Full Extension of rear leg

[weegiecoach]

I was at a coaching conferance last week and comment was made that you do not need full extension of the rear leg. A video clip of Powell was shown with the angle of the back of the knee only at 142 degrees. This was to assit in bring the rear leg through quicker. This was about 50m into the race

I was under the impression that you required full extension

Any comments ?

[pierrejean]

I would turn your question this way : Will elasticity properties of musles-tendons of the legs assist in bring the rear leg through quicker, hence the need the stretch it with a full extension?

[duxx]

@weegiecoach

I was at a coaching conferance last week and comment was made that you do not need full extension of the rear leg. A video clip of Powell was shown with the angle of the back of the knee only at 142 degrees. This was to assit in bring the rear leg through quicker. This was about 50m into the race

I was under the impression that you required full extension

Any comments ?

The similar comment was given by Bosch&Klomp in their book (Running - Biomechanics…). If I remember correctly they stated that during the Vmax the rear leg if fully extended AFTER it leaves the ground and EMG activity is almost none during this priod. Trying to push far back with foot can yield ‘long axis rotation’ which demand further correction in next stride (neutralizing twist momentum of the body) which demands overstriding, thus longer ground contact and greater deceleration forces and thus lower maximal speed. This apply for vmax phase not to acceleration phase. For further detail I would suggest taking a look at this book. Great biomechanical analysis, but poor strength training exercise choices IMO.

[Charlie_Francis]

@duxx

The similar comment was given by Bosch&Klomp in their book (Running - Biomechanics…). If I remember correctly they stated that during the Vmax the rear leg if fully extended AFTER it leaves the ground and EMG activity is almost none during this priod. Trying to push far back with foot can yield ‘long axis rotation’ which demand further correction in next stride (neutralizing twist momentum of the body) which demands overstriding, thus longer ground contact and greater deceleration forces and thus lower maximal speed. This apply for vmax phase not to acceleration phase. For further detail I would suggest taking a look at this book. Great biomechanical analysis, but poor strength training exercise choices IMO.

the action is down and not back. once in contact with the ground, the response is automatic- thus the appropriate extension will occur without thought and any attempt to influence it by pushing will result in a slowing effect. The faster you are, the closer to BDC that degree of extension will occur. We’ve covered his numerous times before.
Extension can be individual, with differences noted between Asafa and Usain.

[TopCat]

For those who don’t know Asafa can’t actually fully straighten his leg even passively. I’ve been there while he is being worked on and he cannot straighten it. In normal life I would consider this a disability. Maybe some people think it is an advantage but it certainly isn’t coached or deliberately worked on.

[maris]

@TopCat

For those who don’t know Asafa can’t actually fully straighten his leg even passively. I’ve been there while he is being worked on and he cannot straighten it. In normal life I would consider this a disability. Maybe some people think it is an advantage but it certainly isn’t coached or deliberately worked on.

That’s very interesting and I didn’t know that!

[weegiecoach]

@pierrejean

I would turn your question this way : Will elasticity properties of musles-tendons of the legs assist in bring the rear leg through quicker, hence the need the stretch it with a full extension?

PJ

Could you expand on this ?

Thanks

[izzle1989]

@Charlie_Francis

the action is down and not back. once in contact with the ground, the response is automatic- thus the appropriate extension will occur without thought and any attempt to influence it by pushing will result in a slowing effect. The faster you are, the closer to BDC that degree of extension will occur. We’ve covered his numerous times before.
Extension can be individual, with differences noted between Asafa and Usain.

so sprinters should only focus on stepping down not back