Gait kinematics & kinetics at three walking speeds in individuals with chronic ankle instability and ankle sprain copers

Background: Individuals with CAI have demonstrated a more inverted foot position during walking when compared to a healthy control group. Copers are individuals who have had an ankle sprain but learn to cope and return to pre-injury levels of function and may be a better comparison group than healthy controls because they have had the same initial injury. Research question: A controlled laboratory study was performed to simultaneously analyze differences in lower extremity walking gait kinematics, kinetics, and surface electromyography (EMG) between individuals with CAI and copers at a preferred walking speed (PWS), 120% preferred walking speed (120WS), and standardized walking speed (SWS) of 1.34 m/s. Methods: Thirty-six (18 coper, 18 CAI) physically active individuals participated. Three-dimensional kinematics and kinetics at the ankle, knee, and hip and EMG amplitude for fibularis longus, tibialis anterior, medial gastrocnemius, and gluteus medius muscles were analyzed. Ten consecutive strides from each speed were analyzed using statistical parametric mapping (SPM). A 2 x 3 group by speed ANOVA and post-hoc t-tests were used to compare differences between the coper and CAI groups. Results: The CAI group had more ankle inversion at IC (PWS: MD = 4.2 degrees, d = 1.08; 120WS: MD = 5.0 degrees, d = 1.28; SWS: MD = 6.6 degrees, d = 1.37) and greater peak inversion throughout swing at all three walking speeds (PWS: MD = 4.2 degrees, d = 0.89; 120WS: MD = 4.4 degrees, d = 0.91; SWS: MD = 6.2 degrees, d = 1.21). The CAI group had greater peak hip adduction during swing (PWS: MD = 4.5 degrees, d = 0.96; 120WS: MD = 4.1 degrees, d = 1.04; SWS: MD = 3.6 degrees, d = 0.98). Significance: The CAI group demonstrated greater ankle inversion at IC and during the swing phase and greater peak hip adduction during the swing phase compared to the copers. As the speed increased, ankle inversion in the CAI group also increased which could be linked to greater risk of recurrent sprains. Therefore, modeling gait training programs after the coper mechanics may be advantageous.