The Russians studied skill development in sport more than anybody. In weightlifting one of their leading coaches, Medvedyev, had a 7-year plan to take a promising 10 or 11 year from child to international competitiveness, planned down to the day.
As the plan progressed, the percentage of work dedicated to different training demands varied. By the time a trainee has pass into the final phase (Master of Sport International Class), he would only be performing the competition lifts for about 16% or 17% of overall training volume. The rest was taken up by a very large collection of assistance exercises, rotated as necessary.
After a while, the emphasis was on getting stronger. Their pattern of movement from tens of thousands of repetitions was sufficiently fixed that all that was left was maintaining the pattern and making them stronger.
I've heard similar for other sports too... That their Judo and Wrestling training has very little competition and much more drilling and supplementary conditioning.
They had a cadre of sports scientists who worked on a range of sports and shared findings. I'm most familiar with weightlifting because that's my sport, but from one of my textbooks you can see how they applied common principles across a range of sports.
As the plan progressed, the percentage of work dedicated to different training demands varied. By the time a trainee has pass into the final phase (Master of Sport International Class), he would only be performing the competition lifts for about 16% or 17% of overall training volume. The rest was taken up by a very large collection of assistance exercises, rotated as necessary.
After a while, the emphasis was on getting stronger. Their pattern of movement from tens of thousands of repetitions was sufficiently fixed that all that was left was maintaining the pattern and making them stronger.