When it comes to sumo deadlift and difficulty locking at the top this is usually not a strength issue more so than a technical issue.
If you struggle with your lockout on Sumo deadlift here are 3 tips that can help you.
1. Keep Pulling & Be Patient Off The Floor
One of the hardest things about Sumo deadlifts is getting it moving. You can’t lock it if it doesn’t leave the floor. Too many sumo deadlifts were left on the floor before the bar started to move. Be patient on Sumo deadlifts and keep pulling.
2. Get The Bar Moving Fast
The faster you can get the bar moving off the floor the better. In training try to have the bar moving as fast as possible. Treat your warm ups like they are heavy, get tight and get fast. The faster the bar moves off the floor the better chance you have of locking it out.
3. Lock The Knees Fast
As soon as the bar comes in contact with the area of your knees lock your knees as fast as you can. If the bar is above your knees and the knees aren’t locked you are making the lift much harder than it has to be. Learn to “Snap” the knees and lock them as fast as you can. Squeeze and flex your quads and lock your knees.
Give these tips a try with your lockout and let me know if they help you.