STAGE 3 : Sizing system
7.3 Examinations of mobility restrictions caused by clothing
It should be noted that, as already mentioned, the static positions recreate move-ments. The muscle work is static rather than dynamic work. Even for trained subjects, it is difficult to precisely replicate the muscular work of a movement in a static posi-tion. It can be assumed throughout that the body geometry will vary in both cases. As a result the measurements could also be different. This is fundamental to investigate. As 3-D scanners are unable to record movement, 4-D scanners should be seen as a solu-tion for these analyses.
Fig. 7.14 Exemplary presentation of implementation of differences in clothing.
measurementsandmobilityrestriction(from3Dto4Dscanning)187
7.3.1 Mobility restrictions caused by clothing
Clothing restricts the movement of the wearer to different extents according to the flexibility and elasticity of the material. In the area of fashion, good ergonomics are not part of the target values. Here, visual appearance takes center stage. Mobility restrictions, that is, the reduction of the ROM, are accepted by the customers (Gill, 2018). Critical movements are avoided if possible. The tight pencil skirt is not intended for stepping over hurdles, and you cannot mount an engine overhead wearing a sport coat. The combinations of material stiffness and pattern reduce mobility; in these examples, either the step size or the shoulder rotation is restricted. For example, excessive and overly dynamic movements in fashionable clothing can lead to seam damage (Schmid and Mecheels, 1981).
Such damage remains for the most part without serious consequences for the wearer in everyday life. The situation is very different for PPE, military equipment, and sport or outdoor wear. Movements here are repeated multiple times and are often highly dynamic. This stresses seams and materials maximally. If areas are stressed too much, the protective effect or functionality can be reduced (Baytar et al., 2012). Ergo-nomics are as just as important requirement as the protective function for these prod-ucts. Mobility restrictions at work or during sport represent a further physical, and therefore also mental, strain (Akbar-Khanzadeh et al., 1995). Clothing can severely restrict the performance of the wearer, if they permanently have to act against resis-tance. Impairments of this kind result in longer processing times (in a work environ-ment), earlier muscle fatigue, and higher stress (Adams and Keyserling, 1993). In a physically demanding job (e.g., in the fire department), clothing should be as support-ive as possible (Watkins and Dunne, 2015). The goal of clothing development in this context must, therefore, be maximum protection with minimal impairment of the mobility of the wearer. In some cases, even clothing-technical solutions for the passive support of the users can be realized.
Most clothing products are developed on the basis of the standard anthropometric posture defined in standards and size charts (see Section 7.2.2). The persons to be recorded stand upright, legs hip width apart, and arms slightly spread laterally (Ashdown, 2011;Kouchi, 2014;Morlock, 2015a, b;ISO—International Organisation for Standardization, 2010). People are, however, in this static position for very short moments throughout the day, as they are predominantly in movement. They walk, sit, bend the torso forward, or stretch the arms out upwards. Above all at work and dur-ing sport, the body posture changes regularly and dynamically. With each movement the body dimensions and geometry vary (seeSection 7.2). The variations in body propor-tions have a direct effect on the fabric and on the whole clothing product. The material is stretched or deformed. This also influences the interaction between body and clothing.
An increase in material stretch usually also means an increase in clothing pressure on the body (Lim et al., 2006). If the pressure is too great, the wearer feels the clothing is uncomfortable and can be limited in his mobility. To counter this, clothing must accom-modate for the changes in the body and expand or reduce analogously to it. This can be achieved on the one hand by material characteristics or by the tailoring. Woven fabrics are limited in their flexibility due to their binding and thus also the associated distortion resistance. In general, knitted fabrics are more elastic and stretchable than woven fabric.
They have a high elasticity, which can adapt to the changes in girth and length of the body. However, not every material can be used in every field of application. Not every ROM can be compensated for solely by material properties. In many cases, design adjustments are necessary.
Clothing-technical solutions for the reduction of mobility restrictions so far have been scientifically considered in individual examples (Boorady, 2011; Ashdown, 2011). Concrete examples in PPE are protective work parts with preformed knee areas or jackets for overhead work with specific armhole construction and elastic elements (seeFig. 7.15). In sports, results from application analysis lead to, among others, bicy-cle or motorcybicy-cle parts with preformed fit for the riding position. The patterns were adjusted so that the parts fit perfectly with a 90 degree angle in the hip and knee joints.
