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Article Excerpt
The purpose of this study was to examine women's leisure time physical activity (LTPA) before pregnancy, during pregnancy, and through the first 7 months postnatal. Pre- and postnatal women (n = 309) completed the 12-month Modifiable Activity Questionnaire and demographic information. Multilevel modeling was used to estimate a growth curve representing the average change in LTPA over time and intraindividual variations in the average growth curve over time. Growth curve estimates for the linear, quadratic, and cubic trends were significant (p < .05), indicating that LTPA declined during pregnancy but then increased following birth. The results also demonstrated that the individual trajectories of LTPA varied substantially from the average growth curve. One demographic predictor variable (having other children at home) was significant (p < .05).
Key words: childbirth, exercise, individual trajectory, pregnancy
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Being pregnant or adjusting to life with a new baby is characterized by many physical and behavioral challenges such as coping with nausea, fluctuating mood states, lack of sleep, unregimented feeding patterns, and weight gain (Heron, O'Connor, Evans, Golding & Glover, 2004; Lacroix, Eason & Melzack, 2000; Mindell & Jacobson, 2000; Mottola & Campbell, 2003; Ohlin & Rossner, 1996; Poudevigne & O'Connor, 2005). One additional behavioral change includes decreased physical activity participation (Symons Downs & Hausenblas, 2004; Mottola & Campbell, 2003; Pereira et al., 2007; Schramm, Stockbaurer & Hoffman, 1996).
Researchers who have examined the influence of pregnancy on women's physical activity patterns have shown that physical activity levels decline with the onset of pregnancy (Hausenblas & Symons Downs, 2005; Mottola, 2002; Mottola & Campbell, 2003; Poudevigne & O'Connor, 2005). Although pregnancy and exercise studies have produced fairly consistent results, Poudevigne and O'Connor (2005, 2006) criticized those findings, indicating that scientifically strong conclusions are difficult to reach because of infrequent assessments of physical activity (e.g., only two to three times during pregnancy) and the limited number of studies that measured physical activity using scales with established reliability and validity.
Investigations of women's physical activity participation during the postnatal period have demonstrated equivocal results. For example, some researchers have shown that physical activity levels increased in the postnatal period (Van Raaij, Schonk, Vermaat-Miedema, Peek, & Hautvast, 1990), while others have shown that physical activity levels stayed the same as in the latter stages of pregnancy (Blum, Beaudoin, & Caton-Lemos, 2004; Grace, William, Stewart & Franche, 2006; Stein, Rivera & Pivarnik, 2003).
While these studies provide information on activity patterns during pregnancy and in the postnatal period, perhaps the most informative studies in terms of understanding exercise patterns during this time of transition are those that examined exercise participation before pregnancy, during pregnancy, and in the postnatal period. We are aware of only three studies that investigated physical activity and pregnancy during these three time periods. Two of the three studies demonstrated that leisure time physical activity (LTPA) continuously decreased as pregnancy progressed and that postnatal LTPA increased slightly compared to LTPA measured at the later stages of pregnancy (Pereira et al., 2007; Schramm et al., 1996). In another study, the results showed that women's strenuous and moderate exercise behavior was significantly lower during pregnancy and in the postnatal period compared to prepregnancy. However, there was no significant difference in exercise behavior during pregnancy compared to postnatal (Symons Downs & Hausenblas, 2004).
Studies of physical activity across prepregnancy, pregnancy, and postnatal periods have provided considerable information on exercise patterns during this time of transition. While the information provided by these studies may be useful, the methods employed have inherent limitations in terms of furthering our understanding of longitudinal patterns of activity associated with pregnancy and the months following childbirth. Thus far, studies have focused on changes in physical activity using discrete time period designs (i.e., one measure of physical activity during each period before, during, and after pregnancy). While these study designs can provide information about longitudinal variations in behavior and possible curvilinear trends, Collins (2006) argued that longitudinal designs should integrate a theoretical model of change and an appropriate temporal design. Therefore, the timing of observations should correspond with hypothesized models of change. As noted above, pregnancy and the year following birth offer a number of complex challenges, therefore subtle and important variations in LTPA may also occur within each discrete phase (e.g., from month to month, rather than simply during pregnancy or during the postnatal period). This information, if studied, could provide important data regarding when physical activity changes occurred and the circumstances surrounding changes, rather than simply how much change occurred from one discrete measurement to the next (e.g., second trimester to 6 months postpartum). Thus, an investigation of physical activity at multiple, brief, and regularly spaced intervals stands to advance our knowledge of women's LTPA before, during, and after pregnancy.
Furthermore, studies to date have only examined group variations in activity (i.e., the average changes that occurred in the sample over time) as the focus of analysis. These methods and the statistics applied (e.g., repeated measures analysis of variance) examined changes in the group means over time and treat individual variations in behavior (about the mean trends) as error. The problem is that the average levels of activity during pregnancy and after pregnancy provide information to describe the average person in the sample, but those data may not describe the activity patterns of any of the individuals involved in the study, Because growth (or change) is a phenomenon that occurs within the individual and can vary considerably across individuals (Collins, 2006), investigating longitudinal trajectories of physical activity change as both intra- and interindividual variations or hierarchical growth curves stands to advance our knowledge of individual physical activity trajectories of change before, during, and after pregnancy.
Therefore, the purpose...
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