Predicting the oxygen cost of walking in hemiparetic stroke patients

Abstract : OBJECTIVE: To verify the relation between spontaneous walking speed (Sfree) and oxygen cost of walking at Sfree (Cwfree) in post-stroke hemiparetic patients and to test the validity of a prediction model to estimate Cwfree based on Sfree. DESIGN: We included 26 participants (mean age 65.1 years [SD 15.7]) with mild to moderate disability after stroke who walked at Sfree using mobility aids if necessary for 6min. The Cwfree was measured at a stabilized metabolic rate by indirect calorimetry with the Metamax 3B spiroergometry device. The relation between Sfree and Cwfree was analyzed by the correlation coefficient (r) and coefficient of determination (R2). The Cwfree prediction model was developed from a regression equation, then tested on a second population of 29 patients (mean age 62.1 years [SD 13.4]) with the same inclusion and exclusion criteria. RESULTS: For the 26 participants, the Sfree and Cwfree were highly correlated (r=-0.94 and R2=0.97), which allowed for formulating a regression equation and developing the Cwfree prediction model based on Sfree. The prediction model tests yielded accurate results (mean bias -0.02mL.kg-1.m-1; 95% limits of agreement -0.31 to 0.26mL.kg-1.m-1). The relation between Cwfree estimated by the model and measured by Metamax was high (R2=0.98). CONCLUSION: Cwfree was strongly correlated with Sfree, which allowed for the development of a valid Cwfree prediction model. A practitioner could estimate the energy expenditure of walking for a patient without using an indirect calorimeter.