Oxygen Consumption Estimation VS.Normalized Concentric Energy in Diplegic Children

Energy expenditure is considered an essential tool for assessing functional ability. However in most motion analysis laboratories this is not routinely measured. When the goal of surgical treatment is to functionality or to make easier the task effort, energy assessment provides a unique and important tool. An energy consumption index which can be highly correlated with metabolic energy expenditure is presented in this work. It would enable physicians and researchers to evaluate physical performance on an individual basis and to perform retrospective studies. Since by definition concentric contraction of muscles is power generating while eccentric contraction is power absorbing, this work is focused on the concentric (positive) power intervals. It is assumed that energy cost increase during pathological gait due to the high percentage of concentric contractions. Then, concentric areas of power generation in the kinetic power graphs of hip, knee and ankle in children with cerebral palsy were calculated and then normalized with respect to subject weight, thus obtaining the Normalized Concentric Energy (NCE) index. The concentric energy obtained from NCE calculation on kinetic data from 42 diplegic children with the metabolic energy expenditure (oxygen consumption) were analyzed and compared. Four regression models (linear, exponential, quadratic and cubic) were carried out and a model validation was performed. The cubic regression model showed the best fit to dataset.