I agree with abhjeet, because prepare by, reviwer, approver must be aware with the SOP content only after the can complete their job. Also the change in sop is proceed through change contol procedure where we take the review comment and signature of relavent individuals, mostly reviewer and approvers are covered in change control. Hence while he aaproved the change , he is well aware with revised content.
Training is required to aware the people for changes or updation in the SOP or document. This procedure alredy completed for prepared by, reviwer & approver during change procedure. So training not required for this people on implimetation of SOP or document.