Perception and reality: The mismatch between absolute and relative physical activity intensity during pregnancy and postpartum in United States women

Objective: To explore whether a mismatch between absolute physical activity intensity (PAI) and relative selfreported PAI exists during pregnancy and postpartum. Methods: Women from the PIN3/Postpartum study completed physical activity questionnaires during pregnancy (n = 770; Trimester 2: T2, Trimester 3: T3) and postpartum (n = 181; 3 months: PP3, 12 months PP12) (2001-2005). Activities women engaged in were assigned Metabolic Equivalent (MET) values for absolute intensity; women self-reported perceived exertion (using the Borg scale) for each activity to provide relative intensity. Hierarchical regression models were used to determine whether a mismatch between absolute and relative PAI (for moderate or vigorous physical activity (MPA; VPA)) differed during pregnancy and postpartum. Models were adjusted for socio-demographic factors. Results: Women commonly overestimated the amount of MPA and VPA they engaged in [T2 MPA mean 60.5 min/ week (49.1, 72.0), VPA 3.7 (-1.4, 8.8); T3: MPA 47.7 (38.9, 56.4), 2.9 (-1.7, 7.4); PP3: MPA 69.5 (43.9, 95.1), VPA 15.8 (1.8, 29.7); PP12: MPA 42.20 (26.8, 57.6), VPA 2.75 (-7.8, 12.9)]. Women overestimated both MPA and VPA to a lesser extent at T3 compared to T2 (MPA: beta for difference:-12.6 [95%CI: -26.0, -0.9]; VPA: -0.9 [-6.4, 4.6]). Women continued to overestimate their MPA at PP3 and PP12. Conclusions: Compared to absolute PAI, perceived PAI was greater for MPA compared to VPA and differences persisted from pregnancy through postpartum. Future research should focus on how perceptions relate to women's actual physiological capacity and whether this mismatch influences the amount of physical activity women engage in during the transition to motherhood.