Back Injury - Deadlifts & Landmine 180s (video Included)

Hi, I'm fairly New to weightlifting and have been have some success improving my lifts and having changed my diet have lost 30lb in 5 months. I started to squat and deadlift a few months in and my deadlift weight really began to shoot up at the higher end of my deadlifts i would do 5x90kg 3x95kg 2x100kg, i started to notice that i was having pain in my my lower back and pelvis that would last a day or two after deadlifting, it didn't feel muscular more like a bone pain and seemed to improve with rest so i ignored it as i only did these exercises once a week.
I also did 2 days of circuits and one of the exercises was the barbell landmine 180 basically a twisting abdominal exercise, these felt fine but the day after i would have a very tight middle back that felt like it was going into spasm.
Anyway after a heavy deadlift day i injured my middle back to the point that i cant bend over and if i take a deep breath i feel suddenly winded, it feels very tight but i have found that a massage seems to easy the tightness as does a hot bath.
Right now i cant do any exercise except a flat bench press with my feet up on the bench, even seated dumbell curls cause the pain to come back again, so i have decided to toataly rest untill i feel recovered.
Here is a video of me deadlifting, i would really appreaciate if anybody could critisise my technique and offer any advice on what im doing wrong or what might have caused the injury (although this isnt the lift where i felt the pain in my middle back this was taken a week or so earlier)

Thank you

[youtube]qCY2dNQjNqU[/youtube]

You're hyperextending your spine by leaning back so far at the top of a rep. Stop doing that; there's no need to exaggerate the lockout.

what will said. though your injury shouldnt have been from that

I would say your lower back pain is coming from overexaggerating the lockout. The middle back pain, if it was from a deadlift, im gonna say is because you didnt tighten up your shoulders enough and allowed them to sag.

Thank you for the input guys I wont be deadlifting for a while but will try not to "Hyperextend" at the top when i get back into it looking at the video i can now see what im doing wrong.

As for the middle back pain im having is it possible that the landmine 180s could have caused it and the deadlift made the problem worse, my back always feel a bit stiff the day after these and maybe i should have rested it instead of going onto a deadlift day the following day when my back didn't feel 100%

Thanks

[QUOTE=Clarky121;1215064141]
As for the middle back pain im having is it possible that the landmine 180s could have caused it and the deadlift made the problem worse, my back always feel a bit stiff the day after these and maybe i should have rested it instead of going onto a deadlift day the following day when my back didn't feel 100%[/QUOTE]

It's generally considered that the lower back is the slowest-recovering of body parts, so it's a good idea to either do your Deads and landmine work on the same day, or put a couple of non-lower-back-involved days in between them.