Objectives Spondylolysis is a common source of low back pain (LBP) among adolescent athletes. We aimed to investigate the occurrence of LBP and spondylolysis, and the potential associations of weekly training and match exposure, and maturity status with spondylolysis among male youth football players. Methods Male players (n=98) from six teams were followed over three consecutive seasons (U15-U17). Training and match exposure (min), and pain/injuries were self-reported weekly. Clinical examinations were conducted if a player reported LBP and abstained from football training/matches for 1 week or reported LBP for 4 consecutive weeks despite participating. MRI was used to determine if the LBP was due to spondylolysis. The maturity level was estimated biannually by X-ray of the left hand, along with body height and weight. Risk factor analyses estimated the association between an increase in total weekly training and match exposure and the risk of spondylolysis, and between maturity factors and the risk of spondylolysis. Results Of 98 players, 46 reported back pain at least once, 18 fulfilled the criteria for a clinical examination and 13 underwent an MRI scan, identifying 12 cases of spondylolysis. Risk factor analyses showed a significant association between increased total weekly training and match exposure and the risk of spondylolysis. No association was shown between any maturity measure and the occurrence of spondylolysis. Conclusion Increased training and match exposure in the weeks before injury was significantly related to a diagnosis of spondylolysis. Maturity measures were not related to increased risk.
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