http://www.medicalnewstoday.com/releases/262025.php
"The most prevalent reasons for arm pain and tiredness can be boiled down to five major issues," Guettler adds. "The following behaviors can lead to arm pain and tiredness which can then lead to the most significant shoulder and elbow injuries."
- Pitching for more than one team during the same season
- Pitching more than one game during the same day
- Pitching on back-to-back days
- Pitching in a league without pitch counts or playing year-round
- Throwing curve balls before high school