Originally Posted by Aimee Anaya
The reason you are shooting your hips up is because your quads are not strong enough to support the load and open the knee at that angle (as a result of low-bar back squatting), so you have to refer to your posterior chain strength in order to stand up with heavy loads.
This is what happened to me due to the low bar back squat as well. I am now working front squats in instead of back squats to try and strengthen up my anterior chain. I also find that increasing hamstring flexibility helps.