anthropometric and physiological characteristics of ...

ANTHROPOMETRIC AND PHYSIOLOGICAL CHARACTERISTICS OF YOUNG SOCCER PLAYERS ACCORDING TO THEIR PLAYING POSITIONS: RELEVANCE FOR COMPETITION SUCCESS CARLOS LAGO-PENÃS,1 LUIS CASAIS,1 ALEXANDRE DELLAL,2 EZEQUIEL REY,1 1 AND EDUARDO DOMIŃGUEZ 1

Department of Sports Sciences, Faculty of Education and Sports Sciences, University of Vigo, Pontevedra, Spain; and Department of Sports Science and Exercise, Strasbourg University, Lyon, France

2

ABSTRACT Lago-Penãs, C, Casais, L, Dellal, A, Rey, E, and Domıńguez, E. Anthropometric and physiological characteristics of young soccer players according to their playing positions: relevance for competition success. J Strength Cond Res 25(X): 000– 000, 2011—The aim of this study was to establish the anthropometric and physiological profiles of young soccer players according to their playing position and to determine their relevance for competition success. Three hundred and twenty-one young male soccer players participated in the study. Players, age 15.63 (61.82) years, range 12–19 years, were classified into the following groups: Goalkeepers (n = 35), Central Defenders (n = 53), External Defenders (n = 54), Central Midfielders (n = 61), External Midfielders (n = 46), and Forwards (n = 72). The anthropometric variables of participants (height, weight, body mass index, 6 skinfolds, 4 diameters, and 3 perimeters) were measured. Also, their somatotype and body composition (weights and percentages of fat, bone, and muscle) were calculated. Participants performed the 20-m progressive run test to estimate their relative V_ O2max, a sprint test (30 m flat), and 3 jump tests (squat jump, countermovement jump, and Abalakov test). External Midfielders were the leanest and shortest. In contrast, Central Defenders and Goalkeepers were found to be the tallest and heaviest players. They also had the largest fat skinfolds. In general, the results show that heavier and taller young soccer players performed better in vertical jumps and 30-m sprint, whereas leaner players performed better in the 20-m progressive run test. Players were classified into 2 groups according to the final ranking of their teams at the end of the season. Players from successful teams performed

Address correspondence to Carlos Lago-Penãs, [email protected]. 0(0)/1–10 Journal of Strength and Conditioning Research ! 2011 National Strength and Conditioning Association

slightly better than players from unsuccessful teams in the physiological test, but these differences were not statistically significant. Moreover, players from successful teams were found to be leaner and more muscular than their unsuccessful counterparts.

KEY WORDS positional roles, association football, youth soccer players, prepubescent, evaluation INTRODUCTION

S

occer is a sport characterized by short sprints, rapid acceleration or deceleration, turning, jumping, kicking, and tackling (9,15–17,25). The time– motion analysis has been well analyzed during competitive match play (e.g., [12]). Previous studies described how players covered between 10,496 to 11,779 m per official game and how about 9.2% of the activities were considered high intensity (12–17). A decrease in the highintensity distance and the total sprint distance covered as matches progressed were also mentioned by Di Salvo et al. (17), whereas Bradley et al. (9) demonstrated that the total distance covered at high intensity in the last 15 minutes of a match was 20% lower than that recorded during the first 15-minute period. These physical demands were also analyzed according to the different positional roles (2,3,9,12,15,17,25). It has been reported that in a professional match, a Midfielder covers a significantly greater distance than does a Defender or a Forward; a Defender dribbles a shorter distance than the others do, whereas a Forward performs significantly more sprints than a Defender or a Midfielder does (15,17,25). Other than the different physiological demands between playing positions, it has been reported that professional soccer players have positional differences with regard anthropometrical aspects such as body mass, height, and body mass index (BMI) (33). This evidence suggests that specific physiological demands and anthropometrical prerequisites exist for different playing positions and result in the selection of young players based on VOLUME 0 | NUMBER 0 | MONTH 2011 |

1

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

Young Soccer Players’ Characteristics and Playing Positions

TABLE 1. Age (mean 6 SD) and number of players classified according to their playing positions. Team

Age

U15 U17 U20 Total

13.72 6 15.69 6 18.11 6 15.54 6 Age (y)

Players (n) Goalkeepers 0.49 0.42 0.80 1.85

128 108 85 321

External defenders

Central defenders

External midfielders

Central midfielders

Forwards

15 24 20 22 23 24 9 18 21 9 22 29 11 12 12 15 16 19 35 54 53 46 61 72 15.63 6 1.82 15.33 6 1.81 15.57 6 1.76 15.59 6 2.05 15.53 6 1.90 15.63 6 1.82

superior physiological performances and anthropometrical advantage (19,20). However, match play demand is different in youth team categories, and therefore, the physical and physiological profiles of players differ from those of adult players. Independent factors including age, biological maturity, number of years of training, morphology, and anthropometry affect the physical and physiological profile of players (11,32). Game intensity is lower in youth soccer players with a total distance covered around 9 km for the U18 category and 6.2 km for the U12 category, lower heart rate (HR) responses (93% of HRmax in elite adult players vs. 82% of HRmax in U18) and a lower blood lactate concentration (10 mmol!L21 in elite adult players vs. 5 mmol!L21 in the U12 category) (10,30). Therefore, the selection of players for a specific playing position based on their physiological performances may not be appropriate for youth age groups. In this context, previous studies investigating the positional differences in physiological performance among youth soccer players are limited, and the results have been inconsistent

