Anthropometric Characteristics and Somatotype of Young Slovenian Tennis Players

Abstract

Tennis is a demanding sport that requires physical abilities and optimal body composition. The aim of this study was to investigate the anthropometric characteristics, body composition, and somatotype development of young Slovenian tennis players (754 boys and 514 girls aged 12 to 18 years) over the last two decades. Using standardised anthropometric measurements and the Heath-Carter method, somatotypes were calculated and analysed by age and gender. The results showed clear age- and gender-specific trends and differences in both somatotype profiles and detailed anthropometric characteristics. Significant differences were found in height, body mass, BMI, skinfolds, girths, and limb lengths, with gender differences becoming more pronounced in the older age groups. In boys, mesomorphy increased with age, reflecting an increase in musculature, while in girls, a shift from ectomorphic to endomorphic profiles was observed during adolescence, probably influenced by pubertal and hormonal changes. Significant sex-specific differences were observed in all three somatotype components in most age groups, especially in fat mass and muscle. The longitudinal design provides valuable data and insights into the evolving physical profiles of adolescent tennis players that support more effective talent identification and training. Despite the changes that have taken place in tennis over time, standardised measurement protocols ensured comparability, making the results relevant for practitioners working with adolescents in tennis development.

1. Introduction

Tennis is a popular racket sport with more than 87 million players worldwide [1]. In recent decades, tennis has developed from a predominantly technical sport into a more explosive, physically demanding, and dynamic sport [2]. It requires high performance in the areas of speed, agility, strength, and power [3,4], as well as cardio-respiratory capacity and muscular endurance [5]. Tennis requires technical, tactical, and mental skills and high levels of motor and functional capacity, which is also linked to anthropometric characteristics [6]. A pronounced arm span and height in male tennis players and body mass in female tennis players have a positive influence on the transmission of higher speed to the racket head through longer connecting body segments [7,8].

Body composition is considered a determinant of athletic health and performance of athletes [9]. It describes the quantity of the various components of the human body. Body composition can be determined at the cellular level, which includes fat cells, body cell mass, and intra- and extracellular water, and at the tissue level, which includes adipose tissue, lean soft tissue, and skeletal muscle mass [10].

Optimal body composition for a particular racquet sport is essential for the development of a successful athletic career [11], for the assessment of general health [12], and as a useful method for talent recognition in tennis [13]. The percentage of body fat in young tennis players is around 13% [14]. It has been found that tennis players at the highest level are always significantly higher, with values of around 19–21% in women [15] and 7.3–16.5% in men [16]. Compared to other racquet sports, elite tennis players had lower fat mass than elite senior table tennis [11] and paddle [17] players and more than elite badminton [18] and squash players [19].

The somatotype is defined as the quantification of the current morphological constitution and composition of the human body [20]. It is expressed in a three-level assessment, with each level representing the components of endomorphy, mesomorphy, and ectomorphy in the same order. The Heath-Carter method [21] is based on anthropometric measurements such as mass, stature, skinfolds, widths, and circumference measurements [12].

Elliott et al. [22] observed young boys and girls and came to the conclusion that they exhibit ectomesomorphic somatotypes. Berral-Aguilar et al. [13] found differences between the sexes: the men were mesoectomorphic, and the women endomesomorphic. In a study of elite male and female junior players, these somatotype profiles were confirmed [23], suggesting that these parameters have not changed in players who are still developing [24].

Given the lack of longitudinal studies, our aim was to describe the anthropometric characteristics, body composition, and somatotype of young tennis players over the last two decades in order to analyse trends, improve the method of identifying talented athletes, and increase the effectiveness of training young tennis players through advice on lifestyle, nutrition, and fitness training.

