A couple of words from my personal experience. When I was attending high school and college in Russia I used to do track and field. My results were pretty good for a non-professional college level:  100 meter sprint – 11.5 seconds, the long jump – 7.1 meters.  I trained four times a week for two hours, for a total of 8 hours a week. I need to add that during most weekends, I was playing soccer in the summer and skiing in the winter. So I trained for about 12 hours a week.  I have never had injures and I am very thankful for all my track and field coaches.

Most Russian Sports scientists recommend that junior sportsmen train for no more than 15 hours a week until 16 years old.  My son, between the ages of 8 and 12, played tennis for no more than 6-8 hours a week plus 2 hours of special fitness training. He was a top 10 player in Belarus. click here for complete story