Research on the male lower torso for improving underwear design

Abstract

Increasing demands on contemporary men's underwear have affected the design method, including structure, knitted materials in accordance with male body morphology, comfort perception, and possible reshaping of soft tissues. The aims of this paper are to study body measurements to renew and to improve anthropometric and methodological databases, to classify the male lower torso into several size-based subtypes, and to refine body measurements for underwear design for the Chinese market. By means of scanning technology, we have obtained new information about male bodies’ morphology and established the sizing system for labeling of underwear in according with consumer demands. The new classification has two main levels and six stages to determine the lower torso and prominent local areas in the front and back. The new body measurements have improved the method of underwear design, making the underwear more comfortable and suitable for individual morphological features.

Keywords

3D body scanner body measurements classification male lower torsos underwear

Contemporary styles of men's underwear are gradually developing, and this has become an area of rapid innovation in the men's clothing market.¹ There are many kinds of men's underwear according to their function and application (daily, sports, shaping, etc.). Consumer demand is affected by many aspects, such as market responsibility, brand, uniqueness of underwear,² and the possibility of customizing the body morphology.³ Wear comfort is the priority.⁴

Currently, men's underwear is designed on the traditional basis, using body measurements (such as waist girth, hip girth, weight, or height), and final garments are labeled as medium, large, etc.⁵ The body measurements mentioned cannot support and reflect all functions of underwear, because it is impossible to design suitable garments without some crucial measurements related to lower body morphology.⁶ Populations of males in certain countries wear different categories and types of underwear, depending on the anthropometrical and morphological characteristics of their lower bodies, climate, social mentality, etc. However, the general methods of manufacture are similar.⁷ Some national and international brands use different sizing systems and size charts for underwear styles due to different geographic traditions.⁸ Moreover, similar methods of underwear labeling and a limited approach to male body groups are not enough to offer the necessary garment features and different styles.⁹ Consumers with distinct physiological characteristics and non-typical bodies generally use the same sizes at present.¹⁰ Therefore, consumers and pattern-makers need more information about the specific features of underwear wearing comfort, functionality, and many other aspects that are necessary for customization.

The existing pattern-drafting methods for men's underwear are very simple, and are based on several body measurements and final garment dimensions.³ Figure 1 shows the scheme of traditional measurements that are taken from the body and those used to create ready-to-wear garments.

As shown in Figure 1(a), there are three main body measurements: the natural waist girth W_G, (smallest girth at waist level, WL), hip girth H_G (largest girth at hip level, HL), and crotch depth (the distance between WL and seat level). The crotch depth is measured in the sitting position and is affected by the thickness of buttock tissues.

Figure 1(b) shows five dimensions (front and back length, crotch depth/from waistband to bottom, waistband length, and hip length) used to produce ready-to-wear garments. The dimensions are not equal to the body measurements, and the properties of knitted material (such as elongation in vertical and horizontal directions) will be affected by the differences between the two sets of measurements.

As mentioned above, there are no accurate, detailed, scientific pattern-drafting methods for underwear prototypes. Therefore, to create a new method for men's underwear pattern block drafting, we need additional and new information to enhance customer satisfaction, to make the underwear more close-fitting and comfortable, and to reduce production costs for some kinds of underwear with positive functions (pressure, push-up, etc.).¹⁴ Additional body measurements should be added to describe the male morphology more precisely.¹⁵ Improvements and development of underwear design cannot be achieved without structural changes of databases that hold this information.

During our earlier work, we collected information on the opinions and needs of more than 470 males from China, France, Russia, and Bangladesh.¹⁶ Most respondents stressed the importance of underwear size, type, and front crotch; moreover, the majority of respondents also said that the simple way underwear are labeled (medium, large, etc.) does not give them good choices when buying underwear. In earlier experiments we studied the comfort and structural design of men's underwear for more comprehensive and integrated analysis.¹⁷ Traditional body measurements used for labeling and design of underwear are outdated and unreasonable, and should be adjusted and reformed.

The improvement of men's underwear can be realized through the optimization of style, pattern, structural design, and sizing system updates.¹⁸ It is necessary to use 3D body-scanning technology to obtain additional and more accurate information, including vertical and horizontal measurements that are more suitable for establishing the quantitative differences between body shapes.¹⁹

We aim to solve this problem by producing an underwear pattern design that reduces the risk of unsatisfactory production²⁰ and increases customer satisfaction.

Through the human bodies database statistics measured by a 3D body scanner, data analysis, and screening of important parts of the required data, we have built a measurement-based classification of large, medium, and small body types that reflect the features of lower torsos. The results can be used to define body characteristics and to classify men's underwear according to different sizes, types, or some style of key parts. Finally, in accordance with this classification, designers and pattern-makers can produce different types of men's underwear to satisfy various demands, such as personalized customization or mass production.

The proposed exploration

Objects and methods of research

We have measured some crucial dimensions that can help to provide the basis for subsequent experiments.²¹ Body measurements, referred to here as “traditional” and “new,” were measured in two ways. Traditional measurements were obtained directly using a 3D body scanner; the new measurements were extracted and calculated by using full-size digital images, and horizontal and vertical cross-sections after processing and analysis. We combined the two methods to create a new classification of male bodies.

The group of young males (aged 18–28 years) includes 115 Chinese and 39 Russians without structural deformations of the locomotor system; Chinese occupy a large part of the dataset. We used VITUS Smart XXL (a 360° non-contact 3D body scanner with four laser sensors and two cameras in each column) in accordance with the standard DIN EN ISO 20685 and Anthroscan (3D image-processing software) to determine the relevant body measurements. All subjects were required to wear their own general and comfortable tight-fitting boxers (fit, thin, no sagging, no shaping), and the genitals should be allowed to naturally droop. The main measurements are shown in Table 1 – as can be seen, there are a wide range of body measurements.

Table 1.

