Muscle activity during lifting: Examining the effect of core conditioning of multifidus and transversus abdominis

BACKGROUND: It is well accepted that both multifidus and transversus abdominis muscles have a vital role in maintaining spinal stability. OBJECTIVE: To determine if multifidus and transversus abdominis could be strengthened by a six-week conditioning program and to establish if the amount of electromyographic (EMG) activity in external oblique differed in a lifting and holding task after the conditioning program. METHODS: EMG activity of external oblique during a lifting and holding task was obtained. Multifidus cross-sectional area and transversus abdominis width were measured using real time ultrasound in six males and five females, with no back pain (mean age of 26.3 (± 5.4) years). The participants then performed a six-week muscle-conditioning program for multifidus and transversus abdominis, after which the EMG activity of external oblique and dimensions of multifidus and transversus abdominis were re-measured. RESULTS: Both multifidus and transversus abdominis significantly increased in size. There was significantly less activity in external oblique during a lifting task after the conditioning program, with no change in external oblique activity during a holding task. CONCLUSIONS: this study may indicate a link between the dimensional increase of multifidus and transversus abdominis, and the decrease in EMG activity in external oblique during lifting.