Difficulty: Beginner | Prerequisites: None
This material covers the ergonomic principles behind setting up a safe computer workstation, drawn from OSHA's Computer Workstations eTool evaluation checklist. It sits within occupational health and safety coursework and is relevant to anyone studying workplace ergonomics, human factors, or occupational health compliance. The core idea: a properly arranged workstation promotes neutral postures, which reduce the risk of musculoskeletal disorders. You do not need prior ergonomics knowledge, but a basic understanding of human anatomy (spine, joints, major muscle groups) helps.
OSHA's Computer Workstations eTool provides an evaluation checklist for setting up ergonomically sound computer workstations. The goal is to arrange every element, from chair to keyboard to monitor, so the user maintains neutral postures throughout the working day. A "no" answer to any checklist item flags a problem that needs correcting by adjusting equipment, replacing furniture, or changing work habits.
Neutral posture
A body position in which joints are naturally aligned and muscles are at their resting length, minimising stress on tendons, ligaments, and nerves. Think of it as the posture where nothing is being stretched, compressed, or twisted unnecessarily.
Lumbar support
The part of a chair's backrest that curves forward to fill the natural inward curve of the lower spine. In simple terms, it is the padding or mechanism that stops your lower back from rounding out when you sit.
Waterfall edge (seat pan)
A downward-curving front edge on a chair seat that reduces pressure on the underside of the thighs and behind the knees. Think of it as a gentle slope rather than a sharp ledge at the front of your seat.
Negative keyboard slope (negative tilt)
A keyboard position in which the back edge sits lower than the front edge, the opposite of the raised-feet arrangement most keyboards ship with. In simple terms, the keyboard tilts slightly away from you so your wrists stay flatter.
Musculoskeletal disorder (MSD)
An injury or condition affecting muscles, nerves, tendons, joints, cartilage, or spinal discs, often caused or aggravated by repetitive motions or sustained awkward postures. Think of it as the category of injuries (carpal tunnel, tendinitis, back strain) that poor workstation setup is meant to prevent.
Footrest
A stable, angled platform placed under the desk for users whose feet do not reach the floor when the chair is at the correct height. In simple terms, it brings the floor up to you when the desk cannot come down.
Bifocal / trifocal accommodation
Adjusting monitor height and tilt so that users wearing multi-focal lenses can read the screen through the correct portion of their glasses without tipping their head back. Think of it as making the monitor meet the lens, not the other way round.
Micro-break
A brief pause (30 seconds to a few minutes) during sustained computer work, used to change posture, stretch, or rest the eyes. In simple terms, a short interruption that lets muscles recover before fatigue accumulates.
The overarching principle of the OSHA workstation checklist is that every piece of equipment should be arranged so the body stays in a neutral posture. The checklist walks through the body from head to feet.
Head and neck balanced and in-line with the torso: ears sit directly above the shoulders, not craned forward or tipped back.
Head, neck, and trunk face forward, not twisted to one side to view the monitor or documents.
Torso is vertical to slightly reclined. A slight backward lean (100–110 degrees at the hip) is acceptable and can reduce spinal disc pressure.
Shoulders relaxed and not elevated (shrugged). Upper arms hang in line with the torso.
Upper arms are not elevated or stretched forward unless they are resting on a supportive work surface.
Elbows close to the body, not extended forward or flared outward, unless supported by armrests or the work surface.
Forearms approximately parallel to the floor. The angle between upper arm and forearm should be roughly 90 to 100 degrees.
Wrists and hands straight and in alignment with the forearm: no bending up, down, or sideways.
Thighs approximately parallel to the floor. Lower legs approximately perpendicular to it. A slight downward slope of the thighs (knees slightly below hips) is also acceptable.
Sufficient clearance under the work surface so thighs are not trapped between lap and desk.
Legs and feet have enough forward clearance to get close to the keyboard.
Feet rest flat on the floor, or on a stable footrest if the work surface height cannot be lowered.
Any sharp or square edges that contact hands, wrists, or forearms must be padded or rounded. Hard desk edges pressing into the underside of the wrists are a common source of nerve compression.
The chair is the single most adjustable piece of a workstation, so OSHA devotes an entire checklist section to it.
Backrest height is adjustable so lumbar support sits at the curve of the lower back.
Back should be fully supported by the chair's lumbar region. If you can fit a fist between your lower back and the backrest, the lumbar support is not doing its job.
Width: wide enough for comfortable entry and exit.
Depth: deep enough to support the full thigh, but not so deep that the user cannot engage the lumbar support (a gap of two to three fingers between the back of the knee and the seat edge is the usual test).
Front edge does not press into the back of the knees or calves. Thighs should not hang off the front edge either.
Cushioned with a rounded "waterfall" front edge to prevent pressure points behind the knees.
Height is adjustable and allows alignment with the work surface: feet flat on the floor, thighs parallel to it.
If used, armrests should be adjustable in height and width (up/down and in/out).
They support forearms during computer tasks without forcing the shoulders to shrug.
They must not prevent the chair from rolling under the work surface.
Five-leg base for stability (four-leg bases tip more easily).
Casters matched to the floor surface: soft casters for hard floors (so the chair does not roll away), hard casters for carpet.
If provided, the head rest is adjustable and does not push the head forward past neutral alignment.
All adjustments should be straightforward and possible to perform while seated. If a user has to stand up and flip the chair over to change the height, they are unlikely to adjust it regularly.
This section covers the keyboard, mouse, trackball, touch pen, roller mouse, joystick, and touchscreen.
The keyboard/input device platform must be stable and large enough to hold both the keyboard and the pointing device.
