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This study evaluated factors that contribute to the increased energy cost of locomotion in youth. The subjects were 321 8-18-year-old youth, similar dispersed by age and sex. Oxygen uptake (VO[2]) was measured during rest (REE), running at 8 km x h-[1] and cycling at 16 km x h[-1], using a COSMED K4b[2] metabolic system. Developmental stage was obtained via questionnaire. Stature, body mass, and skinfolds (triceps & subscapular) were measured. Both sexes had similar absolute VO[2] (mL x min[-1]) at rest (p = 0.065) and running (p = 0.084), but the males had a higher VO[2] during cycling (p = 0.046). There were no sex differences in relative VO[2] (mL x kg[-1] x min-[1]) at rest (p = 0.083); however, the males had a higher VO[2] than the females during cycling and running (p /= 0.003). During running the relative VO[2] was related to skinfolds, fat-free mass, and resting energy expenditure (p < 0.05). Neither age nor developmental stage was a significant contributor. The results indicate that the VO[2] of locomotion is most closely associated with fat-free mass. Thus, to compare youth of varying age or pubertal developmental status, fat-free mass should be taken into consideration. [ABSTRACT FROM AUTHOR]

Objective: To determine if overweight adolescent girls are more likely to overreport physical activity compared to normal-weight girls. Methods: Participation in physical activities and perceived intensity of activities were assessed from the previous day physical activity recall (PDPAR) in 1021 girls aged 11-14 years old (37% overweight). Daily minutes of moderate to vigorous physical activity (MVPA) were measured using accelerometery. Results: Girls in the 'at-risk for overweight' and 'overweight' categories had 17.7% and 19.4% fewer minutes of MVPA per block reported on the PDPAR compared to normal-weight girls (P<0.05). Conclusions: Overweight adolescent girls tend to overreport their total amount of physical activity. [ABSTRACT FROM AUTHOR]

This qualitative descriptive study explored the understanding of physical activity from the perspectives of middle-school children (n = 12; ages 11-15 years) who participated in 15 collaborative exploratory meetings (approximately 1.5 hours/meeting) that were audiorecorded. Content analysis was completed; a pediatric nurse specialist and the participating children validated the findings. The children understood physical activity concretely, considering everything they did as physical activity based on their primary criterion of body movement. The children adeptly recalled activities and activity time duration, but struggled with categorizing the intensity of their activities. Domains of activity included home and school; social activities crossed both arenas. The study contributes to our knowledge of children's understanding of physical activity, highlighting the concreteness of the children's thinking, including their perspectives on evidence and conclusions based on their notions of evidence. Implications for nursing are discussed. Copyright © 2008 by Elsevier Inc. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine whether there were differences in vertical jump height and lower body power production gains between complex and compound training programs. A secondary purpose was to determine whether differences in gains were observed at a faster rate between complex and compound training programs. Thirty-one college-aged club volleyball players (11 men and 20 women) were assigned into either a complex training group or a compound training group based on gender and pre-training performance measures. Both groups trained twice per week for 4 weeks. Work was equated between the 2 groups. Complex training alternated between resistance and plyometric exercises on each training day; whereas, compound training consisted of resistance training on one day and plyometric training on the other. Our analyses showed significant improvements in vertical jump height in both training groups after only 3 weeks of training (P < 0.0001); vertical jump height increased by approximately 5% and 9% in the complex and compound training groups, respectively. However, neither group improved significantly better than the other, nor did either group experience faster gains in vertical leap or power output. The results of this study suggest that performing a minimum of 3 weeks of either complex or compound training is effective for improving vertical jump height and power output; thus, coaches should choose the program which best suits their training schedules. [ABSTRACT FROM AUTHOR]

PURPOSE: The primary aim was to determine the energy expenditure (EE: kcal.kg(-1).h(-1)) in terms of caloric cost and metabolic equivalents of activities commonly performed by children and adolescents. Secondary aims were to determine at what age and pubertal developmental stage values approach those of adults. METHODS: In this descriptive study, 295 volunteer youth 8-18 yr of age completed 18 common physical activities (including rest) while EE was measured continuously with a portable metabolic system. Three sets of activities were assigned in random order for each subject. Activities ranged from television viewing and video game play to running and rope skipping. Pubertal development was estimated from a self-report questionnaire. RESULTS: At rest, VO(2) and EE were highest in the youngest children and decreased with advancing age and higher pubertal stage in both genders. The age-adjusted and puberty-adjusted energy expenditure values were generally lower than the compendium MET values for sedentary and moderate activities but were more varied for high-intensity activities. However, the ratio of activity EE to REE was comparable in children and adults. CONCLUSIONS: Energy expenditure per kilogram of body mass at rest or during exercise is greater in children than adults and varies with pubertal status, thus using the definition of a MET in the compendium of physical activities without adjustment is inadequate for energy estimation in children, until a child reaches Tanner Stage 5. However, the ratio of activity EE to resting EE in children appears to be similar or slightly less than in the compendium, suggesting that the compendium MET increments used with our adjusted EE values more closely approximate the true EE of activities in children than present adult norms. [ABSTRACT FROM AUTHOR]

