physiology experts: why exactly is it easier for me to run on the treadmil than it is on motionless surfaces?

zxcvzxcv wrote:

If the treadmill didn't pull your leg back when your foot is resting on it, whether you are running or not running, then you wouldn't fall off the back of the treadmill if you kept it there. Obviously, the belt pulls your leg back while your foot is resting because the belt is moving in that direction relative to your body and the ground. How could you possibly think otherwise?

This is one of those things where everyone would be better off trying to explain color to a blind man. It's your COM that is moving forward at the same relative speed as the treadmill is moving and creating forward propulsion just like outside on the road.

Does your foot get pulled back if you rest it on a the treadmill? Yes because you are not using propulsion to counteract the speed of the treadmill.

But in the gait cycle during midstance in running, your COM is moving forward and it has nothing to do with pulling the leg back, you are catapulting your COM forward along a trajectory by moving your your hips ahead of your foot. You don't pull your leg back when running, you move your mass over the leg. You do the exact same on a treadmill.

All that happens on the treadmill is that it is counteracting that forward force production by moving in the opposite direction. Your speed relative to the treadmill is the exact same as it outside. The reason the treadmill doesn't pull your leg back biomechanically is because you are still moving your COM forward at the same speed as you do outside.

What happens during the support phase. As a thought experiment, imagine the support phase takes two seconds. How is the moving treadmill the same as the motionless ground in that scenario?

paper bag wrote:

What happens during the support phase. As a thought experiment, imagine the support phase takes two seconds. How is the moving treadmill the same as the motionless ground in that scenario?

Your leg is doing the same movement during the support phase. Your hips and COM are staying relatively stationary on the treadmill, but the leg is still supporting your weight as your leg follows the treadmill belt backwards. Your leg is tense, then slightly relaxes/tenses in pulses due to vibrations, and then tenses again to spring you off, just as if your COM were moving over your planted foot on the ground.

And the guy with the 30ft wide asphalt analogy gets it. Imagine I have a 1-mile (or 0.6km) long runway that is sliding in one direction. If you are on top and running in the opposite direction.

Are you running on a treadmill, or running on the ground at that point?

Treadmills require you to run from the behind. It is much easier to overstrike outdoors.

Whaaat wrote:

And the guy with the 30ft wide asphalt analogy gets it. Imagine I have a 1-mile (or 0.6km) long runway that is sliding in one direction. If you are on top and running in the opposite direction.

Are you running on a treadmill, or running on the ground at that point?

Now imagine if that sliding runway stopped sliding as fast for a moment when your foot was in contact with the ground so that it was moving faster when you were in the air and slower when you were in contact with it.

Now imagine running on flat ground at 7 mph with a tailwind of 7 mph.

paper bag wrote:

Now imagine if that sliding runway stopped sliding as fast for a moment when your foot was in contact with the ground so that it was moving faster when you were in the air and slower when you were in contact with it.

Now imagine running on flat ground at 7 mph with a tailwind of 7 mph.

Huh?

whaaaaat? wrote:

paper bag wrote:

Now imagine if that sliding runway stopped sliding as fast for a moment when your foot was in contact with the ground so that it was moving faster when you were in the air and slower when you were in contact with it.

Now imagine running on flat ground at 7 mph with a tailwind of 7 mph.

Huh?

Imagine you are wearing a really long superman cape and running in front of me. I'm running behind you and step on the cape. Does the cape slow down in relation to the ground at that moment?

paper bag wrote:

whaaaaat? wrote:

Huh?

Imagine you are wearing a really long superman cape and running in front of me. I'm running behind you and step on the cape. Does the cape slow down in relation to the ground at that moment?

You need to get a better treadmill.

Whaaaat? wrote:

UphillOllie wrote:

Let's see 0.5/50" stride = 0.01. Gee that's 1% and it's 1% downhill.

Not quite, because the deflection is localized and does not remain constant during the stride.

Try again. You aren't running downhill.

The math don't lie!

I'm not seeing any real physiological evidence that a treadmill can corrupt your running FORM. now ankel weights, yes. Just ask world renowned university of Colorado coach Jim Sanchez. He has proven that ankel weights cause injuries and bad form.

On a treadmill, your arms and legs are kept straight in line where they should be. If there is a serious incline, then you will be force to be more if a toe striker; which many of us need to be anyways (just view bekele form).

All in all, a moving belt on a treadmill is helping you out and propelling you forward. Just like when you are at the air form and they have those flat escalators that get you from a to b faster. IT IS THE EXACT SAME PROCESS. THE FLAT ESCALATOR THINGS AT AIRPORTS ARE PROPELLING YOU FORWARD JUST LIKE A TREADMILL.

