It applies ISO 7933:2023 (Predicted Heat Strain), AS 4967:2019, and AS/NZS 4824:2021 to model how thermal load, physical exertion, and cognitive demand combine to produce fatigue risk in a specific operational role, then uses that model to design roster and control measures calibrated to the real work rather than a generic shift-pattern.
Why physiology, not just scheduling
Fatigue is a physiological state, not just a function of hours worked. Two roles with identical rostering can carry very different fatigue risk if one involves sustained heat exposure or physical exertion and the other doesn't. Commercial fatigue-scoring tools are built to assess roster patterns at scale across many industries, which makes them fast to deploy but blind to role-specific physiological load. OHP's approach starts from the opposite direction: model what the body and cognitive system are actually being asked to sustain, then assess the roster against that.
The standards behind the model
ISO 7933:2023 (Predicted Heat Strain) provides the heat-balance structure OHP uses to model thermal load on the body during physical work, the same standard used internationally in occupational heat-stress assessment.
AS 4967:2019 and AS/NZS 4824:2021 cover personal protective ensemble classification, relevant wherever protective clothing or equipment adds thermal or physical burden to a role, common across defence, emergency services, and resources-sector frontline work.
This methodology draws directly on Anthony Walker's PhD research in thermal and occupational physiology, which forms part of the validation basis for how OHP models heat and physical load in fatigue risk assessment. Anthony's broader research record, 37 published outputs and nearly 600 citations (Google Scholar), sits alongside 15 years of operational firefighting experience with ACT Fire and Rescue, including station officer command.
How this shows up in an engagement
The methodology is built into every stage of The Crucible Method. In Scan, physiological demand modelling identifies which shifts or roles carry fatigue risk that standard roster metrics would miss. In Sprint, that modelling informs the specific control measures designed. In Build, the physiological model becomes part of the standing governance framework, so reassessment stays grounded in actual role demand as operations change.
Frequently asked questions
What standards does OHP use to assess fatigue risk?
ISO 7933:2023 for heat-strain modelling, and AS 4967:2019 and AS/NZS 4824:2021 for personal protective ensemble classification where equipment or clothing adds thermal or physical load to a role.
Why does physiological modelling matter for fatigue risk management?
Because fatigue risk depends on what a role actually demands physically and cognitively, not just the hours in a roster. Generic fatigue-scoring tools miss role-specific load, which can under-control risk in physically or thermally demanding frontline work.
What is OHP's research background in this area?
OHP's founder holds a PhD in thermal and occupational physiology, with a peer-reviewed research record of 37 outputs and nearly 600 citations (Google Scholar), combined with 15 years of operational command experience in emergency services.
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