Previous studies have demonstrated quadratus lumborum asymmetry in cricket fast bowlers, but there has been conflicting evidence regarding the relationship to lumbar spine injury, particularly vertebral bone stress injuries. This study investigated the relationship between quadratus lumborum asymmetry and lumbar spine injury in adolescent cricket fast bowlers.The study was a prospective cohort design.Magnetic resonance imaging of 38 adolescent cricket fast bowlers was completed prior to a cricket season, and the cross sectional area of the quadratus lumborum muscle was measured at each lumbar spinal level. The bowlers were followed through the cricket season and those that reported lumbar spine injuries were investigated and classified as either having a soft tissue injury or a bone stress injury. The pre-season cross sectional area of quadratus lumborum was associated with injury status at the conclusion of the cricket season.Twenty-one percent of the cohort developed lumbar bone stress injuries during the cricket season. There was no significant relationship between lumbar spine injury and quadratus lumborum cross sectional area.A high incidence of lumbar bone stress injuries was demonstrated in adolescent fast bowlers. Unlike previous research that demonstrated a link between lumbar spine bone stress injuries and quadratus lumborum cross-sectional area, no such relationship was found.