Effect of specific gait modifications on medial knee loading, metabolic cost and perception of task difficulty

Background: The metabolic cost and cognitive demand of altering natural gait have not been well studied. The purpose of this investigation was to assess three modified patterns - toe out, ipsilateral trunk lean and a medial weight shift at the foot - on the basis of 1) medial knee joint load reduction, 2) metabolic cost of performance and 3) subject perception of task difficulty. Methods: 12 healthy individuals underwent 3 dimensional motion analysis and metabolic testing to assess the gait mechanics and energy expenditure of natural gait and the three experimental gait patterns, performed to a self-selected moderate degree. Walking speed was controlled. Perceived workload was assessed using the NASA Task Load Index. Findings: Trunk lean significantly reduced first peak knee adduction moment (down arrow 32%, P < 0.001) as well as KAM impulse (down arrow 35%, P < 0.001), but was costly in terms of energy expenditure (up arrow 11%, P < 0.001) and perceived workload (up arrow 1178%, P < 0.001). A moderate toe-out pattern significantly reduced the second peak knee adduction moment (down arrow 32%, P < 0.001) and KAM impulse (down arrow 14%, P = 0.026), but had no effect on the first peak. Conversely, toe-out was least demanding in terms of additional energy expenditure (up arrow 2%, P = 0.001) and perceived workload (up arrow 314%, P = 0.001). Medial shift did not reduce knee adduction moment. Interpretation: The prioritization of joint load reduction versus additional metabolic and cognitive demands could play a substantial role in the clinical decision making process of selecting a modified gait pattern. (C) 2013 Elsevier Ltd. All rights reserved.