Biomechanics and Intrinsic Foot Muscle Roles in Subjects With Chronic Ankle Instability

Three groups of participants : Chronic ankle instability, lateral ankle sprain copers and healthy controls. INCLUSION CRITERIA: For all three groups : Physically active male subjects between 18 and 44 years of age Able to run at low speed. For homogeneity purposes, the investigators will only recruit subjects who perform a regular physical activity on a weekly basis, including competition participation. Chronic ankle instability : A history of at least one significant ankle sprain that occurred at least 12 months before study enrolment, associated with inflammatory symptoms, creating at least 1 interrupted day of desired physical activity; The most recent injury occurred more than 3 months prior to study enrolment; At least two episodes of giving way in the 6 months prior to study enrolment, recurrent sprain, and/or "feelings of instability"; and Poor disability status according to the Cumberland Ankle Instability Tool (CAIT) (score ≤ 24/30). Lateral ankle sprain copers : A history of one significant ankle sprain that occurred at least 12 months before study enrolment, associated with inflammatory symptoms, creating at least 1 interrupted day of desired physical activity; A return to at least moderate levels of weight-bearing physical activity less than 12 months after initial sprain without recurrent injury, episodes of giving way, and/or feelings of instability; Minimal, if any, level of self-reported disability (CAIT score ≥ 28/30); and Minimal, if any, alteration in self-reported function (ADL- and Sport-subscales ≥95%). Healthy controls : The same inclusion criteria as the LAS coper group, with the exception reported in the exclusion criteria. EXCLUSION CRITERIA: For all three groups : Being younger than 18 years Any medical contraindication to physical exertion, Any systemic or neurological disease, A recent surgery, A difference in leg length of more than 3 cm, Pregnancy, A body mass index higher than 30kg/m² (due to less accurate motion analysis by absence of anatomical landmarks). LAS copers and controls will also be excluded if: constant or intermittent ankle pain, ankle fractures, or surgeries, and recent participation in a physical revalidation programme. Healthy participants must never have suffered an inversion trauma resulting in disability. For healthy controls : the healthy control subjects may not have suffered from an ankle sprain.