Abstract

Background: One metabolic equivalent (MET) is the amount of oxygen consumed while sitting at rest and is equal to 3.5 ml O2·kg-1·min-1. METs are often used to provide simple, practical, and easily understood values that reflect the energy cost of physical activity. It is plausible that the increase in body mass and absolute submaximal oxygen uptake during gestation has the potential to affect the MET of pregnant women.

Objective: The aim of this study was to measure the MET during the second trimester of pregnancy and to compare this with non-pregnant women. In addition, the measured MET values were compared to those proposed by the Compendium of Physical Activities (CPA).

Design: Ten pregnant and ten non-pregnant women participated in this study. Ventilatory variables and heart rate (HR) were measured during four conditions on two different days: Condition 1 - sitting, Condition 2 - lying, Condition 3 - treadmill walking and Condition 4 - cycling. The women performed two conditions on each testing day; one resting condition followed by one exercising condition. The data were analysed using a two-way ANOVA with repeated measures. Bonferroni’s tests were used when significant differences were detected.

Results: The MET was not significantly different between pregnant and non-pregnant women either at rest or during exercise (p > 0.05). While cycling, the MET obtained by indirect calorimetry (IC) was significantly higher than the CPA predicted MET, regardless of group (pregnant cycling p = 0.002 and non-pregnant cycling p < 0.001). During pregnancy, ventilation and heart rate were significantly greater in both the resting and exercising conditions (p > 0.05). In general, (combined pregnant and non-pregnant data), VE and HR were significantly higher during seated rest, when compared with supine rest and all ventilatory variables, HR and ratings of perceived exertion (RPE) were significantly higher during cycling, when compared with walking (p > 0.05).

Conclusion: METs were unaffected by pregnancy at rest or when undertaking either walking or cycling exercise during the second trimester of pregnancy. The MET of cycling was significantly underestimated by the CPA, when compared to IC, in both groups.

Keywords: Pregnancy, exercise, rest, metabolic equivalent, low intensity exercise.

Graphical Abstract