Postural stabilization after single-leg vertical jump in individuals with chronic ankle instability.

OBJECTIVES: To investigate the impact different ways to define reference balance can have when analysing time to stabilization (TTS). Secondarily, to investigate the difference in TTS between people with chronic ankle instability (CAI) and healthy controls.

DESIGN: Cross-sectional study.

SETTING: Laboratory.

PARTICIPANTS: Fifty recreational athletes (25 CAI, 25 controls).

MAIN OUTCOME MEASURES: TTS of the center of pressure (CoP) after maximal single-leg vertical jump using as reference method the single-leg stance, pre-jump period, and post-jump period; and the CoP variability during the reference methods.

RESULTS: The post-jump reference period had lower values for TTS in the anterior-posterior (AP) direction when compared to single-leg stance (P = 0.001) and to pre-jump (P = 0.002). For TTS in the medio-lateral (ML) direction, the post-jump reference period showed lower TTS when compared to single-leg stance (P = 0.01). We found no difference between CAI and control group for TTS for any direction. The CAI group showed more CoP variability than control group in the single-leg stance reference period for both directions.

CONCLUSIONS: Different reference periods will produce different results for TTS. There is no difference in TTS after a maximum vertical jump between groups. People with CAI have more CoP variability in both directions during single-leg stance.