Measured Moderate-to-vigorous Physical Activity Research Articles

Fundamental movement skills and physical activity among children living in low-income communities: a cross-sectional study

BackgroundAlthough previous studies have demonstrated that children with high levels of fundamental movement skill competency are more active throughout the day, little is known regarding children’s fundamental movement skill competency and their physical activity during key time periods of the school day (i.e., lunchtime, recess and after-school). The purpose of this study was to examine the associations between fundamental movement skill competency and objectively measured moderate-to-vigorous physical activity (MVPA) throughout the school day among children attending primary schools in low-income communities.MethodsEight primary schools from low-income communities and 460 children (8.5 ± 0.6 years, 54% girls) were involved in the study. Children’s fundamental movement skill competency (TGMD-2; 6 locomotor and 6 object-control skills), objectively measured physical activity (ActiGraph GT3X and GT3X + accelerometers), height, weight and demographics were assessed. Multilevel linear mixed models were used to assess the cross-sectional associations between fundamental movement skills and MVPA.ResultsAfter adjusting for age, sex, BMI and socio-economic status, locomotor skill competency was positively associated with total (P = 0.002, r = 0.15) and after-school (P = 0.014, r = 0.13) MVPA. Object-control skill competency was positively associated with total (P < 0.001, r = 0.20), lunchtime (P = 0.03, r = 0.10), recess (P = 0.006, r = 0.11) and after-school (P = 0.022, r = 0.13) MVPA.ConclusionsObject-control skill competency appears to be a better predictor of children’s MVPA during school-based physical activity opportunities than locomotor skill competency. Improving fundamental movement skill competency, particularly object-control skills, may contribute to increased levels of children’s MVPA throughout the day.Trial registrationAustralian New Zealand Clinical Trials Registry No: ACTRN12611001080910.

Response

Dear Editor-in-Chief: We thank Dr. Shephard for his interest in our study and for drawing attention to the inconsistencies between self-reported and objectively measured moderate to vigorous physical activity (MVPA) in association with academic achievements. We agree that self-reported questionnaires are very important for measuring self-concept of physical activity in association with academic achievements. Our finding of a positive association between self-reported physical activity and academic achievement supports the previous studies reporting that physical activity is not harmful to academic achievements (5,8) and may even enhance academic performance (2,4). However, one of the main weaknesses of self-reports is that children may overestimate their physical activity (1). According to our preliminary analysis, children who overestimated their physical activity compared to the objective measures were more often children who had high grade point average. This may indicate social desirability bias leading to overestimation of time or intensity of physical activity, which may partly explain inconsistent results between self-reported and objectively measured MVPA in association with academic achievements. However, inconsistencies in previous studies may also be due to the objective methods of measuring physical activity. For example, accelerometer does not assess all activities, such as swimming and cycling or activities that require lifting a load (6). Furthermore, objective measures of MVPA mainly illustrate physical activity that accelerates HR and respiratory frequency, whereas self-reported MVPA may illustrate broader construct and context of physical activity including skill-specific physical activity requiring balance and agility, which hardly accumulate activity counts (7). In addition, as Dr. Shephard highlighted, and as we speculated in our study (7), 1 wk or less of objective measurement may not be enough to accurately depict children’s physical activity in everyday life. This is particularly important concerning learning and the mechanisms potentially explaining the association between physical activity and academic performance. Physical activity may enhance learning via increasing cerebral circulation, levels of neurotransmitters, and neuronal activity in the brains (8). In addition, the benefits of physical activity may be mediated through motor learning and psychosocial mechanisms (8). All of these processes take time and, therefore, longer accelerometer wearing times and several measurement periods should be considered when studying the effects of physical activity on learning outcomes. Lastly, sedentary activities, like using electronic media, have become a pervasive part of children’s everyday life, influencing physical activity and providing unprecedented opportunities for diverse forms of learning in formal and informal settings (3). Considering the complexity and dynamism of the environments young people are living and learning today, we believe that in future studies, diverse methods used together to measure physical activity may provide the most fruitful insights into the associations between physical activity and academic outcomes.

