I was looking at the site everybodies posts that shows how to do exercises. And they have SLDL and another type where you do the same thing but keep your back straight and don't let it round on your way down. This is how I do them. They both stated they worked the same thing and targeted only hams. But the first was listed as a compound exercise and when you kept your back straight it was classified as a isolation exercise. What's the difference? How does keeping your back straight instead of rounding it change the exercise?