750 Introduction to Industrial Hygiene

Risk Factors Inherent in the Task

• Grip: There's a right way and a wrong way to grip an object. This combination of force and posture, if not accomplished correctly, may result in harm to the hand. Two basic grips are used when handling tools, equipment or materials.
• The Pinch Grip depends on the fingers to exert the force and manipulate the object. This grip strategy requires much greater muscle strength and, consequently, is more likely to cause an injury.
• The Power Grip uses the muscles of the entire hand to apply force and manipulate objects. Consequently, it's the most effective and safest grip to use.
• Exertion: Exertion in the workplace refers to the physical effort required to perform tasks, and depending on whether the effort is static or dynamic, it can place different types of strain on the body and increase the risk of injury.
• Static Exertion: Standing, sitting, or otherwise remaining in one posture for a long duration while you perform a task can increase the likelihood of injury. Static exertion combines force, posture, and duration to create a condition that quickly fatigues our muscles which increases the chances of acquiring a cumulative trauma disorder (CTD). The greater the force, more awkward the posture, and longer the duration, the greater the risk.
• Dynamic Exertion: Work requiring heavy physical exertion places a greater demand on the body's cardiovascular system to provide the necessary oxygen and metabolites to muscle tissue. If a muscle group's demand for metabolites and oxygen cannot be met, that muscle group will become fatigued, increasing the risk of injury. When the muscle is tired and sore, it's fatigued, and injury may more likely occur. If the entire body becomes fatigued, an actual cardiovascular failure may occur.
• Repetition: Repetition is a measure of how frequently we complete the same motion or exertion during a task. The severity of risk depends on the frequency of repetition, speed of the movement or action, the number of muscle groups involved, and the required force. Repetitiveness is influenced by machine or line pacing, incentive programs, piece work, and unrealistic deadlines. Cumulative Trauma Disorder (CTD) is a term used to describe a range of injuries that result from repeated physical actions or sustained postures over a prolonged period. These injuries typically affect the musculoskeletal system and can result in pain, discomfort, and functional limitations in affected body parts such as hands, wrists, forearms, shoulders, and neck.
• Velocity/Acceleration: Angular velocity is nothing more than the speed at which the body part moves. Acceleration is the rate of change of the speed at which the body part moves. For example, a drummer's hand/wrist may move very rapidly back and forth while drumming. The faster that back and forth motion occurs, the greater the risk of injury. Other factors like the weight of the object being moved will also increase risk.
• Recovery time: Recovery time is a measure of the rest (or low stress activity) period available to the muscle group between similar exertions. Recovery time is important in preventing muscle fatigue because oxygen and metabolites are allowed to rejuvenate while uric acid and other waste products are removed from the muscle group. Recovery time needed will lengthen as the duration of the task increases.
• Duration: Duration is a measure of length of time of exposure to a risk factor. Of course, the assumption is that the longer the duration of exposure, the greater the risk of injury. Duration may be measured in seconds, minutes, hours, days, weeks, months, and even years. When evaluating individual risk factors, IHs take into account other factors such as the worker's physical conditioning, posture, force, weight, temperature, stress, etc.
• Awkward Postures: Tasks that require working in awkward postures or being in the same posture for long periods of time increase risk of injury. Using positions that place stress on the body, such as prolonged or repetitive reaching above shoulder height, kneeling, squatting, leaning over a counter, using a knife with wrists bent, or twisting the torso while lifting.
• Clothing: Have you ever worn thick leather gloves while trying to accomplish some kind of intricate manipulation of small objects? Try it, you will be frustrated. Whenever you wear gloves, more grip force is required to do a particular task. With the need for more force, increased risk of injury occurs.Wearing bulky clothes, like heavy rain gear or protective clothing for removing hazardous waste, will increase the effort required by muscles to do work. Any time you increase the force necessary to complete a task, risk of injury also increases.

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