Did I answer my own question? Yes, but the only question is to how much aid does the belly really provide. By my exertion, I would say it makes running 40 percent easier than running outside. Treadmills have endless advantages. The top 3 being easy digital access to your progress, adjustment of incline and hills, and avoidance of injury by slipping on a gosh darn frozen ice sickel.

While I dont see that down hill treadmills need to be invented YET, all you would have to do is prop a box under the back of the mill, and boddabing boddaboom. You have down hill running instantly at your service.

The great assistance of a moving belt on a treadmill, while forcing you to stay on and forcing you to make each step, is almost like cheating; all you need is a good adult movie to watch while doing your workout. That will make you stay on, stay hard, and become a champion.

fyodor.nash wrote:

The mechanics aren't the same. The "ground" on a treadmill is being propelled forward by motors and the speed of the "ground " is maintained by some sort of dumb feedback mechanism programmed into the treadmill. This means that when you push off it, the motors will ease off a bit so that the speed doesn't increase while you're in the air. Then when you land, the belt will slow down and cause the motors to work harder to maintain speed. This effectively translates to the treadmill doing some of the work for you to maintain pace.

This is the smartest post so far. OK, clearly the air resistance is a factor, as could be miscallibration. And thanks to Newton, we know the "staying in place" factor is bunk.

But a treadmill ISN'T just moving ground. In particular, it is much lighter, and your feet act on it in a way that isn't captured by an inertial reference frame. Imagine that you were running on a treadmill at 8 mph, but whenever you left the ground it quickly accelerated to 12 mph and then back down to 8 mph just in time for you to land. Well, your "average speed" would be much different than the speed you actually ran. Imagine now that the belt was extremely light and the belt motor was extremely weak. Every time you landed, the belt motor would be overwhelmed, and the belt would go the speed of your foot until you pushed off and the motor could speed it up again. So a similar thing would happen where the belt was moving slower while you were on it.

The question is: does this have a practical effect on actual real-life treadmills? It feels like it would be very small, and the air resistance effect we know is significant. But who knows? Any mechanical engineers around?

no the ground does not do the same thing wrote:

Think about what is happening in the time interval when the foot is in contact with the ground. This time interval is not zero.

During that time, the ground exerts force on the foot, preventing it from moving forward with the rest of the body. The foot exerts equal and opposite force on the ground, preventing itself from sliding forward. The interaction between the foot and the treadmill belt is the same. You only think something is being "pulled backwards" when you consider the runner's center of mass as stationary, instead of the running surface.

In efficient running, nothing is being pulled anywhere by the surface. Rather the runner's own muscles pull the leg backward so that the foot is at rest relative to the surface just before it strikes. This minimizes braking force (which "pulling the foot back" is) and is one of the most important things a runner can know. Learn it or forever slog.

can anyone confirm if watching an adult movie while running downhill on a treadmill will keep me hard and make me a champion?

The "belt pulling the foot" stuff is all nonsense. But there are a couple ways that a treadmill is easier.

1) As most have noted, the lack of air resistance becomes significant at workout paces. Much less so at easy run paces.

2) The belt actually does not move at a constant speed in most treadmills. When your foot hits the belt, you instantly cause the belt to slow down slightly, and the motor has to increase power to maintain the correct speed. When you're airborn, the belt suddenly increases speed slightly, and it reduces power to compensate. The result is that even if the treadmill is perfectly calibrated using the tape test, it's on average moving slightly slower during the time when your feet are planted. Better treadmills have this effect to a lesser degree. Woodways hardly have it at all because there's so little friction on their rollers.

On the other hand, I have no doubt that there are biomechanical differences due to the different flex of the deck compared to roads, the potential for a clipped stride if you're too close to the front or your belt is small, and perhaps most important, simple unfamiliarity with treadmill running (which is why people who aren't used to treadmills often don't do as "well" in VO2max tests).

Put me in the category of thinking treadmill at same pace is more difficult. Can't even hold my 5k pace (current!) for a mile on those things.

the430miler wrote:[/b

While I dont see that down hill treadmills need to be invented YET, all you would have to do is prop a box under the back of the mill, and boddabing boddaboom. You have down hill running instantly at your service.

The treadmills at my gym do go downhill to -3 degrees.

Maybe this just me, but

8:00 pace feels difficult on a treadmill and very easy outside.

5:30 pace intervals feel easy on a treadmill, but difficult outside.

WHY?!!!!

If a 2% grade is used on a treadmill, how does that affect one's foot-plant? If the grade is increased to mimic the effort of a flat outdoors run, does the foot-plant difference cause any kind of effect?