(19,23). Malina et al. (23) studied elite young soccer players aged 14 years with 4.5 years of training experience and found that there were no differences among Defenders, Midfielders, and Forwards in vertical jumps, 30-m sprint time, and intermittent aerobic endurance. Another study by Gil et al. (19) reported that Goalkeepers had a significantly lower aerobic capacity than did Defenders, Midfielders, and Forwards. In addition, Forwards had the best performance in 30-m sprints and vertical jumps compared with the performance of Goalkeepers, Defenders, and Midfielders. However, these players were aged from 14.7 to 21.5 years (19), and important information regarding positional difference in youth players might be masked. Wong and Wong (31) studied 70 U14 male soccer players with 5 years’ training experience and found that there were significant positional differences in anthropometry among youth soccer players, but no significant positional differences in physiological performances (maximal vertical jump, ball shooting, 30-m sprint, and V_ O2max). Reilly et al. (28) studied 31 young male soccer players and showed that elite players were significantly leaner, possessed more

TABLE 2. Physical characteristics and somatotype of soccer players (mean 6 SD).* Goalkeepers Weight (kg) 67.48 Height (cm) 172.49 BMI (kg!m22) 22.53 Endomorphy 2.91 Mesomorphy 4.11 Ectomorphy 2.58

External defenders

6 11.57† 58.81 6 6 8.43§ 167.32 6 6 2.44k 20.87 6 6 0.70# 2.52 6 6 0.99 3.72 6 6 0.98 3.01 6

Central defenders

9.19 70.03 8.35 175.07 1.78 22.76 0.63 2.92 0.90 4.01 0.80 2.61

Central midfielders

6 9.81‡ 62.13 6 7.27‡ 168.25 6 2.16{ 21.79 6 0.92# 2.65 6 1.12 3.93 6 0.89** 2.64


Forwards

6 10.27 58.04 6 10.76 61.18 6 8.39 166.04 6 9.52 168.41 6 2.18 20.87 6 2.41 21.33 6 0.66 2.36 6 0.63 2.38 6 0.96 3.75 6 0.86 4.03 6 0.95 2.98 6 1.08 2.90

6 12.08 6 9.68 6 2.36 6 0.64 6 1.29 6 0.90

*BMI = body mass index. †Goalkeepers vs. external defenders and external midfielders, p , 0.01. ‡Central defenders vs. external defenders, central midfielders, external midfielders, and forwards, p , 0.01. §Goalkeepers vs. external midfielders, p , 0.05. k Goalkeepers vs. external defenders and external midfielders, p , 0.05. {Central defenders vs. external defenders, external midfielders, and forwards, p , 0.01. #Goalkeepers vs. external midfielders and forwards, p , 0.01. **Central defenders vs. external midfielders, and forwards p , 0.01.

2

the

TM

Journal of Strength and Conditioning Research


the

TM


| www.nsca-jscr.org

Figure 1. Measurements of different skinfolds of soccer players, classified according to their playing positions (mean 6 SD).

aerobic power, and were more tolerant to fatigue than subelite soccer players were. Other studies have provided physiological profiles of youth soccer players, but they varied according to the continent. Wong and Wong (31) concluded that Asian youth soccer players perform poorly in the following tests: isokinetic muscular strength of quadriceps and hamstrings, maximal oxygen uptake (V_ O2max), 1RM strength, sprint starts, 20- and 30-m sprints, as compared to players from other

continents. Da Silva et al. (16) related that Brazilian youth players presented physical and physiological profiles different from that of European soccer players, notably they were shorter and had a lower aerobic capacity. However, further studies are needed to provide a complete physiological and physical profile according to the different playing positions. Consequently, the first purpose of this study was to establish the anthropometric and physiological profiles of youth soccer players according to their playing positions. The second purpose was to determine the relevance of these profiles and characteristics for competition success. These findings could facilitate talent identification, the selection of youth players, and training design. The hypothesis of this study is that characteristic anthropometric differences exist between different playing positions. Moreover, we believe that there are no differences in physical performance between different playing positions because in comparison with highlevel adult soccer, in youth soccer, match intensity and 21 21 Figure 2. Relative maximal oxygen consumption (ml!kg !min ) according to the playing positions of soccer duration are of a lower level, players (mean 6 SD). weekly training volume and VOLUME 0 | NUMBER 0 | MONTH 2011 |

