No, it’s the same thing - it’s all relative - as others have already pointed out, you’re already on a big treadmill called ‘The Earth’.
Motorized treadmills also tend you assist you with your kick.
Put a dot on the treadmill. Regardless of whether it is moving on it’s own or you are propelling it, that dot will always move away from you (well, it will loop around and pass under you again, but that’s only because the treadmill is small - every time you pass it, you are a treadmill-circumference further away). Put a dot on the road, and you’ll get further away from it as you run, too.
If you apply no force on a self-propelled treadmill, then nothing happens. You stand still, and the dot stays beneath you. If you apply no force on an automatic treadmill, you move back with the treadmill but the dot stays beneath you. You essentially are not moving, and you expend the same amount of energy either way.
Now assume that you are running at a steady 5 mph, on a self-propelled treadmill. Your dot moves away from you at 5 mph. The force you are applying is enough to keep you going at 5 mph. You had to apply increasing force to get to that speed, and then a constant amount of force to maintain it.
The automatic treadmill is similar. You start it up, and it accelerates. Either you apply no force, and you get shot off the back of it like a bad cartoon, or you apply force to accelerate relative to the track of the treadmill, you reach a steady 5mph, and then apply a constant force to maintain that speed. Your dot moves away from you at 5mph, exactly as before.
I think, though, that you would actually exert less force on the automatic treadmill because you don’t have to overcome the friction of the track on the rollers; the motor would be taking care of that. It probably applies a little more than 5mph worth of force, the roller friction is applied, and the resultant is a 5mph track. But on a self-propelled treadmill, you’d have to add a little more force to deal with that opposing friction to maintain 5mph. I have no idea what the coefficient of friction is for a treadmill relative to its rollers. I don’t know how significant it is (presumably, the friction has been reduced as much as possible).
Lets isolate this all down to just one motion: you have just stepped with your right foot and your left foot is on its way over. Actually, lets make this even easier and make it walking. So your right leg is straight out and your left is taking its time coming forward. Slow your image way way down. When you are walking on normal ground, you engage your right gluteus maximus (and related muscles) much more than when you are walking on a treadmill. Can you see it? While you are on the treadmill, the function of your right leg is much more “balance your body while the treadmill takes your foot back to simulate walking motion” than “propel your body mass forward.”
Yes, your left leg is doing the same amount of work in both cases, and YES, your are still moving away from an arbitrary point on the treadmill, and I think this is where most people get hung up on the “its all relative” train of thought. As for the Earth=megatreadmill argument, that doesn’t need to be mutually exclusive with my explanation above. Take the treadmill from my example. Now slow it down to half its speed, half of that, until it is moving at whatever rate the earth is spinning at. Thats it.
edited to clarify.
When you are running, regardless of whether it is on a treadmill, on the very fast treadmill called the Earth, or on anything, you are a system. That system can be treated the same regardless of what you are running on.
To understand this in a simple moment, just ask yourself what happens to your upper body if you stop running on the treadmill. 
No. No no no no no. Your body doesn’t CARE what the pavement under it is doing, staying still or moving backward. The motion is the same: propelling you forward compared to the surface against which you are pushing.
If you don’t understand this, then try this thought experiment: make the treadmill really long. Put a camera on it. what will the camera show you doing? How will that be different from what a camera located at a place along the path you are jogging show in the non-treadmill scenario? Answer: not one whit different.
It’s all RELATIVE, dammit. :smack:
Ok I’ve thought it through one more time and I still stand by my statement. Think about it like this: Try balancing on a moving treadmill on one leg–you’ll fall off. So once your foot goes back far enough, bring your other foot down, farther forward and balance on that leg. Rinse, repeat, make that motion a little more fluid, see where I’m going? Try that same thing on normal ground and you’ll never get past step one, balance on one leg. Because in that case, you need to actually get your body moving. Essentially, the treadmill allows what would be your “pushing off leg” on normal ground to slack off and fill more of a “just balancing while the treadmill does the work for you” kind of role. Your thought experiment especially shows where you are wrong (and I thought I addressed this in my original post): What the camera, or any other external observer doesnt show you is the amount of work your legs are exerting on the ground. When the ground moves back from under you, it’s doing part of that work for you, because your body’s inertial tendency is to stay where it is in relation to the earth, i.e. move forward in relation to the treadmill. This is clear as day in my mind, and yet I can’t seem to express it to you better. Sorry 
On a treadmill you are having to push up and forward. On a treadmill just up. Instead of walking, think of hopping. If you make small little up and down hops (think boxers jumping rope) on a treadmill the treadmill motor does the forward bit for you. To cover the same ‘ground’ on a road your muscles, in addition to proving the energy for 'up, would have to also provide the energy for ‘forward’ (that had previously been provided by the motor). More muscle coming into play = spending more effort.
