People with recurrent ankle sprains do not change their ankle strategy in anticipation of a perturbation event

Methods Two groups of participants were recruited: 14 with no history of ankle injury (age 22.6 ± 0.7 yrs, 10 females) and 14 with a history of two or more ankle sprains (Age 21.1 ± 0.2 yrs, 9 females, 6 ± 2.5 sprains). Participants stood in single leg stance on an inversion perturbation platform. The perturbation platform dropped 15 degrees in the frontal plane on a trigger activated by the researcher. Movement Oscillation at the ankle was measured via a 3Space fastrak (Polhemius Ltd) with a receiver taped one cm above the lateral malleolus. Oscillation was determined as the standard deviation of the movement in the frontal plane (mm) measured over 10s while the platform was horizontal. Three conditions were investigated: standing with no change in the platform, standing with a 15 deg drop occurring at a specified time, and standing with a drop occurring at anytime. Data were compared between groups using a Mann-Whitney U test, as the data were not normally distributed.