Exercise During Pregnancy: Increased Oxygen Uptake and Metabolic Demand

INTRODUCTION: Current guidelines for exercise during pregnancy are limited in their precision on exercise intensity as the established compendium for exercise modes and intensities is based on estimates in non-gravid adults. To address this gap, we used indirect calorimetry to measure prenatal exercise energy demand during standard aerobic exercises in order to compare intensity to published standards. METHODS: Participants (n = 7; 30.7 ± 3.3 yrs of age) completed 5 minutes each of exercise at low and moderate intensity for walking and cycling, on the same testing day, separated < 1 minute. For the first 5-minute bout, the participant performed an external work rate that elicited low intensity exercise, i.e., 40 - 59% peak aerobic capacity (VO 2 peak). This was followed by 5 minutes of the same exercise mode at moderate intensity, i.e., 40 - 59% VO 2 peak. This process was repeated on a cycle ergometer. Measured VO 2 was compared with ACSM-estimated VO 2 at each trimester. Reported results were presented separately for low and high exercise intensities. RESULTS: Measured absolute and relative VO 2 during walking and cycling exercises were significantly higher (p < .001) in all trimesters compared with predicted values, which corresponded with a 35% higher measured MET value. CONCLUSIONS: These findings highlight a critical underestimation in the quantification of effort during prenatal exercise, which is essential to address to safely prescribe exercise for this unique population.