Indirect calorimetry on the metabolic rate of sitting, standing and walking office activities

Metabolic rate was measured on 60 college students (30 women and 30 men) while reclining at rest (Re), sitting (quiet-SQ, typing-ST and filing-SF), standing (quiet-STQ, typing-STT and filing-STF), and walking on a treadmill at 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 km/h. Each activity was measured for 10 min (30 min for Re) using a wearable high-precision metabolic system (COSMD K5) that samples the oxygen consumption rate (V˙O2) and carbon dioxide generation rate (V˙CO2). Metabolic rate was then calculated per the ISO 8996 method. The average metabolic rates were 0.8 (SD = 0.2) met for reclining, 0.9 (SD = 0.2), 1.0 (SD = 0.2), and 1.2 (SD = 0.2) met for SQ, ST, and SF, 1.0 (SD = 0.2), 1.1 (SD = 0.2), and 1.3 (SD = 0.3) met for STQ, STT, and STF, and were 1.8 (SD = 0.3), 2.1 (SD = 0.3), 2.5 (SD = 0.3), 3.0 (SD = 0.4), 3.8 (SD = 0.5), and 4.9 (SD = 0.6) met for walking at 1-6 km/h. Differences were found between these measured metabolic rates and those presented in existing international comfort standards. ISO and ASHRAE standards overestimate metabolic rate for sitting and standing activities by 10-20%, and underestimate metabolic rate for walking activities by 5-9% in ISO, and by more than 20% in ASHRAE. No gender differences were found in metabolic rates of all the activities tested. We encourage further development of a database of metabolic rates for offices activities for people of different age, race, and geographical locations.