Physical Activity During Pregnancy: Associations Between Levels and Types of Physical Activity and Low Back Pain–Related Disability in Portuguese Pregnant Women

Low back pain (LBP) is one of the most prevalent musculoskeletal conditions during pregnancy and frequently impairs daily living activities and quality of life. The association between different levels and types of physical activity (PA) and LBP-related functional disability remains insufficiently explored. This study aimed to examine the association between PA levels and types and functional disability among pregnant women with LBP. A cross-sectional analytical study was conducted involving 192 Portuguese pregnant women. Data were collected through an online questionnaire comprising the Pregnancy Physical Activity Questionnaire and the Oswestry Disability Index (ODI). Most participants engaged predominantly in light-intensity or sedentary activity (69.1%), with minimal participation in vigorous activity (0.8%). Functional disability was generally mild (mean ODI = 11.5 ± 7.35); however, 42.2% of participants reported moderate disability and 11.0% severe disability. Advancing gestational age showed weak associations with increased domestic activity (r = 0.146, p = 0.044), decreased occupational activity (r = −0.295, p = 0.001), and higher functional disability scores (r = 0.142, p = 0.049). Parity was associated with differences in total PA levels (p = 0.005) and domestic activity (p = 0.001). Higher ODI scores were weakly associated with light-intensity and sedentary activity (r = 0.144, p = 0.047), whereas severe disability demonstrated a moderate association with sedentary behavior (r = 0.529, p = 0.014). Overall, lower levels of PA, particularly sedentary behavior, were weakly associated with higher LBP-related disability; however, the observed associations were generally weak and should be interpreted with caution considering the cross-sectional design.