2. Materials and Methods

2.1. Participants

A total of 1268 young Slovenian tennis players (754 boys and 514 girls) with an average age of 13.4 ± 1.9 years were included in this retrospective observational cohort study. Across the age categories (U12, U14, U16, and U18), repeated measurements resulted in a total of 2125 data entries, with an average of 2.15 repeated observations per person. All of them participated in regular training, were highly ranked on the national ranking list (top 10 national ranking), and were selected by the national coach to participate in the annual measurements of adolescent tennis players organised every year at the Faculty of Sport. None of the participants suffered a serious injury at least three months before the test sessions. A sample size calculation using G*Power (version 3.1.9.4, developed at Universität Kiel, Germany) for a Wilcoxon–Mann–Whitney test (two-tailed, α = 0.05, power = 0.80, effect size d = 0.5) indicated that 67 participants per group were required to detect a moderate effect.

All parents or guardians of the participants gave written informed consent in accordance with the Declaration of Helsinki. This study was approved by the Faculty Ethics Committee. Participants were matched by gender (males vs. females) and within each gender by age category. The mean age and number of data entries for each category are shown in

Table 1. Sample characteristics.

	Sex	N	Age Mean ± SD	Avg. Repeated Measures per Person
Under 12	Boys	282	11.1 ± 0.58	(e.g., 1.5)
	Girls	251	11.2 ± 0.57	(e.g., 1.7)
Under 14	Boys	434	13.0 ± 0.58	(e.g., 2.0)
	Girls	328	12.9 ± 0.55	(e.g., 1.9)
Under 16	Boys	351	14.9 ± 0.56	(e.g., 2.2)
	Girls	229	14.9 ± 0.57	(e.g., 2.1)
Under 18	Boys	164	16.8 ± 0.56	(e.g., 2.3)
	Girls	86	16.8 ± 0.54	(e.g., 2.0)
		2125	13.4 ± 1.9	(e.g., 2.15)

.

2.2. Data Collection Procedures

The anthropometric measurements were performed in a physiological laboratory according to the standardised procedures described by the International Society for the Advancement of Kinanthropometry [25]. The anthropometric measurements were performed on the same day for each annual test series, starting in the morning and ending at 2 pm. The test procedures followed standardised ISAK protocols, where the same calibrated equipment was used in all measurement sessions, the measurement technicians were trained according to the same protocol, the measurement supervisor was the same person, and the measurement locations were the same. All measurements were taken by the same examiner on the dominant and non-dominant sides of each athlete. Height was measured using a portable stadiometer and girths were measured to the nearest 0.1 cm using a tape measure. The following longitudinal measurements were taken: leg length and arm length. Then, the transverse measurements were taken: width of shoulders and diameter of elbows, knees, and ankles. The skinfolds were measured three times at each anatomical site to the nearest 0.1 mm using a caliper (Holtain, Crosswell, UK), and the average was used for data analysis. Skinfolds were measured at the back, upper arm, biceps, forearm, chest, abdomen, thigh, hip, and calf. Body circumferences were measured at each anatomical site to the nearest 0.1 cm using an ergonomic tape measure. The circumferences of the flexed and relaxed upper arm, the chest (normal and maximum), the calf, and the thigh circumference were measured. Body weight was measured using a scale (Seca 702, Seca, GmbH & Co KG, Hamburg, Germany) with an accuracy of 0.1 kg.

2.3. Data Processing and Statistical Analysis

All analyses were performed with R (version 4.5.0) in RStudio (version 2025.05.0). Data were first checked for completeness and accuracy. Descriptive statistics, including mean, standard deviation (SD), and range, were calculated for all anthropometric variables separately by age category (under 12, under 14, under 16, and under 18) and gender (boys and girls). BMI was calculated by dividing weight (in kilograms) by height squared (in meters squared). The distribution of somatotypes by sex and age category was visualised with ternary plots showing individual data points and group means for each category and sex. Somatotypes were calculated using the equations of Carter and Heath [21]. Normality of anthropometric characteristics and somatotype components (endomorphy, mesomorphy, and ectomorphy) was assessed within each age category using the Shapiro–Wilk test. As the data in most groups did not meet the assumptions of normality, non-parametric tests were used. The Kruskal–Wallis rank sum test was used to assess differences in somatotype components between age categories. When significant differences were found, pairwise comparisons were performed using the Wilcoxon rank sum test with Bonferroni correction to adjust for multiple comparisons. Statistical significance was set at p < 0.05. Gender differences within each age group were also assessed using the Wilcoxon rank sum test.

