D. Topics in Computer Science · Topics in Computer Science: Sustainability, Ethics, Emerging Technologies and Careers

Healthy Computing: Ergonomic Standards and Workplace Rules

D1.1About 65 minutes

Learning goals

I can explain how laws, standards and policies protect the health of people who use computers at work in Ontario.
I can apply the hierarchy of controls to reduce musculoskeletal risks in computer work.
I can explain why ergonomic design uses adjustability and check a design against a range of users in Python.
I can describe software design choices that support or harm users' health.

Words to know

ergonomic standard
A published set of requirements and guidance for designing work to fit people, such as CSA Z412 for offices.

musculoskeletal disorder (MSD)
An injury or pain in muscles, tendons, nerves or joints, often linked to force, awkward posture and repetition.

hierarchy of controls
A ranking of ways to reduce a hazard, from eliminating it (most effective) to personal equipment (least effective).

engineering control
A change to the physical workplace or equipment that reduces a hazard, such as an adjustable desk.

administrative control
A change to how work is organized, such as break schedules, task rotation or training.

anthropometric data
Measurements of human bodies (heights, reaches) used in design.

electronic monitoring
An employer's use of technology to track employees' activity, location or communications.

From "sit up straight" to "design it right"

In Grade 11 (ICS3U, Computers and Your Health) you learned the health risks of heavy computer use and how to set up your own workstation: elbows about 90°, wrists straight, monitor about an arm's length away with the top at or slightly below eye level, breaks, and the 20-20-20 rule. That is the individual level.

Expectation D1.1 asks for strategies that reduce the impact of computers on human health, and gives ergonomic standards as an example. At work, health is not left to each person's memory. It is built into laws, standards, policies and design. This lesson looks at computer health the way an employer, a health and safety committee or a software designer does.

The legal and standards framework in Ontario

Ontario's Occupational Health and Safety Act (OHSA) requires employers to take every precaution reasonable in the circumstances to protect workers. Musculoskeletal disorders (MSDs) from computer work are one of the hazards employers must deal with.
CSA Z412, Office ergonomics, published by the CSA Group, is a Canadian standard that organizations use to design workstations and run ergonomics programs. A standard is a published set of requirements and guidance; it becomes legally required when a law or a contract refers to it, and it is widely used as a benchmark of good practice even when it is not.
Joint health and safety committees, made up of worker and employer members, are required at many Ontario workplaces and help identify hazards, including ergonomic ones.
Ontario's Employment Standards Act, 2000 was amended in 2021 and 2022: employers with 25 or more employees must have a written policy on disconnecting from work (required since June 2, 2022) and a written policy on electronic monitoring of employees (required since October 11, 2022). The disconnecting policy is a requirement to have a policy; it did not create a new legal right to ignore work messages.

Ergonomists usually name three physical risk factors for MSDs: force, awkward or fixed postures, and repetition. The longer and more often someone is exposed, the higher the risk.

The hierarchy of controls

Health and safety professionals rank solutions by how well they work. Controls near the top remove the hazard for everyone. Controls near the bottom depend on each person doing the right thing every day, so they are weaker on their own (but still useful together with stronger controls).

The hierarchy of controls: start at the top. A schedule of breaks helps, but automating a repetitive task removes the hazard.

Worked example

Example 1: Choosing controls for a help desk

A help-desk team of 12 types tickets for 7 hours a day at fixed-height desks. Three workers report wrist pain. Recommend controls from at least three levels of the hierarchy and say which you would do first.

Elimination/substitution: add ticket templates, auto-filled fields and keyboard shortcuts so far fewer keystrokes are needed; offer speech-to-text.
Engineering: height-adjustable desks and chairs, monitor arms, and keyboards and mice positioned at elbow height.
Administrative: micro-breaks (for example a short break each hour), task rotation between phone and typing work, ergonomics training using CSA Z412 guidance, and an easy way to report symptoms early.
Personal: footrests or other accessories after an individual assessment.
The three workers in pain should be referred for an individual ergonomic assessment and medical advice right away.

Start with the controls that reduce repetition for everyone (templates and shortcuts) and adjustable furniture, then add breaks, rotation and training. Refer the workers with pain for assessment immediately.

Designing for a range of people

People differ in height, reach and vision, so a workstation that fits one person can hurt another. Ergonomic design uses adjustability: furniture and equipment should adjust over the range that covers the people who will use it. Designers check measurements (anthropometric data) for the expected users and make sure the adjustment range covers them, often from a small person to a large one rather than only the "average" person, who may not exist.

The same idea appears in software: text size settings, high-contrast themes and keyboard navigation let one product fit many users, including people with low vision or limited hand mobility.

Example values for a group of users. Desk A's range (yellow) does not cover the users' range (blue), so some users will work with raised shoulders or bent wrists.

def covers(device_min, device_max, users):

too_low = [u for u in users if u < device_min]

too_high = [u for u in users if u > device_max]

return too_low, too_high

elbow_heights = [63, 66, 68, 70, 71, 72, 74, 76]

for name, lo, hi in [("Desk A", 68, 74), ("Desk B", 60, 78)]:

low, high = covers(lo, hi, elbow_heights)

ok = "fits everyone" if not low and not high else f"misses {low + high}"

print(f"{name} ({lo}-{hi} cm): {ok}")

List comprehensions find the users outside each desk's adjustment range (example values).

