How does body size affect ergonomics?

Morphology, which refers to the physical characteristics and anatomical features of an individual, plays a significant role in ergonomics. My “morphology” is close to average height, strength and flexibility for a female of my age, but I have short legs, small hands, and small feet. So what? 

This article discusses how morphology can affect ergonomics. 

Body size and proportions 

Factors such as height, weight, limb length, and body mass distribution can influence how workers interact with the environment. Ergonomic design considerations, such as the height of workstations, seat adjustments, and reach zones, should account for these variations to ensure that tasks can be performed comfortably and without excessive strain or awkward postures. For example, overweight workers with large “middles” may not be able to reach their keyboards without flexing the shoulders a bit; this can cause shoulder, upper back, and neck discomfort. As an average height person, you’d think I could use an average height chair; in fact, my short legs require a special “short” chair cylinder.  I still have a tough time finding gloves that fit me well. 

Joint flexibility and range of motion

Individuals with less flexibility may require adjustments in workspace design, equipment settings, or task requirements. Ergonomics assessments should consider the range of motion required for different job tasks and adapt them accordingly to minimize stress on joints and muscles. For example, a worker with limited knee flexibility won’t be able to squat to retrieve items from low heights, so frequently-used items should not be stored in these locations. 

Anthropometry and reach 

Anthropometry refers to the measurement of human body dimensions. Variations in anthropometric characteristics, such as arm length, hand size, and torso dimensions, can affect reach capabilities and the ability to interact with tools, controls, and equipment. Ergonomic design should consider these variations to ensure that controls, handles, and interfaces are appropriately sized and positioned to facilitate comfortable and efficient task performance for individuals of different morphologies. We typically try to design reach parameters for the smallest worker; if this person can reach, then others with longer reach capabilities will be fine. I think my arms are of average length for a female, but I had a tough time adjusting the radio in my old car without reaching awkwardly sideways. (“Reach” factored into the purchase decision for my new car!)

Strength and physical capacity 

People vary in strength and physical capacity. But not all tall people are stronger – size and strength are not directly related. Ergonomic considerations should account for these differences to ensure that task demands are within the capabilities of all workers, minimizing the risk of excessive exertion or fatigue-related injuries. I am a runner, so I have decent endurance for tasks like walking, but my strength is not great, so if that walk turns into a “carry”, then my lower-than-average grip strength limits my abilities. (I need a cart!) 

So far, we’ve only talked about body size and strength from the worker’s perspective. Now consider those people who work with patients or clients of varying body size. How does human body size affect a worker who has to lift a patient, perform an ultrasound, or position a foot for a pedicure? This is a whole other world, which we’ve touched on before! 

An understanding of morphology is essential for effective ergonomic design. The trend toward obesity continues, and our design efforts should account for this. An aging workforce will also affect users’ morphology. We should account for the diverse range of body sizes, proportions, flexibility, strength, and physical capacities to create a work environment that accommodates individual differences, minimizes strain/sprain injury risks, and promotes comfort, safety, and productivity. Let us help.

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