Re: Pain in aikido?
just my humble opinion.The stretches are good for uke's health, so at least the final pin should always be applied somewhere between "just not comfortable" and "not real pain", i.e. far away from injury. There are exceptions with elderly or injured uke, but only doing soft comfortable locks might not be enough in general.
For the middle part you can do the stretching, too. But I guess, we should always try to find the best point to change the technique and go forward.. So when uke is down (nikyo) or on his toes (sankyo), we do not need to make uke feel the pain that he might get, when he is resistant.
And it is not only true for co-operative uke - in this case one should agree upon a little resistance then and now to ensure the technique is applied well. But a perceptive uke would try to avoid or escape that painful position and thus is unbalanced for a split of a second. If you are perceptive enough to recognise this moment even before it happens, you can do the following part without uke even recognising what has happened and particularly not feeling any pain. I have felt this only occasionally - not to say accidentally - but when classes really focus on this, it might happen more often. I am sure, some shihan can do it whenever they choose, but did not take me as uke for this demonstration.
One good exercise to get there, is to do just a simple shomenuchi ikkyo, only using your two pointer fingers. Unfortunately I am still far away from doing this without the risk of breaking my own fingers. But I try and I try.