Newton’s 1st and 3rd Law and the Power Position

Kolecki Frame By Frame

I got to explain something very simple to the group at Crossfit Unbroken today for the Outlaw Camp.  They all wanted to know what I thought about bar/body contact and how much or how little the bar interacts with the hips in the power position.

I refereed to Newton’s Laws and some basic biomechanics.

Newton’s First Law States: “An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.”

Newton’s Third Law States: “For every action, there is an equal and opposite reaction.”

That applies to the contact at the hips very simply in that how the bar and hips meet determines the actions that follow.  If my hips are moving horizontally toward a bar moving vertically then the horizontal impact of the bar on the vertically moving bar HAS to move the bar horizontally in some fashion.  Newton’s first and third laws demands this.  Furthermore, the power applied by the hips to the bar is reciprocated by bar speed.  This is determined by Newton’s Third Law and in combination with Newton’s First Law, any horizontal force applied to a bar by the hips will cause the bar to move horizontally with reciprocal speed based on the amount of force applied to the bar.

THEREFORE there IS NEVER any reason for the bar to make contact at the hips in such a way that the hips send the bar horizontally at all.  Regardless of what you think about bar/body contact, physics demands that the hips move vertically.  Likely, your body’s segment lengths will determine how violent that contact is at the hips.  However, regardless of segment lengths, the hips MUST be moving vertically or the bar will always track poorly from the power position.

You simply can’t beat physics.



9 responses to “Newton’s 1st and 3rd Law and the Power Position

  1. Spencer, love the post! I have an entirely off-topic question: Sean and I (attended your Medford Outlaw Barbell Camp) have met a guy who has unusually small hands and can’t hold a hook grip. Have you ever encountered this before? Thoughts? Advice?

  2. I agree with you that the hips should move vertically. However, in looking at the bar paths of top olympic lifters, I’d say close to 90% of the bars come out from the body a little bit at that point. I always like to think about it like there are two force vectors: a big one from the hips that points up but slight away from the body and a smaller one from that arms where the lats are pulling the bar back toward the body. The resultant force vector is the “straight up” arrow we are looking for. I’ve never really written this thought down before, just mostly envisioned it in my mind. Is that at all accurate?

    • I was sort of envisioning the same thing while reading this. Speaking strictly from a physics perspective, you’re generating a vertical force vector, Y, and potentially adding a horizontal force vector, X, with the hip bump, which results in some vector, V, that is greater than Y but applied in a slightly outward direction. If we can then treat the arms like a pendulum from a physics perspective, we can translate this greater vector V into the vertical direction by keeping the arms locked, it seems like we could generate slightly higher bar speed than we would be able to in by applying a strictly vertical force. I’m guessing this is exactly what elite lifters are doing.

  3. Pingback: The Weekend Post - 5 Ways Breathing Affects Sport Performance·

  4. Pingback: Practical View of Bar Movement At The Hips | Glory·

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s