Affiliations: [a] Institute of Sport Sciences and Physical Education,
University of Pécs, Pécs, Hungary
Note: [] Corresponding author: Márk Váczi, Institute of Sport
Sciences and Physical Education, University of Pécs, Ifjúság
útja 6., 7624 Pécs, Hungary. Tel.: +36 20 2976362; Fax: +36 72 501519;
E-mail: [email protected]
Abstract: BACKGROUND: It is well established that chronic ankle instability (CAI) is associated with reduced strength in the muscles around the
ankle joint complex. OBJECTIVE: To examine the quadriceps femoris (QF) function in individuals with CAI. METHODS: The mechanical properties of
the QF were assessed in10 physically active individuals with unilateral CAI,
and were compared with 10 healthy controls. Peak torque, rate of torque
development, and stretch-shortening cycle function were determined in both
legs. Injured subjects were selected based on an instability index score, and
were matched with controls by gender, weight, and leg dominance. RESULTS: In the CAI group, when the injured leg's performance was expressed as percent
of the healthy, the fast velocity concentric torque and rate of torque
development were smaller compared to the controls'. In the same group, reduced
positive work and mechanical efficiency, and increased stretch-shortening cycle
contraction time were associated with the magnitude of the ankle instability. CONCLUSIONS: CAI patients may suffer from high velocity contractility
impairment in the QF of the injured side, possibly due to reduced recruitment
of fast motor units. The severity of ankle instability may influence
stretch-shortening cycle function, indicating reduced ability to store and reuse elastic energy.
