The onset of deep abdominal muscles activity during tasks with different trunk rotational torques in subjects with non-specific chronic low back pain

BackgroundAlthough delayed onset of the deep abdominal muscles activity in subjects with non-specific chronic low back pain (CLBP) has been suggested to be related to trunk rotational torque, no study has examined the onsets associated with non-specific CLBP during a variety of tasks with different trunk rotational torque. The aim of this study is to compare the onsets of deep abdominal muscles activity among tasks with different trunk rotational torques in subjects with and without non-specific CLBP.MethodsTwelve subjects with non-specific CLBP and 13 control subjects were included. They performed 8 types of upper limb movements. The onsets of muscular activity of bilateral internal oblique-transversus abdominis (IO-TrA) and trunk rotational torque due to the upper limb movements were measured using a surface electromyography and a three-dimensional motion analysis system.ResultsIn non-specific CLBP group, right IO-TrA activities were significantly delayed during tasks with left trunk rotational torque compared with the control (P < 0.05), while onsets of the left IO-TrA activities were significantly later than those of the control during tasks with right rotational torque of the trunk (P < 0.05). There were no significant differences in onsets of both sides IO-TrA during tasks without trunk rotational torque between non-specific CLBP and control groups (P > 0.05).ConclusionsThe onsets of IO-TrA activities in subjects with non-specific CLBP were delayed during tasks with rotational torque of the trunk in the opposite direction, suggesting a possibility that delayed onset of the deep abdominal muscles during rotational torque of the trunk might be etiology of chronic low back pain.