Showing papers by "Gregory J. Welk published in 2011"
TL;DR: In this paper, the authors assess self-reported and objectively measured physical activity among U.S. adults according to the 2008 Physical Activity Guidelines for Americans (PAGA) using Actigraph accelerometers worn for 7 consecutive days.
809 citations
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TL;DR: Self-reported and objectively measured physical activity among U.S. adults according to the 2008 Physical Activity Guidelines for Americans (PAGA) was assessed, and physical activity estimates vary substantially depending on whether self-reported or measured via accelerometer.
Abstract: This study assesses self-reported and objectively measured physical activity among U.S. adults according to the 2008 Physical Activity Guidelines for Americans. The National Health and Nutrition Examination Survey of 2005–2006 found that fewer than 10 percent of U.S. adults met the guidelines. However, physical activity estimates vary substantially depending on how they are reported and measured.
769 citations
TL;DR: Using %BF instead of BMI may offer additional information in epidemiologic research, fitness assessment, and clinical settings, and future research can identify appropriate cut-off values based on health-related outcomes.
177 citations
TL;DR: Age- and gender-specific aerobic-capacity thresholds for creating separate risk groups were identified using nationally representative growth percentiles and aerobic fitness can be used with moderate accuracy to differentiate between adolescents with and without metabolic syndrome.
162 citations
TL;DR: It is demonstrated that height explained as much variability in walking intensity at a given cadence as did two different measures of leg length and two different stride length tests.
Abstract: Current physical activity guidelines recommend physical activity of at least moderate intensity to gain health benefits. Previous studies have recommended a moderate-intensity walking cadence of 100 steps per minute for adults, but the influence of height or stride length has not been investigated. Purpose: The purpose of the current study was to determine the role of height and stride length in moderate-intensity walking cadence in adults. Methods: Seventy-five adults completed three treadmill walking trials and three overground walking trials at slow, medium, and fast walking speeds while VO2 was measured using indirect calorimetry. Five stride length-related variables were also measured. Results: Mixed model regression analysis demonstrated that height explained as much variability in walking intensity at a given cadence as did two different measures of leg length and two different stride length tests. Conclusions: The previous general recommendations of 100 steps per minute were supported for use where a simple public health message is needed. Depending on height, moderate-intensity walking cadence can vary by more than 20 steps per minute, from 90 to 113 steps per minute for adults 198 to 152 cm tall, respectively. Height should therefore be taken into consideration for more precise evaluation or prescription of walking cadence in adults to provide health benefits.
140 citations
TL;DR: The ActivPAL step function performs better than the Actigraph at the slowest walking speed under treadmill conditions, and the development of a new equation based on the counts–METs relationship that includes a variety of speeds and activities would be useful.
Abstract: The purpose of this study was to determine the validity of the metabolic equivalent (MET) equation and step rate function of the ActivPAL™ physical activity logger in a group of females. Using a standard treadmill protocol, 62 females aged 15–25 years walked on a treadmill at speeds between 3.2 and 7.0 km · h−1 while wearing an ActivPAL. Oxygen consumption was measured using expired gas analysis at each speed and METs for each speed were estimated based on each participant's own resting metabolic rate. A sub-set of 18 participants also wore an Actigraph. Results showed that the in-built equation in the ActivPAL significantly underestimated (P 0.05) to video...
119 citations
TL;DR: This study presents age- and gender-specific percentiles for U.S. youth aged 12-18 years based on NHANES (1999-2002), and adds to the recent application of the LMS statistical procedure for the construction of growthpercentiles for a variety of outcomes.
101 citations
TL;DR: Children engaged in physical activity during recess, though interventions may be needed to increase the intensity of activity in this context.
Abstract: BACKGROUND: School recess provides a daily opportunity for physical activity engagement. The purpose of this study was to examine physical activity levels during recess by gender, ethnicity, and grade, and establish the contribution of recess to daily school physical activity levels. METHODS: Two hundred and ten children (45% boys) from grades 3 to 6 in 4 elementary schools had their physical activity during school quantified using uni-axial accelerometry every 5 seconds for 5 consecutive school days. Data were collected in fall 2009. The proportion of time spent engaged in physical activity during daily school recess was determined using existing age-appropriate cutpoints. The relative contribution of recess to school day physical activity was also determined. RESULTS: Boys were more active than girls during recess. Girls engaged in more sedentary activity than boys. No main effects for ethnicity were observed. Children in grades 3 and 5 were more active than children in grades 4 and 6. Recess contributed 17.9% and 15.5% toward boys' and girls' school day moderate-to-vigorous physical activity, respectively. CONCLUSION: Children engaged in physical activity during recess, though interventions may be needed to increase the intensity of activity in this context. Language: en
88 citations
TL;DR: Appropriate uses of fitness and activity assessments include teaching self-monitoring skills, promoting educational outcomes, providing personalized information about levels of health-related fitness/activity, and assisting in evaluating school-level outcomes over time.
