foot arch characteristics and lower limb overuse injuries in habitually barefoot and shod kenyan adolescents.

Abstract

Title: Foot arch characteristics and lower limb overuse injuries in habitually barefoot and shod Kenyan adolescents. Background: The barefoot habitus typical of early human lifestyles may cause intrinsic foot structural adaptations which could protect lower limbs from impact related overuse injuries. Objective : This study sought to assess foot arch height and flexibility, intrinsic foot muscle strength and prevalence of the common lower limb overuse injuries in habitually barefoot, rural school going adolescents; in comparison to an age, weight and sex matched group from a shod population. Methodology: This was a cross-sectional study conducted in both rural Nandi for the habitually barefoot and a modern setting for the shod group. 38 habitually barefoot (HB) and 38 age, gender and weight matched habitually shod adolescents (HS) were investigated for foot arch characteristics, intrinsic foot muscle strength and lower limb overuse injury prevalence. Arch height at 50% of foot length was measured seated and standing by an arch height index measurement system, and relative arch deformability computed. Intrinsic foot muscle strength was measured using a commercially available foot strength electronic dynamometer. Physical activity was quantified using uni-axial accelerometry. Injury incidence was interrogated via a structured questionnaire and physical examination. Results: The foot arch was higher and more flexible in the HB compared to HS. (Arch height 6.7{5.6, 8.1} vs. 6.2{4.6, 7.2} p= 0.01; Relative arch deformability 0.76{0.58, 1.063} vs. 0.64{0.41, 0.79} p= 0.012, respectively). The HB had stronger intrinsic foot muscles (IFM) than the HS (IFM strength 4.7kgs {3.10, 6.13} vs. 3.30kgs {2.18, 4.35} p= 0.03). There was a higher lower limb overuse injury incidence rate in the HS (28.8% vs. 2.6%, chi-square 9.896, p<0.02). There was no statistically significant correlation between gender, physical activity levels and the measured foot arch characteristics. Conclusions and recommendations: In comparison to shod adolescents, the habitually barefoot were found to have a higher, more flexible medial longitudinal foot arch and stronger foot intrinsic musculature. They also recorded a lower incidence of lower limb overuse injuries. Further prospective studies are recommended to relate the morphological foot differences found between HB and HS, and overuse injuries in all active age groups.