A better way to state it is to say you should learn how to brace properly with your abdominals when lifting heavy. As for the muscles involved, a deadlift isn’

A better way to state it is to say you should learn how to brace properly with your abdominals when lifting heavy. As for the muscles involved, a deadlift isn’t just back or legs or core, it’s all of those. Your Glutes and hamstrings are the “prime movers” that perform the actual movement, while you back and “core” musculature are bracing and stabilizing, allowing the movement to be translated into Bar movement.