Their talents and aptitudes were developed properly over time. Super athletes did not always win their games while growing up. Age appropriate training and recovery time are necessary. A daily regimen of warm up and stretching exercises will decrease muscle tendon imbalances, increase range of motion, promote circulation and improve performance. Lifting should begin no earlier than age 8 to 10.
Training occurs in a controlled, supervised setting.
Proper form and equipment are used, i.e., perform full range of motion exercises. No maximal lifts are allowed. Proper spotters are utilized. No competition among lifters is allowed. Professional pitchers, who most likely enjoy long and successful careers, are those who did not overwork their arms while they were still maturing.