STAGE 3 : Sizing system
7.2 Functional measurements
7.2.3 Analysis of functional measurements
To derive and analyze functional measurements on a larger sample size for the first time, a measurement study was initiated (Morlock, 2015a, b). For this, 93 subjects (men and women) between the ages of 17 and 65 were recorded and measured with a 3-D body scanner. The three-dimensional recording of the subjects was done with the Vitus Smart XXL. They were scanned at Hohenstein in the south of Germany. The participants were from the local area. Nevertheless the random sample shows a good regional distribution.
To cover the variety of body shapes of the population, the clothing size system of the last German sizing survey SizeGERMANY is divided into body height rows and figure types (Hohenstein Institute and Human Solutions GMBH, 2008). The types of men’s figures are determined by the difference between the chest girth and waist girth and in women by the difference between the bust girth and the hip girth. For men the body heights are differentiated between extra short, short, normal, tall, and extra tall.
The types of figures are divided into extra slim, slim, normal, heavy, and extra heavy.
The women accordingly have the differentiated body height rows of short, normal, and tall and the figure types narrow hips, normal hips, and wide hips.
The sample encompasses the size ranges: 42–64 (chest girth: 84–128cm) for men and 36–52 (bust girth: 72–104cm) for women. The body heights and figure types could be largely covered. Although the subjects were randomly selected, a good dis-tribution of body shapes could be achieved.
7.2.3.1 Landmarking
The prerequisite for recording reproducible body measurements in measuring studies is working with anthropometric landmarks. Many landmarks are identified in anthro-pometry by palpation of bony structures under the skin, for example, the spinous pro-cess of a vertebra. Three-dimensional laser scanners only capture the surface of the body. Bony structures are only visible, if at all, on slim people, who are assigned to the small clothing sizes. To be able to reproducibly measure and analyze the length and circumference measurements, physical markers must be applied to the subjects’
bodies prior to the scanning process. So the changes can be traced and contrasted by the movement.
In the area of motion capturing, retroreflective markers are used to perform motion analysis. These enable the identification and tracking of anthropometric points by camera systems. In principle, these markers would also be suitable for use in 3D scan-ners, but they are very expensive due to the retroreflective surface in the purchase price. A cost-effective alternative is commercially available polystyrene balls. In the project, various sizes were tested.
Here, there were two requirements: on the one hand, the smallest possible size, so that measuring sections are not negatively affected, and, on the other hand, that the scanner system can detect these reliably and the visibility is given on the 3-D scan.
Polystyrene balls with a circumference of around two centimeters fulfilled these conditions. The markers were attached to predefined anthropometric landmarks (e.g., the seventh cervical vertebrae and acromion) using a double-sided adhesive tape on the skin (seeFig. 7.3).
In the study, 16 markers on anthropometric landmarks and auxiliary points (such as arm crease) were adhered per test person prior to the scan (seeFig. 7.4).
7.2.3.2 Posture
The analysis of the movement-related change of body measurements is the focal point of the functional measurements. The challenge was to define positions that can be cap-tured with a 3-D scanner and put into practice by subjects in a reasonable time window (seeSection 7.2.3.3). Therefore a limit of 10 scan positions was required. Whole-body scans can be carried out in a few seconds. Nevertheless, it is scientifically proven that postures of subjects exhibit a large variety (Han et al., 2010;Lashawnda and Istook, 2002;Lu and Wang, 2010;Schwarz-M€uller et al., 2018). The postures to be taken for the scan are usually communicated verbally by the scan personnel to the test person.
To implement the instructions the subjects need the ability of proprioception, that is, Fig. 7.3 Example of physical markers on the human body according to anthropometric landmarks.
the awareness of body position and body movement in space. This is not equally dis-tinct in all subjects. The reproducibility of body postures by the subjects represents a significant challenge in the investigation of functional measurements. Even to per-form simple postures, mobility and holding strength are necessary. For example, in the case of one posture in the project, the subjects had to lift the right arm sideways to shoulder height (see position number 5 inFig. 7.5). This could not be performed equally by all the subjects. Some did not have the shoulder joint mobility to bring their arm to shoulder height. Others, on the other hand, found it hard to develop the power to keep their arms steady for the period of recording. Similar differences in performance were found in the “Bend” and “Squat” positions. The problems that arose particularly in these positions are described in more detail hereafter (seeSection 7.2.5). In general a special challenge can be seen in the fact that the static attitudes in the 3-D detection relate to movements. It is certainly much easier to perform movements in natural speed. Four-dimensional scanning systems will provide a solution to this challenge in the future. Nevertheless, future research will also have to deal with the problem of reproducible forms of movement.
Fig. 7.4 Position of the marker.
The derivation of the functional measurements is based on the difference that results when comparing different body positions, for example, the “Bend” to the standing ISO standard posture, which is used to determine the body measurements.
The standing standard posture has been called “Relaxed” since the implementation of the German sizing survey SizeGERMANY (Hohenstein Institute and Human Solutions GMBH, 2008; ISO—International Organisation for Standardization, 2010). It serves as a reference for all measuring sections (Kouchi, 2014; ISO—
International Organisation for Standardization, 1989). In addition, the “Standard,”
“Reach,” and “Seated 1” positions were recorded in the same way as the SizeGERMANY sizing survey. Additionally, six further positions were defined.
These positions are “Reach 2,” “Right Arm Outstretched,” “Lunge,” “Bend,”
“Squat,” and “Seated 2” (seeFig. 7.5). All 93 subjects were scanned in these positions.
