## 4 Discussion
However, these investigations were carried out in the adult athlete population, and this research is one of the first that assesses the classification of BMI in adolescent athletes and relates it to maturation. Therefore, more research is needed, both in handball players and in other sports modalities, to find out whether biological maturation influences BMI or whether the increase in BMI is only due to the development of muscle mass caused by this process [63; 64]. Regarding the limitations of the study, firstly, the gold standard to evaluate the biological maturation, which is wrist and hand radiography [11], was not used to determine the maturity status of the players. This method, although it is the reference method, also has certain disadvantages since it uses X-rays and exposes the participants to certain radiation; moreover, it is a time-consuming, invasive method with a high cost [65]. Another non-invasive option, easy to apply and widely used in previous research with athletes [13; 26], is maturity estimation equations based on regression equations. The one used in this study was the one described by [PERSON] et al. [34], as it has been one of the most widely used in the adolescent athlete population in different disciplines [13]. In addition, the considerations identified in the literature were followed to avoid the inclusion of errors in the estimation of the maturity offset [65]. The sample size and selection of the same were also a limitation, which limits the extrapolation of the results to populations that do not have similar characteristics, and the study design, which, being cross-sectional, was not possible to follow up on how biological maturation affects throughout adolescence. Another limitation of the study is that only biological maturation and diet have been considered as factors that influence kinanthropometry and physical fitness characteristics, but sports performance is a multifactorial issue where other factors, such as genes, lifestyle, socio-economic variables, geographics issues, habits, diet or the age of the parents when the child was born, can have a great influence on the child's development. On the other hand, the KIDMED questionnaire does not report on the amount of food consumed. Therefore, as future lines of research, all these limitations could be addressed with larger samples in longitudinal studies, observing how the maturational process influences kinanthropometric characteristics and performance and carrying out questionnaires that do assess the amount of food ingested. In addition, it would also be interesting to observe the evolution of BMI in this population as biological maturation progresses using appropriate tools, such as the BMI z-score. Additionally, as a practical application of this study, the results presented provide handball coaches of infant and cadet categories with the importance of biological maturation on kinanthropometric and physical condition variables, and it is not advisable to make comparisons among players without considering the effect of biological maturation. At the level of organization of handball competitions, it should be taken into account that the different growth rates shown at this stage can produce competitive disadvantages for players who are later, so regulations can be established in competitions to encourage competition to take place on equal terms and late matuers also have opportunities to participate, as has been proposed in other sports [26; 27]. Furthermore, another practical application for coaches and even for other researchers who evaluate and interpret BMI is that they should use this variable with caution in the adolescent population, as is the case with the adult sports population, since the different body compartments that make up body mass must be taken into account [61; 63].