## 4 Discussion  
In this study, training and match load parameters were recorded (including HMLD) in first division soccer players over one season. By including velocity and acceleration to estimate workload and calculate ACWR, we compared players who sustained a non-contact injury with uninjured players. In addition, the workload parameters were related to the pre-season EP in order to interrelate workload (HMLD) and resilience as measured by EP (v2, v4, \(\mathrm{v_{LT}}\), \(\mathrm{VO_{2 max}}\)). Based on the four weeks before the non-contact injuries, a sensitivity of 78% and a specificity of 80% were calculated for the relationship between the chronic component (CW) of ACWR in the first week before the injury and the \(\mathrm{v_{LT}}\). The observed accuracy for the v2 (CW, first week before the injury) was slightly (3%) higher (sensitivity: 70%, specificity: 91%). Apparently, only the CW of the ACWR is related to the occurrence of non-contact injuries. It is important for soccer coaching, especially for the athletic coaches, to understand that the load must be assessed in relation to the EP level of the players, particularly the aerobic capacity. These findings are in line with several investigations [3; 8; 16], who stated  
Figure 2: (**a–d**). Receiver operating characteristic curve (ROC) depending on week before the injury and different EP parameters related to the chronic component of ACWR. AUC values and 95% CI are reported. (**a**) chronic related to v2. (**b**) chronic related to v4. (**c**) chronic related to \(\mathrm{VO_{2 max}}\). (**d**) chronic related to \(\mathrm{v_{LT}}\). that relatively higher body strength (lower limbs) and a high level of aerobic capacity are important factors for injury prevention. At the same time, these findings are in significant contrast to the widely used approach of calculating ACWR by training duration and the sRPE as an indicator for the internal training loads [3; 6]. This is the first published suggestion based solely on objective load and stress data that takes into account individual aerobic capacity. The aerobic capacity calculated by VO\({}_{\text{2 max}}\) during EP diagnostics was lower in our cohort (\(53.7\pm 4.9\) mL/min/kg) compared to other studies [29; 30; 31]. However, in agreement with previous studies, the injured players had a significantly lower VO\({}_{\text{2 max}}\) than the matched uninjured players (\(53.2\pm 4.0\) vs. \(56.3\pm 6.5\) mL/min/kg; \(d=0.6\)). Various studies have reported and recommended VO\({}_{\text{2 max}}\) values from 62 to 64 mL/min/kg to fulfill the aerobic capacity requirements for male professional soccer players [29; 30]. It should be noted, however, that the endurance diagnostics in this study took place at the beginning of the pre-season. In line with this, [PERSON] et al. [31] measured VO\({}_{\text{2 max}}\) before and after two months of soccer training and reported values of 53.6 \(\pm\) 7.7 mL/min/kg (before) and 64.4 \(\pm\) 5.7 mL/min/kg (after) from soccer players of the first Greek division. The endurance performance data of the studied players were similar to those of German second and third division players, independent from playing position [32; 33]. The importance of aerobic capacity for soccer performance has been widely documented. Moreover, [PERSON] et al. [34] showed that the threshold performance at v4 was highly correlated (r = 0.91) with the ability to recover. Therefore, the authors recommended 15.0 km/h (4.2 m/s) at the 4 mmol/L lactate threshold as a minimum endurance performance level [33] to cope with the demands of a competitive soccer season. Compared to the match HMLD, the absolute and relative total HMLD recorded during the training sessions was significantly lower. This is due to the lower HMLD completed during the training sessions. However, the different relative HMLD magnitudes between the playing positions indicate that the training intensities adequately met the position-specific match demands.