Firefighters have a high incidence of low back pain and injury.
To describe lumbar multifidus and abdominal muscle size characteristics in firefighters and to compare these characteristics to normative reference ranges.
In career firefighters without current low back pain (62 males, 7 females), ultrasonography was used to assess: L4 and L5 lumbar multifidus cross-sectional area (CSA), asymmetry, and thicknesses; and external oblique, internal oblique, and transverse abdominal thicknesses. Comparisons of mean values in firefighters were made to the normative 95% reference ranges for the general population and soldiers.
Mean values for lumbar multifidus and abdominal muscle size in firefighters fell within the 95% reference ranges for the general population and soldiers for all measurements, except L4 multifidus CSA in males and L5 multifidus CSA in females, which were larger in firefighters than the general population.
The majority of lumbar multifidus and abdominal muscle size measurements in firefighters are similar to the general population and soldiers. The larger lumbar multifidus CSA in firefighters compared with the general population warrants further study. These data provide a basis for future research using ultrasonography to assess muscle size in firefighters and other workers in physically-demanding occupations.