Background: Adolescence is marked by changes to the body, including the feet. The Foot Posture Index (FPI‐6) stands out from other foot type classification methods as valid, reliable, and multidimensional. However, the current literature differs according to age group, with little consolidation of normative data in school children, largely due to the influence of such factors as sex, age and body mass index (BMI). Thus, this study assesses foot posture in adolescents according to age, sex and BMI.Methods: The study evaluated 1.394 adolescents from Amparo and Pedreira regions in São Paulo, Brazil. Subjects were positioned barefoot on a wooden base and each foot was assessed by FPI‐6 criteria. Each criterion was scored on a scale of −2 to +2, negative for supinated and positive for pronated posture. Initially the data were assessed for normality using the Shapiro‐Wilk test and descriptive statistics were calculated. To investigate and compare the scores of FPI‐6 with regards to age and body mass index, analysis of variance (ANOVA) was used, followed by post hoc Tukey. To compare the FPI‐6 with regard to gender, an independent student t test was used. All data were analyzed using SPSS version 21.0 and the 5% significance level.Results: Boys had higher scores than girls (p = 0.037) for the right foot, and the group with normal BMI values scored higher than the obese group (p = 0.001). For the left foot, 11‐ and 13‐year‐olds differed (p = 0.024) with respect to age in general. The overweight and obese group scored lower than the normal BMI group (p = 0.039; p = 0.001, respectively).Conclusions: Overall, the feet in this study were classified as normal, with a tendency to pronation, particularly in boys. There were differences between the 11 and 13 year groups and, with regard to BMI, there were higher scores for the group with normal BMI. Therefore, a higher BMI in adolescence is not indicative of a pronated foot type.

The practice of running has consistently increased worldwide, and with it, related lower limb injuries. The type of running surface has been associated with running injury etiology, in addition other factors, such as the relationship between the amount and intensity of training. There is still controversy in the literature regarding the biomechanical effects of different types of running surfaces on foot-floor interaction. The aim of this study was to investigate the influence of running on asphalt, concrete, natural grass, and rubber on in-shoe pressure patterns in adult recreational runners. Forty-seven adult recreational runners ran twice for 40 m on all four different surfaces at 12 ± 5% km · h(-1). Peak pressure, pressure-time integral, and contact time were recorded by Pedar X insoles. Asphalt and concrete were similar for all plantar variables and pressure zones. Running on grass produced peak pressures 9.3% to 16.6% lower (P < 0.001) than the other surfaces in the rearfoot and 4.7% to 12.3% (P < 0.05) lower in the forefoot. The contact time on rubber was greater than on concrete for the rearfoot and midfoot. The behaviour of rubber was similar to that obtained for the rigid surfaces - concrete and asphalt - possibly because of its time of usage (five years). Running on natural grass attenuates in-shoe plantar pressures in recreational runners. If a runner controls the amount and intensity of practice, running on grass may reduce the total stress on the musculoskeletal system compared with the total musculoskeletal stress when running on more rigid surfaces, such as asphalt and concrete.