Ergonomics is defined as fitting the workplace to the worker. A workplace includes not just our work areas but also our tools and equipment. There are seven basic risk factors in the workplace associated with WMSD injuries. If a WMSD is caused by a single risk factor it is usually easy to rectify, however most WMSDs are cause by multiple factors. These risk factors are:
- Duration
- Compression/Contact Stress
- Position/Posture
- Vibration
- Force
- Temperature (Cold)
- Repetition
The Centers for Disease Control and Prevention (CDC) with the National Institute of Occupational Safety and Health (NIOSH) started a collaborative research program to prevent work-related upper limb musculoskeletal disorders (MSDs, conditions involving the nerves, tendons, muscles, and supporting structures of the upper limb). The program has research partners at six universities and one state agency. The goal of the program is to determine the risk for work-related:
- carpal tunnel syndrome
- tendonitis of the forearm and wrist
- shoulder disorders
More information on the
CDC's Upper Limb Musculoskeletal Disorder Consortium 
.
See the free downloadable poster,
Ergonomics: Work Smarter! Ergonomic Risk Factors.
Scenarios
1. Warning sign: "I've been sitting at my computer all morning writing a report and my legs hurt. What should I do?"
Risk: Duration.
Workspace Redesign: It seems that performing an activity while sitting should allow time for rest and present very few threats to health. The reality is that there are many risk factors office workers are exposed to that can cause health problems. One of them is that the human body was made to move, and if you are sitting for too long the blood flow to your arms and legs decreases. This is why you need to take breaks on a regular interval; go to the water cooler, use the restroom, stand up and stretch,
anything to get up and move around. Once every 20 minutes is recommended, but your individual time period may differ.
See the free downloadable poster,
Take Time to Stretch
This problem also points out the fact that most WMSDs are caused by multiple risk factors. Your legs may hurt also because your workstation (i.e. your office chair, desk height, lack of a foot rest, etc.) may be improperly set up causing your posture to be poor.
For more information on posture at your workstation see the free downloadable poster,
Ergonomics: Designing a Comfortable Workstation
2. Warning sign: "I'm an electrician, re-wiring buildings on my instillation. I got this bruise in the palm of my hand and I have no idea where it came from. Any ideas?"
Risk: Compression
Workspace Redesign: Doing your electrical re-wiring you probably use a pair of needle-nose pliers and/or wire strippers. The handles of those tools might not be longer than the length of your hand. If the end of one of the handles stops in the palm of your hand, when you squeeze the
tool the handle end compresses into your palm causing a compression injury, usually a bruise. Selecting the proper tool based on the task and worker's characteristics (e.g., hand dimensions and strength) significantly reduces the risk of WMSD injury and ultimately will result in increased productivity.
Check out the free printable Fact Sheet,
Choose the Proper Hand Tools for You
3. Warning sign: "I work in the parachute packing barn. When I lift up an unpacked 'chute and carry it over to a work table my back kills me. But when I lift up a packed parachute it doesn't. They both weigh the same: what's going on?"
Risk: Position/Posture
Workspace Redesign: The answer lies in biomechanics and the posture you use when carrying packed and unpacked parachutes. Posture and lifting technique can either reduce or increase forces on the body. When you lift up and carry an unpacked parachute, more of its weight is further away from your body. Your arms, torso and back are now acting like a giant lever. The pivot point of this lever is your lower back, and that's where all the torque forces (or moment) are concentrating. A packed parachute may be the same weight as an unpacked one but it's in a smaller package, so you're lifting and carrying it closer to your body. As long as you keep your back straight your torso isn't acting as much like a giant lever, so the forces on your back are smaller and your back pain will be less.
When lifting or carrying an object the closer it is to your body the better. Also keep your back as straight as possible and right before the lift, tighten your core stomach and back muscles.
4. Warning sign: "I do a lot of sanding off old paint with a powered grinder to refurbish transport trucks. At the end of the day my hands are numb and my fingers are pale."
Risk: Vibration
Workspace Redesign: Powered hand tools allow heavier work to be performed with greater speed and efficiency. However the improper design and use of powered hand tools can contribute to WMSDs caused by vibration. Vibrating tools can cause vascular spasms or a constriction of blood vessels in the fingers, which then appear white or pale. Vascular constriction may lead to numbness and swelling of hand tissue, with a loss of grip strength. Vibration-induced white finger, also known as "Raynaud's phenomenon," and hand-arm vibration syndrome (HAVS) cause tingling, numbness, or pain that can be brought on or intensified by exposure to cold. There are preventive actions that can be taken to reduce the impact of vibration:
- Reduce the number of hours or days vibrating tools are used in accordance with the American Conference of Governmental Industrial Hygiene Threshold Limit Values.
- Arrange tasks to alternate use of vibrating and non-vibrating tools.
- Schedule tool maintenance so tools remain sharp, lubricated, and properly tuned.
- Use gloves with vibration-damping materials in the palms and fingers. Ensure workers keep warm at work, especially their hands. To be effective, gloves should fit, be full finger, and comply with ANSI S3.40-2002 or ISO 10819 standards.
- Use tools with vibration-damping handles.
- Keep hands warm and dry.
- Avoid using tobacco or stimulant drugs that may restrict blood flow to the skin by as much as 40 percent.
There is a free printable Fact Sheet called
Selecting the Proper Powered Hand Tool can Make Your Work Safer and Easier
5. Warning sign: "Part of my job as an Army Nurse involves transferring and repositioning patients all day. Towards the end of my shift my back starts to really bother me. How can I re-design this?"
Risk: Force
Workspace Redesign: Under the best case scenario (for example a stable workload, with handles and able to be held close to the body), NIOSH recommends a person only lift 51 lbs. For nurses and other healthcare workers, because patients are not stable loads, do not have handles and typically cannot be held very close to the body, the recommended lifting limit of a patient who is not able to assist is 35 lbs. Yet during a shift a Nurse typically lifts a cumulative weight of 1.8 tons!
To redesign your lateral patient handling task you might consider an air-assisted lateral transfer device. This is similar to an air mattress with holes on the bottom connected to a motorized air pump. This lets the patient float on a mattress with the cushion of air making pushing or pulling to transfer them much easier.
6. Warning sign: "I work in IT and I've been in the office all day. Even though I move around a lot and my chair is adjusted correctly I still get very tired towards the middle and end of the day. Any ideas?"
Risk: Temperature (Cold)
Workspace Redesign: Offices and computer rooms are often kept at a cold temperature for the sake of the equipment. Cold temperature reduces blood flow and is contributing factor to fatigue. If you can't turn the office's thermostat up, consider wearing a hat, light jacket or sweater in order to keep your body's temperature up.
7. Warning sign: "I put together gas masks by hand on an assembly line, and around 3 o'clock my hand starts to swell. How can I redesign my job so this doesn't happen?"
Risk: Repetition
Workspace Redesign: Repetition results from performing the same task over and over and using same set of muscles continuously throughout the workday. Microtraumas to body parts from repetition can result in inflammation of the tendons, muscle irritation or entrapment syndromes, and nerve irritation. The most famous of repetition injuries is carpel tunnel syndrome.
You might stop your hand swelling by rotating your job: instead of putting together gas masks all day switch off every hour and do something else that uses a different muscle group, like delivering the masks or running errands. Whatever you do it's important that it use different muscles than the ones you use while putting together gas masks.
Ever wonder about the folks who put the 20 pound Thanksgiving turkey or 10 pound bag of potatoes on the shelves at your local grocery stores? They face the same WMSDs the Army does. The Center for Disease Control tells us about
Thanksgiving Ergonomics: Reducing material handling injuries with engineering controls.
