# Quantifying Sub-Elite Youth Football Weekly Training Load and Recovery Variation
## 4 Discussion
### Age Group Analysis  
In the present study, all external training load measures presented a significant difference, except DSL (Table 1). Higher TD, AvS, MSR, rHSR, HMDL, average sprint and number of sprints were found in U17 players (moderate to strong effect). U17 players did not present significant differences when compared to U19 players in rHSR, average sprint distance, ACC and DEC. Our findings were consistent with [PERSON] et al. [32], who reported a higher TD covered and average sprint distance for U17 players. The authors also did not find any differences between U17 and U19 players for body impact and relative impacts. In contrast, [PERSON] et al. [33] reported a higher total weekly training load for older groups (i.e., U18). However, the authors measured physiological intensity, resorting to heart rate-based methods which could bias the high-intensity efforts [45; 46; 52]. Additionally, the data of the present study evidence the lowest intensity in U15 players' training sessions regarding rHSR, average sprint distance, number of sprints, ACC and DEC (strong effect). There was an age-related increase in the training intensity and to a greater extent  
Figure 4: Mean training load and recovery status per session according to comparison between playing positions.  
in the training volume [33; 43]. Curiously, U15 players presented a higher TD and MSR when compared with U19 players (strong effect). There was an age-related increase in the training intensity and to a greater extent in the training volume [33]. Due to this fact, associated with a more conscious pacing strategy and better game interpretation with age, it was possible to also increase the exercise economics [53]. Even more interaction effects were found between inter-day, inter-week and age for TD, confirming an increase in the pacing strategy in the aging progression. Training periodization also seemed to influence the TD covered, concerning the training day and weekly microcycle.  
The present investigation confirmed the age-related increase in the training intensity in sub-elite football. However, acceleration metrics have a high variability subsequent to the time-dependent and transient reductions [24; 54]. Nonetheless, it was not clear from that acceleration whether variables increased across different age groups, G. Our study provides news insights about age influence in acceleration movements. We found an interaction effect between age, week, training day and playing position for DEC. In the current age group analysis, U19 players showed a higher internal training load (minimum to strong effect) and a lower recovery status (strong effect). These findings were consistent with [PERSON] et al. [33], who noted a higher weekly RPE load in the older age group (i.e., U18). There was evidence that a higher training load and a good recovery were expected to improve physical performance [4; 18]. Furthermore, we were able to verify a higher training volume in younger players (i.e., U15 vs. U19). It is reasonable to argue that coaching staff tend to code training programs with more volume and less intensity when it comes to younger players. Moreover, a focus on the basic tactical principles and technical skills using constrained training tasks was reported in younger age groups [32]. Nevertheless, the time spent at high-intensity zones and normalizing the session duration may affect the perceived exertion [14].