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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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Lanay M. Mudd, Jim Pivarnik, Claudia B. Holzman, Nigel Paneth, Karin Pfeiffer and Hwan Chung

Background:

Leisure-time physical activity (LTPA) is recommended during pregnancy and has been associated with lower risk of delivering a large infant. We sought to characterize the effect of LTPA across the entire birth weight distribution.

Methods:

Women enrolled in the Pregnancy Outcomes and Community Health (POUCH) Study (1998–2004) were followed-up in 2007. Follow-up efforts were extensive for a subcohort and minimal for the remainder (nonsubcohort). Thus, 596 subcohort and 418 nonsubcohort women who delivered at term participated. Offspring were categorized as small-, appropriate-, or large-for-gestational-age (SGA, AGA, and LGA, respectively) based on gender and gestational age-specific birth weight z-scores (BWz). At follow-up, women recalled pregnancy LTPA and were classified as inactive, insufficiently active or meeting LTPA recommendations. Linear, logistic, and quantile regression analyses were conducted separately by subcohort status.

Results:

Meeting LTPA recommendations decreased odds of LGA significantly among the nonsubcohort (aOR = 0.30, 95% CI: 0.14–0.64) and nonsignificantly among the subcohort (aOR = 0.68, 95% CI: 0.34–1.34). In quantile regression, meeting LTPA recommendations reduced BWz among the upper quantiles in the nonsubcohort.

Conclusions:

LTPA during pregnancy lowered odds of LGA and reduced BWz among the upper quantiles, without shifting the entire distribution. LTPA during pregnancy may be useful for reducing risks of large fetal size.

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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.

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Lanay M. Mudd, Jim M. Pivarnik, Karin A. Pfeiffer, Nigel Paneth, Hwan Chung and Claudia Holzman

Background:

We sought to evaluate the effects of maternal leisure-time physical activity (LTPA) during pregnancy and current child LTPA on child weight status.

Methods:

Women with term pregnancies in the Pregnancy Outcomes and Community Health Study (1998–2004) were followed-up. A race-stratified subset of participants (cohort A) received extensive follow-up efforts leading to better response rates (592/926 = 64%) and diversity. The remainder (Cohort B) had a lower response rate (418/1629 = 26%). Women reported child height, weight and LTPA at 3 to 9 years (inactive vs. active), and recalled pregnancy LTPA (inactive vs. active). A 4-category maternal/child LTPA variable was created (reference: active pregnancy + active child). Children were classified as healthy weight, overweight, or obese using age- and sex-specific Body Mass Index percentiles. Logistic regression was used to assess the odds of child obesity (reference: healthy weight).

Results:

In unadjusted analyses, pregnancy inactivity increased odds for obesity when the child was active (1.6 [95% CI, 1.0−2.6] in Cohort A; 2.1 [95% CI, 1.1−4.0] in Cohort B), and more so when the child was inactive (2.4 [95% CI, 1.2−4.9] in Cohort A; 3.0 [95% CI, 1.0−8.8] in Cohort B). Adjustment for covariates attenuated results to statistical nonsignificance but the direction of relations remained.

Conclusions:

Maternal inactivity during pregnancy may contribute to child obesity risk.

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Megan E. Holmes, Jim Pivarnik, Karin Pfeiffer, Kimberly S. Maier, Joey C. Eisenmann and Martha Ewing

Background:

The role of psychosocial stress in the development of obesity and metabolic syndrome is receiving increased attention and has led to examination of whether physical activity may moderate the stress-metabolic syndrome relationship. The current study examined relationships among physical activity, stress, and metabolic syndrome in adolescents.

Methods:

Participants (N = 126; 57 girls, 69 boys) were assessed for anthropometry, psychosocial stress, physical activity, and metabolic syndrome variables; t tests were used to examine sex differences, and regression analysis was used to assess relationships among variables controlling for sex and maturity status.

Results:

Mean body mass index approached the 75th percentile for both sexes. Typical sex differences were observed for systolic blood pressure, time spent in moderate and vigorous physical activity, and perceived stress. Although stress was not associated with MetS (β = –.001, P = .82), a modest, positive relationship was observed with BMI (β = .20, P = .04).

Conclusions:

Strong relationships between physical activity and stress with MetS or BMI were not found in this sample. Results may be partially explained by overall good physical health status of the participants. Additional research in groups exhibiting varying degrees of health is needed.