Having ran on a lot of treadmills and a lot roads I can tell you treadmills are a lot easier.
The first sentence should have read, “On a road you are having to push up and forward.”
:smack:
Interesting example. But what would happen if you tried jumping rope on a treadmill? It seems to me that it would not be the same as jumping rope on a stationary surface. Somehow, you would have to counteract the motion of the treadmill.
I’ll leave to others to say whether the effort to do so is the same as skipping and moving forward at the same time.
In fact, you don’t need to push forward on the road! Walking is actually just falling forward, and then sticking a foot out in front to vault (ie poll-vault) into your next step. It requires almost zero energy, which is why walking is about as tiring as standing.
Any “pushing foward” is only to counteract either wind or a hill. The other drains of energy are internal friction and lifting your legs (because every time you lift, you use energy, every time they fall, energy is lost). If you jog by lifting your knees, you know the difference. These two are the same on a treadmill.
ok a brisk walk or a run then. at some point you’re going to have to add some force horizontally–but a treadmill would allow you to be lazy in the fashion you described and use less horizontal force, because essentially any horizontal force you exert on the ground is making you fall earlier further in between falls, and the motion of the treadmill accomplishes the same thing. No?
And this is not the same thing as jumping straight up and down on the treadmill. When you do that, you retain the horizontal motion of the treadmill the moment you jump up, resulting in you moving back with the treadmill. That’s why you can throw a ball straight up from the bed of a pickup and catch it, instead of it landing on the spot of road over which you threw it.
Running most assuredly requires pushing forward and a lot of it. Ask any road racer. A camera mounted on a treadmill, as in DSYoungEsq’s example, might show the apparent same thing. What it won’t show is the amount of effort required to achieve it, which is what is asked in the OP.
A question to those who think that running on a treadmill is the same as running on the road: Do you think a runners top speed will be the same on both the road and a treadmill (even if wind were eliminated)?
ETA: Regarding wind, the OP only asks, “Is a person running at 5 MPH on a flat treadmill spending the same effort as a person running 5 MPH on the street?”. The answer is no, much less.
Ignoring wind resistance, there is no difference between running on a treadmill and running on a stationary surface. No difference. All this ‘up vs up-and-forward’ argument is bollocks. Einstein told me to say that.
Clearly, Einstein wasn’t a runner.
There’s also hills, road surface, and posture.
No. The difference between walking and running, why running takes so much more energy, is the effects of internal friction, unrecoverable energy to lift your legs, battling your pendulum’s natural period, plus wind and losses from the road surface. All of these things change between roads and treadmills. But treadmills don’t push your legs back. They just fucking don’t.
You’ve got the wrong quote under my name. Or the wrong name over that quote.
Whether we can agree on a theoretical basis for it or not, it’s empirically quite obvious (to me and many others) that running on a treadmill requires less effort than running on the road at the same pace.
I’m curious about this myself, but any analysis that concludes they are identical activities, physiologically, is to be rejected on the basis of failing to match experimental data. One need not propose a successful counter-analysis to do this.
OK, draw a force diagram. The treadmill is exerting a backwards force on you (don’t believe that? Stand still on a treadmill and see what happens.) Hopefully we can agree that F=MA. So the backwards force being exerted on you by the treadmill, according to Newton’s second law, will cause you to accelerate backwards. But when walking on a treadmill, you don’t accelerate backwards. Why not? Because you are applying a force in the opposite direction, namely forward (horizontally.) So yes, the treadmill is pulling your foot back. But why doesn’t your body go back along with your foot? Because you are exerting a horizontal force to keep your body stationary.
Step up on a treadmill and press start then come back and tell us what the treadmill did to your legs.