Here is something someone recently said on a forum I visit:
The picture below is showing an athlete leaving the blocks with nice arms and leg drive, what could be possible wrong with this start?
Well, look at the back leg, complete extension is no longer advisible for teaching the drive from the blocks, scientists from Russia has decleared that an incomplete extension will advance the sprinters quicker and more powerfully down the track.
While full extension will result in more force application, speed of movement will suffer because of more down time. This also is the same for the entire race, muscles and joints must be used at an optimum point to ensure the best performances.
Full extensions just waste more time and not added advantage in distances are recorded. The results of the study shows clearly that after the initial push athletes that used incomplete extensions cover more grounds, recover legs faster and utilizes less energy.
Well, i would tend to agree. Certainly in the drive phase (10m-max V) and from max V to the finish incomplete extension seems to be the way to go. I know it has been debated before but i am yet to see a pic of Asafa Powell at full ext. (Asafa being the clearest case) nor any other athlete for that matter - very close, but bot full extension.
I think it comes down to optimization. I suspect there is a point in the stride where it becomes more efficient (faster) to recover the leg and start another stride than to “persist” with force application. More time on the ground does equal greater (net) force but the way i look at it is for an athlete of given mass they need to apply a certain amount of total force to run a set time and the force needs to be applied in the most economical way. The evidence seems to suggest that the force is better applied over a higher frequency of strides, rather than greater (ROM) strides.
I would like to see force plate data for sprint strides if anyone has it because i suspect that the force diminishes later on in the support phase, and would continue to diminish. The greatest force must occur at peak elastic reaction and then drop?? Would this mean, as i am saying, that getting to the next stride “early” would be more economical because more of the total time (total of all strides) would be in the higher force region?
That’s my take on it anyway.
Whether this is the same at the start where there is less reaction and more pure drive i couldn’t say. It probably has more to do with setting up a rhythm for the rest of the race.
Interesting. I am also starting to think that too much arm drive at the start is what is making me over stride at the start. Getting my arm all the way up and out I think is causing me to have too much swing time which is causing too much ground contact time. I may post some old video later since I have nothing recent.
Teaching an incomplete extension would be detrimental. You don’t tell an athlete to lean back when jumping… you tell them to keep upright, they lean back naturally.
If you place emphasis on extension the athlete won’t fully extend, but will extend more powerfully. The body knows that if it extends to far the leg won’t bounce up quich enough.
just watch some young skinny punks running away from the cops, there stides are chopping all over the place, no drive, no knee lift, super high turn over, no speed.
guys if you think that X athlete does not achieve full extension then sloe them down and you will see it.in real mode it appears that extension is not there but when you see slow- mo then you’ll see
Please can someone show a frame with an athlete at full extension cos i just can’t see it, and i’ve just been looking through my extensive library of track videos.
Right now I’m defining complete extension as “full extension of the knee joint” with “full” meaning to the extent of its range of motion. Agreed?
In this post i am gonna stick with my assumptions that full extension does not occur and say that it would be detrimental due to the following reason: There appears to be a point in the stride where continued extension could only occur with a subsequent drop in hip height.
From ground contact to BDC can we agree that the support knee is flexed slightly so that a line from hip-to-knee when extended will approximately intersect the ground at the point of contact (the fore foot of the athlete)? Then the question would be how much does the knee extend from this point onwards.
Clearly as the foot goes past BDC the effective lever length must increase to maintain hip height. Ankle extension takes care of most of this.
In the late period of the support phase the foot is behind BDC and as the athlete is covering the ground at such a rate any further extension would only act to make up the difference in lever length required to maintain hip height.
What happens and what you are concentrating on are two different issues. When you have great power, full extension happens BUT it happens even though you concentrate on quick action. The extension is completed AFTER you have ‘moved on’ mentally to the relaxation portion of the cycle before power is applied again.
Quick says too much arm drive is an issue for him- but that likely is because he’s thinking drive, or being powerful, rather than a quick movement. It’s the same principle with the arms as the legs.
Sprinting is the opposite of sex- Quick, not hard!
I have watched it now at least 10 times (in fact I force people to watch it with me when they come over). It is awesome! I learn something new ever time (which does mean I am a bit slow…but I blame that on my genetics).
Thank you all for the rich discussion, I am learning alot here. I am going to ask the person if they could give me an article or report of the russian study (if he has one) so that I can post it here.
To TC0701, here is basically the same video that ACOOPER posted, without the banner:
This seems more simple than I thought. It’s the difference between bounding and sprinting, you get full strength and extension in a bound but the drive leg doesn’t pull through quickly. In sprinting the stride strength and length but more cadence… part of the power in the extension is used to fire the leg back through, in a bound all the power can go in to the drive of the extension.
