Re: aikido practice
I made a comment like that ("forty-something might be too old to learn this stuff") in class once and the cute guy I was training with pointed out gently that he was sixty. I've quit saying things like that, for fear that my older classmates will take the opportunity to prove me wrong....
If you do judo and can already roll and fall, you are unlikely to get a lot of new pain from aikido, except maybe weapons training. (I train four days a week and it takes a bit of extra effort for me to cause myself pain with the open hand arts now, but an hour swinging a sword and my shoulders and back HURT!) Learning ukemi is usually the most painful part, and you should have a nice head start on that.