Relatively few back injuries occur due to a single event. The conventional wisdom that workers should always bend the knees and not the back when lifting may not be correct. And those responsible for designing work should ensure that the most demanding bending loads on the low back are not undertaken shortly after rising from bed.

These are just some of the provocative propositions that participants at a major Irish national conference on work-related musculoskeletal disorders heard last summer. Organised by the Health and Safety Authority and the Irish Ergonomics Society, the conference was a forerunner to next week's European Safety Week. The Safety Week, organised by the European Agency for Safety and Health at Work based in Bilbao, Spain, focuses on musculoskeletal disorders in the workplace and aims to wake people up to the high personal and financial costs they involve.

Despite the fact that work-related musculoskeletal disorders are preventable, they are increasing among the EU's workforce. Ireland's Health and Safety Authority says that there has been a 30 per cent increase in the number of accidents reported to the Authority between 1996 and 1998, involving handling, lifting and carrying.

Musculoskeletal disorders include back pain, back injuries and work-related upper limb disorders or repetitive strain injuries. They can also affect the legs and knees, as well as the arms, shoulders, neck, wrist and elbows. They are associated with working in awkward postures or repetitive fast-paced movements, and can result in permanent disability and in loss of job or livelihood. Work-related musculoskeletal disorders account for up to 40 to 50 per cent of the economic costs of all work-related ill-health in the EU, which is between 2.6 and 3.8 per cent of the gross national product of member states.

A survey by the Dublin-based European Foundation for the Improvement of Living and Working Conditions found that 30 per cent of workers in the EU suffer from backache. Some 17 per cent have muscular pains in their arms and legs and 33 per cent are required to carry heavy loads in their work.

Musculoskeletal disorders are strongly work-related and are frequently caused by poor work systems. Physical causes include heavy loads, poor posture, highly repetitive movements, forceful hand applications, body vibrations and direct mechanical pressure on body tissues. Work environment and work organisation are other causative factors.

Risk factors include highly paced, repetitive or monotonous work, fatigue and work-related psychosocial factors. At that Irish conference last June, Prof Stuart McGill of the University of Waterloo in Canada challenged the conventional wisdom that it is always better to bend the knees and not the back - that is squat, not stoop - when lifting. Many workers prefer to stoop, perhaps because there is "an increased physiological cost in squatting". Citing recent research comparing stooping and squatting when lifting, he said it concluded that "at least in terms of low back compression", neither technique could be justified over the other.

"The case could be made that the important issue is not whether it is better to stoop lift or to squat lift, but rather the emphasis could be placed on placing the load close to the body." This is to "reduce the reaction moment" and "avoid a fully flexed spine to minimise shear loading", he said.

"In fact, sometimes it may be better to squat to achieve this, or in cases where the object is too large to fit between the knees, it may be better to stoop, flexing at the hip but always avoiding full flexion to minimise posterior ligamentous involvement."

Commenting on the daily change in spine length, he said there could be an increased risk of back injury early in the morning. Managers and people responsible for the design of work should "design jobs so that the most demanding bending loads on the low back are not conducted early in the morning or shortly after rising from bed".

The current practice, which tends to require workers and medical personnel to identify "the single cause of injury" - that is a specific event accounting for an injury - is not attuned to recent advances in the scientific understanding that "much injury is the result of cumulative trauma".

The Health and Safety Authority has prepared an information pack with practical suggestions for increasing awareness of musculoskeletal disorders at work.

jmarms@irish-times.ie