5.6 Controls, Human Performance, and Evaluation

Choosing Controls That Actually Change The Work

The hierarchy of controls applies directly to ergonomics. Elimination removes an unnecessary manual-handling step. Substitution uses a lighter component, smaller package, or less forceful process. Engineering controls include lift assists, adjustable stations, conveyors, fixtures, tool balancers, better handles, automation, and layout changes. Administrative controls and training can help but are weaker alone, and PPE is the last resort. The most-tested principle: a stronger control changes the physical demand of the task; a weaker control depends on worker behavior while the exposure remains.

Tie each control to the risk factor it targets:

BCSP also lists modern work-practice controls such as exoskeletons, job rotation, and early-symptom intervention. Treat an exoskeleton as an engineering-adjacent aid that offloads specific demand (e.g., overhead or back) — useful, but it must be matched to the actual risk factor and verified in use, not bought as a blanket fix.

Human Performance And Error

Human performance belongs in ergonomics because people work within limits. Fatigue, pace pressure, poor visibility, confusing or identical controls, awkward access, staffing shortages, and long duration raise both physical strain and error likelihood. A task that looks safe in a short demonstration can become risky during a peak run or after several hours without recovery.

When the exam shows a worker error after a hard shift, the narrow answer blames attention. The stronger answer asks whether the task design made the error likely: hard-to-read labels, look-alike controls, awkward reach, time pressure, excessive force, or poor feedback. Ergonomic thinking and human-factors thinking both look for the system conditions that shape behavior — consistent with the system-safety logic elsewhere on the ASP exam.

Designing Administrative Controls Well

Administrative controls need careful design:

• Job rotation must move workers among tasks that load different body regions — rotating among three jobs that all load the same shoulder achieves nothing.
• Breaks/micro-pauses must be realistic for the production system, not theoretical.
• Staffing changes must not simply spread an excessive exposure across more people without planning a durable engineering fix.

Evaluation Closes The Loop

Finally, evaluate. Confirm the control was installed, workers were trained, supervisors support it, maintenance owns upkeep, and exposure actually fell. Useful metrics include symptom trends, discomfort surveys, REBA/RULA observation scores, equipment-use rates, near misses, first-aid patterns, quality data, and worker feedback. For ASP strategy, prefer answers that define the risk, select a matched control, and verify effectiveness, and be skeptical of answers that rely only on awareness, discipline, or personal toughness.

Human Performance: Workload, Fatigue, And Error Modes

Human-factors content on the ASP draws on classic principles. Cognitive workload has a sweet spot: too much demand causes errors and shortcuts, while too little causes vigilance loss on monitoring tasks. Fatigue accumulates over a shift and is worse on the circadian low of night work (roughly 0200–0600), so error-likely and high-force tasks should not be scheduled when alertness is lowest.

Designers reduce error by applying mistake-proofing (poka-yoke) — connectors that fit only one way, interlocks, and forcing functions — and by following population stereotypes (up means on, clockwise means increase, red means stop) so a stressed operator's expectation matches reality.

Cost-Justifying The Control

The ASP also expects you to speak the language of management. Ergonomic fixes are justified with the same cost-benefit and payback logic used elsewhere on the exam: estimate the direct and indirect cost of MSDs (medical, indemnity, lost time, replacement labor, rework, turnover), compare it with the installed cost of the control, and compute a simple payback period. A lift table that prevents one serious back claim usually pays back in months, which is why engineering controls are defensible even when they look expensive next to a free 'lift safely' poster.

Framing the recommendation as a return on investment, not just a safety preference, is often the discriminator between two otherwise reasonable exam options.

Closing The Loop

The full cycle — identify, assess, control by hierarchy, and verify with leading and lagging indicators — is the backbone of every ergonomics question. When two answers both 'fix' the problem, pick the one that changes the task and proves the change worked, and reject the one that depends on the worker simply trying harder.