3. Results

Descriptive statistics, including mean, standard deviation, and range, are presented for anthropometric variables in four age categories (under 12, under 14, under 16, and under 18) separately for boys and girls (

Table 2. Anthropometric characteristics and skinfold measurements.

		Under 12		Under 14		Under 16		Under 18
		Mean ± SD	Range	Mean ± SD	Range	Mean ± SD	Range	Mean ± SD	Range
Height (cm)	Boys	149.25 ± 6.39	130.70–176.50	161.00 ± 8.56	137.90–186.20	174.58 ± 7.64	150.40–197.10	180.59 ± 5.57	167.90–195.30
	Girls	151.03 ± 7.29	133.00–176.80	161.81 ± 6.79	142.00–181.50	167.63 ± 5.69	154.00–184.70	169.76 ± 5.57	156.40–184.40
Weight (kg)	Boys	39.01 ± 6.28	24.10–67.70	48.16 ± 9.04	29.00–86.00	61.88 ± 9.42	38.50–94.20	71.27 ± 6.92	58.90–92.10
	Girls	39.77 ± 6.75	26.50–61.70	49.50 ± 7.74	30.50–80.90	57.72 ± 6.69	37.30–77.80	62.00 ± 6.56	48.00–81.20
BMI (kg m−2)	Boys	17.43 ± 2.03	13.55–26.05	18.45 ± 2.19	13.97–28.11	20.20 ± 2.05	14.71–26.99	21.83 ± 1.88	17.74–28.74
	Girls	17.36 ± 1.96	14.08–23.82	18.83 ± 2.14	11.65–26.60	20.54 ± 2.04	14.81–28.82	21.46 ± 1.72	17.72–26.57
Calf skinfold (mm)	Boys	10.87 ± 4.45	4.20–26.00	10.98 ± 4.40	3.80–31.60	9.37 ± 3.29	3.80–25.40	8.73 ± 3.24	4.20–27.80
	Girls	11.90 ± 4.58	3.40–31.60	12.52 ± 4.18	2.30–35.60	13.96 ± 4.56	4.00–32.20	14.23 ± 4.86	7.00–32.00
Thigh skinfold (mm)	Boys	15.62 ± 5.87	4.00–36.00	14.81 ± 5.56	4.00–38.80	12.50 ± 4.31	5.20–28.00	11.71 ± 4.11	5.20–31.20
	Girls	17.18 ± 5.49	6.20–38.00	17.84 ± 5.15	1.80–40.00	21.21 ± 6.06	3.40–42.20	22.84 ± 5.87	6.80–36.40
Suprailiac skinfold (mm)	Boys	8.03 ± 4.40	3.00–26.80	8.63 ± 4.59	2.60–32.60	8.81 ± 3.66	3.50–28.40	10.25 ± 4.21	4.00–27.80
	Girls	9.68 ± 5.08	3.60–35.60	11.36 ± 5.28	1.20–38.40	14.02 ± 5.60	4.10–39.40	14.86 ± 4.64	5.20–27.20
Abdominal skinfold (mm)	Boys	9.76 ± 6.53	1.10–32.20	10.22 ± 6.60	3.00–40.00	9.88 ± 4.76	4.00–33.20	11.07 ± 5.12	4.00–32.40