Using Ecological Momentary Assessment to Understand Where and With Whom Adults’ Physical and Sedentary Activity Occur

This study used Ecological Momentary Assessment (EMA), a real-time self-report strategy, to describe the physical and social contexts of adults' physical activity and sedentary activity during their everyday lives and to determine whether these patterns and relationships differ for men and women. Data from 114 adults were collected through mobile phones across 4days. Eight electronic EMA surveys were randomly prompted each day asking about current activities (e.g., physical or sedentary activity), physical and social contexts, and perceived outdoor environmental features (e.g., greenness/vegetation, safety, and traffic). All participants also wore accelerometers during this period to objectively measure moderate-to-vigorous physical activity (MVPA) and sedentary activity. Home was the most common physical context for EMA-reported physical and sedentary activity. Most of these activities occurred when participants were alone. When alone, the most commonly EMA-reported physical activity and sedentary activity was walking and reading/using computer, respectively. When in outdoor home locations (e.g., yard and driveway) women demonstrated higher levels of MVPA, whereas men demonstrated higher levels of MVPA when in outdoor park settings (ps < .05). Men but not women demonstrated higher levels of MVPA in settings with a greater degree of perceived greenness and vegetation (p < .05). The current study shows how EMA via mobile phones and accelerometers can be combined to offer an innovative approach to assess the contexts of adults' daily physical and sedentary activity. Future studies could consider utilizing this method in more representative samples to gather context-specific information to inform the development of physical activity interventions.

Associations of objectively assessed levels of physical activity, aerobic fitness and motor coordination with injury risk in school children aged 7–9 years: a cross-sectional study

ObjectivesPhysical activity (PA) is important for children's health but entails an inherent risk of injuries. The objective of this study was to assess activity-related correlates of injuries in children of...

Patterns of Objectively Measured Moderate-to-Vigorous Physical Activity in Preschool Children

Identifying periods of the day which are susceptible to varying levels of physical activity (PA) may help identify key times to intervene and potentially change preschool children's PA behaviors. This study assessed variability of objectively measured moderate-to-vigorous physical activity (MVPA) during weekdays and weekend days among preschool children. One hundred and eighty-eight children (aged 3 to 5 years; 53.2% boys) from a northwest English city wore uni-axial accelerometers for 7 consecutive days. Higher levels of MVPA were recorded in boys, particularly those who attended preschool for a half day. Children who attended preschool for a full day engaged in 11.1 minutes less MVPA than children who attended for a half day. After-school hours were characterized by a decrease in activity for all groups. Patterns of activity during the weekend were smoother with less variability. This study identified discrete segments of the week, specifically afterschool and during the weekend, when preschoolers engage in low levels of PA. Higher levels of MVPA among children who attended preschool for less time each day suggests that the structured preschool environment is related to decreased activity. Consequently, there is a need for interventions in young children to focus on school and home environments.

Is Measurement Error Altered by Participation in a Physical Activity Intervention?

There is no "gold standard" measure for moderate to vigorous physical activity (MVPA); some error is inherent to self-report and device-based measures. Few studies have examined agreement between self-report and device-based measures in the intervention trial context or whether the difference between measures is influenced by intervention participation. MVPA was measured at baseline and after 6 months by Active Australia Survey (AAS) and by the GT1M accelerometer (≥1952 counts per minute) in the intervention (n = 135) and usual care control (n = 141) participants of a randomized trial targeting weight loss by MVPA increases and energy intake reductions in adults with type 2 diabetes. Agreement (for each group at each assessment) was examined using the Bland-Altman approach and regression-based modeling. Because the differences between MVPA measures varied with average values ([AAS + GT1M] / 2), they were examined as a percentage of average physical activity. t-tests were used to assess unadjusted group differences and changes over time. ANCOVA models tested intervention effects on measurement error at follow-up, adjusted for baseline. Agreement worsened, and variability in the difference measures became greater, as the average amount of MVPA increased. Measurement error differed significantly between groups at follow-up (P = 0.010) but not at baseline (P = 0.157) and changed significantly within the intervention group (P = 0.001) but not the control group (P = 0.164). There was a statistically significant effect of the intervention on measurement error (P = 0.026). Measurement error of self-report relative to the accelerometer appeared to be affected by intervention. Because measurement error cannot be definitively attributed to self-report or accelerometer, it would be prudent to measure both in future studies.

