M-mode Ultrasound Detects Changes In Lumbopelvic-hip Muscle Activity Using Body Mass Normalization Technique

Abstract

M-mode or motion mode allows for non-invasive assessment of contractile tissue movement from echogenicity changes. This method has been used in muscles surrounding the lumbopelvic-hip complex, including the gluteals, however this measurement has not been explored to our knowledge in the rectus abdominis, external oblique, or erector spinae. A normalization technique has not been utilized for M-mode to ensure proper comparison within and between groups as normalization strategies have been applied with other musculoskeletal ultrasound techniques, such as B-mode imaging. PURPOSE: To determine activity ratio and timing of rectus abdominis (RA), external oblique (EO), erector spinae (ES), gluteus maximus (Gmax), and gluteus medius (Gmed) with a body mass normalization technique. METHODS: Ten healthy, physically active individuals with no history of low back or lower extremity injury (21.1±0.7yrs, 67.1±14.8kg, 168.1±6.9cm, 5F) participated in this study. B-mode ultrasound images were collected at rest and during contraction: supine, hook-lying for RA and EO; prone for ES; and side-lying for Gmax and Gmed. Thickness from B- and M-mode images were normalized to body mass (kg) and timing of M-mode was measured in seconds (s). Contracted muscle thickness was divided by rested muscle thickness to calculate activity ratios from B-mode images. Paired t-tests were used to compare activity ratios and contraction timing (cm-s/kg) between muscles. RESULTS: There were no significant differences (p>.05) between activity ratios, although the EO had the largest activity (1.66±0.72). The RA followed with the second highest activity ratio (1.48±0.38), then ES (1.34±0.43), Gmed (1.30±0.51), and finally Gmax (1.06±0.27). ES exhibited the greatest output from the M-mode normalization technique (0.019± 0.004cm-s/kg) and EO had the least at 0.0053±0.002cm-s/kg (p<.001). CONCLUSIONS: The anterior musculature assessed, EO and RA, generated the largest activity ratios, while ES and EO had the greatest disparity detected during motion. The balance of activity between anterior and posterior muscles of the lumbopelvic-hip complex should be noted especially with M-mode activity with this body mass normalization application as the variance in size of muscle plays a major role in how ultrasound data may be interpreted.