Originally Posted by
Jeff Illingworth
See how your elbows start "up" and then "drop" and then go back "up"? That is usually an indication that you aren't holding the bar correctly and your your upper back is rounding a bit. It's hard to tell what's going on as the bar on your back and your hands are hidden due to the angle of this video.
Also, watch your knees, especially as the set progresses. See how they shoot forward more and more? You're getting soft in the hole and loosing your hamstring tension. Don't let your knees pop forward like that.