3


Young Soccer Players’ Characteristics and Playing Positions power, players performed 3 jump tests (squat jump [SJ], a countermovement jump [CMJ], and an Abalakov test [ABA]). The raw data and other information are available at http://www.hi20.es. Subjects

Three hundred and twenty-one young male soccer players participated in the study, which was conducted near the end of the first half of the soccer season (weeks 19–20 of the 42-week season). These players were Figure 3. Velocity of soccer players according to their playing position (mean 6 SD). members of regional representative teams competing at the highest level of competition for intensity are lower, and youth players accumulate fewer years their category in Spain. The number of players in each team of training compared to adults. and their average age are shown in Table 1. Players were classified according to their playing roles into 6 groups: METHODS Goalkeepers, Central Defenders, External Defenders, Central Experimental Approach to the Problem Midfielders, External Midfielders, and Forwards. To ascertain whether anthropometric characteristics are relevant The training season starts in August with 8 weeks of physical to success in matches of the youth soccer players, several body conditioning training, including endurance training in particular. measurements were taken, such as height and weight, 6 skin This is followed by Soccer-specific training. Players trained for fat folds, 4 diameters, and 3 perimeters. To determine the 90 minutes 3 times per week and played a match during physiological characteristics of the soccer players, the 20-m the weekend. Each training season generally consisted of a progressive run test was used to estimate aerobic capacity. Players 15-minute warm-up, 20-minute technical training, 20-minute performed a 30-m flat sprint to measure velocity. To measure leg tactical training, 30-minute simulated competition, and

Figure 4. Jump test performances by players classified according to their playing positions (mean 6 SD).

4

the

TM



the

TM

6.70 6 1.91 29.89 6 6.33 9.83 6 1.39 14.74 6 2.91 10.84 6 1.35 48.71 6 1.71 16.33 6 1.85 6 1.60 6 5.71 6 1.42 6 2.59 6 1.39 6 1.49 6 2.02 6.37 28.06 9.62 13.98 10.90 48.19 16.80

Study Protocol

1.77 5.35 1.21 2.47 1.57 1.70 1.61 *The residual percentage is always 24.12%, and therefore, it has been deleted from the table. †Goalkeepers vs. external defenders, external midfielders, and forwards, p , 0.01. ‡Central defenders vs. external defenders, central midfielders, external midfielders, and forwards, p , 0.05. §Goalkeepers vs. external defenders and external midfielders, p , 0.01. k Goalkeepers vs. external defenders, p , 0.05. {Goalkeepers vs. external midfielders and forwards, p , 0.05. #Central defenders vs. external midfielders and forwards, p , 0.01.

Percentage (%)

| www.nsca-jscr.org

5-minute cool-down. Within the team, all players of different positions trained together except for the Goalkeepers who dedicated the technical training session to specific training. The study was conducted according to the Declaration of Helsinki, and the protocol was fully approved by the Clinical Research Ethics Committee. All players and their parents were properly informed of the nature of the study without being informed of its detailed aims. Each player and his parents or guardians were informed of the experimental risks and both signed an informed consent document before the investigation.

7.15 6 29.99 6 9.94 6 14.97 6 11.41 6 48.28 6 16.23 6 2.23‡ 5.12‡ 2.35‡ 2.36‡ 2.09# 3.05 3.11 8.52 6 33.39 6 11.23 6 16.87 6 12.07 6 47.68 6 16.14 6 6.59 6 1.27 28.49 6 5.05 9.55 6 1.21 14.17 6 2.21 11.21 6 1.40 48.31 6 1.87 16.37 6 1.48 6 2.17† 6 6.12§ 6 1.25k 6 2.79§ 6 1.58{ 6 1.69 6 0.95 8.18 32.49 10.55 16.26 11.99 48.02 15.88 Fat Muscle Bone Residual Fat Muscle Residual Weight (kg)

Central midfielders Central defenders External defenders Goalkeepers

TABLE 3. Body composition (weight and percentage, mean 6 SD) of soccer players playing in different positions.*


Forwards


Anthropometry, Somatotype, and Body Composition. The height (cm) and weight (kg) of each player were measured, and the BMI was calculated as weight (in kg) divided by height (in m2). Skinfolds (mm) were measured at 6 sites: triceps, subscapular, abdominal, suprailial, thigh, and lower leg, using a skinfold calliper (Holtain 610, Crymych, United Kingdom). Each individual measurement and the sum of the 6 measurements were used for analysis. The perimeters of the upper arm, thigh, and lower leg were measured (cm); also measured were the following 4 diameters (cm): biepicondylar humerus (elbow), biestyloid at the wrist, biepicondylar femur (knee), and bimaleolar at the ankle. All the measurements were made following the guidelines outlined by the International Society for the Advancement of Kinanthropometry. Afterward, weights and percentages of fat, bone, and muscle were calculated to evaluate body composition, using the formulas of Faulkner (18), Rocha (29), Wurch (34), and Matiegka (24). The endomorphy, mesomorphy, and ectomorphy components of the somatotype were also calculated (19). Physiological Tests

