Center of mass motion and the effects of ankle bracing on metabolic cost during submaximal walking trials

The goal of this research was to examine the relationship between center of mass (CoM) motion and metabolic cost and to assess secondarily the effects of equinus gait on metabolic cost during walking trials at various velocities. Twelve (n = 12) healthy male adults walked in four brace conditions, including fixed equinus, at three different walking speeds. Metabolic measures and 3D kinematic data were collected during each trial. Significant main effects for velocity were observed on both dependent measures, net O₂ cost (p < 0.001), and CoM vertical excursion (CoMz) (p < 0.01). Correlation analysis showed significant positive correlations between net O₂ cost and CoMz that were strongest at fast velocities. Further, analysis revealed the cost of walking at a comfortable speed in the equine position was 28% greater than walking in braces without springs or springs in neutral position and 64% greater than walking in shoes alone. CoMz does correlate with metabolic cost as measured by net O₂ cost. Also, normal subjects walking in equinus have an increased net O₂ cost and increased CoMz when compared to walking with shoes alone or the other brace conditions at all velocities.