Determination of step rate thresholds corresponding to physical activity intensity classifications in adults

Journal ArticleBackground: Current recommendations call for adults to be physically active at moderate and/or vigorous intensities. Given the popularity of walking and running, the use of step rates may provide a practical and inexpensive means to evaluate ambulatory intensity. Thus, the purpose of this study was to identify step rate thresholds that correspond to various intensity classifications. Methods: Oxygen consumption was measured at rest and during 10 minute treadmill walking and running trials at 6 standardized speeds (54, 80, 107, 134, 161, and 188 m?min-1) in 9 men and 10 women (28.8 ? 6.8 yrs). Two observers counted the participants? steps at each treadmill speed. Linear and nonlinear regression analyses were used to develop prediction equations to ascertain step rate thresholds at various intensities. Results: Nonlinear regression analysis of the metabolic cost versus step rates across all treadmill speeds yielded the highest R2 values for men (R2 = .91) and women (R2 = .79). For men, the nonlinear analysis yielded 94 and 125 step?min-1 for moderate and vigorous intensities, respectively. For women, 99 and 135 step?min-1 corresponded with moderate and vigorous intensities, respectively. Conclusions: Promoting a step rate of 100 step?min-1 may serve as a practical public health recommendation to exercise at moderate intensity

Physical activity differences by birthplace and sex in youth of Mexican Heritage

Journal ArticleBackground: One of the goals of Healthy People 2020 is to increase physical activity (PA) and reduce health disparities among different racial and ethnic segments of the U.S. population. Few studies have been conducted to examine PA differences by birthplace and sex in youth of Mexican heritage. Methods: Participants were 101 youth (43 boys, 58 girls, 59% U.S.-born, 41% Mexico-born) who wore a sealed New Lifestyles NL-1000 pedometer for 7 consecutive days. Results: Mexico-born youth took more steps, on average, than their U.S.-born counterparts (P = .038). However, moderate-to-vigorous intensity (MVI) time did not differ between Mexico- and U.S.-born youth (P = .146). By contrast to birthplace, sex-related differences were more consistent, as boys took more steps (P = .005) and accumulated more MVI time (P = .043) than girls. Only 4% of our sample met either one or both of the PA recommendations. Conclusions: We conclude that PA may differ by birthplace and by sex in youth of Mexican heritage, as U.S.-born girls were the least active segment of our sample. Culturally sensitive interventions to increase daily PA must become a higher public health priority for youth of Mexican heritage, in particular, for U.S.-born girls of Mexican heritage

Children and Pedometers: A Study in Reactivity and Knowledge

International Journal of Exercise Science 6(3) : 230-235, 2013. Pedometers are simple inexpensive tools that are widely used for the measurement of physical activity. Reactivity is always a concern when using pedometers. An issue not yet addressed is the role previous knowledge has on the impact of reactivity. The primary purpose of this study was to examine if reactivity exists in 4th-6th grade students and if prior knowledge about pedometers had an effect on reactivity. Participants included 109 (54 females) 4th- 6th grade students from a suburban charter school. Prior to data collection, students completed a questionnaire to measure their knowledge of pedometers. Pedometers were worn from after-school until before school each day for two weeks with half of the students wearing sealed devices the first week, then switching to unsealed. Steps were counted and pedometers were redistributed each afternoon. Repeated measures ANOVA results showed no significant differences in step counts between unsealed and sealed conditions, or when knowledge and experience regarding pedometers was included as a covariate. Pedometers are inexpensive and reliable tools that researchers and educators can use to measure physical activity. In this study reactivity did not occur with older elementary students and a student’s knowledge of pedometers did not affect reactivity

Factors Influencing Muscular Strength and Endurance in Disadvantaged Children From Low-Income Families

