If you look at normal athletes vs. elites I think you will find a big difference between stride frequencies. Yes GCT can be viewed as an artifact of speed, but the ability of an athlete to handle that artifact and/or move beyond it is dependent on speed of vertical force production.
I don’t really see that it is dependent on vertical or horizontal by your statement. Shorter GCTs simply require the sprinter to be capable of producing more force in a shorter amount of time due to the shrinking GCT…but that does not spell vertical forces in and of itself. It also points out that artificailly reducing GCT actually makes it more difficult to produce force, by the same logic. I think the answer is force production, so I don’t want to shorten GCT any more than will naturally result from the increased speed, because short GCT equals more difficult time producing the necessary force.
Also, Weyand and Mann have said more or less the same thing. Speed is limited by vertical force production.
Its my understanding Weyand has backed off of this assumption, and recognizes the important of the horizontal component. Don’t quote me on that, but some of his work does suggest that.
Finally, I would just like to add a few things that might clarify the way I view what happens. An athlete I coached last last year ran 11.1X in the 100m. His strides averaged .23 seconds and he took roughly 49 in the 100m. If you extrapolate that out to 43 strides, his time becomes 9.89. So yes, improvement is most likely to come from stride length improvements. I do think if he ever made it to that level some increase in stride frequency would have occurred as well. It would be harder to measure, but I don’t think it makes it any less important. My post was mostly written to clarify how vertical force can influence stride frequency while flight time is the same. I think it is also important to note that top speed does not peak in a race when stride length is longest, it peaks when stride frequency is greatest.
Do you have data showing that frequency is greatest at Max V, but horizontal displacement is not? I’m only intersted in the Max V phase, not the earlier drive phases because these are different animals. I’m not doubting you, I just haven’t seen that. And its always been my interpretation of the convential wisdom that increasing frequency via training is extremely difficult, as opposed to increasing stride length, which can be improved.
I also view vertical force production as a function of body angles rather than relative to the ground. So an athlete coming out of the blocks is pushing ‘vertically’ because the force is vertical relative to the body. This is a definition of convenience, admittedly, but I use it because I think it makes the implications for sprint technique more obvious. It means that both horizontal and vertical force are the same, only depending on the amount of time the athlete has accelerated. And thus both stride length and stride frequency are dependent on ‘vertical’ force.
Many people may assume vertical forces are not actually perpindicular to the surface, but the motion is horizontal and dictates the horizontal plane, and vertical is 90 degrees from this and is parallel to the force of gravit. In reality the force a sprinter produces is always at some angle between horizontal and vertical. We break it down into vertical and horizontal to understand the physics, but there is more or less one propulsive force at some angle.