	Girls	11.67 ± 6.88	3.60–39.20	13.05 ± 6.52	4.00–40.00	15.79 ± 6.61	5.00–40.00	16.53 ± 6.02	5.20–33.20
Subscapular skinfold (mm)	Boys	6.90 ± 3.15	3.00–28.20	7.13 ± 3.09	3.40–26.60	7.38 ± 2.04	4.00–19.80	8.68 ± 2.90	4.80–30.60
	Girls	7.64 ± 3.73	3.60–24.20	8.26 ± 3.27	3.60–28.80	9.61 ± 3.57	5.00–32.80	10.54 ± 2.95	6.00–21.20
Tricep skinfold (mm)	Boys	10.22 ± 3.61	4.20–21.80	9.67 ± 3.65	3.80–26.40	8.40 ± 2.72	3.80–23.40	8.86 ± 4.54	4.10–60.50
	Girls	10.68 ± 3.60	4.60–27.40	10.98 ± 3.23	5.00–27.20	12.80 ± 3.68	4.40–31.20	13.37 ± 3.38	4.00–21.40
Bicep skinfold (mm)	Boys	5.29 ± 2.19	2.00–15.00	5.38 ± 2.43	2.40–16.00	4.63 ± 1.61	2.40–13.20	4.61 ± 1.31	2.60–9.40
	Girls	6.04 ± 2.64	2.30–24.00	6.17 ± 2.21	1.10–16.20	6.91 ± 2.47	2.80–19.00	7.20 ± 2.45	3.20–15.80
Forearm skinfold (mm)	Boys	7.20 ± 2.32	3.20–16.20	6.82 ± 2.24	3.20–20.00	6.10 ± 1.63	3.00–15.80	5.96 ± 1.51	3.40–13.60
	Girls	7.36 ± 2.31	3.20–19.00	7.56 ± 2.01	4.00–14.80	8.22 ± 2.08	3.10–16.20	8.24 ± 2.24	4.00–17.00
Chest skinfold (mm)	Boys	8.32 ± 4.31	3.00–25.80	7.78 ± 4.22	2.60–30.00	6.80 ± 2.63	3.20–20.40	6.70 ± 2.47	4.00–20.40
	Girls	8.32 ± 4.50	3.00–36.20	8.27 ± 3.86	2.80–24.60	9.29 ± 4.16	2.80–35.40	8.98 ± 2.80	4.00–19.40
Upper arm girth (cm) *	Boys	21.45 ± 2.36	16.00–29.30	22.91 ± 2.43	17.50–31.50	25.26 ± 2.45	18.10–33.00	27.24 ± 2.00	20.60–32.30
	Girls	21.70 ± 2.32	8.60–30.50	23.16 ± 2.07	17.60–30.20	24.88 ± 1.98	18.00–32.00	25.77 ± 1.65	22.00–32.80
Upper arm girth (cm) **	Boys	23.05 ± 2.31	18.20–31.20	24.81 ± 2.57	18.30–33.70	27.68 ± 2.72	19.90–36.80	29.96 ± 2.26	17.60–35.50
	Girls	21.79 ± 2.07	17.70–29.80	24.66 ± 2.21	14.00–33.50	26.42 ± 2.03	18.90–33.00	27.35 ± 1.64	23.10–33.10
Thigh girth (cm)	Boys	44.71 ± 4.49	35.10–60.60	48.03 ± 4.79	31.90–69.50	52.40 ± 4.35	40.80–66.40	55.74 ± 3.69	35.40–63.80
	Girls	46.21 ± 4.13	35.70–58.40	50.56 ± 4.55	31.20–68.00	54.93 ± 4.05	40.40–66.00	57.33 ± 3.43	50.10–64.50
Calf girth (cm)	Boys	30.63 ± 2.41	25.40–39.20	32.96 ± 2.76	26.30–43.50	35.71 ± 2.65	26.00–44.40	37.64 ± 4.05	33.00–83.80
