# Effects of Extracurricular Sports in Prepubertal and Pubertal Girls
## 4 Discussion  
This is the first study that analyses the influence of the extracurricular sport typology on the body composition, respiratory fitness, and physical condition of prepubertal and pubertal girls. The main findings were that morphological, physical, and respiratory adaptations vary according to the growth stage (i.e., prepubertal and pubertal) and the practised extracurricular sport (i.e., individual or collective). However, significant differences according to the extracurricular practised sport were found only in prepubertal girls, partially confirming the initial hypothesis. The existing evidence suggests that the transition from prepuberty to puberty increase girls' fat mass regardless of their daily physical activity [42]. This study is line with this evidence and our second hypothesis, as pubertal girls (either PUB-CSs or PUB-ISs) showed higher fat mass pubertal girls. However, this is a cross-sectional study, while diet and active life were not controlled, so cause-effect cannot be set from this study. The transition from prepuberty to puberty is also associated with a muscle mass increase in girls [43, 44]. Nonetheless, this increment seems to be higher in girls participating in extracurricular sports [19, 45]. This might explain why both pubertal groups showed a higher muscle mass even when the average age (PUB-CS = 13.90 \(\pm\) 1.14 years; PUB-IS = 13.87 \(\pm\) 1.29) was lower than the age period (around 15 years old) during which muscular strength and muscle mass gain are accelerated [43]. The fact that both fat mass and muscle mass increase during adolescence also explains why both groups (PUB-CS and PUB-IS) displayed higher BMI levels than the prepubertal girls, which is in line with a previous study in pubertal girls participating in extracurricular sports [46]. Thus, care must be taken when tracking changes in adolescence using the BMI. It has been suggested that the extracurricular sport typology plays a significant role in the body composition [47]. However, this is partially evidenced in the current study as PUB-CSs and PUB-ISs did not show differences in their body composition. It is important to highlight that only two sport typologies were defined in this study, so future studies attempting to confirm or reject our findings should consider more sports typologies. The fact that PRE-CSs showed a higher muscle mass might be due to the demands of collective sports (i.e., jumps, changes of direction, acceleration, deceleration, sprinting, etc.) [48]. However, additional studies are needed to confirm these findings. Furthermore, PRE-CSs showed a higher fat mass and percentage fat mass than PRE-ISs, which might be due to the demands of the practised sports but also due to their food habits [49] or daily activity. Therefore, future studies should also attempt to control the diet of prepubertal and pubertal girls and measure the daily activity. In line with previous studies [50], girls' pulmonary capacity improved with age regardless of the sport typology. This might be due to several reasons; however, maturity is likely to be the main reason for the higher respiratory capacity of pubertal girls, as it causes an increase in the lungs' dimensions and the muscles participating in breathing [51, 52].