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.
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.
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.
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:
Chronic health disorders from longer exposition include in particular:
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:
Chronic health disorders due to long, uninterrupted exposure include, in particular:
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:
Chronic health disorders and damage to health due to long, sustained exposure include, in particular: