Reference Values for Isometric Ankle Strength: A Scoping Literature Review and Comparison with Novel Data from 683 Athletes

The aim of the study was to obtain body-mass normalised reference values of isometric ankle strength through a thorough literature review and consequent meta-analysis of the acquired data. A total of 133 studies with a total of 3755 participants were included in the final analysis. The results were sorted by the angle in the knee joint (extended, partially flexed, flexed) while the ankle joint was always in a neutral position. For easier comparison, the results were normalised to body mass (Nm/kg). The adult population (18-65 years) reached higher values than the older adult (65+ years) population. In the adult and athlete populations, the plantarflexion strength was highest when the knee was extended. Conversely, the strength values of plantarflexion were highest when the knee was flexed in the elderly population. Dorsiflexion strength was the highest when the knee was partially flexed in all populations. Our results appear to be similar to the results of previous studies conducting similar measurements on smaller sample sizes. We only managed to obtain a limited range of values for athletes. Consequently, we included an additional analysis of our existing database for ankle strength (683 athletes from 10 different sports). The athletes reached higher values than the general adult population and there were noticeable differences in strength between individual sports. With the obtained normalized reference values, kinesiologists, trainers, physiotherapists and other experts in the field will be able to better interpret the values they will obtain from their own measurements.