I don’t know. It seems like a chicken/egg case here. Do you fun faster because you decrease GCT or does GCT decrease because you are running faster? You really need the strengh (power) capability to absorb and recoil ground reaction forces (both verical and horizontal GRFs) in order to decrease GCT, so it all boils down to strength capabilities.
The Arampatzis study was mentioned with regards to stiffness because it demonstrates to spring theory proponents that propulsive forces are needed during a maximal sprint. Spring theorists (such as Peter Weyand) state that no propulsive forces are needed once peak and/ or terminal velocity are reached in a sprint. The Arampatzis study merely demonstrates that a minimal GCT is needed for propulsion to occur.
As far as focus, a recent forum submission above this one briefly discusses as to whether the athete should place focus on the ‘step down’ or the rapid conversion of hip extension to hip flexion in early swing phase. Maybe its more appropriate to focus on one of these. I don’t have the absolute answer. I guess that one’s gotta try a few things and see what works best.
IS THERE PROPULSION AT TO SPEED? OR IS CANCELLED OUT BY THE BREAKING FORCES?
First, there two ways in which the term ‘propulsion’ is used. There is absolute and net propulsion.
Yes there is absolute propulsion that is added by the sprinter at top speed. There has to be because Net propulsion is zero. The breaking forces are cancelled out by the propulsive forces, which gives you a net of zero.
This is where spring theorists disagree. They state that there is no absolute force that is supplied by muscles during peak velocity. But the spring theory has to be incorrect on this one because such a scenario is not possible if net forces are zero.
In summary, you need propulsion at peak/terminal velocity in order to counteract the breaking forces, in order to maintain a constant average velocity where net forces are zero.
The video clips below, developed by Dan of www.wannagetfast.com, are intended to demonstrate his theory that at top speed we simply bounce vertically…not so much horizontally. If we actively pawed back like some gurus claim, would I not slip forward?
One clip here shows top speed (very little horizontal push).
The clip below shows acceleration (lots of push) this is why there is slipping.
Note: Dan. I did cut some of the video from both. I can replace both with the full footage from each.
The first video, with the athletes sprinting on the track, well they were bouncing both vertically and horizontally. It's just that the camera was moving with the athlete which gives the illusion that they are only going up and down. [They're moving forward so they have to be 'bouncing' forward.]
The other video about falling forward. Well it has to do with the concept of touchdown distance to center of gravity (TD-CG). What the falling forward means is that the TD-CG is zero, (ie., they are in the same vertical plane) or lower. For a runner to maintain stability the TD point has to always be slightly in front of the CG. When TD-CG is zero or less (meaning that TD is behind the CG) the vector forces on the torso, which are centered around the hip, will cause the torso to rotate forward in relation to the hip, which results in a rapid falling forward.
You are describing the paw back as a push. In actuality it is first a 'pull' then it is a 'push'. It is a pull from the time of toe touch to where TD and CG are in the same vertical plane (TD=CG). It is a push from TD=CG to toe-off.
What the gurus of propulsion claim is the need to pull-push, not just push.
You are describing the paw back as a push. In actuality it is first a ‘pull’ then it is a ‘push’. It is a pull from the time of toe touch to where TD and CG are in the same vertical plane (TD=CG). It is a push from TD=CG to toe-off.
What the gurus of propulsion claim is the need to pull-push, not just push.[/QUOTE]
How can I be doing anything without slipping? If I pull I slip forward…it doesn’t make sense?? That’s me by the way (don’t laugh) that would be ice, not a track. It’s kind of slippery. If I actively pulled or pushed or whatever, I would fall.
This should be done by an independant test subject because Im very sceptical, Im serious when It comes to analyzin videos and Dan in that second clib is exaggerating the second clip to prove his point. Have an independant athlete follow these instructions and you will see much different movments in that second clips.
I think you are putting the cart before the horse. The problem is not developing stiffness, but generating the power needed to get the hips high enough that would make a demand for more stiffness. If you can generate it, the stiffness will take care of its self.
Test for this:
1.jump as high as possible
2. try to land on your feet and not in a pile.
3. if your knee caps are not in your skull, you just develop the stiffness needed to handle your force output.
Come on with the independent study? I tell you what, look close; I have a helmet and elbow pads on. I wanted to make sure… in case I was wrong I wouldn’t kill my self. Who else was I going to get to test this? I know, I could get that guy from Jack Ass?
No, I really think it kind of proves the point. Instead of saying independent, or the ice wasn’t slippery, or I Tried harder in the second clip (which by the way you are right, I tried to run faster leaning forward) lets formulate some science to answer this video. I am very interested to hear these opinions.
Many people fail to grasp the spring model and its implications. This goes for both its proponents and its opponents.
For example, the spring model does not imply that the muscles do not need to be actively contracted. It is the tension (force) of the muscle that is responsible for stretching the, serially connected, elastic tendon!
