Pose = crazy???

Correct...Gravity is what pulls your foot back to the ground regardless of whether you use pose form or not.

The question was directed to Asterix because his initial response to it was: "Since we're talking about a vertically acting force, I've got problem saying it is gravity."

If he doesn't believe it is gravity I want to know what force he thinks it is.

perhaps you are right

ST wrote:

Correct...Gravity is what pulls your foot back to the ground regardless of whether you use pose form or not.

The question was directed to Asterix because his initial response to it was: "Since we're talking about a vertically acting force, I've got problem saying it is gravity."

If he doesn't believe it is gravity I want to know what force he thinks it is.

Actually you seemed to miss my point. There is muscular activity involved in returning the foot to the ground. I have no idea why you think it is an important point that gravity is actually causing the body to move downward, no one is arguing that gravity does not cause downward motion of the body. The effects of gravity as well as the effects of muscular activity to overcome gravity (not harnass it) can be observed by watching the movement of the center of mass. The movement of the limbs are more the result of muscular activity (and the resulting momentum forces) than gravity.

I don't miss your point. It does not apply.

I want Asterix to tell me what force brings his foot back to the ground because, he said he cannot say that gravity is the force.

You cannot raise your foot and employ muscular activity to bring it back to the ground unless you can appy force in a downward vector. To apply muscular force in a downward vector you have to push against something. What are you pushing against? Nothing.

Gravity is an integral component in the movement of running on this earth.

I am not debating with you. Asterix says he cannot agree that gravity is pulling his foot down. I want to know what force brings 'his' foot back to the ground.

Gatorade, ST, et al.:

Things are getting jumbled here what with people claiming that quotes have been taken out of context, arguments about who does/doesn't use Pose, comments on good form, etc. I'd like to simplify this and ask a simple question. Please answer as simply as possible, preferably with a yes/no:

Does Pose claim that a person can run across level ground without pushing off (i.e., applying no horizontal force component), instead relying on gravity to move foward (i.e., letting "gravity do the work")?

Big OOPS on my part that obviously causes a lot of confusion. That should have been written "I've got NO problem...".

Completely different meaning there!

True, but is completely irrelevant to anyone who is not trying to conduct the most precise of experiments. As far as everyday activities are concerned, you're pretty much good with the 10m/s/s approximation.

That continues to be contradictory! Gravity is NOT one of the vectors that is combined to give forward motion. Draw a force diagram!

Forward motion is entirely due to the horizontal force applied through your foot that is countered by the frictional force between your foot and the ground. That is why you wear spikes on the track and can't move much at all when you are wearing dress shoes on ice. Gravity is the same in both cases.

After you leaned forward and fell, is your center of mass higher, lower or the same as before?

Anser: lower. How do you get it back to the starting height? If you're Jack on the POSE forums, apparently you can then fall back up. The rest of us live in a world where you must push through your legs to drive your mass at an upwards angle that therefore has a horizontal (forward motion driver) and a vertical (paying back gravity with interest) component.

Running you can either fall and then spend energy to raise yourself, or, as it appears all elites do, raise yourself (while primarily driving forward) and then 'fall' back to the next landing.

Chart the center of mass of any elite runner and you will see that their center of mass is highest when they are completely airborne in the middle of their stride.

This is in complete contradiction to your POSE description of 'falling forward'.

If you are not providing a horizontal vector when running, then any forward lean or push will result in your feet flying backward while your center of mass has no net horizontal motion. End result would be you flat on your face on the ground exactly where you started from.

Since that is obviously not happening, there MUST be a force in the horizontal direction imparted through the point of contact with the ground. That would be the frictional force between your shoes and the ground. It also explains why ice skaters need to angle their feet when they want to move forward since trying to imitate walking motions would provide minimal horizontal force due to the noticeable lack of friction.

Done! - clarified my mistype from before and introduced you to the concept of friction.

My slip-up and missing that crucial 'no' has caused you mounds of confusion and for that, my apologies.

For clarification purposes, I'll defer to JimFiore's question asking for a clear and concise explanation of whether POSE specifies that "gravity does the work" or not.

