The effects of foot type and heritability on balance and plantar pressure distribution of female twins.

AIM: Posture and plantar pressure distribution can influence several factors, including both foot type and heritability. Therefore, the purpose was to assess the influence of foot type and heritability and their effects on foot characteristics. Static and dynamic balance and plantar pressure distribution was assessed, and the participants were pairs of female twins.

METHODS: Sixteen monozygotic and fourteen dizygotic pairs with no history of injuries were included in this causal-comparative study, divided into three foot types by navicular drop test: pes planus, pes rectus and pes cavus. Static balance was measured using the stork test and dynamic balance using the SEBT test. Plantar pressure distributions were measured by the emed platform. Two-way ANOVA, F test, heritability estimate, intraclass correlation coefficient and Fisher Z test were used for statistical analysis.

RESULTS: No significant differences were found between foot types or zygosities in static and dynamic balance and peak pressure (P>0.05). Within-pair variances were significantly different in dynamic balance in PL and L directions (P<0.05). Heritability was 0.43, 0.52, 0.62, 0.65 and 0.39 in static balance and dynamic balance variables in P, PL, L and mean of eight directions, respectively. Genetic factors revealed no influence on peak pressure. Within-pair correlations were significantly different in dynamic balance results in PL and L directions (P<0.05).

CONCLUSION: Foot type and zygosities had no influence on balance or peak pressure. Genetic factors moderately influenced postural balance, but not peak pressure. The current study is an asset to identify and manage influential factors in these variables for female twins.