INTRODUCTION

From long time ago, it is well known that development state could be different in teenagers with same chronological age. Consequently, maturity assessment is needed to be taken in consideration in adolescent sport stratification in order to equalize competition and in the management of body development in athletes. The peak height velocity (PHV) is a common method used to examine the maturational state in adolescent body development¹. In order to determine this PHV an equation based on gender, age and anthropometric components has been previously validated². Maturity offset equation was a noninvasive and reliable method to determine the biological age in teenagers. Furthermore, these equations have presented a correlation with skeletal age offset, showing a maturational commonality between these two methods. Chae et al.³ described that the age at PHV differs in function of gender and the height velocity growth was higher in boys that in girls. Additionally, it has been mentioned⁴ that men reach their PHV later than women.

A previous study⁵ investigated the influence of several factors (relative age, anthropometry and fitness) in the career attainment outcomes in 580 junior league rugby players. These elements could have a real impact in the career attainment of these rugby players. Consequently, talent identification programs should pay attention to biological age. Philippaerts et al.⁶ analyzed changes in PHV and physical performance in male youth soccer players. Interestingly, many physical sport performances such as balance, speed, muscular endurance, explosive strength, agility, cardiorespiratory capacity and anaerobic endurance presented a peak evolution during the peak height velocity. Perhaps, these improvements could be connected with changes in body development and composition. Additionally, Buchheit and Mendez-Villanueva⁷ examined the role of maturity status in match running performance, focusing on maximal sprinting and aerobic speeds. More mature soccer players exhibited higher values on match running performance. However, another research⁸ discovered that adolescent growth could affect to vulnerability for injuries in soccer players. Athletes exhibited a higher significant probability to suffer traumatic and overuse injuries during the year of PHV than the year before. Moreover, days missed as consequence of injuries, match and training injury incidences were higher during the PHV year. Maturation and growth are potentiality risk factors for injuries in youth soccer players.

Bidaurrazaga-Letona et al.⁹ studied the elements involved in identification and selection of young soccer players. Body size and maturation are important factors to pay attention. Highlighting that identification and promotion of young soccer players by coaches are based on factors which are age-dependent. Another research¹⁰ studied maturity-specific relationships of static/dynamic balance with power and strength analyses in young male soccer players they examine athletes pre- (-3 years to >-1 year from PHV), circa PHV (-1 to +1 year from PHV) and post- (>1 to +3 years from PHV) PHV state. Relations between balance and muscle power/strength were described, these associations were increased with maturity, indicating a possible enhancement in body composition. Supplementary, another study¹¹ analyzed the effect of maturation in selection procedures in basketball. Basketball players reached their PHV at an earlier age than general population, suggesting a possible connection between maturity timing and selection procedures in basketball. Therefore, it seems that PHV could play an essential role in young soccer player’s selection, sport performance and injury risk.

The purposes of the present research were to examine the PHV and maturity offset in youth soccer players and analyzed relations between maturity offset values and anthropometric components.

MATERIAL AND METHODS

RESULTS

The mean height was 167.63 (10.52) cm, the sitting height was 87.36 (6.67) cm, the global value for leg length was 80.27 (4.78). The medium weight in the sample examined was 60.12 (12.43) kg, the mean values for triceps, thigh and calf skinfolds were 9.17 (2.81) mm, 11.70 (4.30) mm and 7.83 (2.74) mm. The values for arm relaxed, thigh and calf girths were 25.57 (3.16) cm, 47.45 (5.07) cm and 35.11 (3.21) cm respectively. In Table 1 can be observed these anthropometrical characteristics for the three different teams examined.

The mean age in the athletes analyzed was 14.97 (2.08) years, the average PHV was 13.97 (0.53) years and the median maturity offset was 1.00 (1.92) years. In Table 1 can be viewed the age, and the maturity for the three age categories analyzed.

The mean fat mass was 13.49 (3.65) %, the average muscular transverse areas for arm, thigh and calf were 41.70 (10.82) cm², 154.87 (38.02) cm² and 85.76 (17.67) cm² respectably. In Table 2 can be observed these values in the three soccer categories examined.

In Table 3 can be observed the correlations found between the different variables analyzed. It has been obtained significant correlations between the three muscle areas examined and the maturity offset, indicating a positive relation between them. Other correlations between maturity offset and body development points have been reported.

In Figure 1 can be observed increases on the three muscle areas in the three groups analyzed. A non-lineal growth in muscular masses can be noticed.

*Value was significant different from the rest of the groups at p<0.05.

Figure 1 Increases on muscle transverse areas studied. 

The objective of this study was to determine maturity offset values in youth soccer and correlations between maturity offset values, anthropometrical components and muscle transverse areas. Maturity offset values differ in functions of the age category while the PHV tend to be similar in the three teams studied, indicating that one group was in a previous developmental state to the PHV, another team was immediately after the PHV and the another category had reached the PHV some time ago. In accordance with the results of a previous study⁸, players from U-16 category could present a potential higher risk of suffering traumatic and overuse injuries than younger athletes because they were in the year of the PHV. Based on the results of this study, the players from this team could possibly benefit of preventive injury training.

