## 4 Discussion
Coordinated coupling of the upper and lower body segments during the loading phase may be a result of the population tested. Healthy athletes presumably have better motor control and coordinate their torsos in a synergistic fashion with their lower extremities to improve mechanical efficiency by reducing counter-productive movement. Furthermore, this may demonstrate torso control by the participants to reduce torsional forces experienced at the knee that has been observed in cutting tasks when torso lean/excursion is excessive [28]. Likewise, the amelioration of the torsional force and modulation of body segments may help maintain the center of gravity within the base of support so that the individual successfully executes the task (does not fall over). Prospective research should be conducted on unhealthy or non-athletic populations to determine if uncontrolled torso movement can be observed during the loading phase of a unilateral 180\({}^{\circ}\) jump task. Investigating 'less athletic' or impaired populations will further elucidate motor control capabilities, differentiating key differences in task execution compared to elite-level athletes when performing this specific task. Whereas the loading/take-off phase exhibited relative uniformity between participants, the greatest amount of variation was observed during the landing phase of the 180\({}^{\circ}\) jump (refer to last 50% of Figure 1). CRP plots displayed three common landing strategies amongst participants: thorax (shoulder)-led movement, pelvis-led, or simultaneous in-phase landing. Although these three strategies were performed, it should be noted that each individual only utilized one of them and with varying degrees of phase coupling. In some cases, individuals were close to a relative phase angle of 180\({}^{\circ}\), which represents an anti-phase movement (similar to arms swinging in separate directions at the same rate during normal gait). Furthermore, the phase coupling between the thorax and pelvis was not constant, meaning the rates at which the two segments rotated in conjunction with one another were at different rates throughout the second half of the unilateral 180\({}^{\circ}\) jump task, suggesting a dissociation between the segments during the landing portion of the task. CRP best describes the passage of energy through a system [39; 40], in this case, the human body. Each participant utilized a slightly different strategy to dissipate the high torsional energy in order to execute the task and land successfully. The fact that many strategies with different degrees of variation were observed demonstrates the principle of equifinality of movement solutions due to the vast number of DOF [41; 42]. Although there are multitudes of strategies to complete the task, it stands to reason a shoulder-led strategy may be the most deleterious for structures around the knee. If the shoulders lead with the pelvis following, upon landing when a high load rate force is transmitted up the kinetic chain the shoulders will have little range left for further excursion to enable energy dissipation. Instead, it could likely result in a resultant force transmitted back down to attempt to be dissipated by the pelvis movement. This could result in greater hip flexion and hip internal rotation, which has been linked to greater knee valgus moments [29; 30; 31]. A pelvis-led strategy may enable better dissipation of excessive energy because it can pass up through the entire kinetic chain. However, because this study is cross-sectional this theory is conjecture on the part of the authors. Similar to research involving drop jumps [23; 43; 44], future research could yield information regarding which strategy portends greater injury risk and what relative phase angles indicate problematic upper torso and lower body coupling during rotational sporting tasks. Further evidence to support this approach can be observed in the test-retest reliability (ICC) scores (see Table 1).