The mean of body measurements and standard deviation (cm)

Nationalities	Height	Natural waist girth	Hip girth	Crotch height
Chinese	174.4 ± 9.3	76.2 ± 6.8	94.2 ± 5.5	77.5 ± 5.3
Russian	180.1 ± 4.3	79.6 ± 4.8	96.9 ± 4.9	80.7 ± 3.0
Range	156.1–206.7	63.5–89.9	80.9–114.1	65.3–90.9

In this study, SPSS software was used to analyze the data and to verify the accuracy of measurements, including use of descriptive analysis, correlation analysis, variation trend analysis (diagrams), and linear regression analysis. Anthroscan, CorelDraw, Photoshop, and Richpeace CAD were used for visual presentation, image processing, and structural design (Figure 2).

Determination of crotch point

We selected vertical cross-sections through the crotch point Cr as the main information resource on the morphology of male lower torsos. The overlapping method of vertical cross-sections was used to establish the differences between the male lower bodies. At first, we cut the standing body in the sagittal plane using Anthroscan. It should be noted that this profile cross-section at the posterior part is almost closed at the vertebrae, and at hip level is closed to the sacrum. Therefore, the soft tissues are not especially affected at the seventh cervical (C7) or natural waist back point (WB). All anthropometrical points were located from the data using Anthroscan. Figure 3 illustrates our approach to the determination of Cr.

Figure 3(a) shows the scheme of the new method that we proposed to find the location of Cr. First, we drew two straight lines. Line a is from WB and tangents to the middle-lower section of the thoracic vertebrae. Line b is from WB to the end of the sacrum or coccyx as the peak point on buttocks. These two lines basically conform to the contour characteristics of the thoracic vertebrae and sacrum (or coccyx). Second, we located the middle point of the natural waist width in the sagittal plane by dividing the width in half. Third, we drew two new lines a′ and b′ in parallel to a and b through the middle crossover point of the natural waist width. Fourth, we drew the bisectrix line from the crossover point down to the bottom of the profile section to divide the angle between a′ and b′ in half. Cr can be found as the endpoint of the bisectrix line.

Cr is similar to the perineum under the lower torso and between thighs;²² it is located very near the ischium position and is affected by the tilt angle of the whole pelvis. There is a two-point connecting line between the iliac crest and ischium, which represents the tilt of the innominate bone.²³ Cr is an important point that is not easy to locate by means of manual measurement.

As shown in Figure 3(b), the larger the posterior pelvic tilt, the larger the lumbar kyphosis and sacrum downward; the larger the anterior pelvic tilt, the larger the lumbar lordosis and sacrum upward.²⁴ We know the tilt change of the innominate (pelvic tilt) affects the direction of the sacrum. For a normal spine (normal standing posture), the vertical guideline from C7 has a small offset (anterior) from the superior of the sacral promontory.^25, ²⁶ It is difficult to define the positions of Cr accurately by using the body scanner owing to the following misleading factors: limitations of light penetration between two thighs, the influence of underwear, the genital position as affected by underwear design, and standing posture.

Figure 3(d) shows four profile contours that were extracted from the scanned bodies and which presented special morphological characteristics, such as different genitals bulges, sacrum bulges, and upper torsos (vertebrae). We can see the obvious difference between the locations of Cr-new (black color) and Cr-old (white color) as defined by the body scanner. Cr-old was found by Anthroscan and its location (near the genitals or buttocks) as caused by machine measurement error is not reasonable; however, the location of the Cr-new point does not depend on body shape, genitals, or buttocks bulges.

Figure 3(e) shows the scheme for the new method of location Cr. In order to prove the accuracy and reasonableness of the new method, we divided HL by vertical line which is arising from new Cr point into front distance c and back distance d. The points c′ and d′ were separated by the Cr-old point determined by the scanner. Through re-measuring and comparing the profile sections, we obtained the data shown in Table 2.

Table 2.

The profile sections of male lower torsos and location of maximum differences (cm)

	c	d	Ratio (c/d)	c′	d′	Ratio (c′/d′)
Range	7.0–13.1	10.7–17.8	0.5–1.0	6.7–17.2	6.9–18.4	0.4–2.5
Mean (SD)	10.1 ± 1.3	14.0 ± 1.6	0.7 ± 0.1	11.3 ± 2.1	12.8 ± 1.6	1.0 ± 0.4

SD, standard deviation.

As can be seen, the range of c with the new method is greater than that of d, because the normal position of Cr is close to the anterior part of the human body (genitalia); the average distance of d is 3.9 cm and greater than c; the ratio c/d ≤ 1 is correct (excepting special types such as pelvic anterior tilt of a great degree). The difference between c′ and d′ is larger, which leads to the deviation of Cr; the ratio between c′ and d′ is from 0.4 to 2.5 cm; the mean is 1.0 cm with larger standard deviation 0.4 cm.

Figure 4 shows the results obtained by old and new methods.

As can be seen in Figure 4, the results of the old method are not consistent and so are unreasonable.

The new method has been tested step by step many times on bodies with different shape characteristics, and the results are more accurate than those determined by Anthroscan. The new method combines human anatomy with human morphology.

Schedule of indexes of profile cross-sections

To overlap the profile sections of lower torsos extracted from scanned bodies, we used two axes – WL as the horizontal axis, and the vertical axis from Cr. First, we drew the vertical line through Cr. Second, we put all WL that were established by Anthroscan together to create one horizontal guideline. We overlapped the profile sections according to two rules: first, put all Cr on a vertical guideline; second, put all WL on a horizontal guideline.

We overlapped all the profile sections for the next analysis. We took profile sections of the Chinese and the Russians for an example for comparison. To draw the average cross-sections, we used the average body measurements of 115 Chinese and 39 Russians. Figure 5 shows the method we proposed to find the average profile section.

First, we drew four vertical fixed lengths from WL downward to Cr (Figure 5(a)):

median (50th percentiles, Q2) distance to the level of the maximum belly (at profile view) circumference (7.94 cm);

median distance to the level of the genitals peak point (26.45 cm);

median of BR length in according with Cr vertical line (31.40 cm);

median distance to the level of the buttock peak (21.50 cm).

Second, we drew six horizontal fixed lengths from the vertical guideline equal to values as follows (Figure 5a)):

median distances to natural waist front (45.40 cm) and back (25.0 cm);

median distances to maximum belly front (45.17 cm) and back (24.89 cm);

median distance to hip bulge (20.50 cm);

median distance to genital bulge (46.0 cm).

Across seven points we drew the average vertical cross-section of the Chinese males (Figure 5(a)). We used the same method to draw the Russian average section (Figure 5(b)). The characteristics were measured from both overlapping profile sections, as Figure 5(c) shows.

New body measurements

We calculated additional body measurements to improve the pattern-making of men's underwear. Figure 6 shows the primary and additional body measurements extracted directly from the scanned lower torsos.

WL is the natural waist line; WF and WB are the waist front and waist back points, respectively; HL is the hip line across the peak of the buttocks, HB is the peak of the buttocks; GL is the genitals line/level across the bulge peak point; GF is the genitals peak point; CrL is the crotch line; Cr is the crotch point; TL is the thigh line.

Figure 6(a) shows the well-known body measurements of W_G, H_G, and CL, and the 10 primary body measurements obtained using the 3D body scanner. Figure 6(b) top shows the horizontal and vertical measurements; Figure 6(b) bottom shows the curved measurements.

The body measurements were divided into three groups:

1 Primary horizontal measurements:

WB_D: distance from concave waist back to vertical guideline;

HB_D: distance from buttock peak to vertical guideline;

GF_D: distance from genitals bulge peak to vertical guideline;

Abd_D: distance from front abdomen to vertical guideline.

2 Primary vertical measurements:

Δ(W_H – H_H): vertical distance from natural waist to hip level;

H_H: hip height;

W_H: natural waist height.

3 Primary arc measurements:

CL: full crotch length from WF through Cr to WB;

H_SL: side length from natural waist to hip;

T_SL: side length from natural waist to thigh.

Figure 6(b) shown 18 additional measurements that were calculated after processing our data in order to describe some crucial characteristics of male bodies. The additional measurements are expressed in abbreviations:

1 Additional horizontal measurements:

ΔGW = GF_D – Abd_D: difference between natural waist front and genitals bulge;

ΔWH = WB_D – HB_D: difference between hip peak and natural waist back;

Δ(H_G – W_G): difference between hip and natural waist girth;

NW_G: new waist girth as waistband located below natural waist level;

NT_G: new thigh girth as underwear bottom in horizontal and slope directions.

2 Additional vertical measurements:

Nav_H: navel waist height;

GF_H: height of genitals peak following wearing habits;

Cr_H: crotch level height;

BR = W_H – Cr_H: distance from natural waist to crotch level;

h_G = GF_H – Cr_H: difference between genitals peak point and crotch level;

h_T = Cr_H – T_H: difference between crotch and new thigh level (or underwear bottom);

h_H = H_H – Cr_H: difference between hip and crotch levels;

h_W = W_H – NW_H: difference between natural waist and waistband levels.

3 Additional arc measurements:

CL_F: front crotch length from WF front to Cr across genitals peak;

CL_B: back crotch length from Cr to WB through hip middle groove;

Cr_SL: side length from natural waist to crotch level;

ΔF = CL_F – BR: value describing genitals bulge;

ΔB = CL_B – BR: value describing hip (buttocks) bulge.

As shown above, h_G describes the genitals position, which is indefinite upward or downward according to personal wearing habits. ΔF is a quantitative characteristic of the genitals volume. ΔGW describes the genitals bulge in the horizontal direction (as the small width of the gray rectangle in Figure 6(b)) by GF and WF. It will be a negative value when the abdomen (waist front) bulge is larger than the genitals bulge. From our statistics, 25% of scanned males have a negative value of ΔGW (average negative mean value is –0.68 cm), and 75% of scanned males have a positive value of ΔGW (average positive value mean is 0.80 cm).

Results and analyses

Comparison of profile cross-sections

Table 3 shows the overlapped profile sections of the two groups and the differences for the Chinese and the Russians.

Table 3.

The profile sections of male lower torsos and locations of maximum differences (cm)

Overlapped profile sections	No.	Locations of differences	Differences (cm)
Overlapped profile sections	No.	Locations of differences	Chinese	Russians
	1	Natural waist front	6.9	6.3
	2	Natural waist back	9.8	5.5
	3	Buttock peak level	11.5	17.5
	4	Hip back	4.7	4.5
	5	Genitals bulge	5.4	4.1
	6	Crotch level position	8.1	12.3
	7	Genitals peak level	11.7	18.0
	8	Natural waist depth back	7.7	7.0

As can be seen in Table 3, the biggest differences are in the following important parts: front bulge–buttocks; buttock peak–genitals; height of Cr–body rise; crotch front–crotch back divided by Cr. The key differences are numbers 3, 5, and 7, and these are crucial in particular for functional underwear, especially those with “push-up” and lifting effects of buttocks or genitals.

In order to analyze the possibilities of male torsos reshape and obtain “push-up” effects by pressing on the soft tissues, 15 nude males without underwear and in daily underwear were scanned and measured in parallel, with written permission for the naked scanning. To analyze the phenomena of soft tissues lifting, curved lines were drawn according to the shape and contour of the testicles and the penis. According to our tests, the lifting distances are 2.1–8.8 cm for genitals and 0.2–1.1 cm for the peak of the buttocks.

Statistical analysis of new measurements

In most anthropometric applications, the number of measured people should be enough to do statistical reliable conclusions.²⁷ However, if the number of subjects obeys a normal distribution, a smaller value can be used to obtain accurate results. We controlled the number of all body measurements to be sure the data followed a normal distribution.