"You cannot raise your foot and employ muscular activity to bring it back to the ground unless you can appy force in a downward vector. To apply muscular force in a downward vector you have to push against something. What are you pushing against? Nothing."

Errmmm, inertia/momentum? (otherwise how would you move any body part in mid-air)

15.10 wrote:

"You cannot raise your foot and employ muscular activity to bring it back to the ground unless you can appy force in a downward vector. To apply muscular force in a downward vector you have to push against something. What are you pushing against? Nothing."

Errmmm, inertia/momentum? (otherwise how would you move any body part in mid-air)

You are also pushing against the antagonist muscles. Agonists Every muscular action is actually resisted by opposing muscles and tendons on the other side. Gravity means the muscles have to do less work than they otherwise would, though.

I have always pictured efficient running to use gravity a bit. I am no scientist so I might be thinking fundamentally wrong here but I've pictured it like this:

You use gravity to coil up a spring in a vertical direction. Gravity acts vertically of course so that's a no brainer. But while you're doing this, the top of the spring is moving forward while the bottom part is stationary, in contact with the ground. Thus when the time comes for the spring to uncoil and release its energy, it is no longer horizontal, it is leaning, at an angle, the stored energy is thus released at an angle, resulting in some vertical motion and some *horizontal* motion

In the case of running, the "spring" is your muscles and tendons and the ankle joint. They are quite elastic though, not a perfect spring of course. So when they release their energy, you also must use your muscles to push off the ground (again at an angle, not vertically) to maintain your forward momentum. You are, of course, using your muscles to push off (POSE denial of this seems ridiculous) but SOME of the forward energy you have comes from that "spring" and the energy stored while coiling that spring comes (in part, not completely) from gravity.

That's my poor-man's, physics-ignoramus analysis. Works for me anyway.

Rip away.

Jim,

Here is the answer you are looking for direct from the Pose tech website. Enjoy!

I would have appreciated a simple answer rather than a pointer to an article that could be misinterpreted. That was the whole point of asking the question. Be that as it may, I shall quote the final segment of said article:

"So to sum it all up, there is push off in running, but it happens by itself. Muscular elasticity does it for us and we actually use our voluntary muscular efforts just to hold the body right."

This seem to be saying that "muscular elasticity" (which I assume refers to stored energy in the muscles/tendons due to the prior landing) creates the push-off and the only voluntary active use of the muscles is simply to keep the body from falling to the side or crumpling.

Is it safe then, for me to conclude that the answer to my question is "Yes, Pose claims that a person can run across level ground without using their muscles to supply a horizontal force, instead relying on gravity (i.e., the energy stored in the muscles) to do that work for them"?

I would have appreciated a simple answer rather than a pointer to an article that could be misinterpreted. That was the whole point of asking the question. Be that as it may, I shall quote the final segment of said article:

"So to sum it all up, there is push off in running, but it happens by itself. Muscular elasticity does it for us and we actually use our voluntary muscular efforts just to hold the body right."

This seem to be saying that "muscular elasticity" (which I assume refers to stored energy in the muscles/tendons due to the prior landing) creates the push-off and the only voluntary active use of the muscles is simply to keep the body from falling to the side or crumpling.

Is it safe then, for me to conclude that the answer to my question is "Yes, Pose claims that a person can run across level ground without using their muscles to supply a horizontal force, instead relying on gravity (i.e., the energy stored in the muscles) to do that work for them"?

agonist wrote:

In the case of running, the "spring" is your muscles and tendons and the ankle joint. They are quite elastic though, not a perfect spring of course. So when they release their energy, you also must use your muscles to push off the ground (again at an angle, not vertically) to maintain your forward momentum. You are, of course, using your muscles to push off (POSE denial of this seems ridiculous) but SOME of the forward energy you have comes from that "spring" and the energy stored while coiling that spring comes (in part, not completely) from gravity...

