Worksite back and core exercise in firefighters: Effect on development of lumbar multifidus muscle size.

BACKGROUND Firefighting is a dangerous occupation with a high incidence of low back pain and injury. Abnormal back muscle function and morphology has been linked to low back pain and poor physical performance. The effect of exercise training on back muscle size and symmetry has not been investigated in firefighters. OBJECTIVE The purpose of this study was to assess the effect of worksite exercise training for eliciting lumbar multifidus muscle hypertrophy in firefighters. METHODS A cluster randomized controlled trial was conducted with healthy, career firefighters (n=64) from a medium-sized fire department. Participants were randomized by fire station to exercise training (n=36) (supervised back and core exercise performed on duty, 2X/week, 24 weeks) or control (n=28). The cross-sectional area (CSA) of the L4 and L5 lumbar multifidus muscle was assessed with ultrasonography at baseline and following the intervention. RESULTS At 24 weeks, no significant differences were noted between the groups in the adjusted (by baseline scores and body mass) L4 and L5 lumbar multifidus muscle CSA and asymmetry values. CONCLUSIONS A worksite exercise training program targeting the back and core is not effective for eliciting hypertrophy of the lumbar multifidus muscle in healthy firefighters.