Normative data for passive ankle plantarflexion–dorsiflexion flexibility

Objective. To describe the normal distribution parameters for measures of passive ankle plantarflexion–dorsiflexion flexibility obtained from a large sample of able-bodied young adult subjects. Design. Seven variables were assessed and descriptive analyses were conducted. Background. While assessment of plantarflexion–dorsiflexion flexibility is an important component of a clinical examination of plantarflexion contracture, there is limited normative data available that can be used as a reference for clinical decision-making. Methods. Data were collected from 300 able-bodied male and female subjects aged between 15 and 34 years. Both ankles were measured. Load–displacement curves were collected using a manually controlled instrumented footplate. Six variables were extracted from these curves: passive torque at zero and 10 deg, passive stiffness at zero and 10 deg, and two coefficients from an equation fitted to the curve (i.e., k and b). The seventh variable, passive dorsiflexion range of motion, was quantified using a clinical procedure. Results. Flexibility variables did not differ between the left and right ankles, nor between the dominant and non-dominant legs. All variables were normally distributed. These distributions can, therefore, be adequately described using their mean and standard deviation values. Conclusions. This study has substantially increased the available database on plantarflexion–dorsiflexion flexibility and forms the basis of norm-referenced clinical tests.