LOADS and LIFTING

• Back pain is big $

• Back troubles– Are painful– Reduce activity and mobility– Cause absences from work– Affect a relatively young part of the work force

(age 20-40)

Who’s most affected

• Physically active jobs

• But can’t usually be pinned on a single incident

Understanding Back Pain

• Why is most back pain in the lower back?

• What are early physiological changes in the back?

• What are the eventual results of continued deterioration?

How is Back Pain measured

• Intervertebral disc pressure

• Biomechanic modeling

• Intra-abdominal pressure

• Subjectively

Intervertebral Disc Pressure

• Idea is that bending back puts uneven pressure on the discs

• “Lift with your back straight”

• Force transferred through arms and upper back creates torque

High pressure

Low pressure

Biomechanical Models

• Torque = Fd

• Bent back increase torque through distance

• 20kg load has a predicted compression force of 12, 138N (huge)

• Farther load is from the spine, the greater the torque

Intra-abdominal Pressure

• Pressure created by abdominal muscle contraction

• Hernias

• Lifting belts

• Suggest 90mmHg is a safe limit

• Weightlifters can go much higher 150mmHg

Subjective Approaches

• Obtained by questioning – is this too hard? Too easy

• Look at Tables 7.2-7.4 in text

• Acceptability by Lift Weight and Lift Height

• For Different Actions lifting lowering pushing pulling

Problems with making Lifting Recommendations

• Vary with individual health and fitness

• Vary with type of load

• Vary with lifting technique

• NIOSH limit 23kg max

• All lifting situations need to be examined for safety

How to Lift Properly

• Keep your back straight, bend your knees• Keep the load close to your body• Try to have the load start at knee height, not from

the ground• Provide handles or hooks• Don’t rotate or twist• Use mechanical aids if possible• Pushing and pulling is easier than lifting if the

force can be transferred.