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Ergonomic risk factors are the physical stressors in work environments that lead to musculoskeletal disorders (MSDs)—the most common type of workplace injury and a major focus of occupational health regulation. You're being tested on your ability to identify these risk factors, explain how they cause tissue damage, and recommend evidence-based interventions. This connects directly to broader course concepts like the hierarchy of controls, dose-response relationships, and the interplay between work design and human physiology.
Don't just memorize a list of risk factors—understand the biomechanical mechanisms behind each one. Exams often ask you to analyze a workplace scenario and identify multiple risk factors operating together, or to compare why two different jobs produce similar injuries through different pathways. Know what cumulative trauma means, how tissue tolerance works, and why some interventions target the source while others target the worker.
These risk factors involve physical forces acting on body tissues. When mechanical stress exceeds tissue tolerance—or when moderate stress is applied repeatedly without adequate recovery—injury occurs.
Compare: Repetitive motions vs. forceful exertions—both cause MSDs through mechanical loading, but repetition damages tissue through cumulative microtrauma while force causes damage through acute overload. FRQs often present jobs with both factors and ask you to prioritize interventions.
These factors involve body positions that place tissues at mechanical disadvantage. Joints have optimal operating ranges; working outside these ranges increases internal forces and accelerates fatigue.
Compare: Awkward postures vs. static postures—awkward postures stress tissues through mechanical disadvantage, while static postures cause damage through sustained loading without recovery. A worker frozen in a bent position experiences both simultaneously.
These risk factors involve physical agents in the work environment that affect tissue function or worker capacity. They often interact with mechanical factors to amplify injury risk.
Compare: Vibration exposure vs. contact stress—both can cause nerve and vascular damage to the hands, but vibration acts through mechanical oscillation of tissues while contact stress works through sustained compression. HAVS is specifically a vibration-induced condition.
These factors represent the built environment's fit to the worker. Poor design creates or amplifies other risk factors; good design eliminates hazards at the source.
Compare: Poor workstation design vs. inadequate lighting—both are environmental factors that create other risk factors rather than directly damaging tissue. Fixing these upstream issues often eliminates multiple downstream problems, making them high-value intervention targets.
| Concept | Best Examples |
|---|---|
| Cumulative trauma mechanism | Repetitive motions, static postures |
| Acute overload mechanism | Forceful exertions |
| Postural strain | Awkward postures, static postures, prolonged sitting/standing |
| Neurovascular compromise | Contact stress, vibration exposure, cold exposure |
| Environmental amplifiers | Extreme temperatures, inadequate lighting |
| Upstream design factors | Poor workstation design, inadequate lighting |
| Hand/wrist specific risks | Repetitive motions, vibration, contact stress, forceful gripping |
| Back injury risks | Forceful exertions, awkward postures, prolonged sitting, whole-body vibration |
Which two risk factors both cause tissue damage through sustained loading without adequate recovery, and how do their mechanisms differ?
A warehouse worker develops low back pain after six months on the job. Identify three ergonomic risk factors that could contribute to this outcome and explain the mechanism for each.
Compare and contrast contact stress and vibration exposure as causes of hand and wrist disorders. What intervention strategies would address each?
Why are poor workstation design and inadequate lighting considered "upstream" risk factors? How does addressing them differ from addressing factors like repetitive motion?
An FRQ describes an assembly line worker performing the same 20-second task cycle for 8 hours, using a vibrating tool while standing at a fixed workstation. Identify all applicable risk factors and prioritize interventions using the hierarchy of controls.