International Journal of Exercise Science 9(3): 306-317, 2016. Examining the correlates of muscular strength and endurance in children from low-income families will provide evidence for interventions to improve these parameters. The purpose of this study was to determine the predictors and trends of muscular strength and endurance in at-risk school-aged children. The sample included 1,232 children (Mean age = 8.8 ± 1.6 years; 625 girls, 607 boys; 60% Hispanic) recruited from three U.S. low-income schools. Children performed health-related fitness testing and wore pedometers for one school week. A stratified random subsample (n = 533) also wore accelerometers to record sedentary behaviors, MVPA, and vigorous physical activity. Generalized linear mixed models were employed to calculate odds ratios (OR) for achieving FITNESSGRAM’s push-up and curl-up standards (met standard = HFZ) from various predictors and to determine odds of achievement across grade levels. A student who achieved the HFZ for VO2 Peak had an OR = 1.66 (p \u3c 0.001) for achieving the HFZ for pushups and an OR = 1.99 (p \u3c 0.01) for achieving the HFZ for curl-ups. Additionally, students whose vigorous physical activity was 1% higher had an OR = 3.25 (p \u3c 0.05) for achieving the HFZ for curl-ups. For cohorts of students separated by one grade level, the OR = 0.48 (p \u3c 0.01) for achieving the HFZ for pushups and OR = 0.71 (p \u3c 0.01) for achieving the HFZ for curl-ups. The results suggest that VO2 Peak, vigorous physical activity, and grade level are significant predictors of muscular strength and endurance in at-risk children

Effect of a 12-Week Summer Break on School Day Physical Activity and Health-Related Fitness in Low-Income Children from CSPAP Schools

Background. The purpose of this study was to examine the effect of a 12-week summer break on school day physical activity and health-related fitness (HRF) in children from schools receiving a Comprehensive School Physical Activity Program (CSPAP). Methods. Participants were school-aged children (; 624 girls and 608 boys; years) recruited from three low-income schools receiving a CSPAP. Physical activity and HRF levels were collected during the end of spring semester 2015 and again during the beginning of fall semester 2015. Physical activity was assessed using the Yamax DigiWalker CW600 pedometer. HRF measures consisted of body mass index (BMI) and the Progressive Aerobic Cardiovascular Endurance Run (PACER). Results. Results from a doubly MANCOVA analysis indicated that pedometer step counts decreased from 4,929 steps in the spring to 4,445 steps in the fall (mean difference = 484 steps; ; Cohen’s d = 0.30) and PACER laps decreased from 31.2 laps in the spring to 25.8 laps in the fall (mean difference = 5.4 laps; ; Cohen’s d = 0.33). Conclusions. Children from schools receiving a CSPAP intervention had lower levels of school day physical activity and cardiorespiratory endurance following a 12-week summer break

The Relationship between Change of Direction Speed in the Frontal Plane, Power, Reactive Strength, and Strength

International Journal of Exercise Science 7(4) : 260-270, 2014. Change-of-direction speed (CODS) is an important quality to performance in multi-direction sports. The relationship between CODS in the frontal plane and power, strength, and reactive strength is largely unstudied. Twenty-three male college students participated in this study. The study used a Pearson’s product-moment correlation to measure the relationship between CODS, power, strength, and reactive strength. A lateral shuffle test was used as the measure of CODS. A lateral hop for distance was used as the measure of power in the frontal plane. A countermovement vertical jump test was used as the measure of power in the sagittal plane. A depth jump was used as the measure of reactive strength in the sagittal plane. A 3RM squat test was used as the measure of strength. There was a moderate relationship between the lateral shuffle test and the lateral hop (r =.541, p = .008 and r =.567, p = .005), but no significant relationships with the countermovement vertical jump, depth jump, or squat test. These results suggest that power should be trained in all planes to improve CODS performance in multi-direction sports, and that CODS should be trained in its sport-specific context

Effect of a 12-Week Summer Break on School Day Physical Activity and Health-Related Fitness in Low-Income Children from CSPAP Schools

Background. The purpose of this study was to examine the effect of a 12-week summer break on school day physical activity and health-related fitness (HRF) in children from schools receiving a Comprehensive School Physical Activity Program (CSPAP). Methods. Participants were school-aged children ( = 1,232; 624 girls and 608 boys; mean age = 9.5 ± 1.8 years) recruited from three low-income schools receiving a CSPAP. Physical activity and HRF levels were collected during the end of spring semester 2015 and again during the beginning of fall semester 2015. Physical activity was assessed using the Yamax DigiWalker CW600 pedometer. HRF measures consisted of body mass index (BMI) and the Progressive Aerobic Cardiovascular Endurance Run (PACER). Results. Results from a doubly MANCOVA analysis indicated that pedometer step counts decreased from 4,929 steps in the spring to 4,445 steps in the fall (mean difference = 484 steps; < 0.001; Cohen's d = 0.30) and PACER laps decreased from 31.2 laps in the spring to 25.8 laps in the fall (mean difference = 5.4 laps; < 0.001; Cohen's d = 0.33). Conclusions. Children from schools receiving a CSPAP intervention had lower levels of school day physical activity and cardiorespiratory endurance following a 12-week summer break