Physical activity, sedentary behaviour and physical self-perceptions in adolescent girls: A mediation analysis

ObjectiveFew studies have examined the relationship between sedentary behaviour (SB) and mental well-being. This study assessed whether SB is associated with physical self-perceptions, independent of participation in moderate-to-vigorous physical activity (MVPA). Previous studies in this area simultaneously entered measures of SB and MVPA as predictors in regression models. In a novel approach, this study used mediation analyses to avoid problems of collinearity between SB and MVPA. DesignCross-sectional. SettingSchool-based. MethodAdolescent females (N = 238) used validated instruments to self-report time spent in SB and MVPA on the previous day, and to provide ratings for physical self-perceptions. Where a self-perception variable was associated with SB, Baron and Kenny's method was used to test if the relationship was mediated by MVPA. ResultsThere were small direct associations between SB and two self-perceptions, which were not mediated by MVPA: ‘sports competence’ (−.022) and ‘physical conditioning’ (−.023). There was also a negative association between SB and perceived ‘physical strength’, which, by contrast, was mediated by MVPA. ConclusionResults for selected self-perceptions indicate that SB may be important to aspects of mental well-being independent of MVPA engagement. Future studies should use longitudinal and prospective designs to (a) assess the causality and direction of associations between SB and self-perceptions; (b) explore how individual SBs relate to self-perceptions; and (c) establish if the magnitude of these associations is clinically relevant.

Validity and reliability of a self-report instrument to assess social support and physical environmental correlates of physical activity in adolescents.

BackgroundThe purpose of this study was to examine the internal consistency, test-retest reliability, construct validity and predictive validity of a new German self-report instrument to assess the influence of social support and the physical environment on physical activity in adolescents.MethodsBased on theoretical consideration, the short scales on social support and physical environment were developed and cross-validated in two independent study samples of 9 to 17 year-old girls and boys. The longitudinal sample of Study I (n = 196) was recruited from a German comprehensive school, and subjects in this study completed the questionnaire twice with a between-test interval of seven days. Cronbach’s alphas were computed to determine the internal consistency of the factors. Test-retest reliability of the latent factors was assessed using intra-class coefficients. Factorial validity of the scales was assessed using principle components analysis. Construct validity was determined using a cross-validation technique by performing confirmatory factor analysis with the independent nationwide cross-sectional sample of Study II (n = 430). Correlations between factors and three measures of physical activity (objectively measured moderate-to-vigorous physical activity (MVPA), self-reported habitual MVPA and self-reported recent MVPA) were calculated to determine the predictive validity of the instrument.ResultsConstruct validity of the social support scale (two factors: parental support and peer support) and the physical environment scale (four factors: convenience, public recreation facilities, safety and private sport providers) was shown. Both scales had moderate test-retest reliability. The factors of the social support scale also had good internal consistency and predictive validity. Internal consistency and predictive validity of the physical environment scale were low to acceptable.ConclusionsThe results of this study indicate moderate to good reliability and construct validity of the social support scale and physical environment scale. Predictive validity was only confirmed for the social support scale but not for the physical environment scale. Hence, it remains unclear if a person’s physical environment has a direct or an indirect effect on physical activity behavior or a moderation function.

Youth physical activity and sedentary time and associations with cardiometabolic health

Commentary on: Ekelund U, Luan J, Sherar LB, et al. Moderate to vigorous physical activity and sedentary time and cardiometabolic risk factors in children and adolescents. JAMA 2012;307:704–12.[OpenUrl][1][CrossRef][2][PubMed][3][Web of Science][4]...

