And not only training on and off the ice. I believe that whole approach is not complex and skater's life and career are not planned and controlled in a fully functional way.
While physical and mental demands had grown enormously - things which should COUNTERBALANCE both physical and mental demands stagnate.
This must lead to imbalance in injury's favour.
I keep going back to Gordeeva and Grinkov. In her book "My Sergei," Katia included details of their training in the USSR, which included that her bedtime was early, but even before bedtime she was supposed to be resting ... and she complied, being an excellent student as well as skater.... still, this may be the time when Sergei was off partying with his age-mates and friends!
Another detail I recall is that they didn't ice skate during the summers. They went to sports camp, where they did other sports like swimming and I don't know what all. No skating ... but there were pix of them doing off-ice lifts. This dovetails with @sisinka's information that a complete break, for months, from the competitive sport is recommended.
It's like Jane Fonda said when people asked her why she quit doing her exercise routine every day: Rest is a principle of the human body.
thank you for this thread, @sisinka. I especially appreciate the whole post about sleep and its importance in recovery and rebuilding ... including the brain and concentration.