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Routinely regarded as 2 of the best glute/ham p-chain exercises.  I am primarily training for SL jump with sprinting as a secondary goal.  I've been doing RDL's pretty much all this time as my primary glute/ham exercise.

I am finally getting access to a GHR machine (gym just got one).  Since all the coaches speak so highly of the GHR as an essential exercise for speed seeking athletes (as well as single leg jumpers), I am very interested in adding it to my routine.   I was wondering if I can replace my RDL's with them. 

I don't want to do both because I already have too much glute/ham volume from other stuff as is already (tons of SL bounding/jumps and sprints).

I'm asking because they do different things.  RDL's are a glute + ham hip extension exercise.  PROPER GHR's are a knee flexion exercise while keeping the hips locked in neutral using low abs + glutes contracting.  Different movements but same muscles involved. 

If I were to replace RDLs with GHR's will I be losing something?

edit:

Should I even replace the RDL's?  I have no experience with GHR's so anyone with experience please shed some light on what exact training effect they have on you

you said it, they do different and complementary things. GHRs are the bossest exercise for hamstring injury prevention, fwiw.

I have no idea. In terms of specificity, yeah, the RDL does indeed seem more specific. I think the thing with the deadlifts (of any kind) is that you can do them wrong - using your back. And if you do, you'll think you're training your hamstrings, hip extension, this and that, when in reality even a slight misposition of the pelvis is significant in terms of recruitment patterns etc.

In the GHR there's less chance for that (unless your form is horrible or something).

When I used to do them, natural GHRs, I didn't had that great of a form either but it was definitely the hamstrings that were recruited, since they were the only ones who could flex the knees (with assistance from the calves).

Also, what you do with the ankles is important too. If you plantar flex your ankles that puts the calves into active insufficiency and they cannot assist the hamstrings in flexing the knee (since the calves are then being shortened both at the knee and the ankle joints) - so if you plantar flex during your GHRs you isolate the hamstrings. If you dorsiflex, you put the calves at a more advantageous position, you negate the active insufficiency, and you're assisting the hamstrings with your calves and make the movement easier.

So, plantar flex the ankles = harder, isolates the hamstrings.
Dorsiflex the ankles = easier, hamstrings are assisted by the calves.

Something to keep in mind.

A few videos of my GHRs (that's the only place where I can do them, BTW, safely):

<a href="http://www.youtube.com/watch?v=t9g5brtWUL0" target="_blank">http://www.youtube.com/watch?v=t9g5brtWUL0</a>

And one GHR with the arms overhead (extremely difficult):

<a href="http://www.youtube.com/watch?v=OHBoX8B_U8g" target="_blank">http://www.youtube.com/watch?v=OHBoX8B_U8g</a>

You can see in the videos I'm bent quite a bit at the hips. That's for two reasons:

1) I'm not strong enough so I shorten the length of my torso by bending at the hips and making the movement easier (since my head/upperbody is closer to the origin point and easier to move around);

2) It's almost impossible to keep completely straight hips since the hamstrings are biarticular and they enter active insufficiency when the hips are extended and the knees are flexed, meaning you can't have both. That's why the leg curls machine has a small bent at the middle - to flex your hips a bit to some angle (say 15-20 degrees) in order to prevent active insufficiency from occuring.

Well, I wrote about this on my website some time ago, see if this helps:

http://www.insane-athletics.com/blog/index.php/analysing-the-one-leg-jump-part-iv-the-importance-of-the-hamstrings/