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Britni R. Belcher, Richard P. Moser, Kevin W. Dodd, Audie Atienza, Rachel Ballard-Barbash and David Berrigan

Background:

Discrepancies in self-report and accelerometer-measured moderate-to-vigorous physical activity (MVPA) may influence relationships with obesity-related biomarkers in youth.

Methods:

Data came from 2003–2006 National Health and Nutrition Examination Surveys (NHANES) for 2174 youth ages 12 to 19. Biomarkers were: body mass index (BMI, kg/m2), BMI percentile, height and waist circumference (WC, cm), triceps and subscapular skinfolds (mm), systolic & diastolic blood pressure (BP, mmHg), high-density lipoprotein (HDL, mg/dL), total cholesterol (mg/dL), triglycerides (mg/dL), insulin (μU/ml), C-reactive protein (mg/dL), and glycohemoglobin (%). In separate sex-stratified models, each biomarker was regressed on accelerometer variables [mean MVPA (min/day), nonsedentary counts, and MVPA bouts (mean min/day)] and self-reported MVPA. Covariates were age, race/ethnicity, SES, physical limitations, and asthma.

Results:

In boys, correlations between self-report and accelerometer MVPA were stronger (boys: r = 0.14−0.21; girls: r = 0.07−0.11; P < .010) and there were significant associations with BMI, WC, triceps skinfold, and SBP and accelerometer MVPA (P < .01). In girls, there were no significant associations between biomarkers and any measures of physical activity.

Conclusions:

Physical activity measures should be selected based on the outcome of interest and study population; however, associations between PA and these biomarkers appear to be weak regardless of the measure used.

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Stephanie M. George, Catherine M. Alfano, Ashley Wilder Smith, Melinda L. Irwin, Anne McTiernan, Leslie Bernstein, Kathy B. Baumgartner and Rachel Ballard-Barbash

Background:

Many cancer survivors experience declines in health-related quality of life (HRQOL) and increases in fatigue as a result of cancer and its treatment. Exercise is linked to improvements in these outcomes, but little is known about the role of sedentary behavior. In a large, ethnically-diverse cohort of breast cancer survivors, we examined the relationship between sedentary time, HRQOL, and fatigue, and examined if that relationship differed by recreational moderate-vigorous physical activity (MVPA) level.

Methods:

Participants were 710 women diagnosed with stage 0-IIIA breast cancer in the Health, Eating, Activity, and Lifestyle Study. Women completed questionnaires at approximately 30-months postdiagnosis (sedentary time; recreational MVPA) and 41-months postdiagnosis (HRQOL; fatigue). In multivariate models, we regressed these outcomes linearly on quartiles of daily sedentary time, and a variable jointly reflecting sedentary time quartiles and MVPA categories (0; >0 to <9; ≥9 MET-hrs/wk).

Results:

Sedentary time was not independently related to subscales or summary scores of HRQOL or fatigue. In addition, comparisons of women with high vs. low (Q4:Q1) sedentary time by MVPA level did not result in significant differences in HRQOL or fatigue.

Conclusion:

In this breast cancer survivor cohort, self-reported sedentary time was not associated with HRQOL or fatigue, 3.5 years postdiagnosis.

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Kerry S. Courneya, Kristina H. Karvinen, Margaret L. McNeely, Kristin L. Campbell, Sony Brar, Christy G. Woolcott, Anne McTiernan, Rachel Ballard-Barbash and Christine M. Friedenreich

Background:

Few studies have examined the predictors of adherence separately for supervised and unsupervised exercise or in postmenopausal women over an extended time period. Here, we report the predictors of exercise adherence in the Alberta Physical Activity and Breast Cancer Prevention (ALPHA) Trial.

Methods:

The ALPHA trial randomized 160 postmenopausal women in Calgary and Edmonton, Canada to an exercise intervention that consisted of an average of 200 min/wk of supervised (123 minutes) and unsupervised (77 minutes) exercise over a 1-year period. Baseline data were collected on demographic, health-related fitness, quality of life, and motivational variables from the theory of planned behavior.

Results:

Participants completed an average of 95% of their supervised exercise and 79% of their unsupervised exercise. In multivariate analyses, 8.1% (P = .001) of the variance was explained for supervised exercise by being from Edmonton (β = 0.22; P = .004) and older (β = 0.15; P = .050). For unsupervised exercise, 21.1% (P < .001) of the variance was explained by being from Calgary (β = –0.39; P < .001), having a family history of breast cancer (β = 0.21; P = .003), and having higher vitality (β = 0.19; P = .011).

Conclusions:

Predictors of adherence may differ for supervised and unsupervised exercise, moreover, predicting adherence to supervised exercise may be particularly difficult in well-controlled efficacy trials.