Study design: This study analyzed relative lumbar and pelvic motion during sagittal plane trunk motion. Patterns of movement were compared during loaded trunk flexion and extension.
Objectives: The purpose of this study was to examine the dynamic relationship between the lumbar spine and pelvis during trunk motion and to determine the effect of direction of lift (up vs. down) on lumbar-pelvic rhythm.
Summary of background data: There is disagreement in the literature regarding whether rotations of the pelvis and lumbar spine occur sequentially or simultaneously during bending and lifting tasks.
Methods: Thirty healthy women, ranging in age from 19 to 35 years, participated in the study. The 3Space Tracker System, an electromagnetic tracking device, was used to monitor simultaneous lumbar and pelvic motion as subjects lifted and lowered a 9.5 kg box with knees extended.
Results: Although lumbar and pelvic motion occurred simultaneously during flexion and extension, there was greater separation of these movements during the "up lifts" than during the "down lifts."
Conclusions: Lumbar-pelvic rhythm varied depending on whether the trunk was flexing or extending. During trunk flexion (down lift) there was a greater tendency for lumbar and pelvic rotations to occur simultaneously, whereas during extension (up life) they tended to occur more sequentially.