Physical activity during pregnancy and postpartum depressive symptoms

Objectiveto examine the associations between total and domain-specific moderate-to-vigorous physical activity (MVPA) during pregnancy and postpartum depressive symptoms. Designa prospective cohort study. Participantsdata were obtained from 652 women recruited from prenatal clinics at University of North Carolina Hospitals during 2001–2005 for the Pregnancy, Infection, and Nutrition (PIN) Postpartum Study. MeasurementsMVPA measured at 17–22 and 27–30 weeks' gestation was investigated as a predictor of depressive symptoms assessed with the Edinburgh Postnatal Depression Scale at 3 months postpartum. Findingstotal MVPA was not associated with depressive symptoms when using either 17–22 weeks' gestation or 27–30 weeks' gestation MVPA measures. In general, there were minimal associations for domain-specific MVPA. The direction of associations between depressive symptoms and work, adult and child care, and outdoor household MVPAs differed by time of measurement. Key conclusionsthe association between physical activity and postpartum depressive symptoms may differ with the timing of assessment. Additional studies (i.e. with a larger sample of women or a sample of at-risk women) following women throughout pregnancy and postpartum are needed to explore differences in the influence of physical activity on depressive symptoms. Implications for practiceassessment of potential risk factors for elevated depressive symptoms, such as participation levels in different types of physical activity, throughout pregnancy may assist in determining who may be susceptible to postpartum depression.

Objective vs. Self-Reported Physical Activity and Sedentary Time: Effects of Measurement Method on Relationships with Risk Biomarkers

PurposeImprecise measurement of physical activity variables might attenuate estimates of the beneficial effects of activity on health-related outcomes. We aimed to compare the cardiometabolic risk factor dose-response relationships for physical activity and sedentary behaviour between accelerometer- and questionnaire-based activity measures.MethodsPhysical activity and sedentary behaviour were assessed in 317 adults by 7-day accelerometry and International Physical Activity Questionnaire (IPAQ). Fasting blood was taken to determine insulin, glucose, triglyceride and total, LDL and HDL cholesterol concentrations and homeostasis model-estimated insulin resistance (HOMAIR). Waist circumference, BMI, body fat percentage and blood pressure were also measured.ResultsFor both accelerometer-derived sedentary time (<100 counts.min−1) and IPAQ-reported sitting time significant positive (negative for HDL cholesterol) relationships were observed with all measured risk factors – i.e. increased sedentary behaviour was associated with increased risk (all p≤0.01). However, for HOMAIR and insulin the regression coefficients were >50% lower for the IPAQ-reported compared to the accelerometer-derived measure (p<0.0001 for both interactions). The relationships for moderate-to-vigorous physical activity (MVPA) and risk factors were less strong than those observed for sedentary behaviours, but significant negative relationships were observed for both accelerometer and IPAQ MVPA measures with glucose, and insulin and HOMAIR values (all p<0.05). For accelerometer-derived MVPA only, additional negative relationships were seen with triglyceride, total cholesterol and LDL cholesterol concentrations, BMI, waist circumference and percentage body fat, and a positive relationship was evident with HDL cholesterol (p = 0.0002). Regression coefficients for HOMAIR, insulin and triglyceride were 43–50% lower for the IPAQ-reported compared to the accelerometer-derived MVPA measure (all p≤0.01).ConclusionUsing the IPAQ to determine sitting time and MVPA reveals some, but not all, relationships between these activity measures and metabolic and vascular disease risk factors. Using this self-report method to quantify activity can therefore underestimate the strength of some relationships with risk factors.

Does the fractionalization of daily physical activity (sporadic vs. bouts) impact cardiometabolic risk factors in children and youth?

ObjectiveChildren and youth accumulate their daily moderate-to-vigorous physical activity (MVPA) in bouts (i.e., ≥5 consecutive minutes) and in a sporadic manner (i.e., <5 consecutive minutes). The study objective was to determine, within children and youth, whether MVPA accumulated in bouts is more strongly associated with cardiometabolic risk factors than an equivalent volume of MVPA accumulated sporadically.MethodsParticipants consisted of 2754 children and youth aged 6–19 years from the 2003–2006 National Health and Nutrition Examination Survey, a representative cross-sectional study. Bouts and sporadic MVPA were measured objectively over 7 days using Actigraph accelerometers. Thresholds of 5 and 10 consecutive minutes were used to differentiate between bouts and sporadic MVPA. A high cardiometabolic risk factor score (CRS) was created based on measures of waist circumference, non-high-density lipoprotein cholesterol, C-reactive protein, and systolic blood pressure. Associations were examined using logistic regression and controlled for covariates (sex, age, ethnicity, socioeconomic status, dietary fat and sodium, smoking, and accelerometry wear time).ResultsThe odds of a high CRS decreased in a dose-response for both the sporadic and bout MVPA measures. Relative to quartile 1, the odds ratio (95% confidence interval) for a high CRS in quartile 4 was 0.25 (0.10–0.60) for sporadic MVPA, 0.17 (0.09–0.34) for ≥5 minute bouts of MVPA, and 0.19 (0.11–0.34) for ≥10 minute bouts of MVPA. The sporadic and bout MVPA measures had a similar ability to distinguish between participants with high and normal CRS. Relative to 0 minutes of MVPA, an equivalent number of minutes of sporadic MVPA and bouts of MVPA had an almost identical odds ratio for a high CRS. The findings were consistent for 5 and 10 minute bout thresholds.ConclusionsThe relations between sporadic MVPA and bouts of MVPA with cardiometabolic risk factors were remarkably similar in children and youth.