	Girls	30.93 ± 2.37	20.80–38.00	33.42 ± 2.63	27.60–56.40	35.38 ± 2.74	24.10–55.80	36.58 ± 1.93	32.60–41.60
Chest girth (cm)	Boys	70.58 ± 4.97	46.20–90.00	76.18 ± 6.02	46.20–100.00	84.18 ± 6.15	60.00–102.20	90.43 ± 4.66	79.00–105.00
	Girls	70.41 ± 6.22	46.10–90.50	75.81 ± 6.48	61.00–92.50	79.79 ± 6.24	64.80–96.60	80.87 ± 5.80	70.40–92.00
Chest girth—max (cm)	Boys	75.12 ± 4.63	64.60–94.00	80.53 ± 6.04	42.10–102.00	88.72 ± 6.10	58.00–106.00	94.81 ± 4.16	83.30–107.90
	Girls	74.79 ± 5.96	61.60–92.30	80.32 ± 6.39	58.70–96.40	84.28 ± 6.92	38.00–99.60	85.52 ± 5.46	74.20–95.50
Shoulder width (cm)	Boys	31.91 ± 2.05	24.00–45.10	34.13 ± 2.39	25.40–40.40	37.50 ± 2.57	27.10–44.00	39.62 ± 2.08	30.40–45.00
	Girls	31.98 ± 1.85	25.90–38.50	34.34 ± 2.04	25.00–39.10	35.86 ± 1.84	25.80–39.50	36.63 ± 1.86	26.50–39.60
Humeral breadth (cm)	Boys	6.07 ± 0.38	5.20–7.00	6.48 ± 0.47	5.30–8.10	6.94 ± 0.47	5.30–8.00	7.04 ± 0.47	4.70–8.30
	Girls	5.89 ± 0.36	5.00–7.10	6.17 ± 0.37	5.00–8.90	6.23 ± 0.34	5.30–7.10	6.40 ± 1.97	5.40–26.20
Femoral breadth (cm)	Boys	8.85 ± 0.42	7.60–10.00	9.29 ± 0.49	6.70–10.70	9.70 ± 0.47	8.00–11.40	9.73 ± 0.68	5.10–10.90
	Girls	8.46 ± 0.45	6.70–10.00	8.66 ± 0.47	6.20–10.00	8.80 ± 0.43	7.50–11.00	8.83 ± 0.44	8.00–10.10
Bimalleolar breadth (cm)	Boys	6.80 ± 0.39	5.00–7.80	7.10 ± 0.43	5.70–8.50	7.46 ± 0.45	5.70–8.80	7.55 ± 0.46	6.10–8.90
	Girls	6.44 ± 0.36	5.00–7.80	6.65 ± 0.42	3.60–8.80	6.67 ± 0.39	5.80–7.80	6.68 ± 0.36	5.80–7.60
Leg length (cm)	Boys	84.67 ± 7.18	59.00–99.00	92.59 ± 7.09	63.40–111.40	100.06 ± 6.94	70.30–118.20	103.70 ± 4.96	83.80–117.30
	Girls	86.05 ± 6.84	61.00–99.90	92.64 ± 6.17	63.70–108.00	95.20 ± 6.22	68.50–108.90	95.21 ± 7.35	71.60–109.00
Arm length (cm)	Boys	66.47 ± 5.92	55.50–90.90	71.77 ± 6.66	59.80–103.60	77.89 ± 6.17	65.20–107.00	79.51 ± 4.60	70.30–111.40
	Girls	66.40 ± 5.96	53.70–92.90	70.95 ± 5.41	61.00–98.60	73.40 ± 5.67	62.10–103.70	74.42 ± 6.54	62.70–98.20

