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Measuring Fuel Consumption Frank Plasschaert Broadly speaking there are three methods of measuring fuel consumption. The heart rate method is an indirect measurement of energy expenditure which has the advantage that the pulse is easily measured but the disadvantage of being rather imprecise. This method assumes a linear relationship between heart rate and oxygen consumption. Furthermore training effects and anxiety can affect the heart rate and therefore decrease the utility of the results. A second option is a method of indirect calorimetry by direct measurement of carbon dioxide and oxygen in the expired air during ambulation. The collection apparatus may be a metabolic cart that is propelled by a technician who walks next to the subject, or it may be a portable apparatus that is worn as a back pack or waist belt. The Cosmed K4b2 (Cosmed Srl, Italy) enables ambulatory monitoring of oxygen consumption, carbon dioxide expired and heart rate. Finally the thermal consequences of energy expenditure can be measured by direct calorimetry such as the Atwater – Rosa human calorimeter. This method is however impractical in the clinical setting of a gait laboratory. In practice efforts have concentrated in two fields of measurements, namely |
heart rate