R. McNeill Alexander is an authority in animal locomotion and biomechanics. He has done research specifically on the spring capacity of human legs and has written many books (which I recommend) on both animal and human locomotion. This is what he says in his book “The Human Machine”:
“The muscles do not necessarily use less metabolic energy because they do less work: they have to exert the same tension, whether the tendons stretch or not. However, the stretching of the tendons and the deformation of the arch of the foot mean that the muscles do not have to lengthen and shorten as much as they otherwise would, and do not have to shorten as fast. It may be that our muscle fascicles are shorter or slower or both, than they would have to be if we did not have springs in our legs. It must cost more metabolic energy to exert tension in a long muscle fascicle, than to exert the same tension in a short one. I explained in Chapter 4 that slow fascicles can exert tension with less cost than fast ones. The spring in our legs enable us to make do with more economical muscles than we would otherwise need.”
Now, I see the evolutionary implications - but what are the important implications regarding sprint training?
You have got to be kidding. This is so bogus I’m not sure where to start. Let’s see:
If you run up on a mat, then take two steps on ice, are you saying this is like running on ice?? You might not have backward forces applied to the ice for those two steps but let’s see you keep running full speed on the ice.
Are you saying that there is no backward force applied to the ground at top speed? You can’t be saying that, so what is the point? That it takes more force to accelerate then to maintain speed?
Please state just what you think this video establishes.
Ok, I will say it again. First off top speed is all individual. Could be four steps could be five steps. Not 30 or 40. (Not for me at least) What keeps me moving forward is the energy I created accelerating. Why is that bogus? The forces are mainly vertical in nature. You cannot refute that…and if you do please explain it. You cannot paw the ground, or pull the ground horizontally, if you do you would be slipping forward correct? Its vertical bounces!
Simple physics: The air resistance will slow you down unless you apply some force to keep moving at the same speed. The only force you have to keep from slowing down is pushing(or pulling, or whatever you want to call it) against the ground.
I must say that discussion going on is great, but unfortunally I didnt have time to read whole thread…
About that running on ice…
This assumes that when the athlete is reached some velocity, there is no breaking nor propuslive forces going on to maintain this speed? What about the wind? So, this can be viewed with the googles of sprint theory of running…
Because athlete is on ice there is no horizontal breaking forces (except air resistance), so there is no purpose of propulsive forces…
Can anyone published those great vids, put some real kinematic data like CM speed? Is there any sliding of the feet over ice during GCT?
Just thoughts…
We can agree that the ice is an almost frictionless surface. This means that the horizontal ground contact forces can only be very small.
When you try to accelerate, you lean forward - so that the body’s center of mass is forward of the ground contact area - to be able to push rather than pull.
On the track with spikes you will be able to produce horizontal and vertical forces which together constitute a diagonally upward force (force vector). Ideally this force will be directed through the body’s center of mass so that no rotation of the body is created.
However on ice no horizontal force is possible and the vertical force will alone act on the body. It will be directed vertically and behind the body’s center of mass, thus creating a forward rotation of the body.
To conclude, it is a LACK of horizontal force together with the lean of the body that will “make you slip”. It is NOT an act of pulling/pushing as there are no pulling/pushing – only the intention to pull/push.
When you are running on “top speed” there is still no horizontal forces but the upright body will allow the vertical force to act trough the body’s center of mass. No rotation is created and you will not “slip”. Thus the lack of rotation is NOT for the reason that there is no intention to push.
I guess you have me confused. Are you suggesting that if I had better balance and foot contacts during the acceleration phase of a sprint, I wouldn’t fall or slip like I did? That really doesn’t say too much does it? The second clip was shot because I knew someone would say the ice wasn’t slippery or you weren’t running hard or other types of ridiculous claims.
The bottom line is that one cannot pull the ground underneath them as they are running top speed. Now, before I get to top speed could this be happening …yes. Once I hit top speed, you are seeing for your self, you are bouncing more vertical. Again, the super ball analogy comes into play. The force imparted by the acceleration is maintained until deceleration. It was funning because as soon as I started slowing down, I started to slip. It was at that point I could control it. When I could control it, I was slipping. If the clip ran from the acceleration part, and I didn’t stop, I would continue to slip less until I was up to speed. However, that top end speed wouldn’t be as great because I didn’t accelerate as smooth and as fast as I did with the rug there. I would not be able to use that horizontal kinetic energy with each top speed contact.
The air resistance will slow you down unless you apply some force to keep moving at the same speed. The only force you have to keep from slowing down is pushing(or pulling, or whatever you want to call it) against the ground.
Again, are you saying a sprinter is not exerting backwards force against the ground during the top speed phase?
Guys, please do some research. There isnt much to debate. During acceleration, horizontal forces are greater than at top speed. We know this based on force plate studies.
We also know that the vertical forces greatly outnumber the horizontal forces, and that the ratio increases as you get closer to top speed. What is the argument about? Funny how people can come online and argue opinions to the death, but when it comes time to put knowledge to the test, we don’t show up.
This thread was started to debate Ross’ methods which still, no one has come up with anything decent enough to say is wrong. And now we are arguing about the spring mass model?
Do the homework guys…Im done posting in this thread.
