Dynamic Postural Stability in Females with Chronic Ankle Instability

BROWN, C. N., B. BOWSER, and A. ORELLANA. Dynamic Postural Stability in Females with Chronic Ankle Instability. Med. Sci. Sports Exerc., Vol. 42, No. 12, pp. 2258-2263, 2010. Purpose: To determine whether females with chronic ankle instability (CAI) demonstrated decreased dynamic postural stability compared with controls in the anterior, lateral, and medial jump directions. Methods: Individuals with CAI (n = 24) reported a history of moderate to severe ankle sprain, two or more episodes of giving way in the past year, and decreased ankle function. The control group (n = 24) reported one or no previous mild to moderate ankle sprain, no episodes of giving way, and no decrease in ankle function. Maximum vertical jump height was measured in the anterior, lateral, and medial directions. Participants jumped at 50% maximum height in the three directions, landed on the involved limb, and balanced for 10 s. Ground reaction forces were collected at 1200 Hz and filtered. Stability indices for anterior-posterior, medial-lateral, and vertical and a composite index were calculated. Independent-samples t-tests compared groups on demographic data and stability indices in three jump directions, with alpha = 0.05. Results: The CAI group demonstrated significantly higher vertical (0.34 +/- 0.04 vs 0.32 +/- 0.03) and composite stability index scores (0.36 +/- 0.04 vs 0.34 +/- 0.03) in the anterior jump direction compared with the control group. Lateral jumps had similar results for vertical (0.33 +/- 0.05 vs 0.30 +/- 0.03) and composite scores (0.36 +/- 0.04 vs 0.33 +/- 0.03). Conclusions: Females with CAI demonstrated stability deficits compared with control group in the anterior and lateral jump directions. Multiple jump directions may be necessary to adequately capture dynamic stability measures.