First, Cronbach's alpha is 0.86 by SPSS, and all data have good scores for the reliability test of internal consistency. We used the Shapiro–Wilk (S-W) test as this is the most powerful normality test in SPSS;²⁸ the S-W test provides better power than the Kolmogorov–Smirnov test,²⁹ and researchers recommend it as the best choice for testing the normality of data.³⁰ We also checked normality visually using the effective diagnostic tool of a Q–Q plot.³¹ Figure 7 shows the significant normal distributions of the Q–Q plot of two body measurements – the crotch height Cr_H and the navel waist height Nav_H.

As shown in Figure 7, both Q–Q plots of crotch height Cr_H and navel waist height Nav_H prove that the 115 measurements of Chinese males obey a normal distribution; this is the same conclusion as provided for the other measurements and their normal distributions. Therefore 115 Chinese young males can be used to represent the male population and n = 115 is a large enough sample to continue this investigation.³²

We applied the method of correlation analysis to choose the key measurements to form the basis of male body classification for underwear design. The traditional measurements, such as girth, allow us to describe and classify the lower torsos only in one dimension. The additional measurements such as lengths, straight distances, girths, etc. can be used to describe the torsos in horizontal and vertical dimensions, but they also reflect the features of the front and back of the body. For example, ΔGW and ΔWH represent male genital size and buttock size; NW_G and NT_G allow to calculate accurately the length of waistband and length of underwear bottom.

We should make sure that the new measurements we have chosen are independent of the primary measurements. If the correlation coefficient is smaller than the crucial coefficient, a strong relationship between the primary and additional measurements does not exist. The crucial correlation coefficient is r = 0.321 for n = 115, and the level of probability is 99.9% (0.001) according to the Bolshev–Smirnov statistical handbook.³³ Table 4 shows the correlation matrix between the additional and primary measurements and the number of strong relationships between them. The results are a fraction, where r is the correlation coefficient and sig. is the p-value of significance; if the p-value is less than the chosen significance level (α < 0.01, two-tailed), it suggests the observed data are sufficiently significant in their correlation. We take NW_G = –8 cm below WL and NT_G in the horizontal position as examples.

Table 4.

Correlation matrix

Additional measurements	Correlation coefficient r/p.										Number of correlation coefficients for strong relationship
	Traditional body measurements			Primary measurements
	W _G	H _G	CL	WB _D	HB _D	GF _D	Abd _D	Δ(W_H – H_H)	H _SL	T _SL
ΔGW	0.05	0.11	0.09	0.08	0.15	0.30	−0.06	0.13	−0.03	0.24	0
ΔGW	0.67	0.28	0.39	0.46	0.14	0.00	0.55	0.23	0.51	0.88	0
ΔWH	0.07	0.08	−0.14	0.50	–0.42	−0.24	−0.22	−0.21	−0.12	−0.26	2
ΔWH	0.51	0.48	0.19	0.00	0.00	0.02	0.03	0.05	0.49	0.11	2
Δ(H_G – W_G)	−0.25	−0.01	0.03	0.26	0.26	0.16	0.13	0.24	0.16	−0.02	0
Δ(H_G – W_G)	0.01	0.89	0.81	0.01	0.01	0.13	0.22	0.01	0.03	0.38	0
ΔF	0.09	0.17	0.57	−0.13	0.13	0.42	0.36	−0.03	−0.22	–0.43	4
ΔF	0.41	0.09	0.00	0.20	0.74	0.00	0.00	0.78	0.22	0.01	3
ΔB	0.23	0.24	0.52	0.13	0.37	0.40	0.36	−0.11	0.19	−0.20	4
ΔB	0.09	0.17	0.00	0.01	0.00	0.00	0.00	0.28	0.28	0.26	4
BR	0.32	0.49	0.22	0.14	0.29	0.28	0.25	0.34	0.29	0.14	2
BR	0.00	0.00	0.00	0.23	0.22	0.00	0.00	0.00	0.34	0.15	6
Nav _H	−0.05	0.16	0.41	0.22	0.36	0.14	0.13	0.40	0.19	0.32	3
Nav _H	0.59	0.09	0.00	0.21	0.00	0.00	0.00	0.00	0.29	0.07	5
GF _H	−0.08	0.12	0.22	0.14	0.29	0.28	0.25	0.34	−0.07	0.16	1
GF _H	0.52	0.37	0.08	0.27	0.02	0.03	0.05	0.01	0.00	0.10	1
Cr _H	−0.05	0.16	0.20	−0.16	−0.04	0.19	0.15	−0.13	−0.03	0.51	0
Cr _H	0.59	0.09	0.56	0.04	0.00	0.18	0.23	0.00	0.12	0.04	2
h _G	0.03	0.16	0.57	−0.14	−0.04	0.46	0.47	−0.03	−0.46	0.25	4
h _G	0.84	0.23	0.05	0.17	.010	0.01	0.03	0.17	0.07	0.69	0
h _H	0.29	0.21	0.52	−0.27	−0.44	0.39	0.42	−0.11	−0.20	−0.21	4
h _H	0.00	0.02	0.04	0.14	0.73	0.07	0.15	0.17	0.07	0.86	1
CL _F	0.06	0.20	0.94	−0.08	0.12	0.65	0.64	0.31	−0.05	0.05	3
CL _F	0.57	0.05	0.00	0.44	0.25	0.00	0.00	0.00	0.94	0.78	4
CL _B	0.17	0.26	0.94	−0.17	−0.15	0.63	0.63	0.26	0.09	0.09	3
CL _B	0.10	0.01	0.00	0.10	0.16	0.00	0.00	0.01	0.11	0.64	3
NW_G (–8)	0.50	0.46	0.13	−0.16	−0.27	0.25	0.23	−0.06	−0.21	0.12	2
NW_G (–8)	0.00	0.00	0.24	0.29	0.02	0.01	0.02	0.85	0.90	0.39	2
NT_G (CrL, 0°)	0.02	0.06	0.04	−0.09	−0.10	0.02	−0.05	0.07	0.03	0.10	0
NT_G (CrL, 0°)	0.86	0.52	0.71	0.38	0.33	0.86	0.66	0.46	0.26	0.89	0

Bold, correlation is significant at the 0.01 level (two-tailed).

