Signup for free!
4.1 Biomechanics: Occupational Biomechanics
The use of mechanics methods, principles, and ideas to study biological systems
A science concerned with the mechanical behavior of the musculo-skeletal system and component tissues when physical work is performed
Lower Back Pain is a major problem in working environments
Common in nurses
Older workers - musculo-skeletal system
Occupational, Sports, Military Biomechanics
More injuries with more muscle exertion
Older the age, the more chance of spraining or hurting something
Overexertion is cited as the most frequent and costly claim (lower back)
- Absenteeism, leads to high workers compensation
Newton's Laws: Static Equilibrium Conditions
Sum of Forces = 0
Sum of Moments = 0
Lower Back Biomechanics
- neck section, 7 disks
- chest section, 12 disks
- back section, 5 disks
- hip portion, fused
5th lumbar disc and 1st sacrum disc
Lower Back Pain
Back pain usually refers to long term disc pain (Generally in L5/S1
Two bones (L5/S1) have tissue in between and a nerve in the back. When bones are moved, tissue can hit the nerve and it causes stinging pain.
Created by weight and distance
The force on the L5/S1 is roughly 10-15 times greater than the force of the load being lifted
L5/S1 is furthest point from movement
There is the most torque/rotational movement
Since it is furthest point away, largest moment is caused
Back muscles do the lifting and Rotating
Small distance from axis of rotation
Small distance to deal with large object
Skeletal System Facts
Upper body is more than half of the body weight
When you lift, you magnify the weight
Soft tissue (annulus Fibrosis) will overflow - can't go forward because of abdominal wall so it goes backwards into nerves causing discomfort called L5/S1 Herniation
Results in spinal nerve compression and inflammation
Most people overestimate their ability to lift things.
Suitcases in airplanes
Athletes tend to get hurt more because they think that they are strong enough, correlation relationship not causual
Estimate on how much you think you can lift, tends to be overestimated so don't use it conclusively.
Lower Back Pain Causes
Explanations as to how the L5/S1 can get damaged.
3. External Load movements on spine must be kept small
Keep load close
Keep load off the floor
Keep torso as vertical as possible
Do not jerk with fast loads
Avoid Asymmetric Lifting
Lower Back Biomechanics
1. The spine needs
muscles to move and stabilize
against external movements often requires in manual lifting.
2. High muscle forces create
high disc compression forces
that can (and do) exceed the tolerance of most lumbar spinal disks.
Disk to Disk Injuries
and twisting poses a special risk to the back and should be avoided.
Risk of spinal trauma
may not be reduced enough by psycho-physical "strength" norms, since resulting tissues forces into lower back may not be sensed until trauma causes inflamation.
Major Types of Back Pain
Disc Related Tissue
Useful Equations to Know
Mload-to-torso = Wload&body *d
Wload&body = upper body weight
d = horizontal distance from the load to L5/S1 disc
Mback-muscle = Fback-muscle X 5 (N-cm)
Fcompression = Wload&body X cos
Î± + Fmuscle
- Î± = angle between horizontal plane and sacral cutting plane, which is perpendicular to the disc
Fshear = Wload&body X
to remove ads