الفهرس 
Functional anatomy of the lumbar spineOnly 14 pages are availabe for public view
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Abstract
Lifting an object with incorrect load knowledge may lead to low back pain and
injuries. The purpose of this study was to examine the effects of different locations of
load’s COM and load knowledge on the erector spinae EMG and trunk kinematics during
squat and stoop lifting tasks. Lumbar erector spinae EMG and trunk kinematics (ROM and
velocity) were collected from 30 subjects (mean age 19.4 years ± (1.3), mean height 175.8
cm ± (5.1), and mean weight 72.4 kg ± (10)). Trunk ROM and velocity were recorded
through 3D Motion Analysis System, while myoelectric activity from the right and left
erector spinae muscles were picked up by using surface electrode at L3 level. Each
participant lifted a 6.5 kg box plus a 4 kg weight randomly placed in one of its selected
five compartments (center, Rt-ant, Lt-ant, Rt-post, and Lt-ant). Four lifting series (5 lifts
per series) were completed, two series of squat lifting with and without knowledge of the
load’s COM location and the other two series of stoop lifting also with and without
knowledge of the load’s COM location. The dependant variables were compared among
five tested load locations using MANOVA with LSD test, while effect of the load
knowledge were tested by using paired t test to compare between known and unknown
conditions. Finding revealed significant differences in the tested dependant variables due
to changes in COM location, with most potent effect when the COM located at left anterior
location. However, considering load knowledge effect, there were non significant
differences for most of the tested conditions except for trunk flexion velocity during stoop
and squat lifting and erector spinae dominant side EMG during stoop lifting. Therefore, it
can be concluded that lifting an object with unknown COM location put a high injury risk
on the lower back especially if it is located toward non-dominant side anteriorly. In
addition injury risk can be minimized if the load’s COM location is located posteriorly
toward dominant side either in stoop or squat lifting.
Keywords: Squat and stoop lifting, Load knowledge, COM location, Erector spinae EMG,
Trunk kinematics