Relaxation during practice
My point was that until someone has practiced the various relaxation techniques mentioned, it is difficult for them to utilize them in the middle of training. Most people find it difficult enough to remember to breathe during their rolls, much less in a technique they are learning for the first time.
O'Sensei, in his doka on sword work, spoke of the need to match certain sounds to particular movements. These are fairly tradional concepts and involve exhaling while moving forward.
I all my years of training and teaching, I have never known anyone who relaxed because they were told to. This too is yet one more technique to be practiced.
Take a deep breath, exhale. Repeat as needed.