Relationships of positional plagiocephaly with lumbar and lower limb injury history and static balance ability in collegiate competitive swimmers

Since the publication of guidelines on infant positioning during sleep, there has been an increase in the incidence of severe positional plagiocephaly (PP). This study aimed to clarify the prevalence and severity of PP among competitive swimmers, and to investigate the relationship between the severity of PP and the history of lumbar and/or lower limb disorders, as well as static balance ability. Thirty collegiate swimmers participated in this study. Participants were assessed for the presence of PP and its severity. Their history of lumbar and/or lower limb disorders were investigated, and a 20-second single-leg stance test with their eyes closed was performed to evaluate their static balance ability. Our results revealed that all participants had the presence of Type I or more severe PP, with eight individuals exhibiting the most severe Type IV. Although the association between PP severity and the presence of a history of low back and lower-limb injury was not significant, a large effect size was observed (p = 0.065, V = 0.49). Among the 15 participants who could complete the single-leg stance test with their eyes closed on both sides, a negative correlation was found between the sway path length for the centre of gravity when using the leg in non-PP side and the PP severity score (ρ = −0.55, p = 0.03). Therefore, among competitive swimmers with at least a certain level of static balance ability, it was suggested that swimmers with more severe PP tend to keep their posture on the side without PP.