Relative position between head and wireless earphones during running

![CDATA[Rationale & Objectives: Listening to music while running is very common in recreational runners but wireless earphones falling out can be annoying. Yet, there is limited data on how earphone design influences the stability. Hence, this study examined the 3-dimensional relative motion between the head and a series of wireless earphones on the market during running. Methods: Thirty regular runners who used to run with wireless earphones were recruited from local running clubs. Six wireless earphones on the market were tested in a randomized sequence. The relative position between the earphone and the head before and after a 3-minute downhill running trial was measured using an 8-camera motion capturing system. In addition, we measured the fallout rate of earphone during the trials and self-perceived fit score for each earphone model. Results: We did not observe any significant difference in the relative position between the earphone and head before and after running between the six models (F=1.129, p=0.348). However, a greater fallout rate was found in a model without ear fins (fallout rate=73.3%, p<0.001) than the other models (fallout rate ranging from 0-30%). Fit scores between conditions were similarly medium (F=1.845, p=0.108). No significant correlation was found between earphone mass and relative positions (r=0.031, p=0.721) and fallout rate (r = -0.232, p=0.658). Conclusions: The relative positions between the earphone and head were similar across selected models, but models without ear fins could be more likely to fall out. The relative positions and fallout rate were not related to the earphone mass. Interestingly, runners may not be able to differentiate the earphone fit by subjective perception.]]