Working in a Sitting Position - Overview

Why is excessive sitting during work a problem?

• context Injuries or illnesses resulting from sitting for long periods are a serious occupational health and safety problem. Sitting jobs require less muscular effort, but that does not exempt people from the injury risks usually associated with more physically demanding tasks. For example, clerks, electronic assembly-line employees, and data entry operators who work in a sitting position also suffer back pain, muscle tenderness, and aches. In fact, reports of varicose veins, stiff necks, and numbness in the legs are more common among seated employees than among those doing heavier tasks.
• context In addition, sedentary time has been found to be associated with health effects such as metabolic syndrome (including diabetes), heart disease, and poor mental health.

How does working in a sitting position affect blood circulation?

• context When the employee can alternate sitting with other body positions, sitting at work may not be as large a risk for injury or discomfort.
• context For those who have no choice and must sit for long periods, the situation is different. Although sitting involves less muscular effort than physically demanding job tasks such as gardening or floor mopping, it still causes fatigue. Sitting requires the muscles to hold the trunk, neck, and shoulders in a fixed position. A fixed working position squeezes the blood vessels in the muscles, reducing the blood supply to the working muscles just when they need it the most. An insufficient blood supply accelerates fatigue and makes the muscles prone to injury.
• context There is also less demand on the circulatory system due to the limited mobility while sitting. As a result the heart activity and the blood flow slow down. Maintaining a steady upright body position while sitting further decreases blood circulation.
• context An insufficient blood flow, specifically blood that is returning to the heart from the lower legs, causes blood to pool. Pressure on the underside of the thighs from a seat that is too high can further aggravate this issue. The result can be swollen or numb legs and eventually varicose veins. Also, a reduced blood supply to the muscles accelerates fatigue. This lower blood supply explains why an employee who sits all day long doing little physical work often feel tired at the end of a work shift.

Can work in a sitting position cause injuries that affect movements?

Limited mobility contributes to injuries in the parts of the body responsible for movement: the muscles, bones, tendons and ligaments. Another factor is the steady, localized tension in certain regions of the body. The neck and lower back are the regions usually most affected. Why? Prolonged sitting:

• context reduces body movement making muscles more likely to pull, cramp, or strain when stretched suddenly,
• context causes fatigue in the back and neck muscles by slowing the blood supply and puts high tension on the spine, especially in the low back or neck, and
• context causes a steady compression on the spinal discs that hinders their nutrition and can contribute to their premature degeneration.

What aspect of working in a sitting position is responsible for ill effects?

A poor body position is largely responsible for the ill effects of prolonged sitting. The duration (length) of sitting, is also a risk factor. Poor body positions can also originate from:

• context job design that requires employees to sit uninterrupted for longer than one hour
• context a workspace that prevents employees from sitting in a balanced position
• context the physical arrangement of workspace elements such as work surfaces, tools, and equipment that do not correspond with the reaches of seated employees
• context chairs that are unsuitable (e.g., too high or low, not adjusted correctly, etc.) for an employee's body size and shape

Is there a good sitting position?

• context For each major joint such as the hips, knees, and elbows, there are ranges within which every healthy person can find comfortable positions. These positions should not impede a person's breathing or circulation, interfere with muscular actions or hinder the normal functions of the internal organs. Varying these positions is the essence of "good sitting". So, good sitting position is one that allows employees to change their body positions frequently and naturally within an acceptable range, and when they want without being restricted by the work station or job design.

What elements of a workplace are important for comfort of the seated employee?

The workplace design should enable the employees to carry out work in comfort and safety while allowing them to make voluntary changes in the working posture. To achieve this, the design should include the following elements:

• context tasks
• context workstation
• context chair

How is a proper chair selected?

• context A basic rule of ergonomics is that there is no such thing as the "average" person; however, providing an individually designed chair for every employee is not practical or possible. A solution is to provide the employee with a fully adjustable chair that can accommodate the maximum range of people (typically 95 percent of the population). The chair must have controls to allow easy adjustment of the seat height and tilt, as well as the backrest height and angle. It is important that the employee can operate these controls from a sitting position. The chair's design must match the tasks. For individuals outside the adjustable range of the chair, determine if alternative chairs can be made available.
• context A trial period is essential to the process of selecting a chair. Employees should try out the chair in the real work situation and ensure it meets the needs of the job before the final selection is made.
• context Please also see the OSH Answers document "Ergonomic Chair" for more information.

How should a job that requires prolonged sitting be designed?

• context No matter how well the workplace is designed, an employee who sits for long periods can suffer from discomfort or negative health effects. The main objective of a job design in this situation is to reduce the amount of time the person spends sitting still. However, while frequent changes in the sitting position are good, they may not be enough to protect against prolonged sitting effects such as blood pooling in the employee's legs.
• context Five minutes of a moderate to vigorous activity, such as walking for every 40 to 50 minutes of sitting, can help protect an employee. These active breaks are also beneficial because they give the heart, lungs, and muscles some exercise. Where practical, jobs should incorporate "activity breaks" such as work-related tasks away from the desk or simple exercises which employees can carry out on the worksite.
• context Another important aspect of job design is feedback from employees. Consultation with employees can help tailor the solutions to the individual and personalize their work.

What elements of an education and training program are important for employees who work in a sitting position?

Individual work practices, including sitting habits, are influenced by proper education and training. Encourage management and employees to adopt methods that reduce fatigue and poor (static, awkward) posture. Explain the health hazards of prolonged sitting and give recommendations on what employees can do to improve the working position. Employees need to know how to adjust the workstation to fit their individual needs for specific tasks. They also must know how to readjust the workstation throughout the day to relieve muscular tension. Emphasize the importance of rest periods for the employees' health and explain how active rest (i.e., involving movement) can do more for keeping employees healthy than passive rest (i.e., more sitting). The effect of such training can reach far beyond occupational situations because the employees can apply this knowledge also in their off-job life.