## 3 Results  
The anthropometric characteristics of the participants are presented in Table 1. Based on the results from the IPAQ, participants were overall classified as having a medium physical activity (PA) level amounting to a weekly average of 2680 \(\pm\) 1936 metabolic equivalents (METs) per minute. The detailed distribution of the participants' age and PA levels can be found in Supplementary Table S1. Briefly, with the exception of one participant being assessed with a low PA level, the majority of them (\(n\) = 14) were assessed with a medium PA level, while six participants were assessed with a high PA level, respectively (Supplementary Table S1). In the control condition, a significant main effect of heel height was found for the CoP parameters (Figure 4). Specifically, path length was significantly increased (F\({}_{2,60}\) = 32.7, \(p\) < 0.001, d = 1.019) following the increase in heel height and post hoc comparisons showed significantly higher values between low- and medium-heel, low- and high-heel and medium- and high-heel height, respectively (\(p\) < 0.001 for all comparisons, Figure 4A). Similarly, the increase in heel height significantly affected the anteroposterior CoP sway range (F\({}_{2,60}\) = 19.1, \(p\) < 0.001, d = 0.779) with the respective CoP values being significantly higher between the low- and medium-heel (\(p\) = 0.001) as well as the low- and high-heel heights (\(p\) < 0.001) (Figure 4B). Post hoc comparisons did not yield a statistically significant (\(p\) = 0.068) difference between the medium- and high-heel heights for the AP sway range. In the case of the CoP mediolateral sway range, there was not a significant effect of heel height (F\({}_{2,60}\) = 3.0, \(p\) > 0.05, d = 0.311) (Figure 4C). Figure 4: Path length (**A**), CoP sway range in anteroposterior (**B**) and CoP sway range in mediolateral direction (**C**) for the low-, medium- and high-heel heights in the two-legged quiet stance postural balance assessment in the control condition (i.e., without any further cognitive load). Data depict the median and the 5 th–95 th percentile as whiskers. * Statistically significant (\(p\) < 0.05) post hoc comparisons between respective shoe heel heights. The two-way ANOVA revealed no statistically significant main effect of cognitive load (F\({}_{2,75}\) = 1.642, \(p\) = 0.202, d = 0.197) and a non-significant interaction effect of cognitive load by heel height (F\({}_{2,80}\) = 0.994, \(p\) = 0.375, d = 0.153, Figure 5A). There was a significant main effect of heel height (F\({}_{1,40}\) = 12.2, \(p\) = 0.001, d = 0.539) and post hoc comparisons showed that path length values were significantly greater with the high compared to the medium heels in all conditions (control: \(p\) = 0.002, dual-task_A: \(p\) = 0.022, dual-task_B: \(p\) = 0.032) (Figure 5A). In the anteroposterior range of CoP sway, there was no significant main effect of cognitive load (F\({}_{2,78}\) = 0.056, \(p\) = 0.943, d = 0.031) or heel height (F\({}_{1,40}\) = 0.218, \(p\) = 0.643, d = 0.069) and no significant interaction of cognitive load by heel height (F\({}_{2,80}\) = 1.288, \(p\) = 0.281, d = 0.175, Figure 5B). In the mediolateral direction, a significant main effect of cognitive load was found (F\({}_{2,77}\) = 4.464, \(p\) = 0.016, d = 0.325), but post hoc comparisons showed a significantly greater range of CoP sway (\(p\) < 0.040) only for the medium-heeled shoe in the dual-task_B condition compared to the control condition (Figure 5C). No statistically significant effect of heel height (F\({}_{1,40}\) = 0.082, \(p\) = 0.776, d = 0.044) and cognitive load by heel height interaction (F\({}_{2,80}\) = 1.237, \(p\) = 0.296, d = 0.172) was found in the mediolateral sway range (Figure 5C). There was no difference in cognitive performance between the medium-heeled and high-heeled conditions compared to the reference sitting condition for both dual tasks (COGN_A: F\({}_{2,35}\) = 0.676, \(p\) = 0.494, d = 0.128; COGN_B: F\({}_{2,38}\) = 1.509, \(p\) = 0.234, d = 0.226, Figure 6).