A system for metabolic measurements, the system comprising: a metabolic monitor 16 configured to: determine first concentration measurements of O2 and CO2 in a portion of gas exhaled by a subject during one or more breaths; and determine a first rate of O2 consumption and a first CO2 volume production of the subject during the one or more breaths based on the determined first O2 concentration in the portion of the exhaled gas and the determined first CO2 concentration in the portion of the exhaled gas; characterized in that the system further comprises: a CO2 monitor configured to: determine second CO2 concentration measurements in the gas exhaled by the subject during the one or more breaths; and determine second CO2 volume production of the subject during the one or more breaths based on the measured second CO2 concentration; and one or more physical computer processors operatively connected the metabolic monitor and the CO2 monitor, the one or more physical computer processors configured by computer readable instructions to: determine a correction factor based on the determined first VCO2 and the second VCO2; and determine a corrected first VO2 using the correction factor and the first VO2. a metabolic monitor 16 configured to: determine first concentration measurements of O2 and CO2 in a portion of gas exhaled by a subject during one or more breaths; and determine a first rate of O2 consumption and a first CO2 volume production of the subject during the one or more breaths based on the determined first O2 concentration in the portion of the exhaled gas and the determined first CO2 concentration in the portion of the exhaled gas; characterized in that the system further comprises: a CO2 monitor configured to: determine second CO2 concentration measurements in the gas exhaled by the subject during the one or more breaths; and determine second CO2 volume production of the subject during the one or more breaths based on the measured second CO2 concentration; and determine first concentration measurements of O2 and CO2 in a portion of gas exhaled by a subject during one or more breaths; and determine a first rate of O2 consumption and a first CO2 volume production of the subject during the one or more breaths based on the determined first O2 concentration in the portion of the exhaled gas and the determined first CO2 concentration in the portion of the exhaled gas; characterized in that the system further comprises: a CO2 monitor configured to: determine second CO2 concentration measurements in the gas exhaled by the subject during the one or more breaths; and determine second CO2 volume production of the subject during the one or more breaths based on the measured second CO2 concentration; and determine second CO2 concentration measurements in the gas exhaled by the subject during the one or more breaths; and determine second CO2 volume production of the subject during the one or more breaths based on the measured second CO2 concentration; and one or more physical computer processors operatively connected the metabolic monitor and the CO2 monitor, the one or more physical computer processors configured by computer readable instructions to: determine a correction factor based on the determined first VCO2 and the second VCO2; and determine a corrected first VO2 using the correction factor and the first VO2. determine a correction factor based on the determined first VCO2 and the second VCO2; and determine a corrected first VO2 using the correction factor and the first VO2.