[quote="SpugFab"]I'm not sure about the back flexibility theory. The reason backs don't bend when deadlifting isn't because you are on the limits of your flexibility. Not being flexible enough at the hips/hamstrings is more likely and admittedly this might tend to go with a more flexible back, we have to do things like put socks on somehow after all.
Just for the record, my hamstrings are super flexible. I've done a forward bend almost every day for the last 10 years or so. I can pretty much touch my palms to the floor without bending my legs.
[quote="SpugFab"]It looks to me like the position you are trying to take during your setup is weak for you, for whatever reason. The first thing your body needs to do when you start to pull is move into a position that lets it move the weight. This involves rounding the back a bit.
Because this move from arched back to rounded back is involuntary, maybe you have less control over it? This could mean the back rounds more than it needs to.
You could try accepting that deadlifting with the arched back isn't viable and take a setup which involves a slightly bowed back. Get tons of air in, brace hard and see it you can maintain that position through the start of the pull.
I mention the breathing because it doesn't look very pronounced to me in the video and it's a crucial part of deadlifting. I want to see some breathing in the next video, something akin to JP's "dying goldfish" impression
Great point. I really can't hold the arched back and all it does is make my back go soff once I initiate the pull. I'll try to start with a slightly rounded back that actually has some tension on it. My breathing was also lousy in that video. Add to that, I didn't have my belt and used one at the gym that could be worn with slacks.