A dynamic approach to standing and sitting means dynamic alternations between standing and sitting, or interrupting activities in the sitting position by spending time working in the standing position.

In this respect, a variety of standing-sitting concepts are available:

• A sitting work desk with an integrated standing desk, whereby the standing desk can be incorporated in or added to the work desk
• A sitting work desk and a detached standing desk, whereby the detached standing desk can either be mobile or stationary
• A sitting and standing desk (as separate solutions)
• Height-adjustable work desk (as an integrated office furniture for work in the stand-ing or sitting position)

Legal principles

The design requirements for office work desks and chairs are stated in Annex 6 of the 2016 Workplace Ordinance. Detailed information is also available in several norms (in particular DIN EN 527 Office Furniture, Office Work Desks, part 1: Dimensions; part 2: Mechanical Safety Requirements; part 3: Inspection Procedure for Determining the Structural Stability and Mechanical Resistance of the Construction DIN EN 1335: Office Furniture – Office Work Chairs, part 1: Dimensions; Determination of Dimensions; part 2: Safety Requirements, part 3: Safety Inspections). The DGUV (German Social Accident Insurance) Information 215-410 also provides details on the design of VDU and office workplaces.

Occurrence

In offices and administrative work, employees complete nearly all of their tasks in a sitting position. In the field of manufacturing industry, the number of jobs performed purely in the standing position is in decline. This is for good reasons: above all, standing requires use of the large muscle groups in the thighs and bottom, and requires much more energy than sit-ting. As employees get tired quickly in this position, standing is especially detrimental for activities that require high levels of concentration. Standing up for a long period of time also places strain on the hips. As the leg-veins muscle pump becomes inactive, blood blockages develop in the blood vessels in the legs, which cause venous diseases such as varicose veins and thromboses. Then there is the lower stability of the upper body, which means standing is less suitable, first and foremost, for activities requiring a high degree of dexterity in partic-ular. In comparison to standing, most people experience sitting to be a pleasant source of relief.

Strains and risks

The most frequent muscular complaints in office jobs are neck pain, headaches, neck-shoulder-arm syndrome and aches and pains in the back. In recent decades, the working conditions associated with these symptoms have been subject to considerable research (Richenhagen et al. 2002). The following have been identified as risk factors for muscular-skeletal disorders or problems:

• Insufficient work equipment and furniture (particularly work desks and chair)
• Problematic positioning of the key work equipment (keyboard and screen)
• A lack of system ergonomics (coordination of work equipment and furniture and ad-aptation to the working environment)
• Unfavourable work tasks which involve repetitive sequences of physical movement.
• Excessive amounts of the working day spent in front of a computer screen with too few breaks and few changes in posture.

To determine the strain on the spinal column, the degree of intervertebral disc pressure is used as the key variable. When standing, the spinal column assumes a similar shape to a double "S", whereby it curves inwards in the area of the cervical and lumbar spine (known as lordosis) and outwards in the area of the thoracic spine and the sacrum and coccyx (known as kyphosis). In this normal positioning of the segments of the spinal column, a relatively moderate degree of pressure is applied to the intervertebral discs between two vertebrae. The muscles of the back are also relatively inactive. If the torso is curved forwards, however, the ends of the inwards pointing vertebral bodies that point inwards move closer together. In this area, the intervertebral discs are pressed together, which means that the internal pressure on the intervertebral discs increases considerably (Schultz et al. 1982). In this posi-tion, the spinal column is largely supported by different ligaments. If the pressure is too high, the likelihood of painful intervertebral disc problems increases, with the possibility of slipped disc.

The intervertebral disc, which is a kind of buffer between two vertebral bodies and is re-sponsible for the flexibility of the spinal column, is not supplied with blood. The nutrient supply instead occurs on the basis of diffusion, which means the passive transport of the nutrients on the basis of drops in pressure. This is achieved by the compressing and releasing of the inter-vertebral discs. A sufficient nutrient supply, therefore, requires movement.

Clinical pictures

At workplaces in which employees spend most of their time sitting down, health problems can arise which can be summarised by the term "muscular-skeletal disorders". Neck pain and headaches, neck-shoulder-arm syndrome, aches and pains in the back and also problems with the lower extremities are primarily attributable to one-sided postures, which means static, physiologically poor postures.
Sitting down at a workplace for long, unbroken periods, particularly in the incorrect way, can lead to problems with the connective and supportive tissue, the cardiovascular system and the central nervous system.

Prevention

The movement required to prevent muscular-skeletal problems can be achieved with a dy-namic approach to standing and sitting. A suitable workplace can be optimally achieved with an (easily adjustable by means of an electrical motor) height-adjustable work desk which enables the employee to work in either a sitting or standing position. In addition to this movement, a sensible division of work tasks into a combination of sitting and standing activi-ties also contributes to the prevention (VDU work interrupted by taking phone calls standing up, trips to photocopier, photocopying work when standing up, etc.). Standing desks, which have a lower potential for prevention than easily height-adjustable work desks (Wittig, 2000/see above), can, above all else, be put to sensible use if the users have the appropriate level of awareness (e.g. due to their own back problems). In this context, it is clear that in addition to the situational prevention (provision of a standing desk), a targeted behavioural prevention is also necessary (promoting the willingness to use the offer), so that the dynamic approach to standing and sitting is actually promoted.
With mixed work (office work with and without computer support), electrically operated, easily height-adjustable work desks should have both a writing desk and a desk for computer work. The dimensions of 1600 x 800 mm are considered the minimum requirement. Due to the different requirements for the written and communication tasks, the positioning of the monitor and especially the lighting, corner-combinations of a writing and computer work desk have proven to be beneficial. In a corner-combination, the usable width of the comput-er area should amount to a minimum of 600 mm. The height-adjustable area of the work desk or computer desk, or, better yet, the total combination, should amount to a minimum of between 680 and 1180 mm.
To enable an individual adjustment to the working person, a standing desk should be height-adjustable between 100 and 135 cm. The surface of the desk should have a minimum size of 300 x 420 mm. If the standing desk is not used for computer work, a tilting mechanism (up to approx. 15°) which is easy and comfortable to operate is a good idea.

Behavioural ergonomics

To ensure that the dynamic approach to standing and sitting is accepted by employees, it is necessary to make comfortable standing possible. If it takes too much effort to achieve a standing working position (e.g. being required to move or adjust office furniture), this will prevent the dynamic approach to standing and sitting. To prevent long walks, and therefore staff resistance, the standing workplace should also be in immediate proximity to the sitting workplace.
Before introducing suitable office furniture, it is necessary to inform the employees of their meaning, purpose and correct use so as to gain wide acceptance. The participation of those affected is of fundamental importance.
Those affected should be trained in dividing their activities into those that they perform in the standing position and those that they must perform sitting down. New personal work-place strategies must be developed so as to support the change in behaviour.
Two to four changes in position per hour have been proven to have a positive impact. Em-ployees should be encouraged to avoid static standing. This can be achieved with the use of a foot rest, for example, which the employee can use to alternate between resting one leg and the other. Periods spent working in the standing position should not last more than twenty to thirty minutes. Dynamic sitting is to be ensured during periods spent sitting down.
In general, the employees must be given role models to bring about fresh thinking and thereby achieve a change in behaviour in their daily work.