7.2.3.3 Recording of the movement-oriented positions
The 3-D recording of the positions was done with the Vitus Smart XXL 3-D body scanner (Vitronic, n.d.). The scanner works with the optical triangulation measure-ment principle and provides a reliable and accurate system that has been tested in numerous previous measuring studies and allows accurate, noncontact, three-dimensional imaging of the human body. The advantage of this method is that, in con-trast to the manual measurement, 3-D data on posture can be extracted and the scanned data are still available for later evaluations. It is part of the category of laser scanners, which scan the surface by means of light and thus create a 3-D scan. This has the
1: Relaxed 2: Standard 3: Reach 4: Reach 2
6: Lunge
7: Bend 8: Squat 9: Seated 1 10: Seated 2
5: Right arm outstretched
Fig. 7.5 The defined positions for the analysis of the range of movement (ROM).
advantage that the scanning process is relatively fast (duration: approx. 10s/scan) and the physical markers on the subject are easily recognizable.
The disadvantage of using a 3-D body scanner for such a measurement survey is that the scan area is limited and, depending on the position, it can lead to severe shadowing of individual parts of the body (Kouchi, 2014). The detectable area amounts to 2100750750mm. Four lasers and eight cameras are positioned in the four columns. The rigid setting makes it difficult to detect horizontal areas and areas such as the armpit or crotch. Furthermore, for positions like “Bend” or
“Squat,” body parts conceal other areas. This also leads to unrecorded points. The lim-ited recording space of the scanner means that not all positions can be scanned. There-fore positions had to be adjusted and referred to the examined areas.
To reduce shadows the use of handheld 3-D scanners were discussed. Compared with 3-D body scanners, they can also be used to detect areas that are concealed by other parts of the body. This is because the device is guided manually around the body. The method requires experience in operation. Even with adequate skill a full-body scan takes several minutes. As a result the subject has to hold the individual positions much longer in comparison with the 3-D body scanner. This is neither fea-sible nor reasonable for many subjects in terms of physical condition. Due to the long recording time, individuals may be scanned using handheld systems. For larger groups of subjects, these scanners are not the method of choice.
For future studies in the field of functional measurements, it must be examined whether body scanners with structured light are better suited for this usage. These enable even shorter recording times and less shadowing than a laser scanner, since significantly more cameras with different viewing angles can be used.
7.2.3.4 Dimensions
In total, 21 measurements were taken from each of the 93 persons in the 10 different positions (seeTable 7.1), which were taken on the 3-D scans in 10 different positions with the aid of the measurement software ScanWorx (Human Solutions Gmbh, n.d.).
These include, alongside the primary measurements, chest girth, other girth, length, and distance measurements. The definition of the measuring sections is basically based on the ISO standard (ISO—International Organisation for Standardization, 1989). However, some measurement definitions had to be adjusted. The arm length was not measured according to the standard from the acromion to the wrist bone, but from the marker position of the “arm crease” (seeSection 7.2.3.1) to the wrist bones. This allowed the determination of the maximum arm reach in the movement that, in connection with the change in back width, must be covered by a clothing prod-uct. The measuring section of the upper arm circumference was also recorded differ-ently. In accordance with standards, measurements are taken at the strongest point directly at the transition from the shoulder to the arm. However, this rule cannot be applied to the measurement taken by 3-D body scans. This is because of the fact that large shadowing occurs at the transition from the shoulder to the arm, and so the mea-surement cannot be taken comprehensively. A standard-compliant registration would lead to measurement errors. The measurement values would be too small
(Kirchd€orfer, 2009). When examining functional measurements, it is crucial to iden-tify areas of the body that are subject to major changes. This was presumed with regard to the upper arm girth not directly at the transition from the shoulder to the arm. For this reason the marker determining the measurement was set on the most pronounced form of the upper arm, when viewed laterally.
In addition to the lengths, girths, and distances, new measuring sections were recorded in the project, such as the distance between seventh cervical and fourth lum-bar vertebrae, to be able to determine the dimensional differences relevant for clothing technology. All defined and recorded measurements are listed inTable 7.1.
The registration of individual measurements is not necessary in every position.
Because, in the different positions, depending on girth, proportional shadowing and overlapping of different body areas can appear on the scan. This can lead to individual measurements not being able to be exactly determined. Here the reliability of the respective measurement had to be evaluated individually for each scan. Nevertheless the aim was to register as many dimensions as possible for as many postures as pos-sible to ensure the comparability of the individual measurements.
From 93 scans in 10 positions, a total of around 8000 body measurements were taken. This demonstrates the very high processing effort that is necessary to research the functional measurements. Even though the sample size of 93 subjects seems to be
Table 7.1 Defined measurements Measurements
1. Body height
2. Chest circumference
3. Underbust circumference
4. Waist circumference
5. Distance—waist to apex point
6. Hip circumference
7. Distance—waist to seat (in seating position)
8. Leg length
9. Shoulder width
10. Across back width 11. Upper arm circumference 12. Back waist length
13. Distance—seventh cervical to fourth lumbar vertebrae 14. Distance—waist to crotch level
15. Knee height
16. Calf circumference 17. Arm length—standard
18. Arm length—arm fold to finger tips
19. Arm length—center-back-neck-point-to-wrist length
20. Upper arm length
21. Thigh circumference
rather small compared to other series measurements, the number of measurements to be taken multiplies due to the different forms of movement to be investigated.
Fig. 7.6shows an example of the registration of individual body measurements in two scanning positions. The markings illustrate the measurement positions. Compa-rability and reproducibility are important points not only for the definition of the mea-surements but also for the acquisition of the scans.