Laura Milnes of System Concepts explores the factors that can increase the risk of musculoskeletal disorders and considers how these can be evaluated and controlled in the workplace.
In the manufacturing sector in 2014–15, according to the Health and Safety Executive (HSE), there were 80,000 cases of self-reported workplace illnesses leading to 2.4 million working days lost. Around half (48%) of these illnesses were musculoskeletal disorders (MSDs).
The term MSD is an umbrella term for a range of disorders of the neck, shoulders and arms (upper limbs), back, or hips knees and ankles and feet (lower limbs). It covers conditions with specific medical diagnoses (eg tendinitis, carpal tunnel syndrome, vibration white finger, epicondylitis aka tennis elbow), as well as other generic conditions (often called repetitive strain injuries or work-related upper limb disorders) where there is pain without specific symptoms/causes. Symptoms may include pain, swelling, tingling or numbness and difficulty moving. MSDs develop over time, often months or years.
Organisations can protect employees’ health and ensure their safety and comfort by designing an ergonomic workplace. If a workplace is correctly designed and equipment and tools are safe and easy to use, staff need not make unnatural or awkward motions, twist their arms or wrists, overextend themselves or put pressure on their backs and limbs; all of which are possible precursors for MSDs.
The scope of ergonomics is broad, but the term generally refers to the science of fitting workplace conditions and job demands to the capabilities of workers. Ergonomic design can help increase productivity, avoid illness and injury, and boost satisfaction and morale among the workforce. In addition to a healthy and satisfied workforce, ergonomic interventions can also offer significant value in terms of decreased turnover, absenteeism and compensation costs.
MSDs can be successfully managed in the workplace by implementing an ergonomics management process to recognise, evaluate and control the risks.
Recognising the risks
A simple risk assessment in the workplace will highlight the work activities that may cause harm. Risk factors that can lead to MSDs include the following.
Awkward postures: where the joints of the upper and lower limbs move toward the extremes in their range of motion. This puts more stress on the worker’s musculoskeletal system. Examples include stooping, reaching, twisting and stretching.
Forceful exertions: gripping, pinching, pushing, pulling and lifting objects place additional force on the body’s joint structures. Muscle effort increases in response to high force requirements, which increases fatigue and the risk of an MSD, especially when there is inadequate time for rest or recovery.
Repetitive motions: a job is considered highly repetitive if the cycle time is 30 seconds or less. When combined with other risk factors such as high force and/or awkward postures, high task repetition can contribute to the formation of MSDs.
Contact stress: repeated or continuous contact with hard or sharp objects, eg resting wrists on the sharp edge of a desk or workstation, the pressing of tool handles into the palms, tasks that require hand hammering, and sitting without adequate space for the knees may create localised pressure, which can inhibit blood flow, nerve function, or movement.
Hand–arm or whole body vibration: regular and frequent contact with vibrating objects, such as grinding tools (hand–arm vibration) can lead to reduced blood flow to the exposed body parts, which causes stiffness and numbness. Operating heavy equipment (whole-body vibration) for extended periods of time can result in digestive and back disorders.
Once you identify the risk factors for the development of MSDs, you need to quantify them and then make measurable improvements to your workplace, ensuring that jobs and tasks are within workers’ capabilities and limitations.
Evaluating the risks
There are a range of ergonomic risk assessment tools available to help quantify the risk of MSDs and prioritise areas for improvement. This list is not exhaustive but provides a summary of commonly used tools.
The Assessment of Repetitive Tasks (ART) tool was designed by the HSE to help risk assess tasks that require repetitive movement of the upper limbs. The tool uses a traffic light approach to indicate the level of risk for 12 grouped factors: frequency and repetition of movements; force; awkward postures of the neck, back, arm, wrist and hand; and additional factors (including breaks and duration).
The Rapid Entire Body Assessment (REBA) tool from Cornell University uses a systematic process to evaluate whole body postural MSD and ergonomic design risks associated with job tasks. A single page form is used to evaluate required body posture, forceful exertions, type of movement or action, repetition, and coupling. A score is assigned for different body regions. Tables on the form are used to compile risk factor variables, generating a single score that represents the level of MSD risk.
The Manual Handling Assessment Charts (MAC) tool was developed by the HSE to assess the risks posed by lifting, carrying and team manual handling. It incorporates a numerical and a colour-coding score system to highlight high-risk tasks.
NIOSH Lifting Equation
The NIOSH Lifting Equation is used to assess the manual handling risks associated with lifting and lowering tasks in the workplace. This equation considers job task variables to determine safe lifting practices and guidelines. The primary product of the equation is the Recommended Weight Limit (RWL) — the maximum acceptable weight that nearly all healthy employees could lift over the course of an eight-hour shift without increasing back discomfort.
Controlling the risks
Correct postures and ergonomic workplace designs will vary depending on the type of work performed (precision, light or heavy) and position (seated or standing), but the following guidelines apply.
Maintain neutral postures: individuals should typically have their elbows at a 90° angle with the back of the hand in line with the outer forearm — no bending inwards or outwards. The head should be straight, shoulders should be relaxed, and operators should neither lean forward at the waist nor lift their arms above shoulder height.
Work in the comfort zone: close to the body, between mid-thigh and mid-chest height. This zone is where the arms and back can lift the most with the least amount of effort. Working in the comfort zone ensures that you are working from appropriate heights and reaches, which reduces MSD risk factors.
Allow for movement and stretching: working for long periods of time in a static position will cause your body to fatigue. This is known as static load. It is beneficial to take periodic stretches and dynamic movement breaks during the work day to get your blood moving and restore your energy.
Reduce excessive force: using mechanical assists, counterbalance systems, adjustable height lift tables and workstations, powered equipment and ergonomic tools will reduce work effort and muscle exertions.
Reduce excessive motions: excessive or unnecessary motions should be reduced if at all possible. In situations where this is not possible, try to eliminate excessive force requirements and awkward postures. Other control methods to consider are job enlargement, job rotation and counteractive stretch breaks.
Minimise contact stress: rounding or padding the edges of sharp or uneven-edged objects or workstations can help. Provide tools with long handles that do not dig into the palm. Spring-assisted pliers or scissors will reduce contact stress on the fingers when opening tools. And consider using knee pads or gloves to pad the body.
Reduce excessive vibration: mechanise or automate the work if possible. Select the lowest vibration tool that can do the work efficiently. Use devices such as jigs and suspension systems. Plan work to avoid individuals being exposed to vibration for long, continuous periods. Where tools require continual or frequent use, introduce job rotation.
Don’t let your workforce add to the MSD statistics — act now!
Last reviewed 24 March 2016