Deadlift Form Check

[aWalkingShadow]

http://youtu.be/_ZDpYDT4u4Y?t=23s

I'd appreciate it if someone could critique my form.
I'm currently running Starting Strength and have been on the program for 2-3 months.
I've been increasing my deadlift by 10lb each workout, so far. My current bodyweight is 156lb, at a height of 5' 10".

In the video, I'm deadlifting 335lbx4. I was planning on getting 5 reps (as written in the program), but I failed to make the last one.
I have missed about 4 training sessions in the last 2 weeks, and due to less training, my appetite decreased and my weight gain began to stall. This may be some of the contributing factors to my failed rep.

Should I start doing 5lb jumps now? Or should I deload 10-20%?

[BareSteel]

5lb jumps are fine. Just get back into the swing of training and eating again.

I see a tendency to start your setup with an over extended spine. Get a big air and brace your abs as hard as you can before you pull.

I also can't tell: Are you doing step 3 in this progression (http://startingstrength.com/resource...8#post182468)? It looks like your shins never touch the bar at the setup.

[aWalkingShadow]

5lb jumps are fine. Just get back into the swing of training and eating again.

I see a tendency to start your setup with an over extended spine. Get a big air and brace your abs as hard as you can before you pull.

I also can't tell: Are you doing step 3 in this progression (http://startingstrength.com/resource...8#post182468)? It looks like your shins never touch the bar at the setup.

I suppose that my over-extension is a result of the "lift your chest" cue. If brace my abs harder, should my spine be more neutral as a result?
You're probably right about the shins; I forgot about that step. Does this mean that my starting hip position is too high?
Also, I notice some upper-back rounding, which gets worse as the set progresses. Is the amount of rounding I exhibit acceptable?

[BareSteel]

I think the over extension is a product of you being a flexible dude and of having a setup that needs a few tweaks. Certainly squeezing the chest will still be part of a good setup, but not to the extent that it produces an arched spine as per your last set. You'll notice that your back is quickly pulled out of over extension when the weight starts moving. A firmer clench with the abs will help. Combine all this and it may just be problem solved (we'll have to see).

Let's see you use step 3 (the shins) correctly next time out. Yes, this will lower your hips somewhat and change your back angle. It's hard, especially for novices, to separate what their upper and lower backs are doing independently of one another. I don't see a major amount of flexion, so I advise sorting out what your low back is doing first - and in the process, you'll likely find that you gain better awareness of how your body feels during a technically sound pull, negating the need to focus on the thoracic spine specifically. If not, we can address it in the future.

[aWalkingShadow]

Thanks. I'll try implementing all your suggestions when I do deadlifts again on Friday.