Targeted material positioning or application-specific pattern designs require basic body shape analysis. The investigation of the body regions that are subject to change processes leads to clear functional descriptions. Thus the corresponding adaptations can be made in the product development process (Watkins and Dunne, 2015;
Morlock, 2015a, b). In addition, it is important to quantify the interaction between cloth-ing and wearer, as well as the mobility restrictions experienced through clothcloth-ing. Cloth-ing products with high ergonomic wearCloth-ing comfort can only be developed through evaluating the limitations of movement first (Saul and Jaffe, 1955; Adams and Keyserling, 1993; Watkins and Dunne, 2015; Lockhart and Bensel, 1977; Gregoire et al., 1985;Alexander and Laubach, 1973;Son et al., 2013, 2014;Huck, 1988, 1991;
Adams, 2000;Graveling and Hanson, 2000;Coca et al., 2008, 2010;Son and Xia, 2010).
Fig. 7.15 Jacket for overhead work with adapted armhole construction and elastic zone.
7.3.2 Methods to analyze the human-garment interface
The development of an optimal fit for mass production is a challenge due to a variety of factors. A decisive criterion is the heterogeneity of the clothing sizes and body shapes of the customers (Morlock and Schenk, 2016;Boorady, 2011). What influence do they have on the interaction between user and product? This should be considered for workwear, particularly PPE. Especially here the fit during movement is of vital importance. Initial research approaches to the analysis of the human-garment interface aimed for an objective evaluation of the products in terms of range of movement and reach. Thus Saul and Jaffe (1955)developed 28 performance tests to research the impairment of gross motor skills through military clothing; an example is the subject sits on the floor with their feet on the test structure. He bends forward as far as pos-sible, and with a bar on the structure, the hip mobility can be quantified (seeFig. 7.16 on the left).
(A)
(B)
Shoulder flexion Shoulder horizontal flexion Hip abduction
Fig. 7.16 Examples for the analysis of the range of motion (Watkins and Dunne, 2015;Adams and Keyserling, 1993).
Lockhart and Bensel (1977)carried out similar studies for military clothing protec-tive against cold climate andGregoire et al. (1985)for protective suits against chem-ical and biologchem-ical warfare agents. The variables in the studies, among others, were mobility, speed of movement, and coordination. These were examined in general per-formance tests: For example, how deep the subjects can bend forward, and what dis-tance they have covered after five steps.Alexander and Laubach (1973)examined the arm reach of air force pilots in clothing protective against cold climate. The test setup was modeled on the working environment of the pilots. They were sitting and had to complete different reaches in a modified pegboard test. Alongside military clothing, such analyses are especially carried out in the area of fire-resistant clothing (see Fig. 7.16 on the right) (Son et al., 2013, 2014; Huck, 1988, 1991; Adams, 2000;
Graveling and Hanson, 2000;Coca et al., 2008, 2010;Son and Xia, 2010). Beginning withHuck (1988)up untilSon et al. (2014), the methods are comparable. The majority of the mobility was quantified by analog devices such as goniometer, flexometer and meter.Son and Xia (2010)used a motion capture system for the analysis of the mobil-ity of the subjects. In principle, qualmobil-ity standards must be complied with for all ergo-nomic analyses.Hsiao and Halperin (1998)established a six step program:
Determination of the relevant body dimensions:
1. Determination of the target group (sex, age, and profession) 2. Selection of the number of subjects (cost-benefit)
3. Data collection as a basis for the statistical evaluation 4. Calculation of specific dimensional changes
5. Implementation of the necessary adjustments to the clothing products
This guarantees solid data for the development of ergonomic products and a practice-oriented use of anthropometric data. The measurement of the range of movement is considered as a recognized method, and the results are considered as objective and quantifiable.
Analog methods, however, do have the disadvantage of being very laborious and prone to mistakes. Two persons are necessary for anthropometric measurement. One measures the subject, and the other notes the results. The accuracy of the measure-ments depends highly on the measurer (Kouchi, 2014). The manual recording of data contains the risk for transfer errors. Landmarks that are used for different measure-ments must be marked consistently. The time required, depending on the number of measurements, is not insignificant and can possibly be stressful for the subjects.
This is because the survey is carried out on an unclothed body (in underwear) and requires a close proximity to the subject. Especially dimensions such as crotch length are usually perceived as rather uncomfortable.
Partially in studies, large differences were seen between the results of measure-ments of different measurers (interobserver error) (Goodwin et al., 1992; Kouchi, 2014). Here, reproducible methods must be developed so that the performers achieve a consistent identification of the anatomical landmarks and use of the anthropometric devices. Three-dimensional scanner systems in combination with semiautomatic mea-suring software reduce said sources of errors. For this reason, 3-D body scanners have been used in various scientific works (seeChapter 6).