Twenty-meter Progressive Run Test. Given that soccer includes intermittent bouts of high-intensity exercise, the 20-m progressive run test is close to the soccer pattern. In this test, players had to perform a series of 20-m shuttle runs at a pace set by an audio metronome with a standard rest interval between shuttles. The time allowed for the shuttles was progressively decreased, that is, the speed was increased. The test was terminated when the player was unable to maintain the required speed. For a detailed description of the test and other information see, Bangsbo (1). Distance covered by players was measured and taken to estimate relative maximal oxygen consumption (V_ O2max) using the formula provided by Leger and colleagues. The validity of this test to estimate V_ O2max has been greatly verified (1,7–9,15,18,19). Thirty-meter Sprint. The players were asked to complete a 10-minute specific warm-up including several accelerations to decide which foot they would have to set on the starting line for the sprint start. Players had to start from a standing position placing their forward foot just behind the starting line and their rear foot on the pedal. They had a 30-m sprint with a stationary start, and timing started as soon as the rear foot left the pedal. Speed was measured with an infrared photoelectronic VOLUME 0 | NUMBER 0 | MONTH 2011 |

5


6

the

61.15 6 61.19 6 168.54 6 168.31 6 10.65 6 10.98 6 48.69 6 48.81 6 21.22 6 21.42 6

13.68 10.92 10.45 9.21 1.15 1.48 1.77 1.50 2.69 2.11

cell (Speedtrap II Wireless Timing System; Brower Timing Systems, Draper, UT, USA). There were 2 trials in total, and a 3-minute recovery was allowed between each trial. The best (fastest) 30-m sprint time was selected for analysis.

57.44 60.07 165.37 169.12 10.84 11.55 48.56 47.87 20.84 20.90

6 9.99 6 8.36 6 8.18 6 8.25 6 1.17 6 1.51 6 1.88 6 2.10 6 1.99 6 1.60

69.68 70.39 175.03 175.11 11.71 12.44 48.17 47.68 22.64 22.89

6 9.85 6 9.94 6 7.39 6 7.29 6 1.90 6 2.24 6 1.70 6 2.07 6 1.90 6 2.44

63.85 6 61.33 6 168.25 6 168.24 6 11.34 6 11.48 6 48.35 6 48.07 6 22.01 6 21.54 6

10.85 9.70 8.71 8.18 1.50 1.66 1.46 1.89 2.14 2.23

58.66 57.58 167.32 165.11 10.95 10.86 48.30 48.31 20.83 20.90

6 9.96 6 11.48 6 8.83 6 10.06 6 1.74 6 1.10 6 1.19 6 1.82 6 2.33 6 2.51

Jump Tests. To measure the explosive power of the lower extremities, players performed 3 jump tests (SJ, CMJ, and an ABA) using a jump mat (Ergojump, Bosco-Systems, Rome, Italy). The SJ was performed with a squat starting position, that is, knees flexed to 90" and hands on hips. From this position, the participants made a maximal vertical jump landing with straight knees on the mat. The Counter Movement Jump (CMJ) is performed standing with straight legs and performing a jump beginning with a counter movement down to a knee angle of 90 degrees. The hands are held on the hips during the jump to avoid any effect of arm-swing. Counter Movement Jump differs from Squat Jump by the fact that the starting position is standing still and a quick countermovement is performed (stretch-shortening cycle) before take off. The Abalakov jump assesses explosive strength, plus the use of elastic energy, plus the coordinate capacity using trunk and upper limbs. The athlete stands upright, as still as possible on the mat with weight evenly distributed over both feet. When ready, the athlete squats down until the knees are bent at 90", while swinging the arms back behind the body. Without pausing, the arms are swung forwards and the athlete jumps as high as possible, landing back on the mat on both feet at the same time. The take-off must be from both feet, with no initial steps or shuffling, and the subject must also not pause at the base of the squat. Jump height was determined based on flight time. Each player performed 2 jumps interspersed with a 1-minute rest between each jump. The height of the jumps was measured in cm, and the best jump of each modality was selected. For a detailed description of the tests and other information, see Bosco et al. (4–8). Players from Successful and Unsuccessful Teams

66.91 68.03 172.52 172.46 11.72 12.24 47.83 47.93 22.32 22.72

6 12.67 6 10.77 6 8.71 6 8.41 6 1.69 6 1.47 6 1.32 6 1.71 6 2.88 6 2.01

Players were classified into 2 groups according to the final ranking of their teams at the end of the season. Players from successful teams were classed as those who were ranked in the top half of the table. Players from unsuccessful teams were classed as those who were ranked in the bottom half of the table. In this study, the anthropometric and physiological characteristics of the players from successful and unsuccessful teams were analyzed to identify the variables associated with success for a given positional role. *BMI = body mass index.

