Rodríguez-Soto AE, Jaworski R, Jensen A, Niederberger B, Hargens AR, Frank LR, Kelly KR, Ward SR.
Feasibility study on the acquisition of lumbar spine kinematic data
from upright magnetic resonance images obtained under heavy load carrying
To characterize the effect of the load on spinal kinematics of active
Marines under typical load carrying conditions from a macroscopic and
lumbar-level approach in active-duty US Marines.
SUMMARY OF BACKGROUND DATA:
Military personnel carry heavy loads of up to 68 kg
depending on duty position and nature of the mission or training; these loads are
in excess of the recommended assault loads. Performance and injury associated
with load carriage have been studied; however, knowledge of lumbar spine
kinematic changes is still not incorporated into training. These data would
provide guidance for setting load and duration limits and a tool to investigate
the potential contribution of heavy load carrying on lumbar spine pathologies.
Sagittal T2 magnetic resonance images of the lumbar spine were acquired
on a 0.6-T upright magnetic resonance imaging scanner for 10 active-duty Marines.
Each Marine was scanned without load (UN1), immediately after donning load (LO2),
after 45 minutes of standing (LO3) and walking (LO4) with load, and after 45
minutes of side-lying recovery (UN5). Custom-made software was used to measure
whole spine angles, intervertebral angles, and regional disc heights (L1-S1).
Repeated measurements analysis of variance and post hoc Sidak tests were used to
identify significant differences between tasks (α = 0.05).
The position of the spine was significantly (P < 0.0001) more horizontal
relative to the external reference frame and lordosis was reduced during all
tasks with load. Superior levels became more lordotic, whereas inferior levels
became more kyphotic. Heavy load induced lumbar spine flexion and only anterior
disc and posterior intervertebral disc height changes were observed. All
kinematic variables returned to baseline levels after 45 minutes of side-lying
Superior and inferior lumbar levels showed different kinematic
behaviors under heavy load carrying conditions. These findings suggest a
postural, lumbar flexion strategy aimed at centralizing a heavy posterior load
over the base of support.
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