With the ankle unbraced, 66 % of the maximal torque level was reached in 326 ms. While braced, the same torque magnitude was reached using 230 ms (p < 0.02), and pre-activation of the peroneal muscles allowed the subjects to reach the same level of torque in 89 ms (p < 0.0005).
Prior to the study, a common reaction pattern to sudden inversion was expected in an ankle stable population, but review of the eversion torque and EMG data from the 13 subjects revealed three different voluntary reaction patterns: 10 subjects showed an efficient activation of evertor muscles; two subjects stiffened their ankles with activation of both in- and evertor muscles; and one subject showed a marginal voluntary activation of the ankle evertors.
The results of the study indicate that the reaction to sudden ankle inversion is not solely automatic. The main part of the torque response is voluntarily mediated and inter-individual differences in strategy seem to exist in healthy subjects.