## 4 Discussion
### Influence of Maturation on Initial Performance  
The results obtained indicate superior physical performance among players with an advanced maturity status, showing a greater performance of post-PHV players in running capacities such as acceleration (5 m sprint), linear velocity (30 m sprint), and intermittent running endurance (vIFT), which strengthens the evidence of the influence of maturity development on physical capacities. A higher physical performance among young football players with advanced maturity status has been widely reported by the scientific literature [22]. Recently, the research led by [PERSON] et al. [34] showed better performance in the post-PHV group concerning neuromuscular performance, acceleration, sprint, and intermittent running capacity, which aligns with the results obtained in this study [17]. Structural changes in muscles (e.g., fascicle length, muscle hypertrophy, tendon stiffness), neural improvements (e.g., fibre recruitment, increased preactivation, reduced agonist-antagonist co-contraction), and other changes (e.g., hormonal or metabolic) during the maturation process are responsible for the enhanced force application and speed in young athletes as they grow [13; 17; 35].  
\begin{table}
\begin{tabular}{l l l l l l l l l} \hline  & & **Pre-PHV** & **Mid-PHV** & **Post-PHV** & **F** & \(p\) & \(\eta\)p\({}^{2}\) \\ \hline overall & n & 58 & 97 & 108 & & & & \\ \cline{2-8}  & time (min) & 8.70 \(\pm\) 1.26 & 8.66 \(\pm\) 1.25 & 8.59 \(\pm\) 1.25 & 0.19 & 0.828 & 0.001 \\  & vIFT (\%) & 87.85 \(\pm\)5.47 & 87.73 \(\pm\) 5.54 & 87.36 \(\pm\) 5.40 & 0.19 & 0.828 & 0.001 \\  & EL (u.a.) & 765.73 \(\pm\) 126.08 & 760.05 \(\pm\) 122.00 & 750.00 \(\pm\) 116.55 & 0.36 & 0.695 & 0.003 \\  & RPE (1–10) & 7.52 \(\pm\) 0.94 & 6.86 \(\pm\) 1.21 \({}^{\rm a}\) & 6.01 \(\pm\) 1.32 \({}^{\rm ab}\) & 31.71 & \(<\)0.001 & 0.196 \\  & IL (u.a.) & 65.60 \(\pm\) 13.61 & 59.00 \(\pm\) 12.28 \({}^{\rm a}\) & 51.60 \(\pm\) 13.58 \({}^{\rm ab}\) & 22.62 & \(<\)0.001 & 0.148 \\ \hline  & & vIFT (\%): percentage of the final velocity in the 30-15 intermittent fitness test; EL: external load; RPE: rate of perceived exertion; IL: internal load; LH: long HIIT; SH: short HIIT. \({}^{\rm a}\) statistically different (\(p\) < 0.05) from pre-PHV; \({}^{\rm b}\) statistically different (\(p\) < 0.05) from mid-PHV. \(n\) = total number of observations (sessions \(\times\) players). & & \\ \end{tabular}
\end{table}
Table 4: _Cont._These growth-related changes enable players with greater maturity status to generate higher absolute and relative power output during runs compared to their less mature counterparts; consequently, each velocity achieved in the 30-15 IFT represents a smaller percentage of their maximum running speed. This factor will directly impact players running economy, increasing energy expenditure in pre-PHV players during the test. Running at a higher percentage of maximum speed requires greater metabolic effort, and, more importantly, it also involves a higher recruitment of type II muscle fibres, which are less efficient and underdeveloped in less mature players [36]. Additionally, it is necessary to consider biomechanical demands such as increased stride frequency or length in less mature players, which may further elevate total energy expenditure [31; 37]. To be considered, during adolescence, a period of motor instability known as 'adolescent awkwardness' may arise, referred to as \"adolescent awkwardness\", which may alter inter-muscular coordination, thus affecting running mechanics, which could further contribute to the increased energy cost and reduced efficiency observed in less mature players, ultimately impacting their running performance [38]. These statements highlight the significant impact of maturational development on running performance, emphasising the physiological, metabolic, and biomechanical advantages of more mature players.