Listen, Barry has a piece of the puzzle. Why is that under fire?
All else stated below applies.
Undestandable…
I created 3 pics, showing what the f*** is happening with forces and C.M. here is the first picture showing that during acc phase you need horizontal force to accelerate you, but while on ice you cant get it, thus GRF pass behind C.M. and rotates you to fall on your face…
With spring model, during Vmax (or speed that is maintaned), there is only vertical comp, and this component passes direclty trough C.M. (on track), and becasuse of this, you can maintain your speed on ice without falling (as showed in first video). This is completely in agreement with spring model (be this force passive or active, GRF is only vertical…)
But…
… this vector cannot be all the freakin’ time under C.M.? Right?
So what if proulsive theory is in right (once again)?
ON TRACK:
During Vmax, your GRF not allways pass thru C.M. thus it creates all-body torque during push-off (that tends to raotate you or your nose), but this torque is zeroed with contralateral leg touch down! ??
ICE:
Ok there is no horizontal force during Vmax, but this force is not all the time under C.M., thus creates torque around C.M. during push off, but as soon contrlateral leg hits the ground it is zeroed! This implys tha body swings back and forth during running…
Again this implyes that something else is throwing you on the nose during acc and not GRF dont passing thru C.M. This also implyes that during Vmax, GRF is not all the time under C.M.
Ok! Am I bulls***ing here or I got some point? BTW did you involwe “blind study”? (the subject does not know that he will run on the ice after a acc)?
1)The air resistance is acting to slow you down.
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If you are not slowing down, there must be a force that is being applied.
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The only place you can put that force is against the ground.
Wannagetfast seems to be saying the sprinter is not exerting horizontal forces. Either he is or he is violating the laws of physics. Which is it? He seems to say that the sprinter isn’t, which is of course absurd.
The video is junk science, to be flattering. If wannagetfast will flatly state whether there are horizontal forces on the ground during a sprinters top speed phase, then I can be done with this.
With a breaking phase (ground acts with a backward directed force on body) and a propulsive phase (ground acts with a forward directed force on body), the vector indeed can act through the body’s center of mass all the time. Of course, in reality there may be some rotation. The athlete rocking forward and backward is an indication of this.
Good point. If there is NO horizontal force during max speed, the vertical force should create (wasted) rotational forces on the body as, during ground contact phase, the foot will change in position relative to the body’s center of mass. Unlike a pogo stick, for example.
Like I mentioned before, the minimal forces exerted horizontally are canceled out by the braking forces. It’s a wash. Vertical forces dominate. Of course there are some minimal horizontal forces. Are you really saying this is what predominates? You can say what you want, but when you can take what the research says and apply it to practical applications that we can see, why do you call it junk science? I think it’s kind of neat that we can show that if horizontal forces were as big in max.velocity sprinting as some say there is, then I would be slipping like the acceleration video in part two. There just not there!!!
Why is that bad?
For Vmax to have only a vertical comp wouldn’t touch down have to be exactly under the COM? That is not the case in sprinting.
I was under the belief that all these great studies showed that the net horizontal forces at vmax was zero, not that there was none.(- horizontal forces subtract + horizontal forces).
Also, how is it that sprinters go foward and not only up at vmax, if the forces are only vertical and they are not running in a vacum?
At absolute top speed, acceleration becomes zero, but is it more than one step when you factor in wind resistance (not a factor on a treadmill where the athlete is stationary), and other factors?
First you say it’s a wash.
If it is a wash, as in no net force on the ground, then the sprinter will slow down due to air resistance. Quickly. He could not sustain max speed for 10 meters.
Then you say “of course there are some minimal horizontal forces”. Then it’s not a wash, is it? If you acknowledge there are horizontal forces, then what is the point of trying to prove there aren’t?
The video is junk science because:
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It does not show a real top speed phase, it shows two steps.
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There is no speed measurement to show that the runner is in fact sustaining speed.
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Ice is not completely frictionless. There can still be horizontal forces without foot slippage.
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You can’t see whether some foot slippage is occurring.
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It would be easy to have not put a second mat down and see what happens if you continue to run. Your having a two step experiment makes me wonder if you’re trying to rig the experiment.
I am still confused as to who is arguing what. Its known that there are horizontal forces acting on the organism, both braking and accelerating.
