1. Skiing: After seven years of dealing with an injured and worn-down knee, I had it replaced at age 63. Went skiing in the alps 4 months later and had total control. Skied like in my twenties.
2. Tae Kwon Do: 20 years experience at age 63. Back to practice after six weeks - felt like a beginner. Another three weeks or so: back to normal. No more kicking trees, but heavy bags without problem.
No signs of damage 11 years later.