* Relaxed; ** flexed and tensed.

). As expected, the values for the longitudinal, transverse, and circumferential measurements increase with age, while the changes in skinfolds vary according to gender and measurement location on the body.

Significant differences in body height, body mass, and BMI were observed across all age categories, from U12 to U18 (all p < 0.001). Among skinfold measurements, the suprailiac, abdominal (except U16 vs. U18, p = 0.137), and subscapular sites showed significant differences in nearly all pairwise comparisons (p < 0.05), reflecting age-related changes in fat distribution. Calf skinfold thickness was significantly different in selected comparisons (e.g., U14 vs. U16, U14 vs. U18, and U12 vs. U18), while thigh and forearm skinfolds showed significant differences primarily between the youngest and oldest groups (U12 vs. U18 and U14 vs. U18, p < 0.05). In contrast, triceps, biceps, and chest skinfolds did not show significant age-related changes (all p > 0.05). Age-related increases were also observed in upper arm, thigh, calf, and chest girths, with all comparisons showing strong statistical significance (p < 0.001). Similarly, both leg and arm lengths increased consistently with age (p < 0.001). However, no significant differences were found in humeral, femoral, or bimalleolar breadths between older categories (e.g., U16 vs. U18, p > 0.05).

Significant sex differences were observed in body height across all categories except U14 (U14: p = 0.053; U12, U16 and U18: p < 0.001). Body mass showed significant differences from U14 onward (U14: p < 0.05; U16 and U18: p < 0.001), while body mass index differed significantly only in U14 and U16 (p < 0.05). Skinfold thickness measurements at the calf, thigh, suprailiac, abdominal, subscapular, tricep, and bicep sites showed significant differences between sexes across all age groups (p < 0.001), except forearm skinfold, which was significant from under 14 onward (p < 0.001) and not in the youngest group (p = 0.1966). Chest skinfold differences were significant from under 14 (p < 0.001) onward but not in the under 12 group. Upper arm girth was significantly different starting at under 14 (p < 0.05), while maximum upper arm girth differences were significant only in the under 16 and under 18 groups (p < 0.001). Thigh and calf girths showed significant sex differences, especially in the older groups (p < 0.05). Bone breadths (humerus, femur, and bimalleolar) and limb lengths showed significant sex differences, especially in the under 16 and under 18 categories (p < 0.001).

Clear differences in somatotype components were found between the age categories in both boys and girls (Figure 1). In boys, endomorphy decreased with age, with significant differences between U12 and U16 (p < 0.001) and an increase between U16 and U18 (p < 0.05). A different trend was observed in girls, where endomorphy was higher at U16 and U18 than at U12 (p < 0.01 and p < 0.05, respectively). Mesomorphy decreased significantly from U12 to U14 in both genders (boys: p < 0.001; girls: p < 0.001) and remained relatively stable in the older groups. Further significant changes were observed between U12 and U16 in boys (p < 0.001) and girls (p < 0.01). Ectomorphy was significantly greater in younger age groups compared to older ones. In boys, U12, U14, and U16 did not differ significantly, but U18 showed significantly lower values (p < 0.05). In girls, a significant decline was observed across age, with U12 and U14 showing higher ectomorphy than U16, and U18 showing the lowest values (all p < 0.05).

In boys, significant differences were found between U16 and U18 (p < 0.05), while in girls, significant differences were found between U12 and U16 (p < 0.05) and between U12 and U18 (p < 0.01). These results indicate age-related shifts in body composition and structure in both genders and reflect typical growth and sports development patterns during adolescence.

Building on this, the results also show significant sex differences in all three somatotype components across most age categories. Endomorphy and mesomorphy differ significantly between genders in all categories (U12–U18, p < 0.001), indicating consistent differences in fat mass and musculature. Ectomorphy shows significant sex differences in U14 (p < 0.05), U16 (p < 0.001), and U18 (p < 0.001) but not in U12 (p = 0.11), indicating that the differences in linearity and leanness become more pronounced with age.

When classifying the players according to their dominant somatotype component (the highest value under endomorphy, mesomorphy, or ectomorphy), clear patterns emerged (Figure 2). Ectomorphs dominated in the younger girls, with 53.1% in the U12 and 55.4% in the U14. In the older categories, endomorphs predominated among girls (U16: 40.6%, U18: 51.5%), i.e., a relative linearity of body shape, possibly with a higher body fat percentage and lower muscle mass compared to other body types. These results indicate a progression from a predominantly ecto-mesomorphic somatotype in the early age categories to a more endo-mesomorphic or endo-ectomorphic somatotype in older girls.

Among boys, mesomorphs predominate in the U12 (52.4%), U16 (52.6%), and U18 (62.4%) categories, while ectomorphs predominate in the U14 (49.4%). The proportion of mesomorphic boys increases in the older categories, indicating a developmental shift towards more muscular and stockier body types as male players age. This indicates a shift from ecto-mesomorphic and balanced mesomorphic types in early adolescence to predominantly meso-ectomorphic or even mesomorphic somatotypes in later developmental stages.

