Ergonomics strives to create a balance between human, equipment, and environment.
It takes into account human physiology and the demands on it by the processes, products, and systems.
It strives to enhance performance and productivity by minimizing human error keeping into account the safety and comfort of the user.
Whether we work in office or work in the comfort of our homes, we need to take into account ergonomic principles and apply them to the tasks, the way we do the tasks and the equipment we use during the task.
It will optimize human well being and overall performance.
Ergonomic Risk Factors
Ergonomic risk factors or hazards are physical factors within the environment that may pose risk to the body’s musculoskeletal system. It can cause injuries which over time can lead to permanent disabilities and loss of function.
Disabilities and injuries of the musculoskeletal system can arise from ligaments, tendons, tendon sheaths, muscles, bones, joints, spinal discs, nerves or blood vessels.
Injuries can be on wrists, arms, hands, legs, knees, feet, neck back shoulder, eyes, etc. Examples of musculoskeletal injuries are carpal tunnel syndrome, epicondylitis, tendinosis, etc.
Over time, exposure to risk factors or hazards can lead to Musculoskeletal disorder. We need to understand these risk factors to avoid injury and loss of productivity.
The risk factors can be divided into:
- Physical Risk factors: Force, fixed or awkward postures, repetitions, contact stress, and vibrations.
- Individual Risk factors: Psychosocial, level of physical fitness, and gender.
Here I am listing 7 Ergonomic Risk Factors you should definitely know about. We will be covering both physical risk factors and Individual risk factors.
Force refers to the amount of effort made by the muscles, and the amount of pressure on different body parts due to demands of the Job.
All tasks as we know requires the body to use muscles to exert some force. Damage occurs when muscles generate moderate to a high level of force repeatedly, for a long duration and or with the body being in an awkward position
Some tasks can result in high force load on different parts of the body. For example, lifting a heavy object that is far away from the body can lead to increase pressure ( compressive force ) in the vertebrae and spinal discs.
This can potentially damage both the spinal discs and the vertebrae.
Forces can compress the muscles, nerves, blood vessels, tendons and nerves leading to damaging the tissues and joints.
When a task requires one to exert a level of force that is too high for any muscle, it leads to damage to the muscles or the related joints, tendons and other soft tissues.
While it is important to consider how much force is being exerted, what is equally important is to know how long the worker needs to keep exerting this force, how many times it is exerted in a fixed period of time, and the posture used while exerting this force.
Low levels of force also lead to injury if the force is being exerted repeatedly for a long duration and also when the posture used is awkward.
FIXED OR AWKWARD POSTURES
Posture is another name for the position of various parts of the body during an activity.
For most joints, a good or neutral posture means joints are being used near the middle of the full range of motion.
The farther a joint move towards either end of its range of motion, or the farther away from the neutral position, the more awkward or poorer the posture becomes.
The strain is put on the muscles, tendons, and ligaments around the joint. For example, when the arm is fully stretched out, the elbow and shoulder joints are at the end of their range of motion. If a worker pulls or pushes repeatedly in this position, there is a higher chance of injury.
It is important to consider how long the worker needs to hold this posture, how many times the awkward posture is used in a given period of time and the amount of force being exerted when an awkward position is used.
Muscles get tired and damaged when they are required to be in an awkward or fixed posture. The tendons, blood vessels, nerves all get compressed resulting in damage.
Sitting for a long duration causes the muscles to hold the head, neck, and trunk in a fixed posture. This causes the muscles to squeeze blood vessels so there is less blood supply to muscle leading to damage.
Sitting upright for long also decreases blood circulation as there is less demand on the circulatory system due to limited mobility. As a result heart activity and blood flow slow down.
It also compresses spinal discs which stop their nutrition from reaching them leading to premature degeneration.
Sitting in a fixed position for long also causes blood to pool up in lower legs leading to swelling, numbness and injury.
The static muscular load is found under these conditions as muscles are tensed over a long period of time in order to maintain a certain body posture. For example, holding the arms in a typing position over the keyboard.
As muscles get no opportunity to relax in this task, it leads to muscle fatigue even if forces applied are very low.
Highly repetitive tasks lead to pain and tissue damage. Risk increases when the same parts of the body are used repeatedly, with few breaks and chances of rest.
Many work tasks and cycles are repetitive in nature and are frequently controlled by daily or hourly production targets and work processes.
Repetitive tasks can lead to fatigue, tissue damage, muscles becoming tired and weak. This eventually causes pain and discomfort.
This can occur even if the force exerted is low and the posture used is not very awkward.
What is considered important is how long the repetitions are being carried out, how much force is being used and the posture required for repetitive tasks.
It is also called as RSI- Repetitive stress injury. RSI risk increases when we do a high-intensity activity for a long time without rest. The poorer the posture during task repetitions, the greater the risks. Repetitive tasks with less force, however, can also call RSI.
A job is considered highly repetitive if the cycle time is 30 seconds or less. In this condition, the same parts and fibers of the muscle are activated for a long duration. This results in stress overload. Fatigue, pain and possible injuries are the consequence.
