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It is probably fair to say that every worker who lifts or does other manual handling tasks is at some risk for musculoskeletal injury. Low back injury is the most likely kind of injury. The complete elimination of this risk is not realistic. However, organizations can reduce the number and the severity of manual handling-related injuries by using safe work practices.
To prevent occupational back injuries, it is essential to identify the factors of MMH that make the worker more susceptible to injury or that directly contribute to injury.
When efforts to prevent injuries from MMH focus on only one risk factor, they do not significantly reduce the injury rate. A more successful approach combines knowledge of ergonomics, engineering, the work environment, and human capabilities and limitations. The following aspects should be considered:
The design or redesign of jobs involving MMH should be approached in the following stages:
Consider using powered or mechanical handling systems if eliminating the MMH tasks completely is not possible. Mechanical aids lower the risk for back injury by reducing the worker's physical effort required to handle heavy objects.
Manual handling such as lifting and carrying can be easier and safer if mechanized by using lift tables, conveyors, yokes or trucks. Gravity dumps and chutes can help in disposing of materials. However, it is essential that the worker is properly educated and trained in the safe use of the available equipment.
Where possible, use mechanical aids. The next step is to decrease the manual material handling demands. There are several ways to achieve this:
It is important that the design of MMH allows the worker to do tasks without excessive reaching, bending, and twisting. These body motions are particularly dangerous and can cause back injury even when not combined with handling loads.
Pace of work, particularly when externally imposed, may significantly contribute to the worker discomfort, and consequently to the onset of musculoskeletal injuries. Generally speaking, pressure to work at a certain pace creates the mental need to work in a hurry. This perception, in turn, creates tension not only in the mind but also in the body. Tensed muscles are much more prone to injury.
For example, pace of work is related to the frequency of a lift. Lifting equations, such as the Revised NIOSH Lifting Equation, use this factor as one of the ways to determine the impact of a lift. Assessments include not just how many lifts are preformed, but the amount of time there is to rest between lifts.
It would be ideal if workers could work at their own pace and have some freedom to take a rest break when they start feeling the effects of fatigue. However, this option might be impractical. It seems reasonable to incorporate two additional 15-minute breaks, mid-morning and mid-afternoon, in addition to the 30-minute lunch break. If that schedule is still not feasible, shorter but more frequent breaks can do as well.
It is also important that people new to a particular job or task be given time to adjust by allowing them more breaks.
The design of the work environment is an important element for back injury prevention.
When the MMH tasks are done outdoors, the temperature conditions including the humidex (in hot weather) or wind-chill factor (in cold weather) have to be monitored very closely.
More details about working and doing MMH activities in hot and cold environments are available in CCOHS publications Groundskeepers Safety Guide, Working in Hot Environments, and Cold Weather Worker's Safety Guide.
The objective of pre-placement screening is to try to determine if an individual is likely to be injured by activities of their work. There is limited research available to help determine the effectiveness of these measures. In general, it appears that the screening is more accurate when job specific tasks can be included and/or evaluated.
When combined with work design, education and training are an important element in the prevention of injuries. Part of this education and training also includes showing the worker how to actively contribute to the prevention of injuries. A program should:
Instruction on how to lift "properly" can be a controversial issue. While there are good guidelines there is no single correct way to perform a lift. Because of this fact, on-site, task specific training is essential. Some general lifting rules include:
It is also important that workers:
Finally, there is an aspect of training that cannot be overlooked if training is to be part of an effective prevention program.
Workers should be educated that muscles, tendons and ligaments are not prepared to meet the physical stress of handling tasks when they are not "warmed up." Pulls, tears or cramps are more likely when stretched or contracted suddenly under such conditions. These injuries can lead to more serious and permanent injury if physically stressful work is continued. Warming up and mental readiness for physically demanding tasks are important for any kind of MMH, but particularly for occasional tasks where the worker is not accustomed to handling loads.