There are still many work tasks that require lifting heavy objects. While Australia’s safety regulators warn against this where there may be a risk of injury, in the “real world” there is often no alternative than to use muscle power.
Australia’s uniform OHS manual handling laws put the onus on the employer to determine if there is a risk of a worker sustaining a musculoskeletal disorder (MSD). If the manual task is hazardous, an employer must eliminate the risk or, if not feasible, reduce the risk as much as the employer can reasonably do so.
There is no mention in the law of safe lifting and little specific guidance by regulators about when lifting heavy weights may be acceptable, such as in instances where materials handling equipment is not as productive or has yet to be developed, or simply not necessary or possible in some workplaces.
In the late 20th century when back injuries were first targeted as a serious worker’s compensation problem, the nominal safe lifting weight for an “average” person was 20 kg. The impact of that can be seen now eg bulk products such as cement, are now available in 20 kg packs.
The safe limit today according to a Sydney university OHS guidance website is 16 kg. It advises that the upper limit is 55 kg but lifting any weight between 16 and 55 kg is potentially hazardous. No-one should lift anything heavier than 55 kg without a mechanical aid, it advises.
The university also quotes conventional workplace training given to workers about how to lift safely, the so-called “bend the knees and keep the back straight” rule combined with warm-up exercises to reduce the risk of injuries. While there is nothing wrong with that, regulators frown on this because it is classified as training, instruction and supervision. This measure has been proven to be one of the most unreliable and ineffective ways of reducing risk. The OHS hierarchy of risk control starts with eliminating the risk which in manual handling terms means adopting mechanical lifting aids.
The university states these are “general guidelines” that should no longer apply in workplaces under modern safety management regimes. The range of a worker’s lifting capacity varies so widely, even between two male adults of the same size and age, that setting a safe weight limit is impossible. “The emphasis now is on the need for each manual handling situation to be assessed in terms of risk, based on its individual characteristics,” the university says.
WorkSafe Victoria’s highly regarded manual handling code of practice states: “The muscular effort required to lift, lower or carry a load depends on more than just the weight of the object. It is also determined by the postures, movements, forces, frequency and duration involved in the task.
“This means that even a relatively small weight may be difficult to lift and require the application of high force. Therefore, it is difficult to specify safe maximum weights that would apply to different tasks, or even to similar tasks done under different circumstances. As muscular effort increases, more stress is placed on structures in the body such as muscles, ligaments, joints and intervertebral discs.
“The greater the effort and stress on the body, the greater the risk of MSD,” WorkSafe says.
These factors are mandated in the current OHS manual handling safety laws enforced by regulators in all states and territories for assessing risk.
While the Victorian code is old, it is still regarded as contemporary. The policy on weight is unlikely to change when the Victorian regulator releases its new statutory compliance code on manual handling later this year, following a revision of its OHS regulations including its manual handling regulations.
In making its point the old code uses the example of lifting a 4 kg load in different postures. Lifting by reaching out requires three times the effort than in an upright position where the load is close to the body. The extra distance in effect increases the weight of the object to 12 kg.
Adding the risk factors such as frequency and duration to any apparently safe lifting task may increase risk of injury.
In some of its more practical non-statutory guidance eg its recent order picking guide, WorkSafe has a risk chart showing what happens when lifting a load 60 times over a two-hour work period in two different postures. Lifting 15 kg loads over that period is unlikely to be a risk if the hands are holding the object at the waist position. But if the arms are raised to shoulder height, the work is hazardous even if the object is half the weight. This would trigger an assessment that may indicate there is a need to introduce materials handling equipment to avoid an injury.