Active Commuting to School and Association With Physical Activity and Adiposity Among US Youth

Walking or bicycling to school (ie, active commuting) has shown promise for improving physical activity and preventing obesity in youth. Our objectives were to examine, among US youth, whether active commuting was inversely associated with adiposity and positively associated with moderate-to-vigorous physical activity (MVPA). We also examined whether MVPA mediated the relationships between active commuting and adiposity. Using data of participants aged 12 to 19 years from the US National Health and Nutrition Examination Survey 2003 to 2004 (n=789 unweighted), we constructed multiple linear regression models that controlled for dietary energy intake and sociodemographics. The main exposure variable was active commuting. The outcomes were BMI z-score, waist circumference, skinfolds and objectively measured MVPA. The product-of-coefficients method was used to test for mediation. Active commuting was inversely associated with BMI z-score (β=-0.07, P=.046) and skinfolds (β=-0.06, P=.029), and positively associated with overall daily (β=0.12, P=.024) and before- and after-school (β=0.20, P<.001) MVPA. Greater before- and after-school MVPA explained part of the relationship between active commuting and waist circumference (Sobel z=-1.98, P=.048). Active commuting was associated with greater MVPA and lower measures of adiposity among US youth. Before- and after-school MVPA mediated the relationships between active commuting and waist circumference.

Sex differences in the variables associated with objectively measured moderate-to-vigorous physical activity in preschoolers

ObjectiveTo investigate variables associated with objectively measured moderate-to-vigorous physical activity (MVPA) in German preschool children. MethodsCross-sectional data was collected from 649 three to six year old children (51% boys) in 52 preschools in south Germany between autumn and spring 2008−2009. Sociodemographic, health and socio-cultural variables that could affect children's objectively measured MVPA minutes, averaged over two to four week and weekend days, were tested in bivariate and multivariate linear regression models. ResultsMVPA was significantly associated with the extrinsic variables age (−4.52min/year of age), health status (5.62min/category), high TV time (9.22min/category) and high parental PA (6.59min/category) among girls. For boys, only the intrinsic variable desire to be active (5.19min/category) was significantly, positively associated with MVPA. The final models for girls and boys explained approximately 10% and 7% of the variance, respectively, in children's MVPA. ConclusionWe found differences by sex in variables associated with objectively measured MVPA in preschoolers. A focus on extrinsic motivators such as parental PA for girls and intrinsic motivators for boys may be an important consideration when designing interventions and PA programs for this age group.

Associations between moderate-to-vigorous physical activity and central body fat in 3–8-year-old children

The aim of this study was to examine the associations between objectively measured moderate-to-vigorous physical activity (MVPA) and central body fat (CBF) indicators by anthropometry and dual energy X-ray absorptiometry (DXA) in young children. This study comprised 110 children aged 3-8 years. The associations between MVPA and CBF measures by anthropometry (waist circumference, waist-to-height ratio, skinfold thicknesses [subscapular, suprailiac, trunk-to-extremity and trunk-to-total skinfold ratios] and total trunk-to-waist circumference), DXA (trunk fat) and a combination of both (total trunk skinfolds-to-trunk fat by DXA) were examined by linear regression. Levels of MVPA showed a significant inverse association with 8 of 9 indicators of CBF after controlling for age, gender and height, and fat-free mass. When total fat mass measured by DXA was included into the model, levels of MVPA remained significantly associated with 6 of 9 indicators of CBF. The results highlight the plausible role of MVPA on CBF in young children but longitudinal studies are necessary.

