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Item A comparison of bilaterally wrist-worn accelerometers on measures of free-living physical activity in adolescents(Montana State University - Bozeman, College of Education, Health & Human Development, 2011) Davila, Edward Moises; Chairperson, Graduate Committee: Daniel P. HeilWith the advancement of technology, the use of accelerometry-based wrist-worn activity monitors (AM) to measure free-living physical activity (PA) has become extremely popular. Whereas the influence of contralateral wrist AM placement has been evaluated in adults, no research has investigated the influence of wrist-worn AM location (dominant [D] versus non-dominant [ND] or left [LW] versus right [RW]) on measurements of free-living PA in adolescents. Purpose: The purpose of the current study was to evaluate the influence of wrist-worn AM wear location (D versus ND and LW versus RW) and AM processing algorithm (single (1R) versus double (2R) regression) on measures of free-living PA in adolescents 12-17 years of age. Methods: Eight boys (Mean±SD: 14.3±1.9 yrs, 53.9±13.6 kg, 160.5±14.5 cm, 20.6±2.3 body mass index [BMI]) and 12 girls (13.9±1.6 yrs, 56.1±9.9 kg, 160.3±7.4 cm, 21.4±2.6 BMI) participated in the study. Each subject wore two AMs for 7 consecutive days (24 hr/day), with one AM attached to the dorsal side of each wrist using locking plastic wrist bands. Subjects were instructed to engage in their usual daily activities. After downloading the raw AM data to a computer, previously validated algorithms (1R and 2R) were used to transform and summarize the data into counts (counts/day), activity energy expenditure (AEE; kcals/day), and duration of time (T; minutes/day) for 1, 5, and 10 minute bout durations within light (L) and moderate-to-vigorous (MV) intensity categories for AMs (D, ND and for LW, RW). Dependent variables (CNT, AEE, T) were compared using two-factor multivariate repeated measures ANOVA (alpha=0.05) for data processed by both algorithms separately. Scheffe's post-hoc analyses (alpha=0.01) were performed for all pairwise comparisons when indicated by the ANOVA. Results: No significant differences existed between mean values for dependent variables for any bout duration within L or MVPA intensity between monitors (D versus ND or between LW versus RW) or processing algorithm. Conclusion: These data indicate that wrist-worn AM location has no significant influence on PA outcome variables in adolescent under free-living conditions. Researchers can now allow participants the freedom to choose which wrist they would prefer the monitor be placed when being assessed.Item Predicting adolescent sexual activity using individual, familial, and extra-familial variables(Montana State University - Bozeman, College of Education, Health & Human Development, 2005) Keller, Julie Ann Atkinson; Chairperson, Graduate Committee: Bethany L. LetiecqThis study examined selected individual, familial, and extra-familial variables that predict adolescent sexual activity. This secondary data analysis used data gathered from a self-report survey, from 397 adolescents age 11 to 18 in three non-urban communities in the Pacific Northwestern United States. The study employed multiple hierarchical regression analyses to examine the strength of selected variables in predicting sexual activity. The final model accounted for 58% of the variance of sexual activity among youth. The best predictors of adolescent sexual activity were peer sexual activity, attitude about sexual intercourse, age, gender, motherαs education, and youth college aspiration. These finding have implications for future research, practitioners and policymakers.Item Stability reliability of habitual physical activity with the Actical® activity monitor in a youth population(Montana State University - Bozeman, College of Education, Health & Human Development, 2011) Taylor, Katelyn J.; Chairperson, Graduate Committee: Daniel P. Heil; Daniel P. Heil, Mary P. Miles, and John G. Seifert were co-authors of the article, 'Stability reliability of habitual physical activity with the Actical® activity monitor in a youth population' in the journal 'European Journal of Applied Physiology' which is contained within this thesis.The purpose of this study was to examine and compare stability reliability of hip-and wrist-worn activity monitor (AM) physical activity (PA) outcome variables for adolescents (12-17 years) under free-living conditions. Twenty-one adolescents (11 girls, 10 boys) wore AMs at hip and wrist locations for a 14 consecutive day monitoring period. The dependent variables were total time (minutes/day) occurring at sedentary (TS), light (T L) and > or = moderate (T MV) intensity PA, and the sum of activity energy expenditure (AEE; kcals/day) occurring at a light (AEE L), > or = moderate intensity (AEE MV) and from total AEE for a monitoring day (AEE T). Intraclass correlation coefficients for each monitoring day (ICC DAY) were calculated to examine reliability of all dependent variables for both AM locations, over bout durations of 1-, 5-, and 10-minutes. Excluding T L measured by the wrist AM location, ICC DAY values for all variables decreased as bout duration increased from 1- to 10-minutes. The number of monitoring days to reach an ICC DAY > or = 0.80 for AEE L, AEE MV, AEE T, T L and T MV across all three bout durations was higher for hip- versus wrist-worn AM, and ranged from 2-26 versus 2-10 days, respectively. Conversely, then number of monitoring days to reliably measure TS was lower for hip AM (4-5 days) versus the wrist AM (6-8 days) locations. Among all the variables, T L had the largest range of necessary monitoring days to reach an ICC DAY > or = 0.80, 7-10 and 6-26 days across all bout durations for the wrist and hip, respectively. Further comparison of the dependent variables by day type revealed that only T L measured at the wrist had significantly different means on weekdays versus weekends (pvalue < or = 0.001) across all bout durations. While not significant, mean values for T MV, AEE MV, and AEE T measured by both hip- and wrist-worn AMs, were higher on weekdays than on weekends. In summary, reliability of time and AEE PA variables was dependent on bout duration and AM location. Generally, to reliability measure free-living PA in adolescents wrist-worn AMs required fewer monitoring days than hip-worn AMs.