Humans are good at adapting body posture to existing preconditions in order to fulfil a task. This may often involve twisting or turning the body in order to reach, fit into an inconvenient space or avoid touching the surface of materials (example: so as not to scratch the paint job of a car). Therefore, it is necessary to determine how much working space around the task will be enough to avoid unnecessary loading, and whether to design for a minimum amount of space or with safety margins. A related aspect is to consider whether the available space will suit all body types and sizes .
An important prerequisite for performing a task is often being able to see what we are doing. If the line of vision is blocked or inconvenient, a human will often move the head, neck or upper torso to improve the line of sight, often bending or twisting. Therefore, visual demands can certainly influence posture. Also, insufficient lighting may have a similar effect even when the line of sight is acceptable, since it may still lead to bending closer to see controls, screen interfaces or instructions. It is a wise safeguard to have a well-lit working environment, particularly to ensure the ability to see written information for workers of all ages.
A high pace of work or high mental load (demanding tasks or working under pressure to perform) can contribute to feelings of stress. Heightened stress levels often increase muscular tension in the body, leading to a persistent internal loading situation that is static and can lead to fatigue. In some cases, tension from stress leads to cramping up and discomfort or pain. Stress can result from the psychosocial environment, demands of the job, the task speed or perceived mismatch between the task and the human’s abilities.
Many environments and tasks demand that the workforce should wear protective gear and clothing – sometimes to protect the human from extreme temperatures, glare, hazardous materials, wetness or dirt (e.g. gloves, glasses, jackets, helmets or visors), and sometimes to protect sensitive products or the environment from humans (e.g. hygiene masks and gloves). From a loading perspective, it is important to consider the additional postural load that these safety measures can bring about. For example, a helmet or visor may be heavy or warm, resulting in extra muscular effort and heat. Another example is that wearing gloves can often reduce surface friction and the sense of touch, leading to compensation with higher grip forces or clumsy use of hand tools.
Finally, it is worthwhile to consider that protective clothing can impede both movement and vision. If loaded in their axial direction, while the hands are highly flexible and responsive instruments of precision work rather than strength. Granted, with training some people are able to increase their force exertion in the hands or the precision of their back and leg movements, but it is generally reasonable to design tasks and workplaces so that they cater to what the body segments are naturally best at.
Bad posture is often accompanied by initial warning signals in the form of tension, discomfort or pain. It often results from unawareness, ignoring signs of pain or discomfort, or underestimating the impact of low-level long-term loading. There is a conception that there are several ergonomics pitfalls or typical scenarios that people often brush off as “not so bad” or just a minor inconvenience, but which may lead to risk for injury.
• Stretching to reach
• Repeated heavy lifting
• Lifting large, bulky, awkwardly shaped objects alone
• High pinch forces
• Handling sharp, hot or cold objects
• Working with hands above shoulders
• Long periods of work holding the same body posture
As mentioned earlier, additional demands (such as seeing, avoiding touching surfaces, psychosocial issues, or compensating for protective gear with posture or force) may be part of these ergonomics pitfalls. Observable work behaviours include bending, pushing, pulling, lifting, hand twisting, unbalanced standing or sitting, and repetitive actions.
Some postures themselves can cause static loading on the body, meaning that forces or torques are applied for so long on the engaged body parts that they are not given sufficient rest. This can lead to fatigue, decreased force/precision performance, and compensation recruitment of extra muscle fibres.
In many cases, static loading leads to constant tension in the muscles which can lead to tiredness, discomfort and cramping or even headaches. Such static postures and loading situations include:
• Bending the back forwards or sideways
• Holding loads in the hands
• Stretching the arms out to the sides or raising them above the shoulders
• Putting weight on one leg, while the other works (e.g. a pedal)
• Standing in one place for long periods
• Sitting in one place for long periods (e.g. computer work or driving a car)
• Pushing and pulling very heavy objects
• Tilting the head forwards or backwards at the extreme end of motion to see
• Raising the shoulders
Good Body Posture
• Feet firmly planted on the ground
• Knees directly above the middle of the ankle joints
• Hips directly above the knees
• Shoulders squarely above the hips
• Head and neck held in a way that aligns the ear directly over the shoulders