Background Functional ankle instability (FAI) is a common pathology in sport which exhibits debilitating residual symptoms. In relation to FAI, many studies have investigated muscle latencies of the peroneus longus and tibialis anterior muscles; however, there is limited research on the gluteus medius muscle which provides stability in the frontal plane. Weakness in the gluteus medius may produce deviations in joint motion, a subsequent loss of stability and may contribute towards a repeated injury at the ankle.

Objective To determine whether FAI participants suffer from a neuromuscular deficit compared to healthy controls, as measured by muscle latency following a simulated ankle sprain mechanism.

Design Cross-sectional study.

Setting University biomechanics laboratory. Participants played at a semi-professional level of soccer.

Participants A convenience sample was used to recruit twenty males with unilateral FAI and twenty male healthy controls. Inclusion criteria included males, aged 18–25 years, who participated in semi-professional soccer and who were right leg dominant.

Intervention Three perturbations on a standing tilt platform simulating the mechanics of an inversion and plantar-flexion ankle sprain. Subject group was the independent variable.

Main outcome measure Muscle latency in milliseconds of the peroneus longus, tibialis anterior and gluteus medius to the tilt platform perturbation.

Results The results indicated that there was a significant (P<.0125) delay in muscle latency of the peroneus longus, tibialis anterior and gluteus medius when comparing the unstable and stable ankle of the FAI group to the dominant and non-dominant ankle of the healthy group.

Conclusion Muscle latency was delayed in both the unstable and stable ankle of the FAI participants, which would suggest a central mechanism of control, or possibly a genetic predisposition to FAI. Rehabilitation prescribed by sports clinicians should focus on both limbs in functionally unstable individuals, as well as more proximal musculature such as the gluteus medius.