Significant differences were observed in almost all anthropometrical elements analyzed in the three categories analyzed. In height, sitting height, leg length, weight, arm, thigh and calf girths the same tendency was found, increasing when the players were older. However, the opposite result was observed in thigh and calf skinfolds, where the younger players exhibited the highest values. Taking all these data in consideration, it seems that these anthropometrical factors could be incremented or decreased in function of having reached the PHV or not. This idea could be supported by the different correlations found between the maturity offset value and some anthropometrical components such as arm, thigh and calf girths, height, sitting height, leg length and weight. Jorquera et al.²¹ observed differences in height and weight between U-16 and U-17 categories in players from several soccer teams. In affinity, another study²² investigated anthropometry and performance in soccer players were born during the same year in order to look for differences between older and younger athletes. Older players were taller, had longer legs and presented a higher fat-free mass. The older athletes exhibited a better score performance. Figueiredo et al.²³ investigated a possible variation in size connected with changes in biological maturation in two age soccer teams. Athletes developed in maturity were heavier and taller than players retarded in maturation. Another research²⁴ reported that in a sample of soccer players from two age groups, the most mature athletes were the taller and heavier and also presented the longest legs length. As it was previously proposed²⁵ growth acceleration should be taken into account by coaches when they work with young athletes because more mature soccer players tend to present anthropometrical parameters more developed.

Interestingly, correlations between the maturity offset and the transverse muscle areas of the arm, thigh and calf have been found, indicating that a higher maturity status is possibly connected with a muscle development in the three areas analyzed. It can be noted that muscle transverse areas increase with the age of the soccer players studied. Particularly, this muscle development specially takes place after having reached the PHV, as can be visualized in the significant difference between the U-14 category and the U-16 category in the three transverse muscle areas examined. Interestingly, increases on muscle development did not follow a lineal tendency as can be observed in Figure 1, U-16 players were in the same year of mean PHV showed a peak in the muscle development in three muscular areas examined. Consequently, it could be speculate that PHV is a crucial period in muscle growth in soccer players. In accordance, Ahmad et al.²⁶ examined the effect of maturity on quadriceps-to-hamstring strength ratio. They observed that with the advanced of maturity, increases in quadriceps and hamstring muscle strength were reported in adolescents of both genders. Perhaps, these increases on muscular strength could be related with a higher muscle development in mature adolescents. Another recent study¹⁰ determined maturity connections with strength and power measures in young soccer players. They performed strength/power measures such as back extensor muscle strength, standing long jump, countermovement jump and 3-hop jump tests. They found that post-PHV athletes exhibited better significant results in these tests. It could be possible that post-PHV who presented higher strength/power measures exhibited a greater muscle development in relation with the result obtained in the current study.

It has been showed that nutrition²⁷ and training programs²⁸ play a crucial role in skeletal muscle synthesis. We have observed a potential increase on muscle areas on PHV state, consequently, it would essentially assure to fulfill nutritional requirements for soccer players on PHV period²⁹ in order to maximize this muscle development. Another study³⁰ found that arm muscle area and PHV were related with a performance parameter in rowing. Even the authors proposed that body components that influence time in rowing could be affect by maturity state in adolescent athletes. This idea would be in agreement whit the results obtained in this study. The current study constitutes one of the first studies that analyze the PHV, anthropometric parameters and muscle development in young Spanish soccer players.

Previously, it has been proposed that methods to analyze PHV, maturation or age estimation present internal limitations^31-32. Malina et al. report that the equations are really useful with teenagers close to the time of PHV, although it has limitations in early and late matured teenagers^33-35. Their studies show that PHV could be influenced by chronological age, early and late maturation and individual differences^34-35.

In addition, a review¹⁶ suggested that radiographic technology would be the most adequate methods to assess PHV and anthropometry methods could overestimated the timing of PHV. Nevertheless, anthropometry methods are more used by clinicians due to their open approachability and easy application. Therefore, PHV evaluation with anthropometric equations could over- or underestimate PHV timing. Consequently, PHV measurements should be contrast with radiographic methods¹⁶.

The studies of Malina et al. conclude that equations are useful for average maturing childrens close to the time of peak height velocity, but have limitations with early and late maturing boys and girls^32-35.

The present study has limitations such as the range of sex we only examined male soccer players or that all of them played in the same soccer team. Moreover, they were not probabilistic selected. The PHV estimate through anthropometric equation-based methods presents internal limitations as an indicator of maturity timing. Radiographic technology could reduce the internal limitations to predict PHV.

CONCLUSIONS

Peak height velocity is a notable point in young soccer player’s body development when relevant increases take part in anthropometrical components and muscle areas. Consequently, it would be valuable for physical coaches, trainers and medical services of soccer teams to consider PHV and maturity offset value when they work with young athletes Anthropometric equations are a quick, simple and accessible way to estimate PHV, although this method could present limitations.