As shown in Table 4, four additional measurements – the difference between natural waist front and genitals bulge ΔGW, the difference between hip and natural waist girth Δ(H_G – W_G), the crotch level height Cr_H, and the new thigh girth at the underwear bottom in horizontal and slope directions NT_G (CrL, 0°) – are completely independent. These four additional measurements can be combined with any primary measurements to create a new approach to pattern block making.

Several measurements have some significant (strong) correlation with the primary measurements, because some of them are optimized and calculated through primary measurements. The additional body measurements have strong correlations (1–4) with primary measurements and need more careful consideration before their combination. Table 4 shows that only two measurements, ΔF and ΔB, have four significant correlations with several primary measurements. For example, the measurement ΔB has significant correlations with CL, HB_D, GF_D, and Abd_D; the measurement ΔWH has significant correlations with WB_D and HB_D. Instead of many measurements, we can use these two measurements – ΔB and ΔWH – for body classification and pattern design. h_G and h_H have four strong correlations, but with insufficient significance.

Though the primary measurements in Table 4 can be measured by the body scanner directly, they are still “new” measurements that can be applied to men's underwear design.

New measurements for the waist

Table 5 shows new additional measurements extracted from the waist area to find the length of the waistband.

Table 5.

Statistics of body measurements taken in the waist area (cm)

Measurements		Descriptives				Statistic for controlling the normal distribution
Measurements		Minimum	Maximum	Mean	SD	Statistic for controlling the normal distribution
Primary	W _G	63.5	93.3	76.24	6.81	0.13
Additional	Cr _H	65.3	90.9	77.50	5.26	0.42
	Nav _H	91.4	117.4	102.57	6.27	0.12
	Δ(W_H – H_H)	17.8	26.0	21.51	1.66	0.99

SD, standard deviation.

The results in Table 5 were analyzed through the S-W normality test by SPSS, all p > 0.05. The data were also checked with a Q–Q plot. All distributions of additional body measurements are close to the linear line, which indicates that the data in Table 5 belong to a normal distribution.³⁴ We chose these four measurements to calculate the waistband length and the differences between the waist girth and the hip girth.

The waistbands of some general functional underwear are very often located below the natural waist and usually below the navel. Therefore, to design the waistband in a comfortable position or underwear style for each body type, we should know the girth of the lower natural waist, here called the new waist girth NW_G.

Through our exploration and analysis of consumer preferences, we found that the average distance between waistband girth (NW_G) and natural waist (W_G) varies and is approximately 7.7 cm (or about 1.7 cm below the navel level, Nav_H). This level is located around and close to the top of the anterior and posterior of the superior iliac spine; the waistband in this position can be supported by both bones and can create a good fixed effect and pressure receptivity.

The average distance between the natural waist and hip level is 21.51 cm, so we set the distance from WL to the lowest position of NW_G as 20 cm. We named this distance between W_G and NW_G as h_W. Cross-sections from scanned bodies with equal separations of 1 cm were taken at each layer. Figure 8 shows the location of cross-sections and the box-plot.

As shown in Figure 8(b), NW_G is greater than W_G, and incrementing sequentially all mean values are presented in a steadily incremental trend. The interquartile range (IQR) becomes gradually smaller as it moves toward 20 cm (near hip level). The average standard deviation is ±6.08 cm. Base on the linear trend of mean values, we found the equation between NW_G and h_W to be:

N W_{G} = 0.02 {h_{W}}^{2} + 0.58 h_{W} + 75.89

(1)

where NW_G is the new waist girth used for the waistband location (cm), and h_W is the decline distance of NW_G from the natural waist (cm). The correlation coefficient is r = 0.997 for a level of probability of 95%.

New waist girth is significantly greater than the natural waist girth for most young males. This equation can be used to calculate the waistband dimension.

New measurements for the front

Consumers will encounter a variety of situations in which they are wearing underwear with individual body characteristics in the front (genitals), such as feelings of different tightness in the genital area provided by different front pouches of underwear.³⁵

Table 6 shows the measurement results taken from scanned bodies in profile cross-section. We used these to explore the features of the genital area, and to propose a new way to describe the front part for classification and underwear design.

Table 6.

Statistics of body measurements taken from the front of bodies (cm)

Measurements		Descriptives				Statistic for controlling the normal distribution
Measurements		Minimum	Maximum	Mean	SD	Statistic for controlling the normal distribution
Primary	BR	26.1	35.4	31.51	1.94	0.12
	Abd _D	41.3	52.3	46.01	2.41	0.08
	GF _D	40.9	52.7	46.82	4.36	0.45
Additional	h _G	–4.4	8.7	3.13	2.86	0.09
	CL _F	35.1	48.1	40.51	2.57	0.41
	ΔGW	–2.9	2.8	0.49	0.68	0.18
	ΔF	5.7	13.6	9.41	1.52	0.54

SD, standard deviation.

All data were analyzed through the S-W test by SPSS, p > 0.05, and were also checked by Q–Q plot. As shown in Table 6, the normality statistics proves that the data distribution is close to the linear line, thus the distributions of data are normal.

New measurements for the hip

Consumers also feel different perceptions of tightness in the hip area provided by different constructions of underwear due to male body characteristics in the back (hip). Different body characteristics, body movements (squatting), and knitted material properties will cause comfortable/uncomfortable feelings and materials deformation.

Table 7 shows the back body measurements taken from profile sections. We used these body measurements to explore the features of the hip area, to improve the design and performance of underwear. All data were analyzed through the S-W test by SPSS, p > 0.05

Table 7.

