Electromyographic activity of selected trunk muscles during dynamic spine stabilization exercises

Objectives: To compare the electromyographic activity of the trunk flexors and extensors during 2 spine stabilization exercises and to evaluate the changes in muscle activity with increasing levels of exercise difficulty. Design: Descriptive study. Setting: Research laboratory. Participants: Twelve healthy subjects without history of lower back pain. Intervention: Subjects were instructed how to perform the Dying Bug and the Quadruped exercises. Electromyographic and motion data were recorded from each muscle group during maximum voluntary isometric contraction (MVIC). Main Outcome Measures: Surface electromyographic recordings of the erector spinae, rectus abdominus, abdominal oblique. and gluteus maximus muscles. Results: During the Dying Bug exercise, the trunk flexors (rectus abdominus, abdominal oblique) were equally active and demonstrated proportional increases in electromyographic activity with increasing level of exercise difficulty. In the Quadruped exercise, significantly greater electromyographic activity was observed in the abdominal oblique compared with the rectus abdominus: however, abdominal oblique activity did not change with increasing level of difficulty. The erector spinae and gluteus maximus demonstrated a significant level effect and were most active during elevation of the ipsilateral leg. At no point did activity of any of the muscles studied exceed 41 % of the MVIC. Conclusions: Results indicated the Dying Bug exercise predominantly recruited the abdominal musculature, while greater activity was observed in the trunk and hip extensors during the Quadruped exercise. The relatively low levels of electromyographic activity observed in both exercises suggests that the intensity of muscle recruitment is not likely sufficient to provide a strengthening effect in healthy subjects. (C) 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.