It is known that the vertical forces greatly exceed horizontal forces at all times during a race. Would you all agree that acceleration is due to greater horizontal forces with a net positive? Would you also agree that the net positive horizontal force is inversely related to velocity of COG?
Lets not forget that although foot contact happens slightly in front of the COG, this act is merely priming the soon after stretch reflex. The various forces surrounding each foot contact need not to be discussed in detail.
The sum of all forces dictates the outcome of the event. A high net velocity is not due to a high net horizontal force, but the ability to control and translate ALL forces to equal a high positive horizontal net velocity.
Since in the anatomically correct position, the fibers of the muscles used most are situated vertical, it makes sense that the vertical forces should be the highest. This may be an odd concept to most, but the situation of the skeletal and muscular system prepare for high vertical forces, and not high horizontal forces.
I agree with a lot of what you’re saying, but assuming he isn’t an elite athlete, I doubt he is going to be holding max velocity for long (it’s been stated that one step may possibly be the limit). Without a second mat, we would see deceleration and of course, a nice spill and probably and injury.
I agree. I am not elite. But I am not slow either. Back when I played (a few years ago) I was fast! Now, why does it have to be more than three steps or two steps? Do your theories not match before then or only after this many steps?
Ok I give…
Peak verticals generally exceed peak horizontals by about a factor of 6 at top speed - it can vary a little person to person. Is that what you wanted to hear? I am thanking my lucky stars that what you are explaining is wrong. If you were right you would have seen an injury! Don’t tell me the Ice isn’t slippery or I didn’t run fast enough, or long enough, or I rigged it. Why so many excuses? Where is your proof? At least I am trying to make the point a visual for all to see. I have had private emails say to me…… “Not sure why that happened on the ice, but listen to my other theories”??
Come on guys?
Juggler and VeloceGatto have a point…
Wannagetfast, what are you really want to say? Over what we are arguing here? Please re-read velocegatto last post…
We need to get one thing straignt concerning horizontal forces. The studies tha Weyand refer to use relatively slow running speed. The most common is Munro, (GRF in running: a re-examintation, J Biomech, 20: 147-55, 1987). Running speeds in that study were 2.5-5.5 m/s, a fast jog or run.
Several other studies (read on) demonstrate much more significant GRFs in the horizontal plane when speeds are increased to sprinting, ie., more thant 8 m/s.
Payne (Ergonomics, 11(2), 123-434, 1968) demonstrates peak vertical (V) forces at 600N and peak H forces at 200N at speeds @ 8 m/s. A 1/3rd ratio, which is much more significant than the 1/10th difference for slow runs.
Fukunaga ((Ergonomics, 24(10): 765-772, 1981) demonstrates max H propulsive force of 200-300N at max speeds 6-8 m/s. Max V forces are 600-900N. Again a 1/3 ratio.
Tsujino (Kobe J Med Sci, 12:1-26, Jan, 1966) demonstrates that max H propulsive force is 36% that of max V force (pretty much the same 1/3rd ratio as the above studies) at speeds of 9.5 m/s (ie., 10.5 sec for 100m).
Further analysis of Tsujino’s data demonstrates that the rate of development of force is greater for H component than for the V component. Rate of development of force is power, thus horizontal power is greater than V power at max sprinting speeds.
Fukunaga also shows that acceleration for each swing leg is 4 m/ss at peak velocity. Thus, with constant running velocity there is still the need for acceleration (or propulsion) of the leg to go forward. This is corroborated by EMG studies that demonstrate large hip flexor muscle activity in early to mid swing phase.
Kyrolainen (Med Sci Sports Exerc, 33(8): 1330-1337, 2001) demonstrates peak V forces at 2134N and peak H forces at 675N at a velocity of 6.5 m/s. This 1/3rd ratio is consistent with the above studies.
Kyrolainen, in addition, demonstrates that when speed is increased from 3 to 6.5 m/s the H forces increases 187%, whereas the V forces increase by only 28%. If you extrapolate this to 9.5 m/s then it shows the ever increasing H forces with increasing running speed.
Conclusion:
- Horizontal forces are significant at peak velocity, thus cannot be ignored in training.
- Horizontal muscle power is greater at peak velocity than vertical muscle power.
- You CANNOT QUOTE studies using slow running speeds to come up with the conclusion that Horizontal GRFs are not significant during peak velocity of a sprint.
