Indirect Calorimetry

Open circuit spirometry (K4b2; COSMED USA) was used to provide breath-by-breath cardiopulmonary data during all ADL activities, using methods previously described.²⁰ In brief, the device was warmed up for 45 minutes and calibrated using a 3 liter syringe prior to testing. Following this, the O₂ and CO₂ analyzers were calibrated using a reference gas of known concentrations. Testing was initiated within 10 minute of completing calibration of the metabolic system. A snug fitting face mask was placed on participants and they underwent a period of acclimatization with the portable gear prior to performing the designated activities. Each participant’s mean oxygen consumption (VO₂) for the eight activity types was determined and converted to Metabolic Equivalents of Task (METs; 1 MET=3.5 ml/kg/min). In addition, continuous heart rate monitoring provided a mean steady-state heart rate for each test.