Statistics of body measurements taken from the hip (cm)

Measurements		Descriptives				Statistic for controlling the normal distribution
Measurements		Minimum	Maximum	Mean	SD	Statistic for controlling the normal distribution
Primary data	H _G	82.8	114.1	94.24	5.50	0.11
	WB _D	22.4	31.0	25.08	1.57	0.05
	HB _D	20.0	25.8	21.24	1.53	0.05
	H _H	75.1	99.4	86.56	4.86	0.24
Additional data	CL _B	34.1	45.8	38.69	2.20	0.81
	h _H	4.0	13.2	9.59	1.73	0.13
	ΔWH	1.1	8.8	3.88	1.15	0.15
	ΔB	3.6	14.5	7.59	1.46	0.10
	Δ(H_G – W_G)	8.4	28.5	18.00	4.26	0.40

SD, standard deviation.

As shown above, ΔB is the parameter for the prominent bulge at the rear (HB) and WB. ΔWH is the parameter for describing the buttock bulge. ΔWH is equal to the buttock bulge and the position (shape) of sacrum and fat mass (location) of soft tissues. ΔWH is represented by the horizontal width of the gray rectangle in Figure 6(b).

New measurements for the thigh

The underwear bottom can be located in different positions. To design the underwear bottom, we should know the new thigh girth NT_G measured in the sloping direction.

Figure 9 displays six kinds of men's underwear. As can be seen, the bottoms are designed in horizontal and sloping directions above or below CrL. We mark some important points, which are located on HL and CrL: point a is on HL, b is on the underwear bottom, and c is on CrL.

In Figure 9(a) the bottom of the underwear is located above CrL. This case includes the different locations of point b (for briefs and trunks), different bottom girth and slope, and different length of side seams. In Figure 9(b) the bottom of the underwear is located below CrL. This case, with the different locations of point b, represents the various underwear styles of tight-fitting boxers (from short to long). The configuration and location of the bottom will affect the bottom girth and underwear style.

Table 8 shows the body measurements that can be used to explore the features of the bottom line in different cases. All data were analyzed through the S-W test by SPSS, p > 0.05, and found to follow a normal distribution.

Table 8.

Statistics of body measurements taken from the thigh (cm)

Measurements		Descriptives				Statistic for controlling the normal distribution
Measurements		Minimum	Maximum	Mean	SD	Statistic for controlling the normal distribution
Primary	T _G	44.60	66.70	54.18	4.01	0.15
	H _SL	19.80	26.00	22.52	1.60	0.40
	T _SL	30.30	40.60	35.10	2.52	0.85
Additional	Cr _SL	27.95	35.95	32.33	2.10	0.77

SD, standard deviation.

In order to analyze the first case of bottom position, we need to measure the thigh girth in the oblique (sloping) direction. We extracted the oblique cross-sections of the thigh. Figure 10(a) shows how we cut the thigh by several oblique sections. Thirteen measurements with equal angular separation were taken at each layer, corresponding to 0–60° (every five degrees).

The vertex of the cut angles is located at the inner thigh and as close as possible to crotch level. When the angle increases to more than 60°, the bottom of the underwear is higher than the iliac crest and near to the WL, so we take 60° as the maximum angle. However, each angle from 0° to 60° has a crossover point with the body contour (Figure 10(a)), so we can measure the side length (SL) from WL to each crossover point of the back contour.

Figure 10(a) also shows the second case, in which the bottom of the underwear is located below CrL. For this kind of underwear, the bottom should be horizontal. We declined the cross-sections per 1 cm from 0 to 10 cm along the thigh, and named this distance as h_T.

Figure 10(b) shows the relationship between the cutting angle and NT_G; the average values of NT_G increases gradually. Figure 10(c) shows the side length measured from the natural waist down to CrL.

The linear relation between SL and NT_G is significantly negative, r = –0.989, p = 0.000. Figure 10(d) shows the relation between the horizontal girth NT_G and h_T, r = –0.998, p = 0.000. The linearity relation is significantly negative with a high adequacy. We derive the one-variable linear equations for calculating new tight oblique girth and horizontal girth NT_G:

N T_{G} = 81.64 - 0.89 \times SL r = - 0.989

(2)

N T_{G} = 0.54 \times h_{T} + 54.59 r = - 0.998,

(3)

where NT_G is the new thigh girth measured below or above the natural thigh level (cm); SL is the side seam length measured from the natural waist (cm); h_T is the range of NT_G below CrL; and r is the correlation coefficient for level of probability 95%.

The measured value NT_G is not recommended for direct application in underwear pattern-making. In order to make the underwear bottom very close to the thigh in accordance with different tensile and recovery properties of knitted materials, we must add a negative increment value (ease) to NT_G.

New classification

Before carrying out the classification, we should know the measurements such as W_G, H_G, GF_D, and WB_D, etc. in Figure 6(a), and BR, ΔF, ΔGW, etc. in Figure 6(b). Table 9 shows the new classification of male lower torsos divided into two levels.

Table 9.

New classification of male lower torsos

Main type	Subtypes algorithms	Intervals (cm)				SD
Main type	Subtypes algorithms	S (small)	M (middle)	L (large)		SD
First level	First stage, H_G	<92	92–98	>98		5.5
First level	Second stage, Δ(H_G – W_G)	>21, mark “−” (Small W_G)	14–21, “Blank mark” (middle W_G)	0–14, Mark “+” (large W_G)	* < 0, Mark “++” (extra-large W_G)	4.3
Second level	Third stage, ΔF = CL_F – BR	<8.3	8.3–10.7	>10.7		1.5
	Fourth sub-stage, ΔGW = GF_D – Abd_D	<0	0–1.1	>1.1		0.7
	Fifth stage, ΔB = CL_B – BR	<6.4	6.4–8.6	>8.6		1.5
	Sixth sub-stage, ΔWH = WB_D – HB_D	<2.7	2.7–4.9	>4.9		1.5
Proportion rates (%)		12–20	64–73	11–17		–

Note. The mark “++”means extra-large, and the fourth and sixth sub-stages further expound on this classification.