78 citations
01 Jan 2011
TL;DR: Appropriate uses of fitness and activity assessments include self-monitoring, promoting educational outcomes, providing personalized informa-tion about levels of health-related fitness/activity, and assisting in evaluating school-level outcomes over time.
Abstract: Appropriate uses of fitness and activity assess-mentsincludeteachingself-monitoringskills,promotingeducational outcomes, providing personalized informa-tion about levels of health-related fitness/activity, andassisting in evaluating school-level outcomes over time(for tracking or curricular assessment).
76 citations
TL;DR: In this paper, a 10-fold cross-validation procedure was used to develop prediction equations using moderate-to-vigorous physical activity (MVPA) estimated from each of the five sets of accelerometer cutpoints as the dependent variable, with estimated MVPA from one of the other four sets of cutpoints (e.g., PT MVPA predicted from FR MVPA).
TL;DR: BMI and skinfold-derived %BF demonstrate reasonable agreement when used to classify adiposity status in children and adolescents as well as optimal BMI thresholds for identifying at-risk children and adolescence based on %BF.
TL;DR: The large data set provided a useful sample to examine the impact of the new fitness standards on the documentation of youth fitness levels in schools and reveal important age and gender differences in reported levels of Fitness levels in school-aged youth.
TL;DR: The current paper reviews historical trends in fitness testing and explains the advantages of a CR framework and methods used for establishing CR standards, providing a background for the subsequent articles in this supplement to the American Journal of Preventive Medicine.
TL;DR: Age- and gender-specific %BF thresholds for creating separate risk groups were identified in relation to metabolic syndrome status and could be extrapolated to younger children using previously created %BF centiles, which potentially allows for earlier identification and intervention of at-risk youth if tracking of current %BF was maintained.
TL;DR: Test the convergent validity of the SOPLAY using temporally matched data from an accelerometry-based activity monitor to find Observations provide valid indicators of MVPA if coding is based on the percentage of youth classified as "vigorous."
Abstract: Background: The System for Observing Play and Leisure Activities (SOPLAY) is a direct observation instrument designed to assess group physical activity and environmental contexts. The purpose of this study was to test the convergent validity of the SOPLAY using temporally matched data from an accelerometry-based activity monitor. Methods: Accelerometry-based physical activity data were obtained from 160 elementary school children from 9 after-school activity programs. SOPLAY coding was used to directly observe physical activity during these sessions. Analyses evaluated agreement between the monitored and observed physical activity behavior by comparing the percent of youth engaging in physical activity with the 2 assessments. Results: Agreement varied widely depending on the way the SOPLAY codes were interpreted. Estimates from SOPLAY were significantly higher than accelerometer PA levels when codes of walking and vigorous were used (in combination) to reflect participation in moderate to vigorous PA (MVP...
TL;DR: Gender comparisons based on both instruments indicated that boys were more active than girls and MVPA levels were higher during climbing/sliding activities and when the activity setting was supervised and equipped.
Abstract: To better understand and promote youth physical activity (PA) it is important to determine settings and characteristics that promote or influence behavior. This study evaluated the utility of a multi-method approach (accelerometers plus direct observation) to better understand youth PA at recess. A total of 100 third through fifth grade children (52 males and 48 females) wore an Actigraph accelerometer during school recess for five consecutive days in both Fall and Spring. Trained observers coded PA behaviors at the same recess periods using the System for Observing Play and Leisure Activities (SOPLAY). Overall, gender comparisons based on both instruments indicated that boys were more active than girls. MVPA levels were higher during climbing/sliding activities (40–50%) and when the activity setting was supervised and equipped (30%). Both assessments indicated that boys were more active but the contextual data from the SOPLAY indicate that differences may vary according to the environmental context.
TL;DR: Findings suggest that vigorous activity may be associated with indicators of MF in adolescents, and that resistance training exercise is associated with the increase of MF.
Abstract: The aim of this study was to examine the associations between objectively assessed physical activity (PA) and muscular fitness (MF) in adolescents, and to determine whether only resistance training exercise is associated with the increase of MF. A sample of 211 Spanish adolescents (105 girls) wore the ActiGraph monitor for 7 days. Participants also completed a fitness evaluation including three MF tests (handgrip strength, a 60-s abdominal test and a standing broad jump), a cardiorespiratory fitness assessment and anthropometric measures. A standardized MF score was computed using the three muscular tests. Adolescent participation in resistance training was self-reported. Linear regression showed that only vigorous PA was significantly (P=0.041) and positively (β=0.133) associated with MF after adjustment by gender, age, pubertal status, BMI, and cardiorespiratory fitness. Significant differences in MF were found between youth in the lowest and upper tertiles of vigorous PA. Moreover, adolescents who were involved in resistance training had significantly higher MF scores compared with youth in low and medium tertiles of vigorous PA, but no significant differences were found when compared with non-lifters from the highest tertile of vigorous PA (P=0.356). These findings suggest that vigorous activity may be associated with indicators of MF in adolescents.
