RT Journal Article T1 A study of the reproducibility and reliability of the musculo-articular stiffness of the ankle joint T2 Estudio de reproducibilidad y fiabilidad de la rigidez Musculo-articular de la articulación del tobillo A1 París-García, Federico A1 Barroso, Alberto A1 Paris, Federico K1 Stiffness K1 Functional response K1 Free vibration technique K1 Reliability AB The objective of this work was to evaluate the reproducibility, reliability and usefulness of the musculo-articular stiffness (MAS) of the ankle joint, measuring it by the free vibration technique. Seventeen (nine males and eight females) healthy university students were included in the study. Force (f), MAS (k) and unitary MAS (ku) (defined as the ratio between the value of stiffness k obtained in the test (absolute terms) and the value of force (f)) were obtained. A test retest protocol was designed and performed on the same day to determine the short-term reproducibility of f, k and ku. Short-term reproducibility of k and ku on 1 day in absolute terms (< 7% Coefficient of Variation (CV)) and relative reproducibility (Intraclass Correlation Coefficient (ICC) and Pearson ≥0.97) for both feet were obtained. The reliability of k and ku in absolute terms (< 9% CV) and in relative terms (ICC and Pearson≥0.93) based on repeating the protocol for 1 week was analysed for both feet. To analyse the usefulness, the Effect Size (ES) ratio=“Trivial” for all variables (for 1 day and 1 week) and the Smallest Worthwhile Change (SWC) ratio (Typical Error (TE)