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Forced Posture of the Body
Not each posture required to execute the work is a forced posture
Only if a posture can only be assumed for a limited period of time, this is called a forced posture of the body. During this period, the subjective exertion increases and the efficiency of the static muscular strength decreases.
In the forced posture of the body, the static muscular strain is high and exceeds the physiological compensation possibilities for muscle circulation and generation of force. Forced postures of the body occur in combination with other types of workload, for example during manual work processes or during activities involving high whole-body forces.
Unfavourable conditions increase the stress
The main workload is caused by the type of static posture of the corresponding regions of the body (back, shoulder/upper arm, knee/leg) in combination with the duration of the individual, uninterrupted postures without any compensating movements. Additionally, there is the overall duration of the activity, as well as unfavourable execution conditions. For example, these include confined space and a lack of possibilities to support oneself using one's hands, but also the limited stability, moisture, cold, and draught.
Three types of static posture stress
The strain caused by a forced posture of the body is complex and affects both the muscles, tendons, bones, joints, and bursae and peripheral nerves and blood vessels. Due to the delimitable effects on certain regions of the body, three types of static posture stress can be defined: working with a bent torso, working with the hands over shoulder level or overhead work, and working while kneeling or crouching down.
Working in a stooped position
This includes work with the upper body leaning forward and bent far over. These postures can lead to strong static overstressing of the posture muscles of the back due to their long and insufficiently interrupted duration. The results can be acute and/or occasional impairments of health and chronic health disorders.
Acute/occasional impairments of health include in particular the following, unspecific back pains:
- Pains in the lower back area:
acute overloading of the muscular-ligamental structures (muscles and ligaments) resulting in back complaints and pseudoradicular syndromes
Chronic health disorders from longer exposition include in particular:
- Chronic back pains with restrictions of the range of motion
In the case of uninterrupted pronounced trunk bending, complaints can be caused and/or existing disc-related illnesses of the lumbar column can be exacerbated.
Working with hands above shoulder level or overhead work
Working with one’s hands above shoulder level and overhead work is manual work that is carried out at or above shoulder level and/or above head height. The shoulder joints are very bent and sometimes abducted. It can lead to very high muscular stresses on the musculature of the shoulders, arms and upper back. In addition, in the event of work above shoulder level and more so in the case of overhead work, pronounced strain of the neck musculature can occur due to leaning backwards, sometimes with twisting of the head. Restrictions of the circulation in the arms due to reduced hydrostatic pressure in the blood vessels reduce the strength of the arm/hand musculature. Because of this, even slight exertions of strength are only tolerable and/or feasible for a few minutes in the case of work with one’s hands above shoulder level or overhead work.
Furthermore, there are close links between complaints and diseases of the shoulders and overhead work.
Acute/occasional impairments of health include in particular:
- Overloads of the muscles and joint and ligament structures (pains, complaints, functional limitations) in the area of the shoulders, arms, neck and upper back, headaches
Chronic health disorders due to long, uninterrupted exposure include, in particular:
- Pain syndromes in the neck region radiating into the shoulder due to chronic dysfunctions and in the case of degenerative changes in the area of the cervical spine and due to chronic dysfunctions of the shoulder and neck musculature (cervical syndrome, cervicobrachial syndrome, cervicocephalic syndrome)
- Degenerative diseases of the shoulder (rotator cuff syndrome, impingement syndrome)
Working while kneeling or similar strains
Working while kneeling can be carried out on one side or both sides, with or without bracing of the upper body by the hands. Knee strains similar to kneeling include work on one side or both sides while crouching, sitting on one’s heels, and crawling (moving on all fours).
Uninterrupted forced postures, simultaneous exertions of strength or frequently recurring, substantial stress from movement increase the risk of inappropriate strain. This applies especially to running on very uneven surfaces or jumping with occasional bending, scissoring or turning movements.
Short-term and long-term impairments of health and/or diseases can occur in connection with activities placing strain on the knees:
Acute/occasional health impairments include, in particular:
- Stressing of the muscular and ligament structures with dysfunctions of the knee joints and irritations and inflammations of the bursa
Chronic health disorders and damage to health due to long, sustained exposure include, in particular:
- Joint damage (arthroses) of the knee joints
- Meniscus damage in the knee joints
- Chronified inflammation of the bursa (bursitis praepatellaris)