The differences described above are further illustrated in the ternary somatotype diagrams (Figure 3), in which the distribution of individual data points highlights the different morphological profiles of boys and girls at different stages of development. These diagrams illustrate the morphological diversity and the influence of age and gender on body composition in this population of young Slovenian tennis players. The somatotypes of boys and girls are quite similar up to the age of 12. They differ with increasing age. The somatotype of boys becomes increasingly mesomorphic over the years, while the dominant somatotype of girls changes from ectomorphic to increasingly endomorphic.

4. Discussion

This is a retrospective, observational cohort study that we have conducted over the last two decades. Our study aims to describe the anthropometric characteristics, body composition, and somatotype of young tennis players over the last two decades. When comparing the anthropometric characteristics of young tennis players, we found only a few studies, most of which only considered the 16-year-old age group and had a significantly lower number of subjects or a lower number of observed anthropometric measurements. Sánchez-Muñoz et al. [23] analysed a sample of elite male and female tennis players (category 16 and younger) who participated in the Davis Junior Cup and Fed Junior Cup over a period of two years. A total of 17 anthropometric variables were recorded for each subject. A comparison of the average height and weight values shows that our male tennis players are smaller and lighter and the girls are taller and lighter than the Spanish tennis players. Young tennis players have similar skinfold values. In both studies, the variables included the same four circumference measurements, with the average values being lower for the relaxed upper arm of our players, higher for the tight circumference, and similar for the other measurements. Our tennis players had lower averages for humeral and femoral breadth.

The aim of Luna-Villouta et al.’s study [26] was to analyse the anthropometric and physical performance variables as a function of chronological age and biological maturity in athletes. Eighty-seven tennis players were analysed (58 boys: 15.1 ± 0.8 years; 29 girls: 15.3 ± 0.8 years), and six anthropometric measures were measured. The age of the tennis players in our study was similar to that of the young Chilean athletes, although we found that our male tennis players were similar in height, while the girls were on average taller and heavier.

Elce at al. [27] analysed 12 anthropometric characteristics of 101 young (74 boys and 27 girls) advanced tennis players aged 8 to 14 years (mean age of boys: 10.83 ± 1.8, mean age of girls: 11.48 ± 2.02 years) and compared the difference between the values of the dominant and non-dominant sides of the body. Considering the age of the athletes included in their study, we compared the values with those of our 12-year-old tennis players. We found that the average values for height, weight, girth, and BMI were slightly higher in our athletes.

As Martínez-Mireles et al. [28] found in a systematic review, somatotype is an important factor that influences athletic performance and affects strength, endurance, and sport-specific abilities depending on the sporting demands. The distribution of somatotypes differs between male and female athletes. The predominant somatotype in elite male athletes was the endomesomorphic type (32.8%), followed by the balanced mesomorphic type (25.2%) and the ectomesomorphic type (18.3%). Among top female athletes, the central somatotype was predominant (31.5%), followed by the endomesomorphic type (22.2%) and the mesoendomorphic type (20.4%). The most common somatotype in elite male tennis players is the mesoectomorphic somatotype, which reflects a lean and muscular physique that is advantageous for the physical demands of tennis and contributes to agility, strength, and performance on the court.

In a study, Sánchez-Muñoz et al. [23] analysed not only anthropometric characteristics and body composition but also somatotype and compared more and less successful athletes. The predominant somatotype was ectomesomorphic in the boys and endomesomorphic in the girls. No significant differences were found between more and less successful top tennis players. The results of our study consistently show that male and female junior players have different somatotypes. However, our study has shown that somatotypes change in young athletes. This is particularly true for girls, where the ectomorphic somatotype predominates in the younger categories (U12 and U14), while from the age of 14, a clear change in the somatotype towards the endomorphic somatotype can be observed. The proportion of mesomorphic players among junior girls is around a third to a quarter.

