## 4 Discussion
As a local parameter, it is subject to large individual variability, which is partly anatomically based, while global parameters such as body lean must be regulated by the central nervous system within a narrower range, as otherwise equilibrium stability would be affected. When analyzing posture parameters with a clinical focus, it is important to distinguish between real changes in posture and measurement errors. One way to distinguish between a real change and a random measurement error is to examine the minimum detectable change (MDC), as recommended by [PERSON] and [PERSON] [53]. The MDC value can be seen as the minimum change that must be observed to be considered a real change. In the context of the clinical observation that muscular exhaustion can increase the pelvic tilt, values \(>\) 3.9\({}^{\circ}\) must therefore be considered relevant. Figure 4 shows an example of an athlete in our study with a significant increase in pelvic tilt during the course of the day, likely due to previous muscular exertion. In this individual case, the pelvic tilt increased by almost 6\({}^{\circ}\). For a parameter that is quite constant over the course of the day but randomly fluctuates, this is an increase that must be considered clinically relevant, particularly because there seems to be an increased risk of injury to the hamstrings if the pelvis is tilted more than 13\({}^{\circ}\)[20]. Therefore, when several firing efforts follow one another in the context of athletic competitions, worsening of the pelvic tilt must still be considered, which can increase the risk of injury. Figure 4: (**a–c**) Change in pelvic tilt during the day in a subject’s habitual posture as a result of muscular exertion (note that in the third measurement, the cut-off value of 13\({}^{\circ}\) according to [PERSON] and [PERSON] [20] is clearly exceeded). Even though the reproducibility of the angle measurement was high, it makes sense to consider individual cases in which the posture parameters are measured multiple times in cases of prolonged exertion. The MDC values shown in Table 6 can be consulted to assess whether the observed changes in posture are clinically relevant. Body lean also proved to be a time-stable parameter with good ICCs (0.74-0.81), presenting no significant influence of the time factor in the ANOVA. However, it changed significantly with activation of the posture. The angle increased, indicating a backward inclination of the body, which was previously somewhat forward-leaning. The body lean is interesting, as there appears to be a correlation with the occurrence of low back pain. [PERSON] et al. distinguished several posture types in this regard. In their so-called \"sway-back\" type, in which the body and trunk are more inclined backward, their studies showed increased values for the body lean angle and trunk lean angle parameters. This posture type is more likely to be associated with the onset of lower back pain [54; 55]. However, as the body lean in our study changed significantly with the activation of posture, care must be taken to ensure a reproducible posture, providing clear instructions to the test subjects when taking measurements. Even parameters that remained stable over the course of the day, such as body lean, showed strong inter-individual fluctuations. Two outliers had values of \(-1.4^{\circ}\) and \(+2.6^{\circ}\). The changes observed in these cases over the course of the day were within the MDC of \(1.42^{\circ}\) for habitual posture. This shows that these are indeed different posture types, as described in the literature; for example, by [PERSON] et al. [55; 56] for children and by [PERSON] et al. [57] for adults. This may be of particular clinical interest, since certain posture types, such as the above-mentioned \"sway back\" cluster, showed a higher prevalence for the occurrence of lower back pain.