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Lumbar spine passive stiffness can be predicted using trunk moment of inertia
Joshua S M Lowery1, Kayla M Fewster2
1School of Kinesiology, The University of British Columbia, 6108 Thunderbird Blvd, Vancouver, BC V6T 1Z3, Canada.
Background:
Many factors have been observed to change lumbar spine passive stiffness. However, it remains unknown if an ideal level of passive stiffness exists. The trunk's moment of inertia is a determining factor to lumbar spine flexion and extension moments that are produced across one's range of motion. Therefore, this investigation aimed to determine if a relationship exists between lumbar spine passive stiffness and the trunk's moment of inertia in healthy young individuals.
Methods:
The passive stiffness of the lumbar spine was quantified in twenty-eight participants using a passive jig. The trunk's moment of inertia was calculated according to anthropometric measures.
Findings:
A significant relationship was observed between participants' trunk moment of inertia and the stiffness within the transition and high stiffness zones in flexion, with individuals with a higher trunk moment of inertia being observed to have a higher lumbar spine passive stiffness.
Interpretation:
These findings suggest that one's trunk moment of inertia may be related to the passive stiffness of their lumbar spine and that one's lumbar spine passive stiffness may be naturally occurring and be proportional to the counter-moments that are required to stabilize the trunk. Furthermore, it presents a novel avenue to be investigated as a possible predictor of one's risk of low back pain and/or injury if discrepancies between moment of inertia and passive stiffness exist.
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