Cathy White, CIH, CSP, CPE The Dow Chemical Company Industrial Hygiene Expertise Center

Cathy White, CIH, CSP, CPE The Dow Chemical Company Industrial Hygiene Expertise Center

Agenda Anatomy of the back Types of force Biomechanics of the back What is the power zone? How to get in the power zone

Anatomy of the Back Vertebrae: building blocks Discs: jelly donuts 3 natural curves When sitting or standing with the natural curves, there is even pressure on the disc. Images courtesy of spine universe

Sitting or Standing How are you sitting right now? Images courtesy of Occupational Biomechanics Please STAND UP for a demonstration of the natural curves of your spine.

High Force Injury Tissue experiences a single high force event Slip/trip Fall Impact with Struck by Activity: hold the ends of the Popsicle stick between thumb and forefinger

Low, Repetitive Force Injury Associated with repetitive movements Activity: paper clips

Low, Constant Force Injury Static muscle loading Hold awkward posture for sustained period of time Activity: mug and putty

Low Back as a Lever

Free Body Diagram 12 25 Center of mass (COM) L5/S1 disc LOAD 100 lbs 20 lbs Hand is holding a 20 lb load. What is the moment generated by the L5/S1 disc? Moment = lever arm X force

Free Body Diagram 12 25 Center of mass (COM) L5/S1 disc LOAD 100 lbs 20 lbs SM DISC = 0 M DISC = (-100 lbs X 12 ) + (-20 lbs x 25 ) M DISC = (-1,200 in-lbs) + (-500 in-lbs) = -1,700 in-lbs

Free Body Diagram 25 12 Center of mass (COM) MDISC= LOAD 1700 in-lbs FES 100 lbs 2 MDISC = MES 1700 in-lbs = FES x 2 in FES = 1700/2 = 850 lbs 20 lbs Force generated by ES is over 40 times greater than the external load weight of 20 lbs!

What is the Power Zone? The power zone is above the knees, below the shoulders, and close to the body In this area workers have the greatest power to perform heavier work tasks Less bending Less stooping Less reaching

Power Zone Applications Get it off the Ground

Solutions to Control Hazards Solution Images courtesy of OSHA

Look at the Floor! Bags Boxes Bottles Seasonal items Talk to people Images courtesy of OSHA

Keep Materials off the Floor Carts Tables Scissor lifts Material handling devices Lever loader with turntable Load pusher/puller Pallet jack with height adjustable forks Stacking wood pallets

Look up High! Reaching overhead Materials in high places Materials stacked high

Avoid Overhead Materials Design shelving storage Only light and infrequently accessed items on the top shelves Tilted bins Use a stepstool or platform Use material handling devices to Hand truck elevate the load Platform

Look at the Infrequent! Look at storage of infrequently used items Ask about non routine tasks Think about seasonal activities

Assess and Control the Infrequent NIOSH Lifting Guide http://www.cdc.gov/niosh/docs/94-110/ Equation assumes 2 handed, smooth lifting in standing position with good footing in a stable environment Lifting Index (LI) Level of physical stress associated with a particular task Identify potentially hazardous lifting jobs Compare the relative severity of two jobs A quick tool: WISHA Lifting Calculator for simple assessments can be used as a screening tool http://www.orosha.org/interactive/lifting/lift_safety.html

Eliminate Reach! Forward reach Reaches behind Reaches to the side Images courtesy of Dan MacLeod, CPE

Minimize Reach Palletizing methods Mechanical assistance Pick sticks Tilt tables Turntable Tilt table Bo peep hook

Don t Forget Twisting! Watch tasks as they occur People may be twisting without realizing it Oftentimes it is easier to twist than to pivot Techniques are hard to control

Eliminate Twisting Redesign is preferred Easier to control Long term Sustainable Load in front of worker by design Conveyor moves product Eliminate lifting (push instead) Lift assist Fork lift Drum lifter moves product

Don t Forget the Office!

Control Hazards in the Office Cart for material transport Standing workstation adjustable to alternate

Key Points Maintaining the natural curves of the spine aids in preventing back pain and injury Deviations of the natural curves of the spine over time can lead to fatigue, pain, and back disorders The low back is an inefficient lever Keeping reaches close and eliminating bending and twisting in design will reduce risk of injury Get in the zone the POWER zone!