This is a great thread! For what it's worth I'm 47 and have been training 6-7 years and I'm still way to stiff, almost robotic. I have a tendency to hold my breath when running through kata, my instructor always used to joke that he'd worry about me performing kushanku as I'd probably pass out before I got to the end. I don't think, for me, it's any of the reasons that Nidan Melbourne gave, it's just about me "learning" to loosen up. I try and concentrate a lot on breathing now rather than the physical movements and trying to stay loose until you snap at the end of a technique, I think I'm improving but like everything in karate with me it takes a hell of a long time. I must try the tip from Th0mas. ps A warning though loosen up too much and you'll get criticised for not putting in enough effort