BMI (kg!m22)

Muscle %

Fat %

Height (cm)

Successful Unsuccessful Successful Unsuccessful Successful Unsuccessful Successful Unsuccessful Successful Unsuccessful Weight (kg)

Forwards External midfielders Central midfielders Central defenders External defenders Goalkeepers

TABLE 4. Anthropometric characteristics and body composition (mean 6 SD) of successful and unsuccessful soccer players classified according to their playing positions.*

Young Soccer Players’ Characteristics and Playing Positions

Statistical Analyses

The results were analyzed using SPSS software (version 17.0; SPSS, Inc., Chicago, IL, USA). A 2-way analysis of variance was used to evaluate group differences. Post hoc comparisons were determined by the Scheffe´ test when the variances were equal and by the Games–Howell test when they were not equal. To analyze differences between the players from successful and unsuccessful teams within each playing position, Students’ t-test was performed using each variable. The level of statistical significance was set at p # 0.05. The results shown are the mean and the SD.

TM



the

TM


| www.nsca-jscr.org

the heaviest compared to External Defenders, Central Midfielders, External Midfielders, and Forwards (p , 0.01). This difference was not statistically significant in the case of Central Defenders vs. Goalkeepers. The weight of the Goalkeepers was higher than that of the External Defenders and External Midfielders (p , 0.01). The BMI (kg!m22) of the Central Defenders was higher compared to that of the External Defenders, External MidFigure 5. Differences in relative maximal oxygen consumption (ml!kg21!min21) between the successful and fielders, and Forwards (p , unsuccessful players for each playing positions (mean 6 SD). 0.01). Also the BMI (kg!m22) of the Goalkeepers was higher compared to that of External The reliability of each test was assessed by intraclass corDefenders and External Midfielders (p , 0.05). relations (ICCs) and coefficient of variance (CV). The results Forwards had less fat than did Central Defenders in the show that these tests were highly repeatable: SJ (ICC = 0.90; triceps, abdominal, suprailiac, and leg sites (p , 0.05). Also, CV = 4.9%; n = 321), CMJ (ICC = 0.93; CV = 4.5%; n = 321), the group of Forwards had less fat than did the Goalkeepers ABA (ICC = 0.96; CV = 3.5%; n = 321), and 30-m sprint in the abdominal, suprailiac, and thigh sites (p , 0.05). (ICC = 0.95; CV = 2.3%; n = 321). Although the repeatability External Midfielders had less fat than did Central Defenders of the 20-m progressive run test cannot be calculated from in the subscapular, abdominal, suprailiac, and leg sites (p , this study because it was performed only once, previous 0.05). When all the skinfolds were added, Forwards (54.68 6 studies have shown that there were no significant differences 13.39 mm) were found to be leaner than Central Midfielders between test–retest distance coverage. (61.54 6 13.79 mm), Central Defenders (66.10 6 15.22), and Goalkeepers (66.52 6 15.73) (p , 0.01) (Figure 1). RESULTS The fat, muscle, and bone weights of Central Defenders were higher compared to that of External Defenders, External Anthropometry, Somatotype, and Body Composition Midfielders, Central Midfielders, and Forwards (p , 0.01). The average weights and heights are shown in Table 2. This difference was not statistically significant in the case of Central Defenders were the tallest players, and they were also Central Defenders vs. Goalkeepers. Also the fat and muscle weights of Goalkeepers were higher compared to those of External Defenders, External Midfielders, and Forwards (p , 0.01) and of External Defenders and External Midfielders (p , 0.01), respectively. Fat percentage was also higher in Central Defenders compared to in External Midfielders and Forwards (p , 0.01) and in Goalkeepers compared to in External Midfielders and Forwards (p , 0.05) (Table 3). The somatotype of the soccer players is shown in Table 2. The endomorphy values were Figure 6. Differences in velocity (seconds) between the successful and unsuccessful players for each playing higher in Central Defenders positions (mean 6 SD). and Goalkeepers compared to VOLUME 0 | NUMBER 0 | MONTH 2011 |

7


Young Soccer Players’ Characteristics and Playing Positions Players from successful teams were able to jump slightly higher (SJ) than their counterparts, but these differences were statistically significant only for the External Defenders (p , 0.05) (Figure 7).

