## 4 Discussion  
This study analyzed how sport-specific training and environments in volleyball and water polo influence certain health-related PF levels (cardiorespiratory fitness and upper and lower body muscular strength/power) among youth athletes involved in these disciplines. The results showed significant differences in HG and PACER percentile levels between volleyball and water polo athletes in this sample, while no significant differences were observed in the SLJ test. These findings offer insights into how sport-specific training influences various dimensions of PF, highlighting how the distinct training environments and methods associated with each sport contribute to health-related fitness development. In this sample, volleyball players demonstrated greater handgrip strength in comparison with water polo players. In volleyball, technical skills such as spiking, setting, and blocking involve dynamic eccentric and concentric muscle activations in the upper extremities that function to enhance handgrip strength through the repetitive use of the hand and forearm muscles [42]. This could explain why volleyball players, who consistently engage in tasks requiring high eccentric and concentric neuromuscular demands in the musculature of the hands and forearms, might develop superior handgrip strength in comparison to water polo players, although both groups demonstrated high average percentiles in handgrip strength relative to the European normative data. While water polo  
Figure 3: Histogram plots with the percentile distribution of volleyball (**a**) and water polo (**b**) players for Handgrip performance. Figure 2: Histogram plots with the percentile distribution of volleyball (**a**) and water polo (**b**) players for SLJ performance. involves gripping and throwing the ball, the aquatic environment significantly reduces the demand for reactive eccentric hand movements. Water polo players exhibited superior cardiorespiratory endurance in the PACER test in comparison with volleyball players. This could be attributed to the characteristics of their training (as described in the Section 2.1) and the continuous aerobic demands of the sport. Water polo athletes are constantly engaged in highly intense physical activity in the water, even during the transition phases of the game, due to the necessity to treat water and remain afloat. This continuous demand for aerobic capacity likely leads to enhanced mitochondrial synthesis and improved oxygen consumption capabilities, thus contributing to better overall cardiorespiratory fitness [43]. The training demands were also greater for water polo athletes (five vs. three practice sessions and an additional two hours per week of physical training in the gym). However, the CRF data of our sample were on average below the 50 th %ile of the European population [35]. In the same study, Italy was ranked in the range of the 26 th and 34 th %tiles for CRF and this is in agreement with the performance of our sample. A potential explanation of these poor performances is related to the limited opportunities Italian youth and adolescents have beyond sport contexts, especially because physical education does not seem to be adequate to support effective physical development [44]. Interestingly, no significant differences were observed in the SLJ percentile data between the two groups. While volleyball players engaged in frequent jumping activities, water polo players also developed significant lower body strength via various high-intensity swimming activities as well their additional land-based training time, which included lower body resistance training. A study conducted by [PERSON] and colleagues [45] suggested that vertical thrust in water, a key movement in water polo, both requires and develops significant explosive strength in the lower limbs, even if the relationship between this skill and ground vertical jump resulted in a poor correlation [46].