10.2 Musculoskeletal Hazards: Manual Handling and Ergonomics on Construction Sites

Why musculoskeletal health is on the SSS syllabus

Construction work involves heavy, awkward loads (blocks, cement bags, rebar, formwork panels, pipes, kerbs), repetitive tasks (tying rebar, laying tiles, plastering), work above the shoulders or at floor level, vibrating tools, and heat. The result is musculoskeletal disorders (MSDs): low back pain, disc injuries, shoulder and neck strain, tendon disorders, hernias, and hand-arm conditions.

The law is general but clear:

• OSHA 1994 section 15(2)(a), (b) and (c): safe systems of work and handling, with information, training and supervision.
• Section 18B: risk assessment of manual handling tasks.
• CDM 2024 First Schedule: principle 4 requires adapting the work to the individual, especially in the design of workplaces, the choice of plant and the choice of working methods, to reduce monotonous work and work at a predetermined rate.

DOSH's Guidelines for Manual Handling at Workplace 2018, and its ergonomic risk assessment guidelines, give the method.

Ergonomic risk factors

DOSH's guidelines describe the following risk factors:

Types of manual handling task

The DOSH guideline covers four types:

1. lifting and lowering
2. pushing and pulling
3. carrying
4. holding and restraining

It also covers handling while seated. Holding does not need a heavy load: even a light load held for a long time can cause injury.

The initial manual handling risk assessment (DOSH 2018)

The initial assessment is a quick screen. If the task is within the recommended weights, a fuller assessment is normally not needed, unless individual workers are at particular risk, such as pregnant workers, young or new workers, or those with health problems or recent injuries. If the recommended weight is exceeded, carry out an advanced ergonomic risk assessment and control the risk.

DOSH emphasises that the recommended values:

• give a reasonable level of protection to around 95% of working men and women
• are not "safe" or maximum weight limits: there is no threshold where handling changes from safe to unsafe
• mean that operations more than about twice the filter values may be a serious risk of injury, even for fit, trained people

Lifting and lowering

The guideline's Figure 5.2 gives recommended weights by hand height and distance from the body, separately for men and women. In the guideline's own example, a man lifting between knuckle and elbow height, close to the body, has a recommended weight of 25 kg. The reductions are:

Repetition (Table 5.2):

Twisting (Table 5.3):

Worked example (DOSH 2018). Starting value: 25 kg. The worker twists about 45° to place the load, so the reduction is 10% of 25 kg = 2.5 kg. The worker lifts 5 to 8 times a minute, so a further reduction of 50% of 25 kg = 12.5 kg applies. The recommended weight is:

$$25 - 2.5 - 12.5 = 10\ \text{kg}$$

If the actual load is heavier than 10 kg, an advanced ergonomic risk assessment is needed.

Construction example: a block layer lifting 15 kg hollow blocks from a pallet on the floor up to a wall at chest height, six times a minute, while twisting, is well outside the filter. Raise the pallet to working height, reduce twisting, rotate tasks, or use lighter blocks or mechanical aids.

Pushing and pulling (Table 5.4)

These values apply when force is applied with the hands, the hands are between knuckle and shoulder height, the distance is under 20 m, the load is on wheels, and the handling aid is well maintained:

The guideline notes that moving a load on a flat surface needs at least about 2% of the load weight in force, and up to about 10% on uneven surfaces. Reduce the weight on slopes and ramps. Keep barrow and trolley routes smooth and level.

Carrying (Table 5.5)

Factors to check:

• floor surface: worn, uneven, wet, sloping or unstable surfaces, or unsuitable footwear, call for an advanced assessment
• environment: extremes of temperature, strong air movement, or poor lighting
• carry distance: 2 to 10 m is acceptable; more than 10 m exceeds the limit
• obstacles: steep slopes, steps, closed doors, tripping hazards and ladders all call for an advanced assessment

Controls

Follow the hierarchy (Section 2.3) and the CDM principle of adapting work to the individual:

Avoid or eliminate:

• deliver materials by crane or hoist to the floor where they are needed
• use pre-cut or prefabricated components
• design out lifting, for example with mechanical block grabs

Mechanical aids:

• trolleys, barrows, pallet trucks, vacuum lifters, panel lifters, hoists, telehandlers with the right attachments
• maintain wheels and surfaces so pushing forces stay low

Reduce the load:

• order smaller bags or lighter blocks where the specification allows
• split loads; use team lifts with a nominated leader and clear signals

Improve the task and layout:

• keep loads between knuckle and elbow height and close to the body
• avoid twisting by arranging the work area
• reduce carrying distances and steps
• provide good lighting and clear, dry routes

Organise the work:

• rotate workers between heavy and light tasks
• schedule rest breaks, especially in heat
• set a realistic pace, not one driven by piece rates alone

Training: teach good handling technique (plan the lift; stable base; bend the knees; keep the load close; no twisting; lift smoothly), but remember that technique training alone does not make an unsuitable task safe.

Health:

• encourage early reporting of aches and pains
• adjust tasks for pregnant workers, young workers and those returning from injury
• provide knee pads, padded gloves and shoulder pads for contact stress

Scenario: the cement bag gang

Workers unload 50 kg cement bags from a lorry and carry them 30 m across rough ground and up a stair to a mixer, all morning. The SSS's assessment:

• the load is far above the filter for any height
• repetition is high
• carrying distance exceeds 10 m
• the route has uneven ground and steps

All of these call for an advanced assessment and immediate control. The SSS recommends:

1. Crane or forklift delivery of palletised bags next to the mixer.
2. A smooth trolley route for any remaining moves.
3. Smaller bags where the supplier offers them.
4. Bag splitters that let workers empty bags at the mixer without lifting them high.
5. Task rotation and rest breaks.
6. A toolbox briefing on reporting early symptoms.