Liberty Mutual — Manual Handling Tables (Snook)
A psychophysical design reference for the safety of manual handling tasks — including pushing, pulling, and carrying alongside lifting and lowering.
What is Liberty Mutual?
The Snook (Liberty Mutual) tables are based on extensive psychophysical testing to determine what forces and weights are acceptable to defined percentages of the working population. The standard design target is a task acceptable to at least 75% of the female population, which automatically protects over 90% of male workers.
When to use Liberty Mutual
Deploy when assessing manual handling that includes significant horizontal pushing and pulling forces (such as moving carts), or when designing jobs specifically to accommodate a diverse-gender workforce.
Primary citation: Snook, S.H. & Ciriello, V.M. (1991). The design of manual handling tasks: revised tables of maximum acceptable weights and forces. Ergonomics, 34(9), 1197–1213.
What Liberty Mutual assesses
The body segments and task variables evaluated in a Liberty Mutual assessment.
What it assesses
- Initial force to start movement vs sustained force to keep moving
- Hand distance from the body
- Lift / lower vertical zones
- Task frequency and travel distance
Scoring and action levels
Final score range: Population acceptability (% of workers)
Developed by: Snook & Ciriello, Liberty Mutual
Liberty Mutual is coming to Ergocure.ai
Liberty Mutual is part of our validated method roadmap. Our engine adds new methods on shared infrastructure — when Liberty Mutualgoes live it will run from the same on-device capture and certified-ergonomist review as our live methods. In the meantime, tell us your environment and we'll map the live methods that fit today.
Related assessment methods
Methods commonly used alongside Liberty Mutual in a complete ergonomic assessment.
Be first to know when Liberty Mutual lands
Liberty Mutual is on our roadmap. Request a pilot of our live methods today, and we'll flag Liberty Mutual the moment it goes live.