A very good summary of low back injuries in young athletes from physiology-pedia.com:
According to the literature low back pain occurs in 10-15% of young athletes. However studies exhibit great variability in prevalence rates, with estimates ranging from 1.1% – 66%, the variability in the studies may be due to:
• Age of the sample
• Sample size
• The authors definition of low back pain
• The low back pain recall period
• Strategy of extracting data and methodology used
The prevalence of low back pain varies between sports and, in some cases, the speciality of the position.
In young athletes the prevalence of low back pain increases with age and females are more likely to suffer from low back pain compared to males of the same age group. The literature suggests that the physical changes that occur during puberty could increase the prevalence for low back pain
Injuries encountered to the lower back in young athletes occur from either an acute traumatic event or repetitive trauma (overuse injury) and are commonly seen in individuals participating in sports such as football, rugby, gymnastics, ice skating and dancing. Evidence has shown LBP occurs is as much as 27% of college football players and between 50% and 86% of gymnasts. Overuse injury can be as a result of repeated flexion, extension and torsion which is performed frequently in gymnastics, ice skating and dancing.