I think you have the basics down, but I'd suggest that if you're talking about the recoil of the ankle extensor muscles, momentum probably plays a bigger role than gravity. At first contact gravity is acting to stretch the calf muscles as the heel comes down to the ground. POSE advocates seem to call for keeping the heel off the ground during the stance phase, but that seems wrong minded to me (maybe I am wrong about their teachings). At any rate, there is not a lot of stretch there as the angle of the ankle is still greater than 90 degrees. The main stretch of these muscles comes as the body moves forward over the point of support, not downward due to gravity. This is the source of stretch that contributes to the recoil proportion of push off. Of course muscle activity plays a role in the entire process, because it is the contraction of the muscles during this process that loads strain onto the elastic component of the muscle. A slack muscle would not return any energy put into it. During this second half of the stance phase, when most of the loading of the calf muscles is occurring, I think the center of mass is moving upward due to knee and hip extensor action, which again suggests that it is not gravity doing this work.

I could go back and pull out a few articles on the kinematics of the gait cycle to make sure I have all this right, but I'm pretty sure that's what is going on.

terryh-

this could be the magness article you mentioned in an earlier post?

http://magstraining.tripod.com/The_Other_Stuff.html#Running_Form

not sure if it's the same one or not, but it's pretty good for a general overview of running mechanics without getting too technical.

I believe he mentioned on one of those old posetech message boards that he has studied under sprint guru Tom Tellez. So I imagine that's where most of his info comes from.

Hi Jim thanks for jumping in on this.

you asked:

\"Does Pose claim that a person can run across level ground without pushing off (i.e., applying no horizontal force component), instead relying on gravity to move foward (i.e., letting \"gravity do the work\")?\"

Your question allowed for ambiguity in a single yes or no answer because gravity is an integral component of the motion described in your second clause.

So I think your conclusion is incorrect. I would answer as follows. The pose article says there is pushoff. The answer to the first clause is yes. The qualified answer to the second clause is; pose says that at some point you have to let gravity do the work to get your foot back to the ground.

You are touching on the points that I made in the outset of my posts. There have been misinterpretations and incorrect inferences related to Dr. Romanov\'s concepts as described on his website. His running style does not contradict the laws of physics. I think the mistake began when people misinterpreted his \"new paradigm\" to be a law of physic when it was a paradigm about the interaction of gravity in running motion.

Jim

As a side thought.

I don't think the influence of gravity is a new paradigm. I was taught by an exercise physiologist to let my foot fall in running 25 years ago. The studies on the interactions of the forces involved in running motion are older then that.

If Romanov wants to say anything is a new paradigm it might be his precise running style. But, again even that is old news.

Then allow me to clarify. Gravity may be an integral component of running (on that we can all agree), but what I want to know is if Pose is saying that all forward motion comes from the release of stored energy in the muscles/tendons. Further, if the answer to the prior question is "yes", then does Pose state that this stored energy is coming from gravity, due to the landing (or some other mechanism)? Now, if you want to ignore the second part, that is, where the energy came from, that's fine. I think one can answer the first part with a simple yes/no. It's not a "Do you still beat your wife" sort of question.

Your answers seem to be "no" to the first, and therefore, "no" to the second. That is, that a runner does indeed push off, and therefore we need not concern ourselves with the source of said energy, although you offer further that the runner will let gravity bring the foot back to the ground. In sum, gravity is used, but not used to supply forward motion.

I'm not trying to be a prick, I'm just trying to distill the essence of what Pose is claiming, in as concise a manner as possible, with no ambiguity. There is no point in arguing about something if all parties haven't defined what it is that they are discussing.

Asterix:

"True, but is completely irrelevant to anyone who is not trying to conduct the most precise of experiments. As far as everyday activities are concerned, you're pretty much good with the 10m/s/s approximation."

Thanks for repeating me, I said it wasn't important to the discussion.

Actually at the poles it is rounded off to 9.86 and at the equator 9.79. 9.8 is commonly used because it is a better fit for most of the world. If you use 10 then you have a 4 percent error. That is a very significant error even in running! The reason you may have seen it used that way in your high school physics class was to make it easier to teach the formulas without having to resort to using a calculator.

As a side note, why do you assume Asterix only has a high school physics background? He has never said anything about his credentials on this thread (at least not that I've noticed).