A widespread health hazard is not instantaneous but gradually brought on by the seemingly innocuous activity of sitting. Sitting in an office environment, particularly resting incorrectly, has been causing back pain and associated disorders in greater numbers in recent history. Currently, more than half of Americans who experience low back pain spend the majority of their workday sitting. Ergonomics—the science of arranging the things with which a worker interacts so that a work space is efficient and safe—is focused heavily on the correct way to work at a desk and sit in a chair.
Some may argue that sitting in general is the core problem, claiming it to be unnatural and merely a byproduct of life in modern civilization. However, while there is substantial evidence indicating that early humans owe much of their success to the ability to walk for extensive periods and remain upright and active, our bodies are also designed to sit. Even when you look at some of our closest living taxonomic relatives, you will find adaptations for sitting. For example, many species of Old World Monkeys have ischial callosities, hairless callous pads on their bottoms that were likely adapted for sitting on rough branches and rocks.
The problem is not sitting but the fact that many of us are sitting far too much. Devoting the majority of your time to the seated position inhibits many of the triggers for your muscles to support themselves. This can lead to things like heart disease, muscle degeneration, strained neck, foggy brain, and leg disorders.
Of course, one solution to this issue is just to sit less, but for many people, that is rarely an option. There is, however, an often-cited “correct way” to stay seated for those who have no choice but remain in chair-bound. This includes not leaning forward, leaving your shoulders relaxed, keeping your arms close to your sides, having your elbows bent at 90 degrees, supporting your lower back, and keeping your feet flat on the floor.
Simply assuming that any worker can just operate in this manner is a bit presumptuous, as the behavior of many is influenced by their surroundings. Ergonomic considerations can help to create a workstation with which the worker can engage with different inputs in a manner not detrimental to the worker’s health or success. ANSI/HFES 100-2007: Human Factors Engineering of Computer Workstations, which was written and published by the Human Factors and Ergonomics Society (HFES), an ANSI-accredited standards developing organization, specifies several principles in human factors engineering for properly designing chair setups in the human-hardware interfaces of computer workstations.
In accordance with ANSI/HFES 100-2007, there are four reference postures: reclined sitting, upright sitting, declined sitting, and standing. The type that most closely resembles the often-suggested posture for mitigating harm is upright sitting, which, according to the standard, keeps the user’s torso and neck approximately vertical and in line, the thighs horizontal, and the lower legs vertical. It can be between 90 and 105 degrees to the horizontal.
However, an ergonomic concept established by ANSI/HFES 100-2007 is that there is not one correct sitting posture, but multiple that adhere to ranges for positioning one’s feet, elbows, thighs, shoulders, and wrists. It is to illustrate this diversity of body positions observed at computer workstations that the standard includes four reference positions.
Regardless which reference posture chosen, ANSI/HFES 100-2007 sets forth specifications for elbow angles, shoulder abduction angles, shoulder flexion angles, wrist flexion angles, wrist extension angles, and torso-to-thigh angles to effectively and variably allow the users to adopt suitable postures. For example, elbow angles are to remain between 70 and 135 degrees, and controls and wires should not intrude into leg and foot clearance spaces.
Please note that ANSI/HFES 100-2007 covers a host of operator-machine issues associated with computer workstations used regularly in offices, and not only those associated directly with chairs. Some input devices addressed by this document include keyboards, mouse and puck devices, and visual displays.
Improving posture grants benefits beyond improvements in physical health as well. For example, there is evidence indicating that adjusting some sedentary behavior can actually help our brains function differently.