Mental stresses are influences upon a human being caused by the work task, the working environment or the work equipment, and impacting upon mental capacity such as clear-headedness, memory or cognitive ability. If these influences are too diverse, too chaotic or too intensive, they may cause excessive mental strain.
Physical stresses arise through unfavourable body postures, rapid or sustained body movements, high force exertion, the handling of loads, or a combination of these aspects. The stresses manifest themselves in strain upon the muscles, locomotor apparatus and spine. Machines and their control stations should be engineered such that stress factors are reduced to a minimum. A risk assessment assists in estimation of a work situation. Corresponding information can be found in the EN ISO 12100 standard and the EN 1005 series of standards.
Stresses acting upon human beings that are environmental in origin, as opposed to those associated directly with the work task, are a significant factor. Examples of environmental stresses are limatic influences such as wind, heat, noise, solids/liquids and gases. Depending upon the nature of the stress, it induces a strain upon the body, as in the case of heat during physical work, or upon mental capacity, as in the case of noise affecting the ability to concentrate. Environmental stresses can often be influenced only indirectly by the design of a machine or installation. It must always be ensured that the machine does not itself have an unfavourable impact and that its use is designed such that human beings are well protected against environmental influences.