The main difference between seated and standing workstations are in reaches and clearances. Seated work requires more leg clearances, and cannot accommodate long reaches. Work surface heights can vary for standing work.
Sometimes, the best type of seating for a workstation may be no chairs at all. Working in a standing position tends to slightly increase the type of reaches possible within the optimum work envelope.
The main difference between seated and standing workstations are in reaches and clearances. Seated work requires more leg clearances, and cannot accommodate long reaches.
“In general, people feel more rested when they sit down vs. stand up and work, and more fatigued if they stand all day,” says Julia Abate, senior ergonomist at the Ergonomics Center of North Carolina, which is housed in the Edward P. Fitts Department of Industrial and Systems Engineering at North Carolina State University. “The best [solution] is actually a combination of both.
“To make the sit vs. stand decision, you must look at the assembly task that will be performed,” adds Abate. “Most people run into problems when they use a chair at a workstation that was designed for standing use.”
According to Abate, sitting is generally a good idea when the work involves more detailed, precision tasks, highly repetitive tasks, or tasks involving visual inspection. “Since the worker is not able to use the body for leverage when seated, seated work should involve light forces or weights less than 10 pounds,” she explains.
To have a correctly designed seated workstation, assemblers must have an adjustable chair that provides good support. “Usually, the chair should not have armrests,” says Abate. “But, if they are present, the chair should move freely in and out of the workstation without interference.”
All work and parts should be within a 25-inch reach, without requiring the worker to twist to the side or reach to the floor. “Lifting should not be done from a seated position, especially heavy lifting or lifting from the floor,” warns Abate.
Clearance is also important. Operators should have adequate clearance for both knees and feet. Typically, a footrest is also useful.
“In general, seated workstations should be designed so that work can be performed at the worker’s seated elbow height,” explains Abate. “Writing is the exception, with work surface height slightly higher than elbow.>br>
“For some precision tasks, it may be useful to angle the work surface up slightly so that the worker does not have to look down as far, which can be fatiguing on the neck,” Abate points out. “The edges of the work surface should be contoured to avoid contact stress to the worker’s arms.”
According to Abate, there are two types of standing: Static standing and dynamic standing. Static standing occurs when a worker is stationary for long periods of time, without moving his or her feet. This can minimize the blood flow to muscles and cause more fatigue. “Use of a footrest may help, or simply redistributing the weight from one foot to the other occasionally will help,” explains Abate.
Dynamic standing involves taking several steps periodically-usually when retrieving parts or moving a product to the next workstation. Dynamic standing, as well as walking, helps distribute more blood flow (and therefore oxygen) to the muscles.
Assembly tasks that require force, involve lifting or working with parts 11 pounds or more, or tasks that involve extended reaches, should be conducted in a standing position. “Standing allows the worker to produce more force than sitting, since the body is not restricted and larger muscles can be better utilized,” says Abate.
“Standing also allows the worker to reach further, although reaches beyond 25 inches may involve more awkward postures (bending at the back),” adds Abate. “Standing work allows the operator more flexibility in the postures that they use when performing tasks.”
Work surface heights can vary for standing work. “In general, work should be conducted at the standing elbow height of the worker,” says Abate. “The work surface may be lowered for tasks requiring more force or raised for precision tasks. Matting or supportive insoles may help reduce any fatigue experienced by the worker.”
Sitting vs. Standing Makes a Big Difference
December 1, 2009