Establishing Waist-to-Height Ratio Standards from Criterion-Referenced BMI Using ROC Curves in Low-Income Children

The purpose of this study was to establish health-related waist-to-height ratio (WHtR) cut-points associating with FITNESSGRAM's body mass index (BMI) criterion-referenced standards in low-income children. A secondary aim was to examine the classification agreement between the derived WHtR cut-points and various cardiometabolic blood markers using current recommendations. Participants were 219 children from low-income schools (mean age = 10.5 ± 0.6 years). Waist circumference, height, weight, and cardiometabolic blood markers were collected in a fasting state before school hours. Receiver operating characteristic (ROC) curves were used to determine WHtR cut-points that associated with a child meeting FITNESSGRAM's age-and sex-specific criterionreferenced standards for BMI. The derived WHtR cut-point was 0.50 (AUC = 0.89, < 0.001; sensitivity = 0.86, specificity = 0.82, and accuracy = 84.3%). Classification agreement using the derived WHtR cut-point with various blood marker standards was statistically significant but considered weak to fair (kappa 0.14-0.34, agreement = 59%-67%, and < 0.01). The WHtR cutpoint of 0.50 can be used with strong accuracy to distinguish low-income children who met FITNESSGRAM's criterion-referenced standards for body composition; however, the evidence was weaker for its use in distinguishing low-income children meeting specific cardiometabolic blood marker recommendations

Establishing Waist-to-Height Ratio Standards from Criterion-Referenced BMI Using ROC Curves in Low-Income Children

The purpose of this study was to establish health-related waist-to-height ratio (WHtR) cut-points associating with FITNESSGRAM’s body mass index (BMI) criterion-referenced standards in low-income children. A secondary aim was to examine the classification agreement between the derived WHtR cut-points and various cardiometabolic blood markers using current recommendations. Participants were 219 children from low-income schools (mean age = 10.5 ± 0.6 years). Waist circumference, height, weight, and cardiometabolic blood markers were collected in a fasting state before school hours. Receiver operating characteristic (ROC) curves were used to determine WHtR cut-points that associated with a child meeting FITNESSGRAM’s age- and sex-specific criterion-referenced standards for BMI. The derived WHtR cut-point was 0.50 (AUC = 0.89, p<0.001; sensitivity = 0.86, specificity = 0.82, and accuracy = 84.3%). Classification agreement using the derived WHtR cut-point with various blood marker standards was statistically significant but considered weak to fair (kappa 0.14–0.34, agreement = 59%–67%, and p<0.01). The WHtR cut-point of 0.50 can be used with strong accuracy to distinguish low-income children who met FITNESSGRAM’s criterion-referenced standards for body composition; however, the evidence was weaker for its use in distinguishing low-income children meeting specific cardiometabolic blood marker recommendations

Dynamic expression of genes associated with schizophrenia and bipolar disorder across development

Common genetic variation contributes a substantial proportion of risk for both schizophrenia and bipolar disorder. Furthermore, there is evidence of significant, but not complete, overlap in genetic risk between the two disorders. It has been hypothesised that genetic variants conferring risk for these disorders do so by influencing brain development, leading to the later emergence of symptoms. The comparative profile of risk gene expression for schizophrenia and bipolar disorder across development over different brain regions however remains unclear. Using genotypes derived from genome-wide associations studies of the largest available cohorts of patients and control subjects, we investigated whether genes enriched for schizophrenia and bipolar disorder association show a bias for expression across any of 13 developmental stages in prefrontal cortical and subcortical brain regions. We show that genetic association with schizophrenia is positively correlated with expression in the prefrontal cortex during early midfetal development and early infancy, and negatively correlated with expression during late childhood, which stabilises in adolescence. In contrast, risk-associated genes for bipolar disorder did not exhibit a bias towards expression at any prenatal stage, although the pattern of postnatal expression was similar to that of schizophrenia. These results highlight the dynamic expression of genes harbouring risk for schizophrenia and bipolar disorder across prefrontal cortex development and support the hypothesis that prenatal neurodevelopmental events are more strongly associated with schizophrenia than bipolar disorder