Reliability and Precision of Sonography of the Lumbar Multifidus and Transversus Abdominis During Dynamic Activities

Objective: To determine the intra-rater reliability and precision of measurement of lumbar multifidus (LM) and transversus abdominis (TrA) thickness using freehand ultrasound imaging (USI) in a range of static and dynamic conditions. Methods: Fifteen asymptomatic participants performed a range of exercises whilst USI was used to measure absolute muscle thickness and change in muscle thickness from rest. Exercise conditions included the abdominal drawing in manoeuvre (ADIM), active straight leg raise (ASLR), contralateral arm lift, both unloaded (CAL) and loaded (LCAL), treadmill walking (WALK) and using the Functional Re-adaptive Exercise Device (FRED). Intra- and inter-day reliability was assessed using intraclass correlation coefficients (ICC), and standard error of measurement was used to assess measurement precision. Results: Good to excellent reliability was achieved for TrA and LM absolute thickness in all conditions. Measurement precision for absolute LM thickness was ≤2.8mm for CAL, ≤1.8mm for LCAL, ≤3.1mm for WALK and ≤3.8mm for FRED, and for absolute TrA thickness was ≤0.6mm for ADIM, ≤0.5mm for ASLR, ≤0.7mm for WALK and ≤0.5mm for FRED. Good to excellent reliability was achieved for TrA and LM relative muscle thickness in all conditions. Measurement precision for relative LM thickness was ≤3.7% for CAL, ≤3.8% for LCAL, ≤6.3% for WALK and ≤7.6% for FRED, and for relative TrA thickness was ≤13.6% for ADIM, ≤6.9% for ASLR, ≤11.1% for WALK and ≤7.2% for FRED. Conclusions: Acceptable reliability and precision of measurement is achieved for absolute and relative measures of deep spinal muscle thickness using freehand USI in relatively static and dynamic exercises.