The first level is based on W_G and H_G, and we defined the total sizes of the lower torso visually (small or large for slim or obese bodies). The mark “*” was used for extra-large W_G for overweight male bodies.

The second level includes the crucial measurements for describing special characteristics of male bodies; the fourth and sixth sub-stages are the options to be added to pattern design and more detailed classification.

Therefore, the main stages to classify male lower torsos are the first, second, third, and fifth.

For the torsos of the first stage the range of H_G is 82.8–114.1 cm; the mean is 94.24 cm; the quartiles are Q₁ = 91.65 cm, Q₂ = 94.10 cm, and Q₃ = 97.75 cm; and the standard deviation is 5.5 cm, tested using SPSS frequencies. The torsos have been divided into three intervals by the value of quartiles. For example, the middle type, “M,” of male body has H_G = 92–98 cm and needs underwear of size 94 cm.

For the torsos of the second stage the range of Δ(H_G – W_G) is 17.8–26.0 cm; and the quartiles are Q₁ = 14.35 cm, Q₂ = 17.65 cm, and Q₃ = 20.80 cm. For example, the torsos of the middle type, “M,” at 14–21 cm, need the size of underwear to be 18 cm.

For the torsos of the third stage the range of ΔF is 5.70–13.60 cm; and the quartiles are Q₁ = 8.30 cm, Q₂ = 9.50 cm, and Q₃ = 10.70 cm. The torsos of middle type, “M,” at 8.3–10.7 cm, need the size of underwear to be 9.5 cm.

For the torsos of the fourth stage the range of ΔGW is –2.90–2.8 cm; the quartiles are Q₁ = 0.00 cm, Q₂ = 0.50 cm, and Q₃ = 1.10 cm. For the small, “S,” type of underwear we recommend ΔGW = 0–0.5, for the middle, “M,” type ΔGW is 0.5–1.5 cm, for the large, “L,” type ΔGW > 1.5. When the value of ΔGW becomes larger, the front pouch should also be larger.

For the torsos of the fifth stage the range of ΔB is 3.6–14.5 cm; the quartiles are Q₁ = 6.40 cm, Q₂ = 7.50 cm, and Q₃ = 8.60 cm. The torsos of the middle type, “M,” at 6.4–8.6 cm, need the size of the underwear to be 7.5 cm.

For the torsos of the sixth stage the range of ΔWH is 1.1–8.8 cm; the quartiles are Q₁ = 2.70 cm, Q₂ = 4.10 cm, and Q₃ = 4.85 cm. The torsos of the middle type, “M,” at 2.7–4.9 cm, need the size of the underwear to be 4.1 cm.

To illustrate the principles of torso classification, Figure 11(a) shows the overlapped horizontal cross-sections of H_G and W_G with similar waist and hip girths, and Figure 11(b) shows the overlapped vertical contours of four torso types.

The first level has two stages. To identify the first stage, we need to measure H_G and W_G. Based on the value of H_G we can classify the torso as S, M, or L according to the intervals established: < 92 cm, 92–cm, and >98 cm. As can be seen in Figure 11(a), the differences exist between the waist and the hip cross-sections: first, the proportional difference between the front and the back; and second, the difference between the locations of soft tissues on abdomen and hip areas. The variety of proportions between H_G and W_G will reflect the lower torso contours; this is the reason why we chose Δ(H_G – W_G) as the second stage of the first level.

After calculating the difference Δ(H_G – W_G), we marked the contour with “++” for extra-large W_G, “+” for large W_G (or similar values of H_G and W_G), “blank mark” for median W_G (called normal W_G), “–” for small W_G. Figure 11(b) shows the influence of Δ(H_G – W_G) on the torso contours when the size of the genitals is stable. We can see the variations of the profile front and back contours of torso types. When H_G equals S and Δ(H_G – W_G) equals “–,” the torso contour is marked as “S⁻” and has the smallest volume. When H_G equals L and Δ(H_G – W_G) equals “++,” the torso contour is marked as “L⁺⁺” and has the largest volume. As can be seen, the main torso changes are concentrated in the abdomen and buttock areas.

For example, if the torso has a small H_G and Δ(H_G – W_G) > 21 cm, it can be classified as “S⁻.” If the torso has a middle H_G and Δ(H_G – W_G) =14–21 cm, it can be classified as “M.” When the torso has a large H_G but it is close to W_G (the difference is 0–14 cm) or when W_G is larger than H_G (<0), it can be classified as “L⁺” or “L⁺⁺.”

The second level has four stages. It characterizes the morphology of male lower torsos and includes the indexes of the front and the back.

The third stage ΔF defines the size of male genitals and lower abdomen (fat or not). ΔB defines the sizes of the hip. After combining them with ΔGW (only to give details about differences between male genitals and waist front bulge) and ΔWH (only to give details about differences between buttock bulges and waist back concavity), the type S, M, and L of the front and back can be presented.

The third and fourth stages are related to the torso front, and ΔF and ΔGW are used to identify the types S, M, and L. If the torso has ΔGW = –0.1 cm and ΔF = 7.5 cm, it can be classified as S.

The fifth and sixth stages are related to the buttock shape, and ΔB and ΔWH are used to choose S, M, and L types. ΔF and ΔB can be used to classify the male lower torsos, and ΔGW and ΔWH to make the pattern block.

Finally, we could classify the lower torsos, for example, as M⁻/LM. It is easy to be clear about the identification of torso type. “M⁻” is the total type of torso based on W_G and H_G, “LM” is the front (ΔF, ΔGW) and hip (ΔB, ΔWH) characteristics. By this method, it is easy to describe the lower torso and to improve the underwear sizing system.

Table 10 shows three examples of lower torsos and their classification.

Table 10.

