A high percentage of the nearly one half million job related back injuries reported each year occur while performing simple tasks as opposed to strenuous undertakings. The reason for this related to posture, levers and horsepower.
When lifting a heavy object we intuitively prepare ourselves. We check our footing, get close to the object and apply steady pressure to move it.
When lifting a light object we show contempt for our backs. Reaching out and bending over to grab an object then bouncing up with it puts a tremendous strain on the back.
Posture: The human spine is curved. The curved shape increases the strength of the spine. The curve in the lower back supports the position of the disks. Bending forward can decrease the curve which increases the possibility of rupturing its disks.
Levers: Imagine the lower vertebrae are nails we are trying to pull out of wood, and the rest of the spine is a nail puller. The further out the force is applied to the puller, the greater the force applied to the nail. Reaching out to lift a weight literally places more strain on your back than lifting correctly.
Horsepower is the ratio of work performed, divided by the time required to perform it. The less time required to perform it. The less time required the more horsepower generated. Lifting a heavy weight is normally performed slowly.
When lifting a light weight, we bounce up at a higher rate of speed. This increases the horsepower of the force on the lower back.
How can we prevent these injuries? Think of the spine as a boom used for lifting. A boom constructed with a weak base. How can we lift with this boom safely?
1. Assuring the base is aligned.
2. By not lifting too heavy a load.
3. By avoiding any quick or jerky movements.
4. By not overextending the length of the boom.
5. By bracing the boom.
Using these rules we can lift a light object, say a pencil, safely.
Get close tot he pencil. Brace the upper body which will support the spine and help maintain the curve of the spine. Lift in an easy relaxed tempo.
Steps for lifting a light object, the pencil.
1. Approach the pencil placing the foot of the lifting hand a couple of inches from it, i.e., right hand - right foot.
2. Bend the knees a few inches to lower the body.
3. Place the non lifting hand on the knee, i.e.: left hand-left knee
4. Bend down just enough and grab the pencil
5. Place the non lifting hand on the knee, i.e., left hand - left knee.
Credit: Bud Johnson, firstname.lastname@example.org
For more information read Section 12 - Manual Lifting of Materials in the Elevator Industry Field Employees' Safety Handbook