Re: Sprint Theory

[Guest guest]

****In the ANALYSIS OF SPRINT MODELS article by Michalow, a

lot was mentioned of the necessity to have strong hip flexors and

extensors. What about the abdominals? The hips rotate, so why not

train the hip and spinal rotators to produce and handle a great

amount of torque.

You may have the most powerful hip flexors and extensors, but if the

spine cannot handle the force generated by the thighs, how can you

successfully increase stride frequency (or decrease swing time). A

useful analogy would be a 1000hp racing car. If the flywheel can only

handle 800hp, it would be wise to focus on strengthening the flywheel

to handle the engine's maximum capabilities.

Michalow wrote:

<The hip flexors act to thrust the thigh forward in the middle part

of swing phase, during contra-lateral stance phase. But in order for

the hip flexors to be able to thrust the thigh forward requires that

a counter-force be generated in opposition to the hip flexor thrust.

This counter-force is generated by the contralateral hip extensors

and calf muscle during stance phase........

Thus, the hip flexors act to improve SL by increasing forward thrust

of the thigh, but they do not directly propel the body forward. The

action of the stance-phase hip extensors, in conjunction with the

calf 'spring,' acts to propel the body forward>

****One might also conclude that the hip extensors and the calves

provide the power needed to propel the body forward and the

abdominals transfer some of that energy to the hip flexors where the

cycle continues.

I would tend to believe that the rotation of the hips acts to improve

SL by thrusting the thigh forward. IMO, this could be one of the

reasons why some of the fastest sprinters maintain a near

vertical " upright torso " during the race so the transfer of energy

between the left and right leg is more efficient than otherwise.

Chelos Sydney Australia

[Guest guest]

<< The fact that you do not have to be

in contact with the ground to generate reaction forces has been well

substantiated in the biomechanics literature. >>

Huh? Here's a question from the terminally puzzled; how do the biomechanists

generate reaction forces without an outside body for contact? I didn't see

that one in Newton's " Principia " !

<<The simple fact that sprinters cover more distance in one stride

proves that the legs must be moving faster in order to cover greater

distance.>>

Referring to the underlined section; doesn't this just mean they have a

greater stride length? Why do the legs have to be moving faster? Is this

comparison for identical instantaneous velocity of the runner's center of

mass?? That velocity (V) being found from the product of frequency and stride

length, then a greater stride length would require a lower frequency (reduced

turnover rate). Or.........am I hopelessly misinterpreting?

By " legs must be moving faster " are you referring to the absolute velocity of

the limb and

not the turnover rate? Obviously, for any given V, the distance covered by

one stride is determined by the " hang time " over that 4cm vertical

displacement the elite sprinter enjoys. The greater the V, then the greater

the distance covered during the " hang time " of a single stride -- So it would

seem that the quicker the sprinter can achieve their highest velocity then

the sooner they can enjoy their greater stride length at any given frequency

(turnover rate). Acceleration is critical to achieving top velocity

quickly and acceleration is dependent on net (reaction) force generated;

the argument comes full circle again and points to ground contact RFD as the

ultimate determining factor. Consciously training for frequency improvement

in sprinting performance is become as supercilious as training to " activate

the TVA " prior to a lifting performance.

Am I way off base here? Please note that I am only asking questions not

attacking suppositions and will gladly admit to no special expertise in track

and field training.

Boardman

Chicago