the presentation focus on the fact that how different forces act on the lumbar spine and with changing the posture or while walking and sitting how much the lumbar spine is able to bear load with in safe limit.

1. ANALYSIS OF FORCES ON
LUMBOPELVIC COMPLEX DURING
ACTIVITIES
Presented by;
SANA MASROOR

2. LOADS ON LOW BACK DURING
FORWARD BENDING

3. FUNCTIONAL CONSIDERATION FOR THE
INTERSPINOUS AND SUPRASPINOUS LIGAMENT
Heylings, D. J. "Supraspinous and interspinous ligaments of the human lumbar spine." Journal of
anatomy 125.Pt 1 (1978): 127.
Interspinous ligament are
not parallel to the
compressive axis ,
supraspinatus ligament are
parallel to the compressive
axis.

4. LOAD ON LOW BACK DURING FORWARD
BENDING WITH FLEXED LUMBAR SPINE
• Lumbar spine subjected to large compression
and shear
• Compressive loading is larger than shear
• 10kN compression can be tolerated but 1000N
shear force cause injury with cyclical loading
• In forward bending when lumbar spine is also
flexing cause the posterior ligament to strain
• If a subject hold a load with spine fully flexed,
myoelectric silence achieve by extensors
muscles
• Anterior shear force increases so that shear
force exceed 1000N,224lb (102kg)
• This example demonstrate spine is at greater
risk of sustaining shear injury (>1000N or
102kg) than compressive injury (3000N or
304kg)

6. ESTIMATING THE MAGNITUDE OF FORCE IMPOSED ON
THE LOW BACK DURING LIFTING

8. Lifting guidelines
• National institute of
occupational safety and health
(NIOSH) has set guidelines to
protect workers from excessive
loads on lumbar spine.
• It has recommended an upper
safe limit of 3400 N (346.5kg)of
compression force on the L5-S1
junction.
• The maximal load-carrying
capacity of lumbar spine is
estimated to be 6400N (653kg),
twice the max. safe force
recommended by NIOSH.

9. 2D ANALYSIS ANALYSIS OF FORCE ON THE PELVIS

11. A. The external moment (MEXT) on the
lumbosacral junction is the sum of the
moments due to the weight of the
head, arms, and trunk (W) and the
moment due to the load being lifted
(F). An increase in the magnitude of
either W or F increases the external
moment on the lumbosacral junction.
B. An increase in the moment arm of the
head, arms, and trunk weight (d1) or
the moment arm of the load (d2) also
increases the external moment
(MEXT) on the lumbosacral junction.

12. Ways to reduce the force demands on the
back muscles during lifting
• Reduce the speed of lifting
• Reduce the magnitude of the external load
• Reduce the length of external moment arm
• Increase the length of internal moment arm

13. Role of increase intra-abdominal pressure
during lifting
• Bartelink first introduced the notion that the valsalva maneuver, typically
used while large loads are lifted, may help unload and thereby protect the
lumbar spine.
• Vigorous contraction of abdominals Muscles → creates rigid column of
high pressure within abdomen that pushes upward against diaphragm,
anteriorly against deep abdominal Muscles (T.A,I.O), downward against
pelvic floor muscles → intra-abdominal balloon → would create an
extension torque on lumbar spine → thereby reducing demands on
lumbar extensor muscles → decrease muscular based compressive forces
on lumbar spine.

14. Additional sources of extension torque used for
lifting
• Passive tension generation from stretching the posterior
ligamentous system
• Muscular generated tension transferred through the
thoracolumbar fascia

17. Loads in the lumbosacral region during bending
and lifting
• Peak joint moment between 200 & 250 Nm are reported at the
lumbosacral joint while lifting or lowering 10 to 15 kg load.
• Estimate compressive loads on the disc range from 1200 N (122kg)to more
than 5500N (560kg).
• Reported peak anterior shear forces range from approximately 400 to
1200N (40 to 122 kg)
• Peak compression loads on the lumbar spine reported 7000N (713kg)
when lifting 27kg of weight. In lumbar spine lifting with flexed lumbar
spine greatly increase anterior shear force by inhibiting the contraction of
the extensor muscles.
• That is why spondylolisthesis is common at L5-S1 junction.

18. Loads on the lumbosacral joint during walking
• Average peak compression force
at LS joint range from 1.7 to 2.52
times of body weight and anterior
shear range from 0.22 to 0.33
times of body weight during speed
walking.
• The resultant force on LS facet
smaller than the load on disc (1.5
times of body weight).
• Reaction force on both peak
during double limb support
phases of gait when pelvis id lifted
anteriorly.

19. Load on lumbosacral joint in sitting
• Slouched sitting posture appear to increase the anterior shear forces on the
lumbosacral junction when the backrest pushes HAT weight anteriorly as the
sacrum rotates posteriorly.

20. SPINE STABILITY

21. Two contrasting lifting techniques: the stoop v/s
the squat lift
STOOP LIFT
• Performed primarily by
extending the hips and lumbar
region while knees remain
slightly flexed.
• requires greater extension
forces from low back and
extensor muscles. this create
large compression and shear
forces.
• 23-34% more metabolically
efficient than squat lift in
terms of work performed per
level of oxygen.
SQUAT LIFT
• Begins with near maximally
flexed knees.
• Reduce demands on low back
tissues
Creates greater demands on
knees. impose large pressures
across the tibiofemoral and
patellofemoral joints.
• Squat lift requires greater
work because a greater
proportion of the total body
mass must be moved through
space.

23. Factors that contribute to safe lift
• Lift with the lumbar spine as close as possible to its neutral (lordotic)
position.
• A lifted load should be light and held close to a body.
• Load is lifted from between the knees.
• Avoid twisting while lifting.
• Lift as slowly and smoothly as conditions allow.
• Lift with a moderately wide BOS.
• Minimize the vertical and horizontal distance that a load must be lifted.
• When lifting, fully use the hip and knee muscles to minimize force
demands on the low back muscles.