BTW: COM= center of (body) mass ??
One thing to keep in mind is the time lag between a muscle group's contraction and the resulting limb action.Â For instance, even though the glutes and hams do contribute to "pulling" the COM over the point of contact,Â most of their work is probably finished during preparation for ground contact as they generate negative foot speed.Â At contact, vastus medialis and hip flexors are already beginning their elastic contractions as "pushes" which keep the hips high enough to allow for an early toe off.Â In other words, a muslce's action is sometimes out of phase with the effect you see on the track.Â Â
This is why cueing is so important.Â Both push and pull cues can be interpreted badly and prolong contact time, since in order to actually perceive the push or pull sensation you usually have to hold toe contact slightly longer.Â A more continous cue that relates to the action as a whole I find is better, like "up and down", "step over" or whatever.
i just saw coach tellez this spring, we all know this theory. so i do believe in the push theory. after his lecture he spent a good 15-20 minutes with me so i could "feel" the push. it was excellent and probally one of the most exciting moments ive ever had as an athlete.
The ability to produce as much force against the ground in smallest possible time means it has to be a push, because a pull increases ground contact time and increased gct = slower speeds.
To be a devil's advocate this isn't necessarily true. In fact, the fastest people are the ones who have negative foot speed at ground contact (maybe indicating a pulling motion) AND the shortest ground contact times.
What mike and Flow have said is true. The sprint stride is a combination of both a push and a pull, but the whole stride itself i dominated by the actions of the biceps femoris (part of the hamstring group). This is given support by an article that mike posted here on the site, entitled "Kinematic, Kinetic & Electromyographic Characteristics of the Sprinting Stride of Top Female Sprinters." Data from this research states that, based on EMG data collected, the biceps femoris, primarily a hip extensor muscle in this case, is one of the most important muscles involved in sprinting.
At contact, vastus medialis and hip flexors are already beginning their elastic contractions as "pushes" which keep the hips high enough to allow for an early toe off.
I'm not exactly sure where you're going with this. Yes, I agree with the sentiment of the post, saying that the action of the limb is slightly out of sync with the contraction of the muscle fibers themselves, but not by very much. I guess I don't see how you think that the vasti and iliopsoas are contracting to flex the hip at contact. Flexing the hip too close to initial foot contact would yeild a "tip-toeing" type of movement, which I think we can all agree is not the best thing for fast sprint times.
Also, if I'm not mistaken, and mike, please correct me if I am, don't elastic contrations take place AFTER the muscle-tendon unit has been sufficiently stretched. That being the case, an elastic contraction of the hip flexors wouldn't take place until well after foot contact, when runner is completing toe off and the hip flexors are stretched to their fullest.
Clarify what you mean for me, because I'm not getting what you're shooting for here.
wow so the biceps femoris tends to do more hip extension work than the gluts during sprinting? i remember reading that article, but this info just occured to me now…
btw when i posted first i had a slightly different comprehension of push and pull than i assume would be right today. my thoughts havent changed, however with my new perseption of the words id like to state that in my belief the push is the overwealming part during maxV running. : P
from what i understand sprinting is a push and a pull simulaneously. the leg in contact with the ground has to apply force in two dimensions in order to sprint. first, at foot strike, the leg must stabilize and counteract gravity by pushing the ground, but at the same time the leg must pull the body over the point of contact. that is why sprinters have large hip extensors/hams and glutes and hip flexors/quads.
i think its definately a push. there is never a time in the sprints when you should feel like you are pulling. biomechanically speaking, it has a pull aspect, but i think the pushing is far more important.
I tend to agree. I think that cueing athletes to push and having them feel a push is more important than a pull. I am very much anti-grab / pull for teaching sprint mechanics but that is not to say that it doesn't happen. I think having athletes feel the vertical push helps to set up better leg stiffness at ground contact, facilitates a more efficient contact position, and activates the muscles in a more appropriate sequence.
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