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Erin White, Jim Pivarnik and Karin Pfeiffer

Background:

Approximately 10% of women engage in resistance training during pregnancy; however there is limited research on this activity. The purpose of this study was to examine associations between resistance training and adverse outcomes.

Methods:

Women completed an online survey and recalled their exercise habits during each trimester of their most recent pregnancy within the previous 5 years. Women also reported pregnancy and birth outcomes. Participants were then categorized into 3 groups based on leisure-time exercise: 1) Resistance + aerobic training (RTAE), 2) Aerobic exercise only (AE), and 3) no exercise (NE).

Results:

284 women completed the survey. Women in the RTAE group resistance trained on average 2.9 days/week for 27.3 minutes/session. The prevalences of hypertensive disorders (HD) and gestational diabetes mellitus (GDM) were significantly lower in the RTAE group when compared with the grouping of AE + NE women. Prepregnancy body mass index (BMI) was the strongest factor related to both GDM and HD. There was no difference in the risk of preterm labor, mode of delivery, or gestational age at delivery by exercise status.

Conclusions:

Our results suggest that women can safely engage in aerobic exercise and resistance training for muscular endurance 3 days/week for 30 minutes throughout gestation.

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Erin White, Jennifer D. Slane, Kelly L. Klump, S. Alexandra Burt and Jim Pivarnik

Background:

Knowing the extent to which genetic and environmental factors influence percent body fatness (%Fat) and physical activity (PA) would be beneficial, since both are tightly correlated with future health outcomes. Thus, the purpose was to evaluate sex differences in genetic and environmental influences on %Fat and physical activity behavior in male and female adolescent twins.

Methods:

Subjects were adolescent (age range 8.3 to 16.6 yr) twins. %Fat (n = 518 twins) was assessed by bioelectrical impedance analysis (BIA) and PA (n = 296 twins) was measured using 3-Day PA Recall. Each activity was converted to total MET-minutes. Univariate twin models were used to examine sex differences in genetic and environmental factors influencing %Fat and PA.

Results:

%Fat was influenced by genetic effects in both boys and girls (88% and 90%, respectively), with slightly higher heritability estimates for girls. PA was influenced solely by environmental effects for both sexes with higher shared environmental influences in boys (66%) and higher nonshared effects in girls (67%).

Conclusions:

When developing interventions to increase PA in adolescents, it is important to consider the environment in which it takes place as it is the primary contributor to PA levels.