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Ergonomics in the workplace (Part One)
Identifying manual handling hazards
This bulletin provides an overview of musculoskeletal injury (MSI) hazards associated with manual handling tasks, with information on contributing factors, required controls and best practices. It is part of the Ergonomics in the workplace series that focus on applying ergonomics to meet Alberta’s occupational health and safety (OHS) requirements.
Manual handling is a common task in the workplace and includes lifting, lowering, pushing, pulling and carrying. There are three primary hazards that can contribute to injury during manual handling:
3 Primary Hazards of manual handling
Having one or more of these hazards present during a manual handling task can increase a worker’s risk for MSIs (also known as musculoskeletal disorders and repetitive strain injuries).
For more details on these hazards, refer to Ergonomics in the workplace: Identifying and controlling MSI hazards.
Awkward or heavy loads
Heavy or awkward loads include equipment, goods, supplies, persons and animals. There is not a specific safe weight limit because many factors can impact how safe a weight is.
For help in determining if the weight of an object being lifted is within a reasonable limit, refer to the lifting assessment tool on page six of this bulletin.
Consider the following when assessing manual handling hazards.
It is the employer’s responsibility to assess the hazards of a manual handling task and control them appropriately.
Before a worker manually lifts, lowers, pushes, pulls, carries, handles or transports a load that could injure the worker, the Alberta OHS Code requires the employer to perform a hazard assessment that considers:
- the weight, size, and shape of the load,
- the number of times the load will be moved, and
- the manner in which the load will be moved.
Workers must also be involved in the hazard assessment.
Heavy loads can increase the chance of overexertion injury, particularly in the back and upper limbs. To determine if a load is within a recommended weight limit refer to the lifting assessment tool on page six of this bulletin.
Loads that are the same weight may have different hazard levels due to their size. Larger loads are difficult to keep close to the body’s centre, increasing the likelihood of awkward postures and stress on the lower back and arms. In pushing and pulling tasks, the load should be a size that the worker can control (e.g. carts should not be loaded so high that the worker’s line of sight is blocked).
Centre of mass
The centre of mass of a load may shift during transport (e.g. people, animals, liquid in containers, etc.). The weight distribution of a load can also impact how much weight a worker can safely lift.
The shape of a load can affect the weight distribution and create an imbalance of effort between the muscles used when lifting.
A load with sharp edges can be difficult to grasp and may result in awkward postures to avoid the sharp edges.
Loads with no handles or unevenly distributed handles require increased grip strength and muscle effort.
The more frequent the lift, the greater the total effort required by the body. Consider how many times a minute, hour or day the load is moved, and the total duration of the activity.
Consider whether there is a long enough rest time between lifts to allow muscles to recover.
How the load is moved
The way a load is moved can affect posture and how the muscles are used. Consider if the load will be lifted, lowered, pushed or carried.
Body movement and position relative to the load
The start and end location of the load can impact a worker’s posture during manual handling tasks. Consider how high and far a worker will need to reach.
The farther the load is away from the body, the more effort required, placing more stress on the back and upper limbs.
Consider what mechanical aids are available to assist with the task. The wrong equipment or poorly maintained equipment may contribute to MSIs.
Personal characteristics such as a person’s age, pre-existing injury or medical conditions, fitness level, experience and skill can affect how much a person can safely lift.
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