Enough hip drive in my squat ? video form check

[Mark Rippetoe]

These squats are high because of your rather pronounced knee slide. Maybe 4 inches of knee slide ruins a squat.

[Josselin]

Hello Rip,

Do you recommend to stop adding 2.5kg each time on the bar untill I fix my form ?
I tweak my back two times earlier this year on squats on my NLP (with 165kg) and I think this is because of this problem. I don't want to get re injured. This is why I'm restarting my NLP.
In your experience, how long does it take for tall guy with long femurs to stop doing this ?

Thank you.

[Mark Rippetoe]

In your experience, how long does it take for tall guy with long femurs to stop doing this ?

About 5 minutes, if I'm coaching you.

[Josselin]

Hi Rip,

I went to Brussels Barbell seminar yesterday and my squat is better now (3rd working set) :
20231021 Squat 140kg set3 BrusselsBarbell - YouTube

There still a bit of knee slide but Steve really helped me with this, I feel much more the stretch reflex in the hamstrings and adductors and the contractions in the quads.

Steve also helped me fix my upper back extension in my deadlift and I feel it much more like pushing the floor away now and I've added 15kg to my 5RM (155kg now).

I'm excited to see how the weight will come up in the next weeks on squat and deadlifts, and I hope I will catch the delay on these lifts compared to my press (I pressed 90KG for 3reps in the seminar, and than 2 sets of 5 at 85kg).

BTW Rip, we were thinking about this with Steve, do you know why the barbell feels heavier with iron plates compared to bumper plates ? Steve also figured this out...

Thank you for your help everyone and especially Steve

[Mark Rippetoe]

I have an idea. What did Steve say?

[Josselin]

I have an idea. What did Steve say?

Steve thinks it is due to the fact that the center of mass of the load on each side is closer to the lifter.

Thinking about this... It makes me think that the bending deformations of the sides of the bar are more important with bumper plates (greater moment arm of the side load against the center of mass of the system)
=> it produces greater up and down oscillations on the sides of the bar especially if the bar speed is important. (acceleration of the side loads on the bar)
=> I guess it helps you on the concentric phase if you apply concentric force at the same time the bar's oscillation is going "up" (like at the bottom of a clean or snatch for olympic lifters)

In other words you will expects the phenomenon with a bar made with a steel with a lower elastic modulus (and/or lower inertia moment)

When you think about the maths behind this, it makes even more sense:
If you want to compute the deformation equation of the Barbell, you have to double integer the moment force equation.
Absolute value of the moment force is increased by the dynamic effect of the load (oscillations).
Thus, the more oscillations, the more deformation...
The more oscillations, the more speed of the side masses on the barbell...
Considering that the acceleration is the derative of speed, the more explosive you are, the greater this phenomenon is.

[Mark Rippetoe]

Precisely correct.

[Josselin]

Today's workout, 3x5 at 142,5kg, it feels way better, what do you think Rip ?

20231023 142.5kg 3rd squat set - YouTube

[Mark Rippetoe]

Now you're lifting your chest about half way up. Stop doing that immediately.