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Stuart J. Fairclough, Nicola D. Ridgers and Gregory Welk

Background:

Vigorous-intensity physical activity (VPA) may confer superior health benefits for children compared to moderate-intensity physical activity (MPA), but the correlates of MPA and VPA may differ. The study purpose was to investigate associations between selected enabling, predisposing, and demographic physical activity correlates, and MPA and VPA during weekdays and at weekends.

Methods:

Data were gathered from 175 children (aged 10 to 11 years). MPA and VPA were assessed using accelerometers. Correlates were measured at child and school levels. Multilevel analyses identified correlates that significantly predicted MPA and VPA.

Results:

Gender significantly predicted weekday MPA (P < .001), and weekend MPA (P = .022) and VPA (P = .035). Weekday VPA was predicted by gender (P < .001), indices of multiple deprivation score (P < .003), BMI (P = .018), and school playground area (P = .046).

Conclusions:

Gender was the most significant correlate of MPA and VPA. Children most likely to engage in weekday VPA were boys with lower deprivation scores and BMI values, with access to larger playground areas.

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Gregory J. Welk, Jodee A. Schaben and Mack Shelley

Homeschooling is increasingly popular, but little is known about how homeschooling affects physical activity patterns or fitness levels. This study compares patterns of physical fitness, physical activity, and psychosocial correlates of physical activity in homeschooled youth and youth attending public school. Fitness levels were obtained using the PACER aerobic fitness test, physical activity levels were assessed with 3 days of accelerometry, and psychosocial correlates were assessed with the Children’s Physical Activity Correlates scale. There were no significant main effects for fitness comparisons, but significant age and gender interactions indicate that variability exists within these samples for fitness. No school type effects were evident for the physical activity measures or the psychosocial correlate measures, but trends in the data suggest the possibility of age-related interactions for the psychosocial measures. Additional research on possible differences between homeschooled youth and youth attending public school is needed to better understand these trends.

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Michelle Ihmels, Gregory J. Welk, James J. McClain and Jodee Schaben

Background:

Advances in BIA offer practical alternative approaches to assessing body composition in young adolescents and have not been studied for comparability.

Methods:

This study compared reliability and convergent validity of three field tests (2-site skinfold, Omron and Tanita BIA devices) on young adolescents. Reliability was determined using intraclass correlation coefficients, convergent validity was examined by computing correlations among the three estimates, differences in estimated body fat values were evaluated using repeated-measures ANOVA, and classification agreement was computed for achieving FITNESSGRAM ® Healthy Fitness Zone.

Results:

ICC values of all three measures exceeded .97. Correlations ranged from .74 to .81 for males and .79 to .91 for females. Classification agreement values ranged from 82.8% to 92.6%.

Conclusions:

Results suggest general agreement among the selected methods of body composition assessments in both boys and girls with the exception that percent body fat in boys by Tanita BIA is significantly lower than skinfold estimation.

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Gregory J. Welk, Joey C. Eisenmann, Jodee Schaben, Stewart G. Trost and Darren Dale

The unique physical and movement characteristics of children necessitate the development of accelerometer equations and cut points that are population specific. The purpose of this study is to develop an ecologically valid cut point for the Biotrainer Pro monitor that reflects a threshold for moderate-intensity physical activity in elementary school children. A sample of 30 children (ages 8−12) wore a Biotrainer monitor while completing a series of 7 movement tasks (calibration phase) and while participating in an organized group activity (cross-validation phase). Videotapes from each session were processed using a computerized direct-observation technique to provide a criterion measure of physical activity. Analyses involved the use of mixed-model regression and receiver operator characteristic (ROC) curves. The results indicated that a cut point of 4 counts/min provides the optimal balance between the related needs for sensitivity (accurately detecting activity) and specificity (limiting misclassification of activity as inactivity). Results with the cross-validation data demonstrated that this value yielded the best overall kappa (.58) and a high classification agreement (84%) for activity determination. The specificity of 93% demonstrates that the proposed cut point can accurately detect activity; however, the lower sensitivity value of 61% suggests that some minutes of activity might be incorrectly classified as inactivity. The cut point of 4 counts/min provides an ecologically valid cut point to capture physical activity in children using the Biotrainer Pro activity monitor.

