They learn how to concentrate. They get praise for almost every step along the way. They learn how the body can move, what it can do, and experience the joy of running and jumping. They can cartwheel down a hill. They can roll out of a fall.
Children are unfit.
Take a look at a schoolyard full of kids and tell me it isn't true. Even Arnold Schwarzenegger and his Presidential Fitness campaign can't stop this trend. So more parents are turning to club sports to get their kids to move. Tennis, gymnastics, swimming-all teach more than just skills specific to the sport. The learning process in any sport teaches kids that they are capable and strong.