TL;DR: Ready for Recess represents a possible means to increase MVPA in OWOB girls/boys, populations least likely to meet MVPA recommendations, but the effect of the intervention was not uniform across all subgroups.
Abstract: Background: The purpose of this study was to determine the effectiveness of Ready for Recess: an elementary school recess intervention targeting staff training (ST) and providing recreational equipment (EQ). Methods: Ready for Recess had 4 intervention schools: 1) EQ+ST, 2) EQ, 3) ST, and 4) control. Moderate-to-vigorous physical activity (MVPA) was assessed with accelerometers at the four schools in 257 3rd- to 6th-grade children. Random intercept models for overweight/obese (OWOB) and healthy weight (HW) for boys and girls separately, examined change in percentage of time spent in MVPA during recess across EQ+ST, EQ, and ST compared with the control from baseline to postintervention. Results: HW boys receiving EQ+ST increased MVPA by 19.4%, OWOB boys receiving ST increased MVPA by 4.5%, OWOB girls receiving EQ-ST increased MVPA by 6.0%, while HW girls receiving EQ decreased MVPA by 13.6% in comparison with the control. Conclusions: Ready for Recess represents a possible means to increase MVPA in OWOB gi...
Journal Article•
TL;DR: Differences in choices of outdoor or indoor PA, after school, explained the gender differences in seasonal activity patterns and detailed temporal profiling of the accelerometer data.
Abstract: The aim of this pilot study was to characterize seasonal variation in the moderate to vigorous physical activity (MVPA) and sedentary behavior of Portuguese school youth, and understand the influence of activity choices and settings. The participants in this study were 24 students, aged 10-13 years. Accelerometers measured daily PA over 7 consecutive days, in different seasons May – June and January – February. In summer, boys accumulated more minutes in MVPA (928 minutes/week) than girls (793 minutes/week). In winter the pattern was reversed with girls accumulating more activity than boys (736 minutes/week vs. 598 minutes/week). The repeated measures ANOVA revealed significant effects for season (F = 5.98, p = 0.023) and inschool vs. out-of-school (F = 6.53, p = 0.018). Youth were more active in the summer and activity levels were higher after school than in school. Summer season provided relevant contexts for youth physical activity accumulation. Winter season may have been a significant barrier to boy’s preferred PA context. Differences in choices of outdoor or indoor PA, after school, explained the gender differences in seasonal activity patterns.
TL;DR: The results showed that PA self-efficacy and enjoyment explained variability in structured PA sessions, and boys were more active than girls, and children varied in PA level partly due to psychosocial factors.
TL;DR: Both location and duration appear to be modifiable correlates of group physical activity level, which may serve to inform intervention efforts to promote physical activity in ASP.
Abstract: Background: Active recreation sessions taking place within after-school programs (ASP) present an opportunity for attending children to attain part of the recommended 60 minutes of daily moderate-to-vigorous physical activity (MVPA). This cross-sectional study’s purpose was to assess relationships between microlevel ASP environmental characteristics and physical activity and sedentary behavior (SED). Methods: During 161 ASP active recreation sessions, 240 children from 7 schools wore Actigraph GT1M accelerometers and were observed up to 6 times per year, over 3 years. To provide microlevel environmental data, trained observers recorded session times, location, duration, organization, equipment, and number of children and staff. Unadjusted bivariate correlations and multivariable regression analyses were used to assess the influence of microlevel environmental variables on MVPA and SED, with regression models controlling for relevant covariates. Results: Across all ASP active recreation sessions, children spent 39 ± 15% in MVPA and 16 ± 11% in SED. Session location, boy-to-girl ratio, and duration were significantly related to MVPA in the regression model. For SED, location and duration were significant influences in the model. Conclusions: Both location and duration appear to be modifiable correlates of group physical activity level, which may serve to inform intervention efforts to promote physical activity in ASP.
TL;DR: The authors evaluated the validez convergente del cuestionario PAQ-A for valorar actividad fisica (AF) in adolescentes with sobrepeso.
Abstract: Objetivo
El objetivo de este estudio fue evaluar la validez convergente del cuestionario PAQ-A para valorar actividad fisica (AF) en adolescentes con sobrepeso.
