## 4 Discussion
In cases where a concurrent cognitive task demands cognitive resources to perform the balance task, people prioritize postural safety [35; 36; 37], so in our experiment, a decrease in cognitive performance due to increased heel height would indicate a prioritization of postural balance. However, we did not find any differences in cognitive performance with increasing heel height in either of the cognitive tasks used, indicating that the cognitive load did not limit the cognitive resources needed for postural balance during the quiet stance. Contrary to our hypothesis, the results did not show any systematic effect of dual-tasking interference on postural performance, thereby suggesting that the cognitive resources required for the execution of the cognitive tasks did not compete with the attentional resources involved with preserving balance while wearing shoes of elevated heel height. Previous studies investigating the dual-task posture-cognition interference have provided inconsistent results with the postural task challenge emerging as a critical factor for the reported discordance [25; 29]. In agreement with our findings, [PERSON] et al. [51], [PERSON] et al. [40] and [PERSON] and [PERSON] [41] did not find any change in postural sway during the barefoot quiet stance in young adult participants while simultaneously executing complex cognitive tasks. Similarly, and closer to the age range of our middle-aged subjects, [PERSON] et al. [42] reported no dual-task interference on postural sway during the concurrent execution of cognitive reaction time tasks. Standing is a very common activity in daily life. It has been reported that approximately 41% of the time spent in activities or postures in daily life is spent standing [52]. Experience-based anticipatory tonic muscle activation contributes to postural balance [53] and may minimize the involvement of higher control centers. Nevertheless, we found a significant deterioration in postural balance with increasing heel height. The deterioration of postural balance with increasing heel height during standing, but without interference of cognitive load, may have important implications for daily life. Despite the availability of cognitive resources, the increase in balance challenge during standing due to increased heel height cannot be fully compensated for, and balance safety is more affected by mechanical demands. Considering these results together, the non-found effect of dual-tasking interference on postural performance suggests that our participants adopted the \"posture-first\" strategy to respond to their perceived level of postural threat and ensure balance safety is not compromised [35; 36; 39]. Prior experience in a specific task is known to improve balance through anticipatory adjustments [54]. In our study, we investigated balance responses in humans who were not habitual wearers of high-heeled shoes and who may have some deficits in anticipatory balance control compared to habitual wearers. Theoretically, the effect of cognitive load would be lower in habitual wearers of high-heeled shoes due to their experience. Therefore, our main finding that cognitive load does not additionally worsen balance performance with increasing heel height will be valid. A limitation of the current study is that the interaction between cognition and postural balance control was examined here in quiet standing, whereas a complementary inclusion of dynamic conditions, such as walking with high-heeled shoes, might have provided additional insight into the allocation of resources during dual tasking. Given that approximately 41% of all daily activities involve standing and approximately 11% involve walking [52], we are confident that our results in standing have important ecological validity. Although the age range of our participants was quite wide (i.e., 21-54 years) and the results of the study can be generalized to a wide age range, we did not study older people and our results may not be representative of this age group.