Pronation or foot movement — What is important

Abstract

ObjectivesDespite difficulties to quantify foot pronation non-invasively and during dynamic tasks, pronation was frequently discussed with respect to injury risk and footwear development. Typically, surrogate measures were used to approximate the movement of pronation showing inconsistent results due to the high variability in the methodology and protocols. This study determines the relationships between all identified pronation variables and aims to reduce the data set to its dominant factors. DesignCross-sectional. MethodsForty barefoot participants (14 F, 26 M) performed four standing tasks (subneutral, bipedal, single-leg with 20° and single-leg with 30° knee flexion), over ground walking (1.5m/s) and running (3.5m/s) trials. Manual assessment data, motion capture data, ground reaction forces, and plantar pressure distributions were collected. Sixty-one commonly used pronation measures were compared using Spearman Correlations and a Principal Component Analysis (PCA). ResultsTwo groups of correlated variables were found, 4.2% of them correlated mainly with the longitudinal arch angle (LAA), the other 10.2% correlated with the Achilles tendon angle (β). The remaining 85.6% were not significantly correlated to each other. ConclusionsThe LAA is representative for the movement of the mid foot and β quantifies rear foot eversion relative to the shank. Since these dominant variables varied independently from each other, both cannot quantify pronation simultaneously. Therefore, it is important to consider and report both, LAA-pronation and β-pronation separately to represent prevalent foot movement properties. Separately assessing the two dominant underlying mechanisms of foot movement may lead to improved guidelines for clinical screening and footwear manufacturing.