Desk A (68-74 cm): misses [63, 66, 76]

Desk B (60-78 cm): fits everyone

Output of the program above (what Python prints).

Software can protect health too

Programmers shape how people use devices:

Break reminders and screen-time summaries help people notice long sessions.
Night modes and do-not-disturb schedules support sleep; work tools can delay sending messages until working hours, which supports a disconnecting-from-work policy.
Designers can avoid attention traps such as endless feeds and streaks that pressure people to keep using an app. Designing to keep people hooked against their own interests is an ethical issue you will meet again in the lessons on ethics in this unit.
Accessibility features (resizable text, captions, keyboard control) reduce strain for everyone and are essential for many users.

Just for fun

"Ergonomics" comes from the Greek words ergon (work) and nomos (law), so it means "the laws of work".

Which makes a chair set to the wrong height a tiny, padded lawbreaker.

Hands-on activity

Ergonomic assessment of a home workstation

You need: a measuring tape, paper, the place where you usually use a computer, and a family member to help.

Sit as you normally do. Have your helper measure (in cm) the height of your elbow from the floor while your arm hangs relaxed and bent about 90°, and the height of the keyboard surface.
Measure the distance from your eyes to the screen and note whether the top of the screen is above, at or below eye level.
Score each risk factor (force, awkward posture, repetition) as low, medium or high for your usual session, with a reason.
Recommend one control from three different levels of the hierarchy of controls. Explain why the higher-level control is better.
Ask your helper to try your workstation. Does it fit them? What would need to be adjustable?

What to look for: measurements recorded with units, a reasoned risk rating, controls correctly placed in the hierarchy, and recognition that a shared workstation must adjust to fit different people. Anyone with ongoing pain should see a doctor or physiotherapist.

Your turn

Name the three physical risk factors for MSDs that ergonomists usually identify.

What is CSA Z412?

List the five levels of the hierarchy of controls from most to least effective.

Classify: (a) a height-adjustable desk; (b) a rule to take a short break every hour; (c) automating a copy-and-paste task.

What two written policies must Ontario employers with 25 or more employees have under the Employment Standards Act?

Why are administrative controls weaker than engineering controls?

Give one software feature that supports users' health.

More practice: warm-up

What does MSD stand for?

Which Ontario law requires employers to protect workers' health and safety?

Which is higher in the hierarchy: substitution or personal equipment?

In the code, what does covers(68, 74, [63, 70, 76]) return?

Why should a workstation used by several people be adjustable?

More practice: on your own

A school lab has fixed desks at 72 cm. Using the example elbow heights [63, 66, 68, 70, 71, 72, 74, 76], a desk height within 3 cm of a student's elbow height counts as a fit. Which students fit? Suggest an engineering control for the rest.

Does Ontario's disconnecting-from-work policy requirement mean employees can never be contacted after hours? Explain.

An app shows an endless feed and sends a notification whenever a user hasn't opened it for a day. Explain the health concern and suggest a design change.

A worker uses a laptop on a couch for 6 hours a day. Identify two risk factors and one control at each of two different levels.

Why is designing for the 'average' user not enough?

Challenge

Write a function fit_report(lo, hi, users) that returns the percentage of users whose elbow height is within the desk's range, rounded to one decimal. What does it return for Desk A (68 to 74) and the example users?

A company argues: "We bought everyone wrist rests, so our ergonomics problem is solved." Evaluate this claim using the hierarchy of controls.

Electronic monitoring software records keystrokes per hour. Explain one way it could harm health and one way it could, if used carefully, help. What should a fair electronic monitoring policy say?

Check your understanding

Quiz

Which control is at the highest level of the hierarchy of controls?

What is CSA Z412?

Ontario employers with 25 or more employees must have which written policy?

A height-adjustable desk is an example of which kind of control?

Why does good ergonomic design use adjustability?

Which is not one of the three physical MSD risk factors named in this lesson?

For parents and teachers

Big idea: D1.1 asks for strategies that reduce computers' impact on human health, such as ergonomic standards. Grade 11 covered personal workstation habits; this lesson moves to workplace systems: Ontario law, CSA Z412, the hierarchy of controls, and design for a range of users.

How to help: Do the measuring activity together and swap roles so your teen sees that one setup doesn't fit everyone. If you work at a computer, describe your workplace's ergonomics program or policies (or lack of them) and let your teen rank the controls.

Common difficulties:

Mixing up engineering controls (change the equipment) and administrative controls (change the rules or schedule).
Thinking personal equipment like wrist rests solves the problem; it is the weakest level.
Overstating Ontario's disconnecting-from-work rule: it requires a written policy, not a right to ignore all contact.
The elbow heights in the lesson are example values for practice, not real population data.

If your teen has ongoing pain, tingling or numbness from computer use, see a doctor or physiotherapist.