DISCUSSION The aims of this study were to establish the anthropometric and physiological profiles of youth soccer players according to their playing positions and to determine the relevance of Figure 7. Differences in the squat jump (height) between the successful and unsuccessful players for each playing these profiles and characterposition (mean 6 SD). istics for competition success. The major finding of this study is that anthropometric characin External Midfielders and Forwards (p , 0.01). In addition, teristics of youth soccer players differed according to the Forwards and Goalkeepers presented the highest ectomorplaying positions, especially for External Midfielders (the phy and mesomorphy values, respectively. leanest and shortest) and for the Goalkeepers and Central Defenders (the tallest, heaviest, and with largest skinfolds). Estimation of Aerobic Capacity However, there are no positional differences in physiological Goalkeepers had the lowest relative maximal oxygen performances. Finally, it appeared that players belonging to consumption (ml!kg21!min21) compared to the rest of the successful teams were leaner and more muscular than those groups (p , 0.01), as estimated using the 20-m progressive from unsuccessful teams. run test (Figure 2). The results of this study support our hypothesis that there Sprint Time were significant positional differences in anthropometry such In the 30-m sprint, Central Defenders were faster than the as weight, height, and BMI. Specifically, Goalkeepers (67.5 kg, other groups. However, this difference was not statistically 1.72 m) and Central Defenders (70.0 kg, 1.75 m) were the significant (Figure 3). heaviest and tallest players, and External Defenders (58.8 kg, 1.67 m), External Midfielders (58.0, 1.66 m), and Forwards Jump Tests (61.2 kg, 1.68 m) were the lightest and shortest. These results In the 3 jump tests, Goalkeepers showed the best performance partially agree with those of the previous studies on U11 to of all the positional groups (Figure 4), but this difference was U17 soccer players, which showed that Forwards were lighter not statistically significant. External Midfielders produced the than Defenders and Goalkeepers were but heavier than shortest jumps. Midfielders, whereas Forwards were shorter than Midfielders, Differences between Players from Successful and Goalkeepers, and Defenders (19,23,31). This disagreement Unsuccessful Teams between the results may be because in this study players were Fat percentage of players from successful teams was lower classified according to their playing roles into 6 groups. than that of players from unsuccessful teams. The BMI of Furthermore, the study of Wong et al. among professional the players from successful teams was lower compared to national players in the Fe´de´ration Internationale de Football that of the players from unsuccessful teams, except for the Association (FIFA) World Cups showed that Goalkeepers Central Defenders. However, these differences were not were heavier and taller than Defenders, Forwards, and statistically significant. The rest of the body components Midfielders (33). In terms of BMI, the present results differed were similar in both groups of players within each playing from the results of a previous study (33) that reported that position (Table 4). Goalkeepers had higher values than Defenders, Forwards, Relative maximal oxygen consumption of players from and Midfielders among professional players. Nonetheless, we successful teams was higher compared to that of the players postulate that anthropometry contributes to success in from unsuccessful teams (Figure 5), but these differences were specific playing positions at a senior level. For example, not statistically significant. taller and heavier players are more suitable to be Goalkeepers Players from successful teams, except External Midfielders, and Central Defenders and shorter and lighter players are performed better in the velocity test; however, these differmore suitable to be External Defenders and External ences were not statistically significant (Figure 6). Midfielders. The results of this study support the fact that

8

the

TM



the

TM

Journal of Strength and Conditioning Research U20 players in different playing positions are characterized by different anthropometry variables, such as weight, height, and BMI. The results of this study generally support our hypothesis that there are no positional differences in physiological performances. Particularly, no significant differences were found in physiological performances except for the 20-m progressive run test where Goalkeepers had the lowest relative maximal oxygen consumption (ml!kg21!min21) compared to the rest of the groups (p , 0.01). Similar results have been published in other studies (19,31). Furthermore, our results also show that Central Midfielders had higher V_ O2max values and a longer corresponding running time compared with the other positional groups, although no significant differences were observed. In their review, Reilly et al. (27) reported that among young players Midfielders had the highest V_ O2max level followed by Forwards, Defenders, and Goalkeepers among the U16 and elite senior soccer players. Moreover, recent studies on a professional senior match showed that Midfielders covered a greater distance than did the other positional groups (14,15,17,25). This study agreed with previous studies, which found no statistical difference in jump height between Goalkeepers, Defenders, Midfielders, and Forwards of U13 to U20 soccer players (19,23,29), although Goalkeepers exhibited the best performance of all positional groups. Stolen et al. (30) reported that at the professional level, Goalkeepers had the highest jump height and Midfielders had the lowest compared with Forwards and Defenders. No positional difference was found in 30-m sprint times, and Central Defenders and Goalkeepers were the fastest. These results are similar to those provided by Wong and Wong (31), However, our results did not conform to the study of Malina et al. (22), which has shown that Forwards had the shortest 30-m sprint time, followed by Defenders and Midfielders, although no significant differences were found. This disagreement between the results may be because in this study players were classified according to their playing roles into 6 groups. Additionally, another study found that Forwards had the shortest 30-m sprint time and were significantly faster than Defenders, whereas Goalkeepers were the slowest (19). However, in the previous study, players had 15 m to accelerate before the first timing light. In our study, players had a 30-m sprint with a static start, and timing started as soon as the rear foot left the pedal. The result of Malina et al. (22) and Gil et al. (19) agreed with the performance characteristics of elite adult soccer players, where Forwards covered a greater distance with a very high– intensity run (.23 km!h21) compared to Defenders and Midfielders (15,25). Therefore, it is reasonable to state that with young soccer players, performance is not significantly different between playing positions, but when approaching professional level, positional differences exist. In general, the results show that heavier and taller young soccer players performed better in vertical jumps and 30-m

