Most people let their elbows drift forward during tricep extensions, which shifts the work to your shoulders. Keep your elbows pinned back toward a wall and pinch your shoulder blades together to feel the full stretch in your triceps. You'll probably need lighter weight, but the activation is worth it.
Stop doing this on your tricep extensions. It's ruining your gains. Most people let their elbows move forward when they're doing their tricep extensions, and this is wrong because this takes all the tension off of your triceps and puts it on your shoulders. So instead, I want you to think about pinching your shoulder blades together, and on the way up, think about pushing your elbows back to the wall behind you. This way, your elbows won't move forward, and you will get a full stretch on your triceps. And I'm going to warn you, this is going to make it more difficult, so you probably have to do less weight, but you'll end up feeling and working your triceps a lot more.