Difference Between Self-Reported and Accelerometer Measured Moderate-to-Vigorous Physical Activity in Youth

We examined differences between objective (accelerometer) and subjective (selfreport) measures of moderate-to-vigorous physical activity (MVPA) in youth. Participants included 2761 youth aged 12-19 years. Within each sex and race group, objective and self-reported measures of MVPA were poorly correlated (R² = .01-.10). Self-reported MVPA values were higher than objective values (median: 42.4 vs. 15.0 min/d). 65.4% of participants over-reported their MVPA by ³5 min/d. The difference between self-reported and objective measures was not influenced by sex, age, or race. There was, however, a systematic difference such that inactive participants over-reported their MVPA to the greatest extent.

Do area characteristics predict change in moderate-to-vigorous physical activity from ages 11 to 15 years?

In light of geographical and epidemiological research suggesting that the socioeconomic environment beyond the family may influence children's physical activity, this study investigated the extent to which neighbourhood socioeconomic conditions predict change in physical activity from ages 10 through 15 years, controlling for the attributes of the individual child and family. Data came from 889 children participating in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development cohort study. Accelerometers measured Moderate-to-Vigorous Physical Activity (MVPA) during the week and weekend, when the children were aged 10, 11, and 15 years. Selected US census block variables were used to create 'independent' area measures of economic deprivation and social fragmentation scores for child's area of residence at age 10 years. Also, parents' perception of neighbourhood social cohesion was measured in terms of relationships with neighbours. All analyses controlled for participant characteristics: gender, ethnicity, household income-to-needs ratio, maternal education, and for United States region of residence. Growth curve analyses indicated that whereas social fragmentation did not predict MVPA over time, greater area deprivation at age 10 years was associated with lower weekday MVPA for boys at 10 years (β=-0.5, p=0.03) and these differences persisted to age 11 and 15 years. This relationship was reversed for girls. Weekend MVPA was not significantly associated with the level of deprivation in the place of residence at age 10 years. Although the census measure of social fragmentation in the area of residence showed no significant association with MVPA, parent-reported neighbourhood social cohesion was positively associated with weekday (β=2.0, p<0.01) and weekend (β=3.1, p<0.01) MVPA minutes across time. This association was most pronounced for boys. Area level factors may be determinants of physical activity among children and youth in complex ways and parental perception of area social environment may be as important for children's activity levels as 'independently assessed' socioeconomic conditions.

Dose-response relationship between physical activity and dyslipidemia in youth

The minimal and optimal amount of physical activity associated with cardiovascular health benefits in young people is unknown. To determine the dose-response relationship between moderate-to-vigorous physical activity (MVPA) with high-risk low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol and triglyceride values in youth. The study sample consisted of 1235 adolescents (12 to 19 years of age) from the 20032004 and 20052006 cycles of the United States National Health and Nutrition Examination Survey. Objective measures of MVPA were obtained over seven days with accelerometers. LDL cholesterol, HDL cholesterol and triglycerides were measured from a fasting blood sample. High-risk values for these lipidslipoproteins were determined using age- and sex-specific thresholds. Logistic regression models were used to determine the dose-response relationships between MVPA and high-risk lipid levels. ORs for high-risk HDL cholesterol and triglyceride values decreased in a curvilinear manner with increasing minutes of MVPA. Compared with no MVPA (0 min), the ORs for high-risk HDL cholesterol values at 15 min, 30 min and 60 min per day of MVPA were 0.29 (95% CI 0.13 to 0.67), 0.24 (95% CI 0.10 to 0.64) and 0.21 (95% CI 0.07 to 0.61), respectively. The corresponding ORs for high-risk triglyceride values were 0.40 (95% CI 0.18 to 0.76), 0.22 (95% CI 0.06 to 0.66) and 0.10 (95% CI 0.01 to 0.51). There was no discernible dose-response relationship between MVPA and LDL cholesterol. Small amounts of MVPA were associated with a large reduction in the likelihood of having high-risk HDL cholesterol and triglyceride values in this representative sample of adolescents.