| www.nsca-jscr.org

sprint, whereas leaner players performed better in the 20-m progressive run test. In agreement with this, Malina et al. (22) found that in young soccer players body mass is the most significant predictor in 30-m sprint performance and that height is the most significant predictor of vertical jump performance. Indeed, as suggested by Wong and Wong (31) a high BMI at an equivalent body fat content and height means a higher lean body mass and thus higher muscular mass. However, the long-term effect of selecting players based on their anthropometry advantage leads to a strong bias for those players who mature early (becoming heavier and taller) to be selected for professional, semiprofessional, and U15 to U18 national teams (16,17,25), and eventually, the proportion of young players who are lighter and shorter decreased with increased age from U11 to U16 (21,26). The results of this study show that players from successful teams are leaner and more muscular than their unsuccessful counterparts are; however, these differences were not statistically significant. The External Midfielders’ profiles deviated from those of the other players from successful teams. The rest of the body components were similar in the players from successful and unsuccessful teams within each playing position. These results agree with the findings of Gil et al. (19). In general, the players from successful teams performed slightly better than the players from unsuccessful teams in the physiological test, but these differences were not statistically significant. These results are similar to those provided by Gil et al. (19) and Reilly et al. (28). Therefore, as suggested by Reilly et al. (28), apart from absolute anthropometry advantages, psychological and soccer-specific skills should also be considered in the selection of young soccer players for developing future high-class players.

PRACTICAL APPLICATIONS The major findings of this study show that there were positional differences in anthropometry between young soccer players but no significant differences in physiological performances (maximal vertical jumps, 30-m sprint, and 20-m progressive run test). Specifically, Goalkeepers and Central Defenders were the tallest and heaviest, and External Midfielders and External Defenders were the leanest and shortest. This study provides a scientific rationale of the coaches’ practice in selecting young soccer players according to their anthropometry for short-term benefits and does not justify such practice in the long-term process of player development. In fact, it seems that coaches could receive short-term benefits by employing heavier and taller players for positions (e.g., Central Defenders and Forwards) that require higher jumping and sprinting abilities; and players with lower BMI for positions (e.g., External Defenders and External Midfielders) that require higher aerobic endurance. Consequently, technical staff should take the present results into account and should not discriminate against younger or late-maturating players who may develop their abilities later. VOLUME 0 | NUMBER 0 | MONTH 2011 |

9


Young Soccer Players’ Characteristics and Playing Positions In this context, Malina et al. (22) suggested that opportunities need to be provided for smaller and/or later maturing talented boys during adolescence. Moreover, it appeared that players belonging to successful teams were leaner and more muscular than those from unsuccessful teams. These results suggest that specific training programs in strength, aerobic activities, and speed could be used to improve specific fitness ability according to the different physiological, anthropometric, and somatotype profiles in youth soccer players. Therefore, training programs need to be modified for youth soccer players, and direct application of the program used by senior players may not be appropriate.

REFERENCES 1. Bangsbo, J. Yo-Yo Tests. Copenhagen,Denmark: HO + Storm & Tiocano Music A/S, 1996. 2. Barros, R, Misutal, M, Menezes, R, Figueroa, PJ, Moura, FA, Cunha, SA, Anido, R, and Leite, N. Analysis of the distances covered by first division Brazilian soccer players obtained with an automatic tracking method. J Sports Sci Med 6: 233–242, 2007. 3. Bloomfield, J, Polman, R, and O’Donoghue, P. Physical demands of different positions in FA Premier League soccer. J Sports Sci Med 6: 63–70, 2007.

14. Dellal, A, Wong, DP, Moalla, W, and Chamari, K. Physical and technical activity of soccer players in the French first division— With special reference to the playing position. Int Sport Med J 11: 278–290, 2010. 15. Di Salvo, V, Baron, R, Tschan, H, Calderon Montero, FJ, Bachl, N, and Pigozzi, F. Performance characteristics according to playing position in elite soccer. Int J Sports Med 28: 222–227, 2007. 16. Di Salvo, V, Benito, PJ, Calderon, FJ, Di Salvo, M, and Pigozz, F. Activity profile of elite goalkeepers during football match-play. J Sports Med Phys Fitness 48: 443–446, 2008. 17. Di Salvo, V, Gregson, W, Atkinson, G, Tordoff, P, and Drust, B. Analysis of high intensity activity in Premier League soccer. Int J Sports Med 30: 205–212, 2009. 18. Faulkner, JA. Physiology of swimming and diving. In: Human Exercise Physiology. H. Falls, ed. Baltimore, MD: Academic Press, 1968. pp. 87–95. 19. Gil, SM, Gil, J, Ruiz, F, Irazusta, A, and Irazusta, J. Physiological and anthropometric characteristics of young soccer players according to their playing position: Relevance for the selection process. J Strength Cond Res 21: 438–445, 2007. 20. Gravina, L, Gil, SM, Ruiz, F, Zubero, J, Gil, J, and Irazusta, J. Anthropometric and physiological differences between first team and reserve soccer players aged 10–14 years at the beginning and end of the season. J Strength Cond Res 22: 1308–1314, 2008. 21. Helsen, WF, Starkes, JL, and Van Winckel, J. The influence of relative age on success and dropout in male soccer players. Am J Hum Biol 10: 791–798, 1998.

