Elitetrack: Sport Training & Conditioning

If we apply maximun force to propell from block,the ground contact time is more.but in the articles,athlets has to reduce the ground contact time while sprinting.which one is the main thing?force or ground contact time?:splat:

Originally posted by kkkumar666
which one is the main thing?force or ground contact time?:splat:

The answer isn't as simple as one or the other because it depends on which part of the race you're speaking of.

The reason ground contact times need to be great in the beginning of a race or jump's approach (during acceleration) is to maximize the impulse-momentum relationship. To build momentum one must create a high impulse. Impulse is the product of force and time. To increase impulse, you can either increase force, time, or both. Thus, in the beginning of a race when an athlete is attempting to develop momentum, it is important to apply as much force as possible over as long a time period as possible (while of course using correct acceleration mechanics). Once at top speed however, momentum has already been developed so the impulse-momentum relationship becomes less important. Also, as a result of a runners increased momentum, their ground contact times will be shorter and they will now be constrained by how much time they have to put force into the ground. Obviously they still want to put as much force into the ground as possible, but now they have a limited time to do it. As a result, at higher speeds, rate of force development (or the ability to generate high forces in short periods of time) becomes more important than simply high impulses or high forces.

thanx mike.i'm running 30mts well but i lose my lead after 30-50.while i'm using more power in 30-40,the others r easily running with relaxed style.i've a question,is it correct to apply the same technique(0-30mts) to the remaining part of the race.my feeling is putting more power to the ground and spend too much time in ground contact.i've read an article of flexible and power athletes.and one thing i'm an flat footed.and i raise my body within first 2 steps.and if i tend to lean, my legs spread widely to get the balance and the race is like zig zag but it clocks best.i applied it y'day.is it correct.i'm an engineering graduate and i'm interested to know biomechanics parameters.which links r best?

Originally posted by kkkumar666
thanx mike.i'm running 30mts well but i lose my lead after 30-50.while i'm using more power in 30-40,the others r easily running with relaxed style.i've a question,is it correct to apply the same technique(0-30mts) to the remaining part of the race.my feeling is putting more power to the ground and spend too much time in ground contact.i've read an article of flexible and power athletes.and one thing i'm an flat footed.and i raise my body within first 2 steps.and if i tend to lean, my legs spread widely to get the balance and the race is like zig zag but it clocks best.i applied it y'day.is it correct.i'm an engineering graduate and i'm interested to know biomechanics parameters.which links r best?

Research has indicated that there are at least two distinct techniques of running during a short sprint (0-20m & 20m and beyond; these numbers will obviously vary but you get the idea). As such you shouldn't try to do the same thing because the goals are not the same. In the early acceleration you should be trying to develop momentum as I mentioned in my previous post. Raising your body up after the first two steps is a definite problem because it moves your ground contact closer to being under your center of mass which is a poor position for acceleration. After completing acceleration, the objective should be to maintain the horizontal velocity developed as efficiently as possible and minimize braking forces.

Originally posted by kkkumar666
thanx mike.i'm running 30mts well but i lose my lead after 30-50.while i'm using more power in 30-40,the others r easily running with relaxed style.i've a question,is it correct to apply the same technique(0-30mts) to the remaining part of the race.my feeling is putting more power to the ground and spend too much time in ground contact.i've read an article of flexible and power athletes.and one thing i'm an flat footed.and i raise my body within first 2 steps.and if i tend to lean, my legs spread widely to get the balance and the race is like zig zag but it clocks best.

you may want to look at your spacing (hands) if you're going zig-zag… they may be too far apart. Also you may be pushing too low..

but as far as the problems after 30m you should examine what;s going on inthe 1st 30m. Areas you may wish to examine:

1) rate and height of heel recovery in the first several steps

2) rate of *total body angle* change

3) range of motion (upper and lowre body in the first portion of the race)

4) a feeling of smoothness

hope this helps.

Kebba

I've applied body leaning in the starting.i feel better.The space between the hands and first leg was 34cms.but now i changed it to 50cms.naturally it doesn't allow me to rise the body in the first few steps.is it ok?does block spacing play important role?

block spacing can play a huge role..  to far aprt can mean there's not enough pressure (in relation to the strength of the athlete) and to close (which many athletes do imho) means that impulse is low *and* that you're setting of a bad chain of events—namely short, constricted movements—when you want the exact oppositve.