3. Forces Acting On The Spine
• Forces Acting On The Spine Include:
– Body Weight
– Tension In The Spinal Ligaments
– Tension In The Surrounding Muscles
– Intraabdominal Pressure
• The Major Form Of Loading On The Spine Is:
– Axial
4. Upright Position
• Spinal Compression
– Resulting From:
– Body Weight + Weight Held
by Arms and Hands
• When Standing Upright
– Total Body Center of Gravity
Is Anterior to the Spinal
Column.
– Spine Is Placed Under
Constant Forward Bending
Moment.
5. Torque
• Defined: The Rotary Effect of a Force
About An Axis of Rotation, Measured as the
Producer of the Force and the Perpendicular
Distance Between the Force’s Line of
Action And The Axis
• To Maintain An Upright Position
– Torque Is Counteracted by Tension in the Back
Extensor Muscles.
6. Spinal Muscles Role In Lifting
• Spinal Muscles Have
Small Moment Arms With
Respect To the Vertebral
Joints.
• Have To Generate Large
Forces To Counteract the
Torque Produced About
the Spine by Body Weight
and Objects Being Lifted.
Erector Spinae
Muscles
7. Why Lift With The Legs?
• Back Muscles, With a
Moment Arm of
Approximately 6 cm,
Must Counter The
Torque Produced by
the Weights of the
Body Plus Any
External Loads.
8. Question: How Much Torque Is Developed By
The Erector Spinae Muscles With a Fm 6 cm?
• 1 lb. = 4.448 Newtons
• Segment Weight Moment Arm
– Head 13 lbs. (58N) 25 cm
– Trunk 73.75 lbs.(328N) 10 cm
– Arms 18.2 lbs. (81N) 20 cm
– Box 24.95 lbs.(111N) 40 cm
• Torque at L5-S1=
• (328N)(10cm) + (81N)(20cm) + (58N)(25cm)
+ (111N)(40cm)
• = ?
• 10,790 Ncm
• Force?
• 0 = (Fm)(6cm) - 10,790 In static position, sum
• of the torques acting at any point is zero.
• Fm = 1798.33 N or (404.30 lbs.)
9. Problem for a 135 lb. Person
• How much force must be developed by the erector
spinae with a moment arm of 6 cm. From the L5-
S1 joint center to maintain the body in a lifting
position with segment moment arms as Specified?
• Segment Weight Moment Arm
– Head 50 N 22 cm.
– Trunk 280 N 12 cm.
– Arms 65 N 25 cm.
– Box Lifted 100 N 42 cm.
• Torque ?
• 10,285 Ncm
• Fm = 1714 N or (393 lbs. Force)
10. What Does The Research Show?
• % Load Compression On L3 During the Upright Standing, Lying Down,
and Sitting.
• Compression Increases More with Spinal Flexion, and Increases Still
Further with a Slouched Sitting Position.
11. Common Injuries Of The Back
– Low Back Pain
– Soft Tissue Injuries
– Acute Fractures
– Stress Fractures
– Disc Hernia ions
– Whiplash Injuries
12. Low Back Pain
75%-80% of Americans Experience Low
Back Pain Sometime During Life.
Second Only to the Common Cold In Causing
Absence In The Workplace.
Mechanical Stress & Psychosocial.
15. JOINTS OF THE VERTEBRAL
COLLUMN
•VERTEBRAL JOINTS
–GLIDING JOINTS -
SLIGHTLY MOVABLE
•SEPARATED BY
INTERVERTEBRAL DISKS
16. THORACIC COMPLEX - RIBS
• 12 SETS OF RIBS
• ARTICULATE WITH THE THORACIC
VERTEBRAE AND STERNUM
• 7 PAIRS OF TRUE RIBS - ATTACH
DIRECTLY TO STERNUM
• 5 PAIRS OF FALSE RIBS
–2 PAIRS OF FLOATING RIBS
–3 PAIRS ATTACH TO STERNUM VIA
COSTOCHONDRAL CARTLILAGE
21. MUSCLES OF THE THORAX
• DIAPHRAM
• INTERNAL INTERCOSTALS
• EXTERNAL INTERCOSTALS
22. INJURIES TO LOWER SPINE,
PELVIS, HIP - CAUSES
• DISK DEGENERATION - Herniation or General
Degeneration
• JOINT DISFUNCTION - Primarily @ Sacroiliac
– Usual Cause - Lack of Normal Movement - Often Disputed
• STRETCHED OR STRAINED LIGAMENTS - ie:
Supraspinous Ligaments
• LACK OF STRENGTH
– Hamstrings, Erector Spinae, Abdominals, Hip Flexors
23. PREVENTION OF INJURIES
TO BACK
• POSTURE - STANDING
– HYPERLORDOSIS
– KYPHOSIS
• POSTURE - SITTING
– CAUSING PAIN TO LUMBO/SACRAL AREA
24. PROPER SITTING TECHNIQUE -
Should Not Be Done Over Long
Periods Of Time
• HIPS SHOULD BE FLEXED
• LEGS SHOULD NOT BE EXTENDED
• BACK SHOULD NOT BE OVERLY ARCHED
26. STRENGTHENING
EXERCISES
• MANY BACK PROBLEMS ARE CAUSED BY WEAK MUSCLES ABOUT THE
HIP AND ABDOMINALS
• WEAK MUSCLES PREDISPOSE BACK TO HYPERLORDOSIS
• INCORRECT SIT-UPS MAY CAUSE HYPERLORDOSIS - CAUSED BY
SHORTENED ILIOPSOAS
• STRETCHING - HAMSTRINGS - ILIOPSOAS - QUADRICEPS
28. LYING ON BACK
• TEST ABDOMINALS - RECTUS
ABDOMINUS , ILIOPSOAS (HIP
FLEXORS)
–(STATIC W/ STABILIZED THIGHS - HIP
FLEX AT 45 DEGREES
• STRAIGHT LEG RAISE
–PAIN WHEN TESTING UNAFFECTED SIDE
- POSSIBLE HERNIATED DISK
–PAIN WHEN TESTING AFFECTED SIDE -
POSSIBLE SCIATIC NERVE STRETCHED
29. LYING ON BACK
(CONTINUED)
• BOWSTRING SIGN
–TO TEST FOR SCIATIC NERVE -
USE PRESSURE TO POPLITEAL
(BACK OF KNEE)
• GAINSLENS SIGN
–TO TEST SACRO-ILIAC
LESSIONS (SWITCHBLADE
LEGS WHILE ON SIDE)
30. OTHER PROBLEMS
OCCURING WITH THE SPINE
• SOFT TISSUE TRAUMA - CONTUSIONS
• NERVE INFLAMATION OR COMPRESSIONS - FROM DISK
PROTRUSIONS
• FRACTURES TO THE SPINOUS OR TRANSVERSE PROCESSES
• SPONDYLOLYSIS (FRACTURE TO INTERARTICULAR PROCESS
• SPONDYLOLISTHESIS (FORWARD SLIPPAGE OF THE VERTEBRA
32. REHABILITATION OF BACK
AND HIP INJURY
• ICE MESSAGE
• MOVEMENT TO REGAIN FLEXIBILITY &
RANGE
• STRENGTHENING EXERCISES
– SIT UPS & CRUNCHES (WORK OBLIQUES AS WELL)
– PELVIC TILTS - (FLATTENING OF BACK AGAINST
FLOOR)
– HIP LIFTS - (FROM LYING ON BACK POSITION)
– BACK EXTENTIONS - TO 90 DEGREES
– PSOAS & HAMSTRING STRETCH - (KNEES TO CHEST)