In our study, mesomorphic and ectomorphic somatotypes predominate in boys, with a tendency towards the meso-ectomorphic type with increasing age. The same results were obtained in the study by Berral-Aguilar et al. [13], who described the mean somatotype in boys (U14 and U16) as meso-ectomorphic and in girls as meso-ectomorphic. In contrast, Martinez-Rodriguez et al. [29] found in a relatively small sample of adult athletes that both tennis and paddle players have a dominant meso-endomorphic somatotype.

This study was conducted on a sample of junior tennis players who, due to intensive biological development, training, and competition, undergo numerous changes that can also be observed in adult athletes. For example, when analysing successful male tennis players at Grand Slam tournaments, Gale-Watts and Nevill [30] found that the body shape of elite tennis players changes over time, mainly in the direction of greater muscle mass rather than greater adiposity.

Anthropometric characteristics can have a significant indirect influence on tennis performance, especially from a technical point of view. For example, a systematic review by Colomar et al. [31] found a positive correlation between serve speed and height, body mass, and BMI in young tennis players, which is even more pronounced in top adult players.

From a practical perspective, the increasing prevalence of mesomorphic profiles in boys as they age indicates a natural progression towards more muscular and athletic body types, likely due to maturation and the physical demands of tennis. Coaches should support this development with progressive strength and endurance training while avoiding early overloading in younger players who are not yet biologically mature. In girls, the shift from ectomorphic to endomorphic profiles during and after puberty likely reflects hormonal changes that contribute to a natural increase in body fat, which is important for healthy development and reproductive function. While this is a normal physiological process, it can also be a sign of changes in exercise intensity, diet, or fitness. If not addressed, increasing endomorphy can affect exercise efficiency and performance. Therefore, programs for adolescent girls should emphasise strength training, aerobic conditioning, and individualised nutritional guidance and should be carefully monitored during and after puberty.

One limitation of this study is that we did not include the observation of biological maturation, dietary habits, and training characteristics of the athletes in this study, as this would have significantly improved the quality of the analysis. Over the last two decades, the sport of tennis has certainly changed, specifically the demands of the game; the training methods; the social environment and conditions for playing the sport; the motivation of young athletes; and finally, the sporting competition have changed. This could also be influenced by possible imbalances in repeated measurements between age groups, over which we had no control.

The anthropometric measurements were carried out under the same conditions and with the same equipment, and the person who trained the measurement subjects and the measurement supervisor remained the same. A long period of time can be a problem for the measurement subjects, but at the same time, the aim of this study was to precisely determine the temporal aspect of the changes in the anthropometric characteristics of young tennis players. This study provides a good and detailed insight into the changes in the physical characteristics of young tennis players, in particular the development of somatotype in athletes, especially girls. It is obvious that the physical development of girls differs significantly from that of boys, which gives tennis experts the opportunity to observe and actively intervene in the development during puberty.

5. Conclusions

This study investigated somatotype development alongside detailed anthropometric and body composition changes in young Slovenian tennis players aged U12 to U18. Our findings revealed significant age- and sex-related differences not only in somatotype profiles but also in body height, mass, BMI, skinfold thicknesses, girths, limb lengths, and bone breadths. The detailed anthropometric characteristics provide valuable normative data for longitudinal monitoring, athlete profiling, and optimisation of talent development strategies in tennis. Specifically, age-related increases were observed in body size and muscularity indicators, while fat distribution showed site-specific variation across adolescence. Sex differences became more pronounced with age, particularly for body composition variables such as skinfold thickness, reflecting differing growth and maturation trajectories between boys and girls. These comprehensive results expand upon previous somatotype-focused studies by providing robust evidence of concurrent anthropometric and body composition development patterns. For practitioners, the findings emphasise the importance of integrating somatotype assessments with anthropometric monitoring to design age- and sex-specific training programs. Such individualised approaches can optimise physical conditioning, support healthy growth, and reduce injury risk during critical developmental windows in youth tennis players. Future research should continue to explore how these morphological changes relate to functional performance and injury prevention, further informing evidence-based training guidelines.