## 1 Introduction  
Knowledge of the biomechanical properties of athletes' bodies is becoming increasingly important in both amateur and professional sports. This includes, for example, the analysis of leg axes, the position of the pelvis, and the extent of spinal curvature. The relationships between such somatic characteristics and both posture and muscle properties have been investigated by [PERSON] [1]. Conversely, the relationships between muscular performance and posture in athletes have been increasingly well researched. For example, lower isokinetic trunk muscle strength in people with poor posture could be found [2]. [PERSON] [3] showed that posture also changes in a sport-specific way. He found that the spinal alignment of soccer players showed a more flattened lumbar lordosis compared to their untrained peers. These changes may be adaptation phenomena of the organism due to sport-specific neuromuscular requirements. These findings provide approaches to specifically improve posture in athletes in a targeted manner. [PERSON] [4], for example, examined how targeted muscular training could improve pelvic tilt. Similar results were also found by [PERSON] et al. [5] and [PERSON] [6]. [PERSON] et al. [7] found that hip muscle stretching may lead to immediate reductions in pelvic tilt, as did [PERSON] et al. [8], who were able to show that hamstring stretching could improve the pelvic position and sagittal spinal curvatures in a standing position. Since it is known that individual posture-related factors can influence athletic performance, posture analyses appear to be particularly important in an athletic context. For example, stabilization of the lumbar region and the thoracolumbar transition is especially important when back squatting and can be adversely affected by an altered lumbar lor-dosis and thoracic kyphosis [9]. An increased pelvic tilt can in turn have a negative effect when sprinting, because anteversion of the pelvis creates tension on the tendon of the long biceps head, which reduces the range of hip flexion. This can affect athletic performance, for example when sprinting [10]. Likewise, an increased pelvic tilt can increase the risk of hip complaints in soccer players, especially in the context of an existing hip impingement [11; 12]. In this context, the examination of posture has established itself in recent years as a helpful method in the field of sports and leisure [13; 14; 15; 16]. Sagittal posture analysis provides information about the alignment of the body segments with respect to each other (local parameters such as the pelvic tilt), as well as the positioning of the body in relation to the base of support (global parameters such as the body lean) [17; 18; 19]. In this line, recent studies have shown that the position of the pelvis in the sagittal plane can influence the incidence of muscle injuries in sports. [PERSON] and [PERSON] [20], for example, examined the relationship between pelvic tilt and hamstring injuries in a prospective study of 76 professional soccer players in the Premier Division over a period of five years. They were able to show that an increase in pelvic tilt from a cut-off angle of \(13^{\circ}\) is associated with a higher incidence of hamstring injuries. They emphasized that poor posture can lead to musculoskeletal pathologies, with pelvic position playing a crucial role in many postural problems [20]. An increased risk of hamstring injury due to a fatigue-related increase in pelvic tilt was also observed by [PERSON] et al. [21]. [PERSON] et al. provided the theoretical basis for this phenomenon. They were able to show that an increase in pelvic tilt led to a significant increase in tissue strain in all regions of the three ischiorcural muscles (semitendinosus, semimembranosus, and long head of biceps femoris). This was greater in the proximal region, which is most susceptible to injury--with more than 1 cm of tissue strain per 5\({}^{\circ}\) of pelvic tilt--when compared to the distal region [22].