Background: In track and field, the load of impact, the coordination and the constraints on the ankle could result in adaptations of the ankle dynamic stabilization. These constraints could play a strengthening role and increase invertor and evertor strength also after a previous history of lateral ankle sprain.
Objective: To compare the ankle invertor and evertor isokinetic strength in track and field athletes (i) with functional ankle instability (FAI), (ii) with history of lateral ankle sprain but without functional ankle instability, and (iii) without any history of lateral ankle sprain.
Methods: Twenty-five track and field athletes (5 female and 20 male, 22 ± 5 years) were included in this cross-sectional controlled study, and divided into 3 groups for comparison: (i) athletes with FAI, (ii) athletes with a previous history of lateral ankle sprain, and (iii) a control group of healthy athletes. The dominant side ankle invertor and evertor isokinetic strength were evaluated concentrically at 120 and 30°/s while the evertor strength was also tested eccentrically at 30°/s.
Results: No significant differences were indicated between the muscle strength of the three groups, except for the concentric evertor peak torque and the evertor-to-invertor ratio (EIR) at 30°/s (P < 0.05). The concentric evertor peak torque and EIR at 30°/s were significantly lower in the group of athletes with a previous history of ankle sprain than in the control group (P <0.05).
Conclusion: Functional ankle instability and/or history of lateral ankle sprain in track and field athletes were not associated with strength weakness of the invertor or evertor muscles. However, as the EIRs were higher than 1.0 for the healthy track and field athletes and those with FAI, it is suggested that the track and field constraints result in adaptations of the ankle dynamic stabilization and then influence invertor and evertor strength balance.