Tracing the Source: OaSIS Physical Strength Ratings and the Matheson PDC
February 26, 2026
Published by Heather Mallard, BA, CVRP-TSA, ICVE, CCVE, RVP | HM Vocational
Introduction
Most Canadian vocational evaluators are familiar with OaSIS — the Occupational and Skills Information System developed by Employment and Social Development Canada (ESDC) — as the primary source for occupational profiles and descriptor data. It is widely used in transferable skills analyses, functional capacity comparisons, and employability reports across the country.
What is less commonly discussed is where OaSIS physical strength ratings actually come from — and how far back the lineage of those ratings goes. Understanding this connection does more than satisfy professional curiosity. It changes how you interpret, apply, and defend physical demand data in a vocational report.
The Lineage: From DOT to Matheson to O*NET to OaSIS
The physical demand categories used in Canadian vocational practice today do not originate with OaSIS. They trace back considerably further — to the U.S. Dictionary of Occupational Titles (DOT), the foundational American occupational classification system that defined and categorized work demands for decades.
In 1993, vocational rehabilitation specialist Leonard Matheson formalized a Physical Demand Characteristics (PDC) framework that operationalized those DOT strength categories into five clearly defined classifications: Sedentary, Light, Medium, Heavy, and Very Heavy. Each classification was anchored to specific weight thresholds, frequency of exertion, and metabolic energy demands — expressed as Metabolic Equivalents of Task (METs). This framework became the standard reference tool for physical demands analysis in functional capacity evaluation and vocational rehabilitation practice, and it remains widely used today.
The DOT was eventually replaced by O*NET — a modernized, continuously updated occupational database developed by the U.S. Department of Labor. Rather than abandoning the foundational physical demand structure, O*NET carried it forward, expressing strength demands on a numerical proficiency scale rather than categorical labels.
Canada subsequently adapted O*NET into OaSIS, converting O*NET's proficiency data into a 0–5 scale for use within the Canadian National Occupational Classification (NOC) system. The result is a Canadian occupational database whose physical strength ratings are directly traceable to the same foundational source data as the Matheson PDC.
Why This Connection Matters
The relationship between OaSIS and the Matheson PDC is not approximate or coincidental. The OaSIS Static Strength descriptor uses the Matheson Physical Demands table directly as its measurement reference — meaning that when an occupation is assigned a Static Strength rating in OaSIS, that rating is grounded in the same weight, frequency, and energy thresholds established by Matheson in 1993.
This has meaningful implications for vocational evaluators. When you cite an OaSIS strength level in a report, you are not simply referencing a government database entry. You are citing a rating that connects back to a well-established, clinically applied framework with decades of use in functional capacity evaluation, disability management, and medico-legal practice. That traceability strengthens the defensibility of your opinion — whether you are writing for WSIB, an insurance company, or a legal proceeding.
The Four Physical Strength Abilities in OaSIS
OaSIS measures four distinct physical strength abilities, each capturing a different dimension of physical demand:
Static Strength
The ability to exert muscle force to lift, push, pull, carry, or transfer objects. This is the primary strength descriptor directly rated against Matheson weight and frequency thresholds. It is the most commonly referenced strength ability in vocational evaluation and physical demands analysis.
Dynamic Strength
The ability to exert muscle force repeatedly or continuously over time. This descriptor measures muscular endurance and resistance to fatigue — not how heavy an object is, but how long or how often force must be sustained throughout a workday.
Trunk Strength
The ability to use abdominal and lower back muscles to support part of the body repeatedly or continuously over time without giving out or fatiguing. This descriptor is particularly relevant in occupations that require prolonged bending, reaching, or sustained postures without core support.
Explosive Strength
The ability to use short bursts of muscle force to propel oneself, throw an object, or apply sudden force with a tool. This descriptor captures ballistic, high-intensity effort rather than sustained exertion, and is most relevant in physically demanding occupations requiring sudden or reactive movement.
Applying This in Practice: A Level 3 Example
To illustrate how this crosswalk works in practice, consider an occupation rated at OaSIS Static Strength Level 3. This maps directly to Medium work on the Matheson PDC — meaning the occupation may require:
Lifting up to 50 lbs occasionally (0–33.33% of the workday / 0–2.5 hours / 0–150 minutes)
Lifting up to 20 lbs frequently (33.33–66.67% of the workday / 2.5–5 hours / 150–300 minutes)
Lifting up to 10 lbs constantly (66.67–100% of the workday / 5–7.5 hours / 300–450 minutes)
Occupations rated at this level in the Canadian classification system include animal health technologists and veterinary technicians, store shelf stockers and order fillers, couriers and messengers, firefighters, and massage therapists — roles that share a common thread of sustained or repeated physical effort across a standard workday.
Being able to articulate not just the OaSIS level but what it means in terms of weight, frequency, and time provides a more complete and defensible physical demands opinion.
A Note on Metabolic Equivalents (METs)
The Matheson PDC also incorporates METs — Metabolic Equivalents of Task — as a secondary measurement indicator for Static Strength. One MET represents the baseline energy expenditure at rest (approximately 3.5 mL of oxygen per kilogram of body weight per minute). All physical activities are expressed as multiples of this baseline, allowing evaluators to describe the cardiovascular and metabolic demands of work in objective, standardized terms.
| OaSIS Level | Matheson PDC | Occasional (0–33.33%) | Frequent (33.33–66.67%) | Constant (66.67–100%) | Typical METs |
|---|---|---|---|---|---|
| 0 | Not Applicable | N/A | N/A | N/A | N/A |
| 1 | Sedentary | Up to 10 lbs | Negligible | Negligible | 1.5–2.1 |
| 2 | Light | Up to 20 lbs | Up to 10 lbs | Negligible | 2.2–3.5 |
| 3 | Medium | 20–50 lbs | 10–20 lbs | Up to 10 lbs | 3.6–6.3 |
| 4 | Heavy | 50–100 lbs | 20–50 lbs | 10–20 lbs | 6.4–7.5 |
| 5 | Very Heavy | Over 100 lbs | Over 50 lbs | Over 20 lbs | Over 7.5 |
Coming Soon: Free Practitioner Reference Guide
A free practitioner reference guide covering this full crosswalk — including all four strength type definitions, the complete OaSIS-to-Matheson table, and workday frequency breakdowns in hours and minutes — is currently in development at HM Vocational.
Follow HM Vocational on LinkedIn or visit hmvocational.ca to be notified when it is available for download.
Heather Mallard, BA, CVRP-TSA, ICVE, CCVE, RVP is an independent vocational evaluator based in Ontario, Canada. HM Vocational provides vocational evaluation, transferable skills analysis, earning capacity assessments, and forensic vocational reports for insurance, legal, and rehabilitation referral sources.
This article is intended as a practitioner resource for educational purposes. It draws on publicly available occupational classification data and established vocational rehabilitation frameworks. It is not an official publication of ESDC, CAVEWAS, or any credentialing body.
