Looks to me like you are not setting your back and bracing before each pull, and you're looking straight instead of keeping a neutral spine by looking roughly 45deg downwards.
34M, 6'5", 220lbs, SSLP since late Oct 2019
Last session: failure on the floor of rep 4 @ 405. Made 425x5 on 1/19. Strained spinal erector in warmups on 1/21. Dl has been all over the place since; a big fucking mess & quite frustrating.
405 failure
Today: 405x2 failure on the floor of rep 3. Came back later and did 390x5.
390x5
Thanks for your time and advice,
Matt
Looks to me like you are not setting your back and bracing before each pull, and you're looking straight instead of keeping a neutral spine by looking roughly 45deg downwards.
Strains happen to the best of us. You'll be fine as long as you stay out of your head.
As was said, you don't seem to be really setting your back for each rep. Loosen your belt one hole, and "squeeze" the chest up as you drop your belly to the bar, and drop your junk between your legs. Then "squeeze" the bar off of the ground rather than trying to yank it.
Widen your grip so the bar can stay on your legs and your hands aren't dragging up your body. And stop deadlifting in squishy running shoes. You just can't stay balanced on midfoot with those. Get some flats or wear your weightlifting shoes.