Variability in Center of Pressure Position and Muscle Activation During Walking with Chronic Ankle Instability

Publication date: Available online 16 December 2017
Source:Journal of Electromyography and Kinesiology
Author(s): Rachel M. Koldenhoven, Mark A. Feger, John J. Fraser, Jay Hertel
Chronic ankle instability (CAI) patients exhibit altered gait mechanics. The objective was to identify differences in stride-to-stride variability in the position of the center of pressure (COP) and muscle activity during walking between individuals with and without CAI. Participants (17 CAI;17 Healthy) walked on a treadmill at 1.3m/s while surface electromyography (sEMG) of the fibularis longus (FL) and plantar pressure were recorded. The medial-lateral COP position was averaged for each 10% interval of stance and group standard deviations (SD), coefficient of variation (COV), and range for the COP position were compared between groups via independent t-tests. Ensemble curves for sEMG amplitude SD were graphed for the entire stride cycle to determine significant differences. The CAI group had increased COP position variability (SD (CAI=0.79±0.47mm, Control=0.48±0.17mm), COV (CAI=1.47±0.87mm, Control=0.93±0.33mm), range (CAI=2.97±2.07mm, Control=1.72±0.33mm, P<.05 for all analyses)) during the first 10% of stance. The CAI group had lower FL sEMG amplitude variability from 1-10% (mean difference=0.014±0.006), 32-38% (mean difference=0.013±0.004) and 56-100% (mean difference=0.026±0.01) of the gait cycle. Increased COP variability at initial contact may increase risk of lateral ankle sprains in CAI patients. Decreased sEMG amplitude variability may indicate a constrained sensorimotor system contributing to an inability to adapt to changing environmental demands.



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