The association between size and symmetry of the lumbar multifidus muscle, and injuries in adolescent rugby union players.

Objectives: This study aimed to investigate the association between size and symmetry of the lumbar multifidus muscle, and season injuries in adolescent rugby union players.

Design: Prospective longitudinal cohort study.

Setting: Pre-season assessment of the size (cross-sectional area) of the lumbar multifidus (L2-5) muscles using ultrasound imaging.