Ergonomics

Awkward postures refer to body positions that are uncomfortable or put certain body parts at a mechanical disadvantage. Muscles and joints work most efficiently in specific positions—usually at the midpoint of the joint’s range of movement. When muscles are put under too much mechanical stress at the same time as they are being stretched, they become more susceptible to injury.

Positions held for long periods of time can cause fatigue to supporting muscles. This can lead to discomfort and increase the risk of injury. Certain positions place increased pressure on different body structures, and holding the same position for a long time can cause damage to those structures. A common example of this is the pressure that is exerted on discs in the lower back whenever the trunk of the body is in a flexed position such as driving or sitting in a chair.

Repetitive movements can lead to the overuse of muscles and tendons. This can subject these structures to microtrauma (e.g., microscopic tears) that cause pain. Performing repetitive movements in an awkward position increases the risk of injury. Over time, muscles and tendons may actually begin to rub against other bony structures, causing wear and tear of soft tissue.

Excessive force occurs when too much physical effort is required to perform a task, placing strain on muscles, tendons, and joints. Lifting, pushing, pulling, or gripping objects that are heavy or awkwardly shaped can increase the risk of injury. When force is applied repeatedly or suddenly, it can lead to muscle fatigue, sprains, or tears. Tasks that combine high force with awkward postures or repetitive movements further elevate the risk of musculoskeletal disorders.

Contact stress occurs when pressure is exerted on a joint. For example, when kneeling on the floor for an extended period, there is contact stress on the knees. Contact stress can cause irritation and inflammation in the body, particularly when combined with awkward postures.

Muscles fatigue faster in hot conditions, and gripping objects or tools can become difficult to maintain with sweaty palms. Alternating between tasks—or taking frequent breaks from the task— may be required when working in hot weather or confined spaces.

In cold conditions, blood flow to the extremities decreases, and this leads to reduced muscle performance. Wearing appropriate clothing and warming up the working muscles through light exercise or stretching before commencing work duties may minimize the impact of cold weather.

Loud noise is another environmental condition that can require sustained attention to a task and create tension within the body. Poor visibility may also lead to impaired hand-eye coordination during a task, or cause an individual to hold the body in an awkward position while straining to see properly.

When a work-related task involves vibration—such as driving a forklift—the blood supply to vibrating areas of the body decreases. This issue hinders proper muscle contraction and leads to more rapid fatigue. 

Whole-body vibration is typically experienced by operators of heavy machinery or utility vehicles. Furthermore, hand-arm vibration occurs in workers who use impact tools or those which vibrate such as rattle guns, drills, or hammers.