Examples of male torsos (cm)

Torso 1		Torso 2		Torso 3
S⁺/SS		M⁻/MM		L/LL
	H: 179.3 H_G: 88.7 Δ(H_G – W_G): 10.7		H: 186.5 H_G: 94.1 Δ(H_G – W_G): 21.2		H: 183.2 H_G: 110.9 Δ(H_G – W_G): 20.5
	ΔF: 6.5 ΔGW: –0.1 ΔB: 5.9 ΔWH: 2.0		ΔF: 10.6 ΔGW: 1.7 ΔB: 6.4 ΔWH: 5.6		ΔF: 10.8 ΔGW: 0.5 ΔB: 9.4 ΔWH: 6.0

As shown in Table 10, the genital bulge (ΔF) increases from torso 1 to torso 2; torso 1 (S⁺/SS) and 2 (M⁻/LM) both have a lean profile image, but have significant difference in the genital bulge, and the abdomen bulge of torso 1 is similar to that of torso 3. Torso 2 (M⁻/LM) has a medium size H_G, small size W_G, normal genitals size ΔF (8.3–10.7 cm), bulge size ΔGW > 1.1 cm, medium buttocks size, and bulge size > 4.9 cm.

Applying the new body measurements to underwear pattern drafting

We apply the new body measurements to pattern drafting of underwear for customization, on one hand, and for mass production, on the other. For customized underwear, it is possible to take the body measurements into the algorithm of pattern block drafting, as shown in Table 11. For mass production underwear, the fixed value can be determined according to the numerical ranges in Tables 9 and 11.

Table 11.

New basic patterns of underwear

Dimensions	Corresponding body measurements	Torso type (small, medium, large)	Reference values (cm)
Length /0–4/ = /12–15/	h_W NW_G below W_G	S, M, L	Design value
Length /1–2/ = /13–14/	h_H H_G above CrL	S M L	0.3·BR – 1 0.3·BR 0.3·BR + 1
Curve /4–6/ = /6′–15/	NW_G, in Table 2	S, M, L	Reference different h_W (add negative ease value)
Length /10–1/ = /20–18/	ΔWH, difference between the crotch back	S M L	2.6 4.1 5.6
Length /24–25/	ΔGW genitals bulge	S M L	0–0.5 0.5–1.5 1.5–3
Distance of /14–24/	According to h_G	S, M, L	0–4
Curves /11–9/ + /9′–21/	According to NT_G	S, M, L	Reference different angles and h_T (add negative ease)

Note: The slashes indicate the distance from one point to another point.

First, we drew a vertical guideline according to BR value (median is 31.4 cm for “M” type), defined NW_G for waistband (/4–6/) and H_G level (/2–3/) by means of H_W and H_H. We calculated 0.25 H_G and 0.25 NW_G as the front and the back width. Then we drew ΔWH (median is 4.1 ± 1.5 cm) along the extension of CrL in the back piece, and made sure that point 24 has the coordinates H_G and ΔGW in the front piece.

The bottom line is usually limited by the side seam and the inseam lines. It changes from small to large size in accordance with NW_G, H_G, ΔWH, etc. Moreover, under the condition of underwear bottom deformation, the length of the bottom in the pattern should be shorter (with negative ease allowance) than the real measurements to maintain a good tight fit.

For the pattern blocks of torsos 1–3, in accordance with Table 10, we can see their comparison in Figure 12(a).

The pattern block of torso 1 has a middle waist length and small front inset rise. The pattern block of torso 2 belongs completely to the middle type, but has the largest front inset rise and smallest waist length; the bottom length is similar as for torso 1. The pattern block of torso 3 has the largest buttock bulge but the middle size for the front inset rise, and the bottom length is longer than for torsos 1 and 2. All mentioned lengths and sizes were calculated in accordance with the new combination of body measurements.

For checking the pattern blocks, we chose two types of torsos (S⁺/SS and M⁻/MM) and sewed two boxer samples. For design of boxers, we chose the knitted material produced by the I'd company (Wuhan, China), consisting of 30% combed flax (70 S), 65% long-staple cotton, 5% spandex (20 D). Figure 12(b) shows the underwear. Both boxers fit to the body, without folds, with good support of the front and back. Both subjects felt comfortable and mentioned that the boxers followed their morphological features in all areas, in both static and dynamic poses.

The experimental check proved that our approach to connect the morphological features of male torsos based on new torso classifications and pattern block making can improve the fit and comfort of men's underwear.

Conclusion and limitations

The main purpose of this paper is to explain how to connect new information about bodies' morphology obtained using body-scanning technology with underwear design. We established the advanced approach combining the classification of male lower torsos, new body measurements, and new rules of pattern block design, which can improve and accelerate mass production and customization of underwear.

We found the way to calculate a new lower-waist girth NW_G and new thigh girth NT_G in accordance with underwear styles. The new method of identification of the Cr point was applied to parameterize the physical characteristics of the male lower torsos. Finally, we classified male lower torsos into distinct groups based on their morphological characteristics.

For practical applications, we obtained methods to apply these new body measurements and classifications to pattern design, prepared the recommendations for designing the underwear pattern, choosing the crucial sections of underwear construction with more reasonable and satisfactory characteristics based on body morphology. The new database could help to create a more detailed classification and to improve the labeling of male underwear to make consumers' choices easier and clearer.

Although this study validates the classification of 115 male torsos, it will be meaningful to continue the exploration by increasing the number of males with more significant morphological differences and ethnicity-based features.

We will complete further research by means of CAD and new modules responsible for manipulating with the properties of knitted materials, pressure comfort, push-up effects, pattern grading, and 3D visualization to unify the morphological features of the male torso and underwear construction into a universal system of virtual underwear design.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work has been fully supported by the Russian Ministry of Science and Education under Project Number 2.2425.2017/4.6 “Development of software for virtual design of system ‘body – clothes’ in static and dynamic and for virtual try-on ‘FashionNet.’”

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