5 sets a day seems a bit excessive in a warmup. If you have the machine on the right setting that would be very taxing to do before getting into heavy lifting. For guys who can handle that load and volume, we move the GHR into the workout and then either add weight (med ball, plate on chest–>behind head–>some hold overhead), or alter the difficulty by progressively elevating the back of the machine. That being said, you could maybe do a few sets of single leg GHR as a W/U and see how that goes, obviously the volume would be lower, but you would still be gaining strength.
