National Safety Month: Ergonomics and Musculoskeletal Disorders
June is National Safety Month! Every week, Neumann Safety Manager James Machamer will share industry insights to promote National Safety Month and help foster a safer work environment. This week’s topic is Ergonomics and Musculoskeletal Disorders (MSDs).
What is Ergonomics?
Ergonomics is a way of designing workstations, work practices, and workflow to accommodate the capabilities of workers. Ergonomic design reduces risk factors contributing to occupational ergonomic injuries and illnesses such as sprains, strains, and cumulative trauma disorders (CTDs).
If work is performed in awkward postures or with excessive effort, fatigue and discomfort may result. Under these conditions, damage can occur to muscles, tendons, ligaments, nerves, and blood vessels. Injuries of this type are known as musculoskeletal disorders (MSDs).
The increased frequency and cost of ergonomic injuries and illnesses affect all industries and occupations, with manufacturing, retail, and service industries taking the hardest hit. These injuries include carpal tunnel syndrome, tendinitis, and MSDs. When reviewing the OSHA 300 Log, approximately 30%-50% of recordable injuries are related to ergonomics!
MSDs increase the cost of doing business directly and indirectly. Direct prices include medical services and higher workers’ compensation premiums. For example, the cost to close an ergonomic-related workers’ compensation claim can average more than $9,000. Indirect costs include employee turnover, absenteeism, and retraining, while productivity, quality, and employee morale suffer. Estimates indicate that the indirect costs associated with MSDs can be 4 to 10 times higher than direct costs. Preventing ergonomic risk factors in the workplace often costs a fraction of a workers’ compensation claim. In smaller companies, one ergonomic-related claim can mean the difference between being above or below the profit margin.
Risk Factors Inherent in the Worker
It’s important to understand that each worker’s ability to respond to the external demands of a task is unique. Workers are individuals, and they should not be lumped into groups when considering ergonomic design. Stereotyping or making generalities about an employee’s ability should not be based solely on age, gender, or strength. At the heart of ergonomic design is the idea that equipment should be designed so that it’s able to meet the unique needs of each employee, not the general employee population.
The Musculoskeletal System
The musculoskeletal system is comprised of soft tissue and bones in the body. The essential parts of the musculoskeletal system are:
- Bones: Load-bearing structure of the body.
- Muscles: Tissues that contract to create movement.
- Tendons: Tissues that connect muscles to bones.
- Ligaments: Tissues that connect bones to bones.
- Cartilage: Tissues that provide cushioning and reduce friction between bones.
- Nerves: The communication system that links muscles, tendons, and other tissues to the brain.
- Blood vessels: Tubes that circulate nutrients throughout the body
Inherent Factors in the Worker
Age of Individuals
Musculoskeletal impairments are among the most common and symptomatic health problems of middle and older-aged individuals. The prevalence of MSDs increases and remains consistent as people enter their working years (ages 25 to 65). By 35, most people have had their first episode of back pain. Nonetheless, age groups with the highest rates of compensable back pain and strains are the 20-24 age group for men and the 30-34 age group for women. In addition to decreases in musculoskeletal function due to the development of age-related degenerative disorders, loss of tissue strength with age may increase the probability or severity of soft tissue damage from a given injury.
Another factor is that advanced age and increased number of years on the job are usually correlated. Older workers have been found to have less strength than younger workers, although hand strength does not appear to decline with aging. In one study, average hand pinch and grip scores remained relatively stable in the 29-59 population.
Strength and Endurance
Muscular strength is the maximum force that a muscle can exert under maximum contraction. The amount of force exerted by the muscles in the arms, legs, and back depends on body posture and the direction of force. For example, when standing, you can exert more force when pulling backward than when pushing forwards.
Muscular endurance is the ability of a muscle or a muscle group to remain contracted over a period of time. There are two types of endurance: static and dynamic.
- Static endurance can be determined by the length of time a limb can maintain a position.
- Dynamic endurance can be measured by the number of times a limb can perform a movement against a certain resistance.
A study evaluated the risk of back injuries and strength and found the risk to be three times greater in the weaker subjects. They found that job matching based on strength criteria appeared to be beneficial.
Lack of physical activity may increase susceptibility to injury, although the relationship between physical activity and MSDs is more complicated than just cause and effect. Physical activity may cause harm; however, the lack of physical activity may increase susceptibility to injury. In addition, a lack of physical activity after injury may increase the risk of further injury.
For most physical activities, fitness is a combination of strength, endurance, flexibility, musculoskeletal timing, and coordination. In a study of male firefighters, physical fitness and conditioning appeared to have significant preventive effects on back injuries. However, the most physically fit group had more severe back injuries.
Although physical fitness and activity are generally accepted as ways of reducing work-related MSDs, the present epidemiologic literature does not give such a clear indication. However, there is clear evidence that stretching exercises have a positive effect on reducing MSDs.
Repetition and Static Work Requires Energy
Strength is important but not necessarily the key. “Heavy work” stresses the heart and lungs, resulting in rapid fatigue and the increased probability of injury as muscles weaken. Consequently, demanding repetitive or static muscular work requires energy, not necessarily strength. You may be strong but not have sufficient energy to do the task.
- Isometric (Static) work occurs when the muscles remain contracted for an extended period of time with no movement, as in holding an object. Muscles do not get the chance to relax and can fatigue quickly.
- Isotonic (Dynamic) work involves repetitive contraction and relaxation of the muscles and is less tiring and more efficient than static work. The motion of the muscles also helps pump blood supplying oxygen and eliminating carbon dioxide.
Ergonomic Hazard Control Strategies
A hierarchy of controls has been used to control ergonomic hazards and determine how to implement feasible and effective controls. ANSI/ASSP Z10-2012, Occupational Health and Safety Management Systems, encourages employers to use the following hierarchy of hazard controls:
3. Engineering controls
5. Administrative controls
6. Personal protective equipment
The control strategies at the top of the hierarchy are potentially more effective than those at the bottom. Following the order typically leads to implementing safer systems, where the risk of illness or injury has been substantially reduced.