Single-leg jump-landing stabilization times in subjects with functionally unstable ankles.

CONTEXT: Factors contributing to functional ankle instability may cause individuals with the condition to land from a jump differently than those with stable ankles.

OBJECTIVE: To determine stabilization time differences during single-leg jump landings between stable and unstable ankle groups and to report the reliability and precision of time-to-stabilization measures.

DESIGN: A mixed design with 1 between factor (ankle group) and 1 within factor (direction) was used to analyze the comparison between our 10 subjects with functional ankle instability and 10 subjects with stable ankles. Time to stabilization (seconds) was the dependent measure. Reliability for time-to-stabilization measures of our 12 additional subjects with stable ankles were assessed using intraclass correlation coefficients (ICC 2,7). Standard errors of measurements were also calculated for time-to-stabilization measures.

SETTING: Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANT(S): Ten subjects with functional ankle instability who reported at least 2 sprains and "giving way'' sensations at their ankles constituted the functional ankle instability group. Ten subjects without a history of ankle sprain injury served as healthy subjects. Twelve additional healthy subjects participated in the reliability study.

INTERVENTION(S): Subjects performed a jump-landing test, which required them to jump 50% to 55% of their maximum vertical jump height and then land on a single leg on a force plate. After landing, they stabilized quickly and remained as motionless as possible in a single-leg stance for 20 s.

MAIN OUTCOME MEASURE(S): Anterior-posterior and medial/ lateral vibration magnitude curve fit time-to-stabilization.

RESULTS: Time to stabilization was longer for the functional ankle instability group (1.98 +/- 0.81 s) than for the stable ankle group (1.45 +/- 0.30 s) (P < .05). Reliability (standard error of the measurement) values for anterior/posterior and medial/lateral time-to-stabilization were 0.79 (0.15 s) and 0.65 (0.26 s), respectively.

CONCLUSIONS: Time to stabilization was longer for subjects with functional ankle instability than subjects with stable ankles. The ankle instability may have impaired the subjects' ability to stabilize after a single-leg jump landing. Reliabilities and standard errors of the measurements of time-to-stabilization measures were moderate and low, respectively.