Establishing Normative Values for the Supination Resistance Test: An International Cross‐Sectional Study

BACKGROUND: The supination resistance test quantifies the force required to supinate the foot and ankle. Although it demonstrates good to excellent intra- and inter-rater reliability and shows potential for predicting foot and ankle biomechanics during walking, assessing the biomechanical effects of foot orthoses, and distinguishing between healthy and pathological conditions, the supination resistance test remains underutilised in both clinical and research settings due to the lack of normative reference values. Thus, the primary objective of this study was to establish international normative values for the supination resistance test based on age and sex. A secondary objective was to compare supination resistance across age groups and between sexes. METHODS: In this international cross-sectional study, supination resistance was measured in 1198 healthy participants aged 18 years and older from North America, the Middle East, and Europe. Supination resistance was compared across age decades and between sexes using a two-way analysis of covariance, with body mass included as a covariate. Correlation coefficients and coefficients of determination were calculated to examine the relationships between supination resistance, body mass, and the Foot Posture Index. RESULTS: Supination resistance was greater in males than in females during the 3rd to 5th and 9th decades of life. In males, it increased from the 3rd to the 5th decade and then progressively declined. In females, it increased from the 3rd to the 6th decade, remained stable through the 7th decade, and then dropped sharply. Body mass accounted for 18.1% of the variance in supination resistance, whereas the Foot Posture Index accounted for only 0.3%. CONCLUSIONS: The international clinical reference values established for the supination resistance test, stratified by age and sex, carry important clinical implications and may support clinicians in screening, monitoring, and managing foot and ankle musculoskeletal conditions. Future research should investigate whether deviations from these normative values represent a risk factor for the development of musculoskeletal injuries and explore the relationship between restoring supination resistance to normative levels and the reduction of clinical symptoms.