4. Bosco, C, Colli, R, Bonomi, R, Von Duvillard, SP, and Viru, A. Monitoring strength training: Neuromuscular and hormonal profile. Med Sci Sports Exerc 32: 202–208, 2000.

22. Malina, RM, Cumming, SP, Kontos, AP, Eisenmann, JC, Ribeiro, B, and Aroso, J. Maturity-associated variation in sport-specific skills of youth soccer players aged 13–15 years. J Sports Sci 23: 515–522, 2005.

5. Bosco, C, Colli, R, Introini, E, Cardinale, M, Tsarpela, O, Madella, A, Tihanyi, J, and Viru, A. Adaptive responses of human skeletal muscle to vibration exposure. Clin Physiol 19: 183–187, 1999.

23. Malina, RM, Pena Reyes, ME, Eisenmann, JC, Horta, L, Rodrigues, J, and Miller, R. Height, mass and skeletal maturity of elite Portuguese soccer players aged 11–16 years. J Sports Sci 18: 685–693, 2000.

6. Bosco, C, Komi, PV, Tihanyi, J, Fekete, G, and Apor, P. Mechanical power test and fiber composition of human leg extensor muscles. Eur J Appl Physiol Occup Physiol 51: 129–135, 1983.

24. Matiegka, J. The testing of physical efficiency. Am J Phys Anthropol 4: 223–230, 1921.

7. Bosco, C, Luhtanen, P, and Komi, PV. A simple method for measurement of mechanical power in jumping. Eur J Appl Physiol 50: 273–282, 1983. 8. Bosco, C, Tihanyi, J, Latteri, F, Fekete, G, Apor, P, and Rusko, H. The effect of fatigue on store and re-use of elastic energy in slow and fast types of human skeletal muscle. Acta Physiol Scan 128: 109–117, 1986. 9. Bradley, PS, Sheldon, W, Wooster, B, Olsen, P, Boanas, P, and Krustrup, P. High-intensity running in English FA Premier League Soccer Matches. J Sports Sci 27: 159–168, 2009. 10. Capranica, L, Tessitore, A, Guidetti, L, and Figura, F. Heart rate and match analysis in pre-pubescent soccer players. J Sports Sci 19: 379–384, 2001. 11. Da Silva, CD, Blommfield, J, and Martins, JCB. A review of stature, body mass and maximal oxygen uptake profiles of U17, U20 and first division players in Brazilian soccer. J Sports Sci Med 7: 309–319, 2008. 12. Dellal, A, Chamari, C, Wong, DP, Ahmaidi, S, Keller, D, Barros, MLR, Bisciotti, GN, and Carling, C. Comparison of physical and technical performance in European professional soccer match—play: The FA Premier League and La LIGA. Eur J Sport Sci 11: 51–59, 2010. 13. Dellal, A, Keller, D, Carling, C, Chaouachi, A, Wong, DP, and Chamari, K. Physiologic effects of directional changes in intermittent exercise in soccer players. J Strength Cond Res 24: 3219–3226, 2010.

10

the

25. Rampinini, E, Coutts, AJ, Castagna, C, Sassi, R, and Impellizzeri, FM. Variation in top level soccer match performance. Int J Sport Med 28: 1018–1024, 2007. 26. Rampinini, E, Impellizzeri, FM, Castagna, C, Coutts, AJ, and Wisløff, U. Technical performance during soccer matches of the Italian Serie A league: Effect of fatigue and competitive level. J Sci Med Sport 12: 227–233, 2009. 27. Reilly, T, Bangsbo, J, and Franks, A. Anthropometric and physiological predispositions for elite soccer. J Sports Sci 18: 669–683, 2000. 28. Reilly, T, Williams, AM, Nevill, A, and Franks, A. A multidisciplinary approach to talent identification in soccer. J Sports Sci 18: 695–702, 2000. 29. Rocha, MSL. Peso osseo do brasileiro de ambos sexos de 17 a 25 anos. Arq Anat Antropol 1: 445–445, 1975. 30. Stolen, T, Chamari, K, Castagna, C, and Wisloff, U. Physiology of soccer: An update. Sports Med 35: 501–536, 2005. 31. Wong, DP and Wong, SHS. Physiological profile of Asian elite youth soccer players. J Strength Cond Res 23: 1383–1390, 2009. 32. Wong, P, Mujika, I, Castagna, C, Chamari, K, Lau, PWC, and Wisloff, U. Characteristics of World Cup soccer players. Soccer J 57–62, 2008. 33. Wong, PL, Chamari, K, Dellal, A, and Wisløff, U. Relationship between anthropometric and physiological characteristics inyouth soccer players. J Strength Cond Res 23: 1204–1210, 2009. 34. Wurch, A. La femme et le sport. Med Sport 4: 441–445, 1974.

TM