Physical Activity, Academic Performance, And Physical Self-description In Adolescent Females

Despite the many health benefits of being physically active nearly a quarter of U.S. adults and adolescents report no participation in leisure-time physical activity. It is recommended that children and adolescents participate in physical activity for at least 60 minutes daily at moderate or vigorous intensity. In addition to potentially enhancing academic performance participation in physical activity may also influence perceptions of physical appearance and global self-esteem which tend to decrease with age in adolescent females. The purposes of this study were to: (a) examine the prevalence of overweight and obesity and the percentage of adolescent females from a rural community that meets physical activity recommendations; (b) examine the relationship of body composition physical activity and sedentary behavior on academic performance; and (c) examine the relationship between physical activity and physical self-concept among adolescent females. Thirty adolescent females (mean age = 15.6 ± 1.3 years) wore an Actigraph GT1M accelerometer for seven consecutive days set to measure in 15-second epochs. Age specific cutpoints were used to determine minutes of sedentary behavior and light moderate vigorous and moderate-to-vigorous physical activity (MVPA). Participants completed the Physical Self-Description Questionnaire (PSDQ) to assess how they perceive themselves physically. Height weight and percent body fat were measured. Grade point averages (GPA) were obtained from school records. Regression analysis was performed to predict GPA from measures of body composition sedentary behavior and MVPA. Measures of physical activity and sedentary behavior were correlated with PSDQ subscale scores with Pearson correlations. Thirty percent of participants (n = 9) were obese (BMI [greater than or equal to] 95th percentile) and another 36% (n = 11) were overweight (BMI between the 85th and 94th percentiles). None of the participants accumulated [greater than or equal to] 60 minutes of MVPA per day. Daily MVPA averaged 9.7 (± 7.1) minutes. Percent fat (r = -.51) minutes of MVPA (r = .34) and time spent in sedentary behavior (r = .32) were significantly correlated (p < .05) with GPA. Together measures of body composition physical activity and sedentary behavior explained 36% of the variance (multiple R = .60) in GPA. The standard error of estimate for predicting GPA was 0.64. Minutes per day spent in light physical activity was negatively correlated (p < .01) with the Self-Esteem (r = -.51) Body Fat (r = -.52) and Global Physical Self-Concept (r = -.48) subscales of the PSDQ. Only the Physical Activity subscale of the PSDQ was significantly correlated with MVPA (r = .36). In conclusion the current sample of adolescent females had a high prevalence of overweight and obesity and was physically inactive. Academic performance was significantly associated with measures of body composition physical activity and sedentary behavior. Time spent in light physical activity was associated with lower self-perceptions of body fat global physical self-concept and self-esteem. Measures of higher intensity physical activity were generally not associated with physical self-perception measures possibly due to the low amount of time spent in MVPA. Interventions to increase physical activity and improve body composition in adolescent girls should be considered not only for their health effects but also for their potential to impact academic performance and psychological profiles.

Using pedometers to measure moderate-to-vigorous physical activity for youth with an intellectual disability

Background Pedometers serve as one of the most feasible and cost-effective methods for frontline practitioners to measure moderate-to-vigorous physical activity (MVPA) of youth with an intellectual disability (YwID) but, historically, pedometers have been unable to measure MVPA. Technological advancements now allow pedometers to measure MVPA via step frequency (steps per minute). Translating the output of this technology into practical information that frontline practitioners and families can use, however, will require accurate step frequency guidelines. Objective The purpose of this study was to identify steps per minute thresholds corresponding to MVPA for YwID. Methods Thirty-eight children and adolescents (10 girls, 11.8 ± 1.8 years) attending a summer camp for youth with an ID walked on a treadmill starting at 2.0 mph and increasing every 2 minutes by 0.5 mph until they reached 4.0 mph. Youth were affixed with a heart rate (HR) monitor. Steps were counted by trained observers using hand-tally counters. Data were collected during the final minute of each speed. HR at each speed was transformed into percentage of heart rate reserve (%HRR), using each participant's resting HR. Percentage of HRR corresponding to 40%HRR or higher was used to define MVPA. Random effects models were constructed to predict steps per minute from %HRR and participant characteristics. Results The results indicated that, on average, 122 steps·min −1 was the minimal threshold for MVPA. Height- and age-specific steps·min −1 ranged from 135 steps·min −1 to 112 steps·min −1. Conclusions These findings provide preliminary thresholds for steps per minute that frontline practitioners working with YwID can use to promote and evaluate MVPA in this population.