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Neal Winkler
10-19-2009, 07:45 PM
How come running and jumping by exerting force through the forefoot recruits the posterior chain, but pushing though the heels while squating/DL/lunging does the same and pushing off the balls of the feet inhibits recruitment of the posterior chain?

Steven Low
10-20-2009, 04:29 AM
Running, jumping, the hip is extending violently = glutes/hammies

Squatting and DLing you can emphasize posterior chain through pushing heels because it focuses on pulling your hips forward (hip extension) rather than knee extension (which is quads).

Shifting weight onto the forefoot focuses more on the knee extension.. which is more quads. In running and jumping, the knee is only slightly bent at impact into the triple extension phase which means that quads are nominally recruited.

Donald Lee
10-20-2009, 11:55 AM
Running, jumping, the hip is extending violently = glutes/hammies

Squatting and DLing you can emphasize posterior chain through pushing heels because it focuses on pulling your hips forward (hip extension) rather than knee extension (which is quads).

Shifting weight onto the forefoot focuses more on the knee extension.. which is more quads. In running and jumping, the knee is only slightly bent at impact into the triple extension phase which means that quads are nominally recruited.

Steven,

I disagree. It seems like you've gotten caught up in the posterior chain craze. The quads are very important for sprinting and jumping. In fact, in vertical jumping, the quads are more involved than the posterior chain.

Neal Winkler
10-20-2009, 12:11 PM
Steven,

I disagree. It seems like you've gotten caught up in the posterior chain craze. The quads are very important for sprinting and jumping. In fact, in vertical jumping, the quads are more involved than the posterior chain.

Donald, that still doesn't answer the question. Could you elaborate more?

Donald Lee
10-20-2009, 01:13 PM
Donald, that still doesn't answer the question. Could you elaborate more?

Well, running is to some extent a horizontal movement. I think the quads play a bigger role in the vertical component of running, while the posterior chain plays a bigger role in the horizontal component. Try pulling your leg back horizontally while landing on your heels. You can't until you roll over onto the ball of your foot. Your gastrocnemius muscle is also one of the muscles that flex your knee, so by landing on your heel, you're inhibiting knee flexion until you roll over onto the ball of your foot. But, theoretically you can still have the exact same running technique post-landing on the heel as with landing on the ball of your foot, which will mean similar recruitment of the quads/posterior chain. However, that doesn't tend to happen often.

With squatting/DLing, you lose stability if you go onto the balls of your feet. Your knees will also tend to come forward, which increases the lever arm from your knees, which increases the recruitment of your quads. You will also be passively contracting your hamstrings, which will lessen hamstring recruitment. With squatting, this is more of a problem with PL-style squatting.

I can't really say much more, because I haven't read too much into biomechanics yet.

Steven Low
10-20-2009, 01:35 PM
Steven,

I disagree. It seems like you've gotten caught up in the posterior chain craze. The quads are very important for sprinting and jumping. In fact, in vertical jumping, the quads are more involved than the posterior chain.
I don't disagree with anything you stated (biomechanically), but the relative contributions of the posterior chain are more important than the quads obviously.

Running is more posterior chain because of the contacting pull off the ground to the propelling forward is more hip extension.

Jumping has a relatively large quad SSC, and accelerational from the the SSC. The hams, especially, aren't recruited as much because there is less of a change in total hip angle and acceleration.

Garrett Smith
10-20-2009, 02:38 PM
Might it simply be where the center of gravity of the body is in relationship to the base of support? That might seem to account for a major portion of the difference.

Steven Low
10-20-2009, 04:55 PM
Might it simply be where the center of gravity of the body is in relationship to the base of support? That might seem to account for a major portion of the difference.
Nah, center of mass is pretty much centered over the mid/forefoot in both sprinting and vertical when the triple extension occurs in both.

Of course, in sprinting your body is slightly leaned forwards, but it shouldn't make a significant contribution.

Scott Kustes
10-23-2009, 09:23 AM
There is little, if any, horizontal component once you are out of acceleration. Once the body hits the max velocity phase (i.e., upright running), the ground force component in sprinting is vertical. Quad recruitment is minor at this point.

Donald Lee
10-23-2009, 11:59 AM
There is little, if any, horizontal component once you are out of acceleration. Once the body hits the max velocity phase (i.e., upright running), the ground force component in sprinting is vertical. Quad recruitment is minor at this point.

I guess. That's the whole spring mass model. I think it's accepted by most coaches nowadays, but I know Dr. Yessis seems to be against it or at least its application. I have been meaning to look more into sprinting, but I haven't gotten the chance yet.