Material y metodos
Doscientos tres adolescentes (96 mujeres) con edades de entre 13 y 17 anos fueron seleccionados para este estudio. Los niveles de AF fueron obtenidos de un diario de 3 dias, una escala comparativa y el PAQ-A. Los adolescentes llevaron el acelerometro ActiGraph durante 7 dias. Los adolescentes fueron clasificados como sobrepeso a partir de los puntos de corte del indice de masa corporal para edad y genero de la International Obesity Task Force.
Resultados
Cincuenta y cuatro (33 hombres y 21 mujeres) adolescentes (27%) fueron clasificados como sobrepeso. En el grupo de adolescentes con sobrepeso, el PAQ-A mostro correlaciones moderadas con la escala comparativa (?=0,52), la AF total y AF de moderada a vigorosa del acelerometro (?=0,52 y 0,43), y la AF total y AF de moderada a vigorosa del diario (?=0,32 y 0,47). No hubo diferencias significativas entre los coeficientes de correlacion de los grupos de adolescentes con y sin sobrepeso.
Conclusion
El cuestionario PAQ-A muestra una razonable validez para valorar actividad fisica en adolescentes espanoles con sobrepeso.
TL;DR: In this article, 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 were examined by linear regression.
Abstract: 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 MV...
TL;DR: A low level of PA in Porto adolescents is a matter of concern and suggests that interventions are needed, and young adults engaged in more moderate-to-vigorous PA (MVPA) than adolescents.
Abstract: Background: The purpose of the study is to evaluate age and gender differences in objectively measured levels of physical activity (PA) in a large and diverse sample of residents from an urban area in Porto, Portugal. Methods: Participants included 822 residents, 334 males (41%), and 488 females (59%), aged 6 to 90 years. GT1M accelerometer was used to assess daily PA over 7 consecutive days, and the measurement was from October (2007) to June (2008). Results: Males were more active than females. This difference was attenuated in the 2 oldest age groups (40−59 and 60+ yrs). An accentuated declined in all PA variables occurred between the youngster group (6−11 yrs) and adolescents group (12−19 yrs). Surprisingly, young adults (20−39 yrs) engaged in more moderate-to-vigorous PA (MVPA) than adolescents. Further, females also had higher MVPA in the fourth group (40−59 yrs) compared with the second group (12−19 yrs). Males had higher compliance rates of PA guidelines than females regardless the age group consi...
TL;DR: A prediction algorithm was designed that would allow the Previous Day Physical Activity Recall (PDPAR) to be equated with temporally matched data from an accelerometer to predict accelerometer minutes of moderate to vigorous physical activity (MVPA) from PDPAR bouts.
Abstract: Background: This study was designed to develop a prediction algorithm that would allow the Previous Day Physical Activity Recall (PDPAR) to be equated with temporally matched data from an accelerometer. Methods: Participants (n = 121) from a large, school-based intervention wore a validated accelerometer and completed the PDPAR for 3 consecutive days. Physical activity estimates were obtained from PDPAR by totaling 30-minute bouts of activity coded as ≥4 METS. A regression equation was developed in a calibration sample (n = 91) to predict accelerometer minutes of moderate to vigorous physical activity (MVPA) from PDPAR bouts. The regression equation was then applied to a separate, holdout sample (n = 30) to evaluate the utility of the prediction algorithm. Results: Gender and PDPAR bouts accounted for 36.6% of the variance in accelerometer MVPA. The regression model showed that on average boys obtain 9.0 min of MVPA for each reported PDPAR bout, while girls obtain 4.8 min of MVPA per bout. When applied to...
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TL;DR: The prediction equation provides a valid and useful metric to aid in the interpretation of PDPAR results and showed good agreement with accelerometer minutes.
Abstract: In this study, school children wore a validated accelerometer and completed the Previous Day Physical Activity Recall for three consecutive days. When applied to the holdout sample, an algorithm of predicted minutes of moderate to vigorous physical activity showed good agreement with the actual accelerometer minutes, providing a valid and useful metric to help interpret results.
TL;DR: Regardless of participating in an acceptable level of MVPA, overfat children had higher resting systolic blood pressure than normal fat children and MVPA did not significantly attenuate blood pressure within a fat category.
Abstract: The purpose of this study was to determine the joint association of fatness and physical activity on resting blood pressure in children. Subjects included 157 children (age 5.5–9.5 years). Moderate-to-vigorous physical activity (MVPA, min/day), body fatness, and resting blood pressure were measured. Four categories were created by cross tabulation of high/normal levels of fatness and high/low levels of MVPA. There were significant differences in systolic blood pressure and mean arterial pressure across the fat/MVPA groups (p < .05). Regardless of participating in an acceptable level of MVPA, overfat children had higher resting systolic blood pressure than normal fat children. MVPA did not significantly attenuate blood pressure within a fat category.