Platform height adjustable so hands rest over the keyboard with elbows at 90 to 100 degrees and close to the torso.
Keyboard set to a horizontal or slightly negative slope (back edge lower than front edge). The raised keyboard feet that tilt the back up actually increase wrist extension and are generally discouraged.
Mouse or trackball located immediately next to the keyboard, not on a separate surface that forces reaching.
Input device positioned as close to the midline of the body as possible, at the same level as the keyboard. A number pad can push the mouse further to the right; a compact or tenkeyless keyboard helps.
Input device fits the hand (not too large, not too small) and is easy to activate. Having an ambidextrous device, or one for each hand, lets the user alternate and distribute the workload.
If a touchscreen device is used for data input for more than two hours per day or 30 minutes at a stretch, a detached keyboard and mouse should be available. Extended touchscreen use forces the arm into sustained elevation.
No sharp or hard edges should contact wrists or hands. Wrist rests, if provided, should be padded and free of square edges, and their height should match the front edge of the keyboard.
Students often think raising the keyboard feet (positive tilt) is correct because keyboards ship that way. It is not. A flat or slightly negative tilt keeps the wrists in a more neutral position.
Students often assume a deeper seat pan is always better because it supports more of the thigh. In fact, a seat pan that is too deep prevents the user from sitting back far enough to use the lumbar support.
Students sometimes believe armrests should be used at all times. If armrests elevate the shoulders or prevent the chair from fitting under the desk, they should be lowered, adjusted inward, or removed.
Students frequently confuse "90-degree elbow angle" with a rigid rule. The OSHA checklist specifies 90 to 100 degrees, and a slightly open angle (closer to 100) is often more comfortable for sustained typing.
⚠️ The 90-to-100-degree elbow angle and parallel-forearms rule appears across multiple checklist sections (workstation, seating, keyboard). Expect it to be tested.
⚠️ "Neutral posture" is the single most important concept in this material. Be ready to define it and identify deviations from it in a scenario question.
⚠️ The five-leg base requirement for chairs is a specific, testable detail that students overlook.
⚠️ Negative keyboard slope versus positive tilt is a common exam question because the intuitive answer (tilt back) is wrong.
⚠️ Seat pan depth and its relationship to lumbar support is a frequently tested trade-off: too deep and you lose back support, too shallow and thighs hang off the front.
⚠️ Know the touchscreen threshold: more than 2 hours per day or 30 minutes at a time triggers the need for a detached keyboard and mouse.
True or false: The ideal keyboard position tilts the back edge upward (positive slope).
Fill in the blank: The angle between the upper arm and forearm at the elbow should be approximately ______ to ______ degrees.
True or false: A four-leg chair base is acceptable if the chair has locking casters.
Fill in the blank: If a touchscreen is used for data input for more than ______ hours per day, a detached keyboard and mouse should be available.
True or false: A seat pan should be as deep as possible to maximise thigh support.
Answers: 1. False (flat or slightly negative slope). 2. 90 to 100. 3. False (five-leg base required). 4. Two. 5. False (too deep prevents use of lumbar support).
Q: A worker complains of tingling in their wrists after long typing sessions. Their keyboard is tilted with the back edge raised, and the desk edge is sharp and unpadded. Identify two ergonomic problems and suggest corrections.
A: First, the keyboard has a positive tilt, which increases wrist extension. It should be set flat or at a slight negative slope. Second, the sharp desk edge is compressing nerves and tendons in the wrist. The edge should be padded or rounded, or a wrist rest should be placed in front of the keyboard.
Q: An employee's chair has a seat pan so deep that they cannot sit all the way back. What ergonomic consequence does this create, and how should it be corrected?
A: The user cannot engage the chair's lumbar support, which means the lower back is unsupported and likely rounds forward. The seat pan depth should be reduced (swap the chair for one with a shorter seat pan, or use a lumbar cushion to bring the support forward).
Q: Why does OSHA recommend a five-leg base for office chairs rather than a four-leg base?
A: A five-leg base distributes weight more evenly and is significantly more resistant to tipping, particularly when the user leans or reaches to the side.
Q: A worker places their mouse on a separate surface to the right of the keyboard, about 30 cm away. What risk does this create?
A: The user must reach and extend the arm away from the body to operate the mouse, which elevates the shoulder and abducts the arm. Over time this can cause shoulder and upper-back strain. The mouse should be placed immediately beside the keyboard, as close to the body's midline as possible.
Q: Under what circumstances does OSHA recommend providing a footrest?
A: When the work surface height cannot be lowered and the user's feet do not rest flat on the floor at the correct chair height. The footrest should be stable, angled, and large enough to support both feet.
This material connects directly to musculoskeletal disorder (MSD) prevention, the broader goal behind every checklist item. If your course covers injury statistics or workers' compensation, the workstation evaluation is the preventive side of that same coin.
It also links to human factors and anthropometry: the reason every dimension (seat depth, monitor distance, elbow angle) is given as a range rather than a fixed number is that bodies vary, and workstation design must accommodate that variation.
Part 2 of these study notes covers monitors, mobile devices, accessories, and general workplace concepts from the same OSHA checklist.
OSHA computer workstation, ergonomic evaluation checklist, neutral posture, lumbar support, waterfall seat edge, negative keyboard tilt, musculoskeletal disorder, MSD prevention, workstation ergonomics, chair evaluation, seat pan depth, five-leg base, 90-degree elbow rule, forearm parallel to floor, wrist alignment, footrest, keyboard input device, mouse placement, touchscreen ergonomics, occupational health, workplace safety, computer workstation eTool