these factors will cost additional energy on the stairs compared to the step machine, I doubt that it's enough to explain my personal experience with the two. When I walk four floors up the stairs at my office I have to catch my breath a bit. However when I walk against the step machine I can keep up for like 20 minutes. I did notice though it was a bit harder when I released the handles, but I could still keep up a solid 10 minutes in one go.
Their counterargument against my reasoning is that I would need to use the same amount of energy to push myself against a step that is moving down to keep myself in place as it is to go up a stationary step, because it's all just relative.
However my countercounterargument would be that since you are walking against gravity, that the relativity argument does not hold up. Relativity is for when you are in a inertial frame of reference and when gravity is involved there is no inertial frame of reference anymore (unless maybe when you are in freefall, but then walking stairs becomes impossible).
Who's right here?
 A: The Galilean relativity principle is old physics but still more than correct enough for use in this type of situation. This states that the laws of physics are the same in in all inertial frames of reference.
So there is no fundamental physical difference between maintaining a position on an escalator that moves steadily downwards, and climbing stairs at a steady pace. The mechanical work you have to do is exactly the same.
Imagine you were walking up the stairs in a narrow stairway with smooth walls. And imagine there are walls behind you and in front of you that always stay at the same distance. There is no experiment you could do to tell the difference between a stationary staircase with motorized walls in front and behind, and a moving staircase with stationary walls.
To deal with your question about energy - you are converting your internal energy into potential energy in either case, in the same quantity. It's just that on fixed stairs the potential energy builds up in your body. On moving stairs the potential energy is removed by the device at the same rate that you add it. In the latter case the energy could in principle be used to power a machine attached to the stairs.
A: You don't use the same force for pushing down your leg on the step machine as compared to a real staircase.
On a staircase, you have your full weight on one leg while the other is up in the air on its way to the next step.
On a typical step machine, the other foot is still in contact with the pedal, taking up some of your weight. And if you use the handles, you'll probably also take up some of your weight with the arms. And both, the other foot and the arms, don't do any work. They are either steady or even gaining energy.
If everything else is identical (step height and stepping speed), you do less physical work because of the lower force that you apply with your "working" leg.
To create a comparable experience, refrain from taking up any weight with either your arms or the "other" leg (and adjust the machine accordingly to provide enough resistance).
A: The escalator effort depends on whether you are maintaining position or drifting.  Even maintaining position requires less effort than walking up stairs, because your mean "step up" distance is half a step.  The "stair" is dropping as you step up to the next level, so to speak.
I can't comment on a "step machine" without knowing whether the machine is motorized, whether it has adjustable friction resistance, etc.