How come Asafa managed to stay near his top speed for 50m with minimal horizontal force being applied to the ground?
I have a feeling, that when a sprinter reaches absolute max. velocity, there’s no turning back; deceleration will take over and the horizontal forces are bust since he’s already “over the edge”. But if the same athlete manages to keep it close to max. velocity – without going “over the edge (like 99,xx%), he MIGHT be able to keep the horizontal forces alive for a much longer period of time – keeping a sensation of ease and forward drive.
Somehow, it looks like sprinters manage to keep their technique in control as long as they are in a horizontal drive phase. This sensation could perhaps be mimicked if there’s a confidence of not going all the way to 100% velocity?
This is certainly John Smith’s strategy for racing/coaching the 100m. And it may have been deduced from analysis of FloJo’s 100m performances in Seoul (conclusion by Frank Dick was that Florence never reached peak velocity in her Olympic 100m races)
In a review of Dr. Nicholas Romanov’s insights on gravity and its effects on running mechanics, Chris Drozd of SportFit noted the following:
Without going too far into force vectors we accept that to run forward the amount of the anterior component (braking force) must be less than the posterior component (intuitively, the propulsive aspect). But, the vertical component predominates, giving back several times bodyweight at foot plant, where the posterior force gives back only 10 to 20 percent. For a 70kg runner (700 newton’s, “n”), that’s about 2100 n to 200 n to 400 n vertical versus posterior components, respectively. Based on Newton’s Second Law: F=ma (force equals mass times acceleration), the posterior component’s 10 to 20 percent impetus is not sufficient to acuate forward motion, as minimum force needed to move the 70kg runner is more than 700 n. Romanov also covered minimum leg angles, trajectory and vertical oscillation. Despite the vertical component being the main effect of GRF, and the minimal leg angle being about 67 degrees from the horizontal, suggesting kanagaroo-like movement vertical oscillation is only 2 to 3 degrees, or 4 to 6 cm at the GCM for the best runners. Romanov asserts this to mean that the GRF provides support rather that propulsion. So, on ice where push off and traction fail, gravity (acceleration) and vertical ground reaction (support) succeed. It works the same on dry land. Maybe the common description / prescription of running stride needs to be revisited. Muscle Elasticity Again, more free motion. Muscle elasticity costs you very little metabolically because you exert no effort to use it.
But substract from this 2100N a bodyweight of 709,81 or about 700N, and you get 1400N of force that “drives you up” - (when you stand V GRF is massgravity, and for 70kg guy it is 700N), and now V/H relation is 28% (400/1400), and it is becoming important…
Yes, but in vertical direction and that is why I substracted 700N from V GRF… but this statement is only valid when some force is in oposiotion to graviti (up direction), but when force is applied perpendicular to gravity, then 0,0005N can cause acceleration to 70kg guy (really small but it is acceleration). What you said right now is like stating that air resistance should exceed 700N to start stoping the athlete, so basically your speed would not be deteoriated until you rund in the face of typhon, cyclom of 100m/s…??? I think that Newton is rotating in his grave, because his equation is used so simplistically by people who dont have BASIC knowldge of Newtonina mechanics…
I don’t know about any studies, but I would not be surprised if <9.8s sprinters, besides applying greater force toward the ground, also show a narrower gap between vertical and horizontal forces than sprinters at >10s. I base my guess entirely on “feel”; that besides having slightly better maximum velocity, they also stay within, individually defined, manageable velocities, thus keeping the “momentum” much longer – destroying the field after 50m.
The maintenance of ”horizontal momentum” is critical in jumping events. Usually, if a jumper reaches maximum velocity 4-7m before the take-off board, the jump usually sucks: Form and technique is compromised when vertical forces “take over”; momentum is lost and the take-off lacks natural lift. However, if the jumper reaches 95-97% velocity 4-7m before the board, and maintains that with ease, he usually don’t destroy his jump as much as if he went over the edge (100%) – keeping technique and form in control at a slightly lesser percentage will be much better (but not optimal) than running faster but being succumbed to overdrive. The best sensation comes from when the jumper keeps his acceleration to the board with ease (keeping it slightly under 100% and keeping horizontal drive the whole way through).
Have you ever noticed how sprinting stays natural (‘thoughtless’ or ‘hind brain’ if you like) as long as you accelerate, and conversely; how numerous thoughts invade your head when deceleration takes over?