Abstract
BACKGROUND: Precise postural control helps prevent anterior cruciate ligament injury. However, it is unknown whether the anticipated postural stability can be improved during a physically uncertain and cognitively demanding task. HYPOTHESIS: Anticipated postural stability will improve through unanticipated single-leg landing with a rapid foot placement target tracking. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 22 healthy female university-level athletes performed a novel dual-task paradigm: an unanticipated single-leg landing with foot placement target tracking. In the normal condition (60 trials), the participants jumped from a 20 cm-high box onto the landing target with their dominant leg as softly as possible. In the subsequent perturbation condition (PC) (60 trials), the initially assigned landing target was abruptly switched randomly, requiring participants to modify their preplanned foot placement position to the newly assigned position. The center-of-pressure trajectory length within the first 100 ms after foot impact (CoP(100)) was calculated as a measure of anticipated postural stability for each trial. In addition, the peak vertical ground-reaction force (Fz(Peak)) was quantified to assess landing load, and the degree of postural adaptation during PC was quantified by fitting an exponential function to trial-by-trial changes in CoP(100). Participants were divided into 2 groups according to increase or decrease in CoP(100), and results were compared between the groups. RESULTS: The direction and magnitude of postural sway alterations of the 22 participants showed a spectrum-like variation during the repeated trials. Twelve participants (sway-decreased group) exhibited a gradual reduction in postural sway (CoP(100)) during the PC, while the remaining 10 participants (sway-increased group) showed a gradual increase in CoP(100). The Fz(Peak) during the PC was significantly less in the sway-decreased group compared with the sway-increased group (P < .05). CONCLUSION: Variation in the direction and magnitude of postural sway alteration among participants suggested that there was individual variation in an athlete's adaptive ability of the anticipated postural stability. CLINICAL RELEVANCE: The novel dual-task paradigm described in this study may be useful for rating individual injury risk based on an athlete's postural adaptation ability and may aid in targeted prevention strategies.