Some examples of repetitions are typing on a keyboard, repetitive lifting, moving and clicking a mouse, operating one piece of equipment all day, looking back and forth between a document and a monitor.
The joints are more susceptible to repetitive motion injuries, especially the wrists, fingers, shoulders and elbows, feet and knees.
When the job involves a high number of repetitions per minute, the greater the strain and more the chances of injuries. Research shows the tendons and muscles in the wrist may not be able to recover where repeated task cycles are less than 5 seconds in length. That is when they are more than 12 times per minute.
It should be noted however that the recovery time of muscles varies for different body parts. For example, shoulder injury chances are high even though tasks are 3 times per minute.
CONTACT STRESS/ MECHANICAL STRESS
The parts of the body which come in contact with an outside element for a long period causes contact stress.
This occurs when repeated exposure to the hard or sharp surface which digs into soft tissue.
Examples are resting arm or wrists on the edge of the desk or work surface, leaning elbows on the desk while working, or sitting in a chair which places pressure on the back of the legs.
It results in irritation of the nerves and constriction of blood vessels. Tissue damage may occur as a result of a single event or to repeated exposure over time.
The parts of the body with the least amount of protective tissue such as fat or muscle are most likely to suffer hard due to contact stress.
As nerves or blood vessels are pinched or bruised, a person with contact stress injury may feel pain or numbness.
It leads to impaired motion and stiffness.
Internal contact stress can occur for example when we bend wrists at an awkward angle while typing. Gripping something with hand grips etc.
Internal contact stress happens when muscles, nerves or other soft tissue rub or press against bones or joints or tendons in a way that causes the tissue to bruise or overextend.
Common areas of contact stress include hand, wrist, shoulder, elbow, and knee.
ALSO SEE: Best Ergonomic Office Chairs Under $200
VIBRATION ( hand-arm or whole-body)
Whole-body vibration causes musculoskeletal problems, digestive problems as well as prostate problems. It can even lead to miscarriages in women according to a research biologist at NIOSH.
Hand-arm vibration can damage the small capillaries that supply nutrients. Vibration can cause a worker to lose feeling in his hands and arms.
This way he is not able to gauge the strength and leads to increased force exertion.
Vibration may result from hand-held tools and therefore exerts vibration strain on the hand-arm system. Hand-arm vibration results in dysfunction of nerves reduced blood circulation especially in the fingers and degenerative disorders of bones and joints of the arms.
The vibration of the whole body is generated by vibrating vehicles while traveling, and platforms such as earth moving machines etc. The vibration is transferred via the seats in the vehicles.
Whole-body vibration can cause degenerative disorders especially in the area of the lumbar spine. The lower back injury is most common in repetitive driving injuries. The effects of vibration are intensified with duration and awkward position.
Repetitive exposure to whole-body vibration, however, can cause pain and tissue damage even if the duration and vibration are less. This happens even if the posture is correct.
INDIVIDUAL RISK FACTORS ( PSYCHOSOCIAL, OBESITY & GENDER)
Important psychosocial risk factors include
- work demands and mental load,(like high workload, high information-processing demands, constant time pressure, the pressure to work overtime),
- job control ( like little or no opportunity to make own decisions, limited break opportunity),
- social support(the poor relationship between co-workers, poor cooperation)
- work stress ( high level of fatigue, high level of emotional tiredness, high level of frustration, poor work-personal life balance)
All the above-mentioned factors affect motor coordination and increase muscle tension and stress. For example, high mental load and work demands may increase muscle tension and cause a decrease in breaks and micro pauses. This may lead to muscle fatigue.
High work stress increases muscle activity and puts a load on the musculoskeletal system.
The stress response can cause physiological changes leading to MSD.
Obese people are more likely to have injuries due to their overweight and a significant amount of stress and strain on muscles, bones and the weight-bearing joints especially in the lower back, hip, knee, etc.
Lack of physical activity combined with an increase in weight leads to improper movement and alignment of the bones and muscles. This increases susceptibility to joint injury and also increases the risk of osteoarthritis.
There is gender-based evidence related to MSD. It states that females are more prone to injuries than men.
This is because of their smaller frames, lower muscle mass, strength, and endocrine hormones. This is the finding of the scientists from Ohio state university.
Government French Institute for health surveillance carried out epidemiological monitoring of MSD. The results show a high prevalence of diagnosed MSD for women.
The results also confirmed the higher exposure of women to repetitive work and low level of control.
TEMPERATURE AND LIGHTING
Extreme temperatures like hot and cold can affect a person’s ability to judge force and strength. Temperatures interfere with sensory feedback.
MSD symptoms are more frequent in cold store work.
The temperature in the workplace affects the body muscles.
Excessive heat increases overall fatigue. Excessive cold makes the hand feel numb. This leads to more force and efforts by the muscles.
If lightning and visual conditions are too much or deficient, it causes muscle strain. This happens as bad lighting conditions cause shadows and glares and make worker adopt an awkward posture to see and work leading to strain.
This results in eye strain, pain, blurring of vision, headaches, irritation, double vision, less flexibility of the lens and dryness.
Knowing these risk factors, one can avoid or find a means to control them and lead a healthier and happier productive work life!
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