Better fitting and more comfortable head protection systems
3D head study leads to ground-breaking research findings
BÖNNIGHEIM (sre) In the course of our lives, almost all of us will have to address the question of head protection, sooner or later. Whether it is during our leisure activities or at work, a helmet helps to reduce or prevent head injuries. However, only a helmet that is perfectly fitted to the individual shape and size of its wearer's head can provide maximum protection (see Figure 1). Helmet manufacturers know this, too, but they have had to work with the limited information about head measurements that was previously available. Above all, there was a shortage of information about head shapes. The problem is that where the circumference of two volunteers' heads is the same, the width of the head can vary by up to 4 cm (see Figure 2). This significant difference cannot be catered for by a single size or shape of helmet. Now, thanks to a research project carried out at the Hohenstein Institute in Bönnigheim and called "Textile-based head protection systems" (AiF No. 16976 N), detailed data about head shapes is available for the first time.
Head size and head shape
The researchers spent about two years measuring the heads of 6000 men, women and children, and thoroughly examining their shapes and dimensions. With the help of more than 40 defined measuring points, they analysed the circumference, width and length of the head and many other important dimensions, and evaluated them statistically (see Figure 3). This enabled them to develop a new sizing chart specifically for heads, to identify typical 3D head shapes for the first time and then work out the typical market share of each actual head shape among the population of Germany. "Since people only wear head protection systems consistently if they are comfortable, getting the best possible fit is very important," says Simone Morlock, who was in charge of the project at the Hohenstein Institute. How well a helmet fits is closely related to the shape of the head. With her team, Simone Morlock has defined five main head types: These range from "extremely round" and "round" through "normal" and "oval" to "extremely oval" (see Figure 4). To demonstrate these types, 3D models were developed which cover the whole spectrum of different head shapes of people living in Germany. Another new element is that the head dimensions are shown in terms of sizes, rather than in the unit normally used in the standards, the percentile. A percentile only indicates the percentages among specific groups of people, but gives no indication of the actual dimensions of the head for each head size. By using the sizing chart produced by the researchers for head sizes 48 to 64, which describes the dimensions of the head and face for the five head types, manufacturers can now offer a better range of sizes and product types. The size-based presentation of head dimensions is a big help in industrial product development, because the sizing charts now show the actual dimensions for each size. The experts have also identified and described differences in the dimensions between age groups and between the genders.
Wearing characteristics and hygiene requirements
As well as the fit, physiological aspects such as moisture transport also have an effect on people's feeling of well-being. "To make sure that helmets not only fit as well as possible but also feel great to wear, we have studied the wearing comfort and hygiene requirements of textile-based head protection systems. This is because the materials that are used affect the climatic conditions under the helmet," says Martin Harnisch. "For the first time, we also included the lining of the helmet in our examination." In the project, the textile lining of ski helmets was studied as an example. By using laboratory tests, it is easy to characterise the different helmet linings in terms of their heat and moisture management and how they feel on the skin (skin sensory functions). For example, nearly all the lining materials took a long time to dry. Any potential ways of improving this were indicated. Unlike in previous studies, the scientists also took account of the hygienic properties of the head protection systems. "Increased sweating inside the head protection generates a warm and humid climate which reduces wearing comfort while also creating ideal conditions for the growth of microorganisms. This can result in undesirable odour formation and possible scalp diseases like various kinds of dermatosis such as tinea capitis," reports Dr. Mucha. To prevent these unpleasant consequences that result from the materials being used, different factors were studied and optimised by the researchers (see Figure 5).
Research findings help improve all head protection systems
In future it will be possible for manufacturers to use the new dimensions and data about shapes and market share to develop helmets that are specifically designed for different customer groups. In the long term, the standards which play such an important role in the field of head protection systems will be able to be updated in line with the latest findings: from personal protective equipment (PPE) in the construction industry to the police, firefighters and the armed forces, and the leisure industry. The additional anthropomorphic data that has been collected will also help to make mouthguards, face masks and ear protectors fit better, especially where they are combined with a helmet.