Definately recommend to everyone to read this.
as an instructor at a University I found this very important reading. I think many people who initially come to aikido come with a 'competitve' mind and try to do techniques very hard or try to resist, causing alot of injury for beginners. Also, particularly younger people, want to be very vigorous and tend to be less aware of the potenital to harm the other person.
I especially liked the quote;
"in the Sumo world, though butting practice is frequent, cerebral disorders are rare."