## 4 Discussion  
In our study, we observed how CoG shifts, investigated here using the xEMU Vest and HUT, affected standing balance. We established a baseline investigation and metrics of how the superior shift in CoG, such as those caused by xEMU spacesuits, impacts an astronaut's balance. The xEMU Vest raised the CoG of the participants superiorly on the torso, mirroring what is observed by the xEMU spacesuit. Our findings showed that when participants donned the xEMU Vest or the HUT, balance (quantified in terms of TOTEX, MVELO, and MFREQ) was the most affected. However, the xEMU Vest and the HUT had opposite effects; the xEMU Vest significantly decreased the amount while the HUT significantly increased the amount of TOTEX, MVELO, and MFREQ. The xEMU Vest results showed improved stability, in line with previous studies with weighted vests [19; 20; 21]. Table 2 shows the xEMU Vest had lower TOTEX, MVELO, and MFREQ compared to that of the unsuited and the HUT. This is the opposite of the HUT, the HUT increases the amount of TOTEX, MVELO, and MFREQ significantly when compared to unsuited and the xEMU Vest. Past research findings from the increased load on the torso (via military backpacks) resulted in increased postural instability [22; 23], increased postural sway [22; 24], and increased balanced impairment [22; 25]. The results from TOTEX, MVELO, and MFREQ of the HUT all support the past literature findings. The HUT and potentially the xEMU spacesuits,which will exaggerate the CoG shift compared to the HUT, introduce instability in terms of TOTEX or the amount of sway (balance adjustments when standing), the speed of these adjustments (MVELO), and the rate of these adjustments (MFREQ). The HUT does not significantly affect ML or AP balance parameters but does significantly affect the ability of the wearer to maintain their balance while stationary. If astronauts are to perform manual tasks in the xEMU spacesuits, which will occur during the planned planetary EVAs in the upcoming Artemis missions and future Martian missions, there will be difficulties in maintaining a specific posture. The amount of instability introduced by the HUT was enough to significantly affect the balance of participants when compared to unsuited and the xEMU Vest. Eyes-closed has been shown to increase instability [26] and can be seen in our data by the increase in data point values from eyes-open to eyes-closed. The inherent instability of the HUT and eyes closed causes greater instability than the HUT alone. The HUT only replicated the effect on the CoG of the participants to a certain extent; in astronauts donning a true xEMU spacesuit, the CoG location will be higher and farther away from the body of the astronaut than that when compared to the HUT. The xEMU spacesuit may weigh up to 160 lbs (72.57 kg), and the portable life support system may weigh up to the same amount or even higher [27]; therefore, these parameters (TOTEX, MVELO, MFREQ) will increase even more with an actual xEMU spacesuit, making the xEMU spacesuit inherently unstable. Spacesuits introducing some level of balance instability is intuitive; however, now we are beginning to understand exactly how balance is impacted. This understanding is important because it will allow scientists and engineers to develop new spacesuits that can minimize the inherent instability and allow astronauts to perform actions and tasks without astronauts fighting to maintain their balance. Astronauts may become reluctant to perform a certain task if they are aware that they will be failing, possibly multiple times, to complete one task. Another possibility is the astronauts may become hesitant and try to be \"safe\" while performing the task, which can lead to the consumption of more resources than necessary; resources will be severely limited during planetary EVAs. As much as astronauts train in preparation for space travel, it is in human nature to hesitate or hold back when performing a task that can lead to an injury or performing a task that has already injured the person.