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David Martínez-Gómez, M. Andres Calabro, Gregory J. Welk, Ascension Marcos and Oscar L. Veiga

Recess is a frequent target in school-based physical activity (PA) promotion research but there are challenges in assessing PA during this time period. The purpose of this study was to evaluate the reliability and validity of a recess PA recall (RPAR) instrument designed to assess total PA and time spent in moderate to vigorous PA (MVPA) during recess. One hundred twenty-five 7th and 8th-grade students (59 females), age 12–14 years, participated in the study. Activity levels were objectively monitored on Mondays using different activity monitors (Yamax Digiwalker, Biotrainer and ActiGraph). On Tuesdays, 2 RPAR self-reports were administered within 1-hr. Test-retest reliability showed ICC = 0.87 and 0.88 for total PA and time spent in MVPA, respectively. The RPAR was correlated against Yamax (r = .35), Biotrainer (r = .40 and 0.54) and ActiGraph (r = .42) to assess total PA during recess. The RPAR was also correlated against ActiGraph (r = .54) to assess time spent in MVPA during recess. Mean difference between the RPAR and ActiGraph to assess time spent in MVPA during recess was no significant (2.15 ± 3.67 min, p = .313). The RPAR showed an adequate reliability and a reasonable validity for assessing PA during the school recess in youth.

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Jodee A. Schaben, Gregory J. Welk, Roxane Joens-Matre and Larry Hensley

Understanding physical activity (PA) correlates in youth is challenging due to the inherent changes in activity patterns, activity preferences, and social norms that occur during the normal developmental transition from childhood into adolescence. This study examines possible age-related differences in physical activity correlates using the Children’s Physical Activity Correlates Scale (CPAC). The Children’s Physical Activity Questionnaire (PAQ) was used to measure typical levels of PA. Results indicate high school youth had lower levels of PA and lower levels on the psychosocial correlates than middle school youth. Parental influence accounted for ~ 15% of the variance in PA while the predisposing factors (perceived competence, attraction to PA) accounted for 20% and 17% of the variance for middle and high school students, respectively. CPAC has similar predictive validity across the age range. The CPAC scale offers potential to help understand factors that influence physical activity behavior during the transition from childhood into adolescence.

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Jung-Min Lee, Pedro F. Saint-Maurice, Youngwon Kim, Glenn A. Gaesser and Gregory Welk

Background:

The assessment of physical activity (PA) and energy expenditure (EE) in youth is complicated by inherent variability in growth and maturation during childhood and adolescence. This study provides descriptive summaries of the EE of a diverse range of activities in children ages 7 to 13.

Methods:

A sample of 105 7- to 13-year-old children (boys: 57%, girls: 43%, and Age: 9.9 ± 1.9) performed a series of 12 activities from a pool of 24 activities while being monitored with an indirect calorimetry system.

Results:

Across physical activities, averages of VO2 ml·kg·min-1, VO2 L·min-1, EE, and METs ranged from 3.3 to 53.7 ml·kg·min-1, from 0.15 to 3.2 L·min-1, from 0.7 to 15.9 kcal·min-1, 1.5 MET to 7.8 MET, respectively.

Conclusions:

The energy costs of the activities varied by age, sex, and BMI status reinforcing the need to consider adjustments when examining the relative intensity of PA in youth.

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Pedro F. Saint-Maurice, Gregory J. Welk, Pedro Silva, Mohammad Siahpush and Jennifer Huberty

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.

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Jack L. Groppel, In-Sik Shin, Jo Ann Thomas and Gregory J. Welk

This study explored the effects of string type and tension on various factors involved with tennis ball–racquet impact in midsized and oversized racquets. String and racquet material, racquet flexibility, and grip firmness were held constant for each test condition. The dependent variables included postimpact and preimpact ball velocity ratio, racquet head displacement, maximum ball compression, and ball contact duration. It was found that racquet size and string material have varying effects on impact. Although changes in string tension do affect the impact, it is not in a linear fashion. Various string tensions change a racquet's flexibility, thus affecting ball velocity and other factors associated with impact. The results of this study demonstrate the complexity of string and frame interaction.

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Kate A. Heelan, Bryce M. Abbey, Joseph E. Donnelly, Matthew S. Mayo and Gregory J. Welk

Background:

Walking to and from school has potential to increase daily physical activity among children.

Methods:

A Walking School Bus (WSB) intervention was implemented for 2 years in 2 schools with a third school as a control. The primary aim evaluated school-wide prevalence of walking to school by self-report 6 times (fall, winter, spring). The secondary aims compared objective physical activity levels among a subsample of research participants (intervention [INT] = 201, control [CON] =123) and between frequency of walking to school groups. INT and CON participants wore an accelerometer during 4 time periods to assess daily physical activity and were measured for body mass index (BMI) and body fat each fall and spring.

Results:

School-wide prevalence of walking to school frequently (>50% of the time each week) was 27% higher in the WSB schools than in the control school. INT obtained significantly more daily physical activity than CON (78.0 [38.9] vs 60.6 [27.7] min/d, P < .05). In addition, across all schools, frequent walkers obtained 25% more physical activity (P < .05), gained 58% less body fat (P < .05), and attenuated BMI by 50% (P < .05) compared with passive commuters.

Conclusion:

This study suggests a WSB intervention may increase frequency of walking to school and establishes a link with increased daily physical activity.