I was always weak at deadlift My weak point is the start of the pull. What can I do to improve this? Or what I'm doing wrong Also as much as I tried my lower back get into an arch Follow to try on my list is, although the low weight, a belt and if that wont work ill forsake the deadlift and move to sumo deadlift
First and second rep looked good, last one looked like shit. I didn't really notice a weakness at the start. Your form just broke down on the third rep. Be careful going to failure when doing reps, you open yourself up for injury
Deficit deadlifts and sumo deadlifts will help with the start of the pull.
Rack pulls, block pulls, lat, and trap work will help with the mid to top end of the deadlift. Include lots of ab work.
I don't see anything wrong with any of the lifts, to be honest. I've seen waaaaay worse form breakdown than that, especially on max attempts. There has been plenty of discussion on these boards about back arch, and plenty of people here who would argue that a flat or slightly rounded back is fine. Look up konstantin konstantinov. He has plenty of deadlift videos on youtube, pulling enormous weights with a rounded back. The video doesn't indicate to me that you need to switch to sumo style, but you can certainly play around with that to see if you like it more. I pull both ways, and my numbers are essentially the same with both styles.
It's hard to tell from the video, but do you initiate the pull with your legs? It helped me to think that quads lift the weight off the ground and everything else follows after that. This really took a lot of pressure off my lower back.
From the looks of it I pull about as much as you do, so take this for what it's worth.
Try getting really tight and pulling the slack out of the bar (without changing your start position). You look like you're already doing this to a degree, but really focusing on it has helped me with speed for heavier pulls. That and making sure your abs are strong and pushed out hard right from the start. The more stable your midsection, the faster you can pull.