## 4 Discussion  
The principal aim of this study was to demonstrate the utility of the unilateral 180\({}^{\circ}\) jump as a potential physical assessment tool by providing descriptive kinematic data. All participants demonstrated similar knee and thigh motion and pelvis motion. During the loading phase there were no significant differences between limbs, with all participants executing internal rotation of the thigh while extending, adducting, and externally rotating the pelvis. These movements portray a \"counter movement\" pattern opposite to the desired action of rotation, by loading the system up similar to the downward movement (knee flexion) preceding forceful knee extension one would observe in a vertical jump. This rotational \"counter movement\" pattern may be performed in an attempt to load the associated musculature and utilize strain energy to facilitate the stretch-shortening cycle. Previous research has indicated hip flexion with hip internal rotation has a greater correlation with large knee valgus moments [29], therefore the observed external rotation of the hips in healthy athletes may be a subconscious attempt to reduce potentially deleterious forces at the knee. During the landing phase there were no significant differences between limbs for thigh rotation (\(p\) = 0.77, d = 0.14) or pelvis movement (Flex/Ext [\(p\) = 0.95, d = 0.03], Add/Abd [\(p\) = 0.6, d = 0.22], Axial Rotation [\(p\) = 0.82, d = 0.08]). For all participants, the thigh internally rotated and the pelvis extended, abducted and internally rotated. For cutting tasks with up to a 110\({}^{\circ}\) change in direction, hip internal rotation in conjunction with hip abduction was associated with larger knee valgus moments [30; 31]. The larger the degree of rotation the greater the rotational forces [30], indicating a necessity to execute the task and not necessarily a greater risk of injury. Since the participants of this study were healthy elite-level athletes, the pelvis moving in line with the rotation of the jump may have been a strategy to reduce torsional forces experienced at the knee and ankle by dissipating energy at a link in the kinetic chain with a greater range/number of degrees of freedom (DOF). There was a significant difference in the frontal plane knee motion during the landing phase between limbs (Add [\(p\) = 0.05, d = 0.79], Abd [\(p\) = 0.01, d = 1.11]). Greater knee adduction was observed in the dominant limb (-4.2\({}^{\circ}\) greater), whereas greater knee abduction was observed in the non-dominant limb (-6.5\({}^{\circ}\) greater). Moreover, it should be noted that these specific findings had some of the strongest ICC values and lowest SEM values (see Table 1). This finding indicates that a bilateral asymmetry is observable even in healthy athletic populations. Due to the cross-sectional nature of this study, it is impossible to indicate which strategy is more beneficial. Uncontrolled knee movement during landing has been associated with greater ACL injury risk in uniplanar drop jump tasks [23] but rotational tasks require greater knee frontal plane excursions to complete [29; 30; 31]. Therefore, prospective evidence is needed to indicate which motion contributes to a greater risk of injury. Furthermore, one motion is most likely not good or bad, but stresses different soft tissue structures more greatly (for example, abduction: ACL, adduction: MCL). Likewise, how the system (body) moves as a whole is more important for understanding the potential injury risk. Visual qualitative assessment of CRP plots indicated that there was little variation between participants during the loading/take-off phase (refer to the first 20% in Figure 1). Moreover, the relative phase angle between the shoulders and the pelvis for the majority of the participants was very close to 0\({}^{\circ}\). A phase angle at or close to 0\({}^{\circ}\) indicates that the shoulders and pelvis were in-phase or moving together.