I know what the difference is, but what does the stiff legged deadlift do that the good morning doesn't? Don't they pretty much accomplish the same thing?
Yep, but because of the positioning of the bar, you're stressing the back (spinal erectors, lower back) a bit more than a stiff legged deadlift. ALSo, because you usually can't go as deep as you can on the good morning, you don't work the hamstrings as much.
SLD = more hamstring involvement
GM = more lower back involvement
I also forgot to say that because you can't lock out on the good morning like you can on the deadlift, you don't recruit your glutes as much either.
I treat good mornings as a core exercise, for abdominals, glutes, and erectors, so I used them when i need more stability in my lifts.
I use SLDLs as a strength and size exercise for when i just need stronger legs.
ie: my deadlift is stuck at 405x1. but when i slap on a belt i can do it for 5 reps easily. I need more good mornings and isometric abdominal work.
what if my deadlift is more like 405x4 raw and 405x5 belted. well then i just need to get stronger hams and glutes, SLDLs come into play. SLDLS also help with grip
usually the first example is the problem.
If you are bodybuilding i wouldn't even suggest doing GMs because the injury potential is too high, and bodybuilding is always maximum muscle stimulation and minimal risk.