PURPOSE: To compare the test-retest reliability, convergent validity, and overall feasibility/ usability of activity-based (AB) and time-based (TB) approaches for obtaining self-reported moderate-to-vigorous physical activity (MVPA) from adolescents. METHODS: Adolescents (206 females and 114 males) completed two 3-d physical activity recalls using the AB and TB surveys, which contained identical lists of physical activities. The participants wore an MTI Actigraph accelerometer for the same period. RESULTS: The TB instrument took about 3 min longer to complete (P = 0.022). Overall 2-d test-retest correlations for MVPA were similar for the two surveys (r = 0.676 and 0.667), but the girls had higher reliability on the AB survey than the boys (girls: r = 0.713; boys: r = 0.568). The overall 3-d correlations for MVPA surveys and Actigraph counts varied by gender (girls: AB = 0.265 vs TB = 0.314; boys: AB = 0.340 vs TB = 0.277). Correlations for vigorous physical activity and Actigraph counts were higher for the AB than for the TB (r = 0.281 vs 0.162). As the interval between completing the surveys and the days being recalled increased, reliability and validity were lower, especially for the AB survey. CONCLUSION: For both genders, either approach is acceptable for obtaining MVPA information on a single day, but the TB approach appears to be slightly favored over the AB approach for obtaining multiple days of MVPA. A 3-d recall period appears to be too long for accurate recall of MVPA information from either instrument. For both genders, the surveys overestimated activity levels; thus, self-reports should be supplemented with objective data. [ABSTRACT FROM AUTHOR]

PURPOSE: To evaluate the tracking of physical activity levels (PA) and aerobic power (VO2max) in African-American (AA) and Caucasian (CA) youth as they age from 8 to 16 yr. METHODS: Subjects were 529 girls and 535 boys for whom data were obtained at least three times over 7 yr and a subset of 387 girls and 404 boys who participated in all years. PA levels were obtained from a survey. VO2max was predicted from a cycle ergometer test. RESULTS: Spearman correlation for VO2max for years 1-7 for AA boys and girls were similar (rho approximately 0.53). Year 1-7 correlations for VO2max for the CA boys and girls were similar (rho approximately 0.50-0.53). The year 2-7 correlations for PA were similar for the AA and CA girls but higher for the AA than the CA boys. The kappa (kappa) statistics for VO2max indicated substantial year-to-year agreement on categorization (high, moderate, and low), with AA girls having the highest agreement and AA boys the lowest. The kappa statistic for high, moderate, and low PA groupings in girls of either ethnicity was quite low, whereas the kappa statistics for the boys were somewhat better. The general estimating equation (GEE) stability coefficients for tracking of VO2max were similar between the sexes and ethnicities (P<0.0001). The GEE stability coefficient for PA was better for the boys than girls and slightly better for the AA than CA. CONCLUSION: Although aerobic power and physical activity levels decline from childhood through adolescence, aerobic power tracks better than physical activity levels. Because tracking within the cohort is only moderate, change is possible if we intervene early in these youth. [ABSTRACT FROM AUTHOR]

PURPOSE: To determine the effect of increasing the aerobic component of the school's physical activity program and improving the knowledge about weight control and blood pressure on the blood pressure and body fat of early adolescents. METHODS: The subjects were 1140 youth aged 11 to 14 years (630 females, 510 males; 64% white, 24.4% African-American, and 11.6% 'other'), who were randomly assigned by school into four treatment groups: exercise only, education only, exercise and education combined, and control group. Heights, weights, and skinfold thicknesses were measured, and body mass index (BMI) was computed kg/m(2). Blood pressure was obtained in duplicate using a random-zero mercury sphygmomanometer. Maximal oxygen uptake was predicted from a submaximal cycle ergometer test. Data were analyzed using analysis of covariance statistics, adjusting for gender, ethnicity, age, socioeconomic status, and initial baseline characteristics. RESULTS: Systolic and diastolic blood pressures increased more in the control group than in the intervention groups (p =.001). The BMI did not change significantly (p =.709), but the sum of skinfolds increased less in subjects in the exercise intervention groups than the education only or control groups (p =.0001). The small increase in (p)VO(2)max of the combined exercise and education group was significantly greater than the education only group (p =.0001). CONCLUSION: An exercise program for youth can have a positive effect on blood pressure independent of body weight loss. [ABSTRACT FROM AUTHOR]

Previous studies on the influence of a rural/urban setting on the prevalence of cardiovascular disease risk factors in children have not sufficiently controlled for socioeconomic status, race, gender, and perhaps, may not have included a representative sample of rural and urban children. This study compared the cardiovascular disease risk factors and rate of obesity of children living in rural and urban settings. It also determined the magnitude of the effect of the rural/urban setting on cardiovascular disease risk factors and obesity when controlling for race, socioeconomic status, and gender. The subjects were 2,113 third- and fourth-grade children; 962 from an urban setting and 1,141 from a rural setting. Height, weight, skinfolds, resting blood pressure, and total cholesterol levels were measured. Aerobic power (pVO2max) was estimated from cycle ergometry. Physical activity and smoking history were obtained from a questionnaire. Clustering anlyses using adjustment for sample error indicated that total cholesterol, blood pressure, smoking, and physical activity levels of rural and urban children were not different (P>0.10); however, body mass index and sum of skinfolds was greater for rural youth (P<0.004). Logistic regression indicated that rural children had a 54.7 percent increased risk of obesity (P=0.0001). This study's results indicate that, in children, a rural setting is associated with obesity, but not with the major risk factors associated with cardiovascular disease. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The purpose of the study was to determine the effect of six months of heavy resistance training (weightlifting) on the bone density of premenopausal women. EXPERIMENTAL DESIGN: A 6-month prospective design with random assignment to groups. SETTING: Measurements of bone mineral density (BMD) were obtained from the Radiology Clinic at North Carolina Memorial Hospital. Exercise sessions were completed in the Physical Education Department facilities at the University of North Carolina, Chapel Hill, NC. PARTICIPANTS: Thirty-five premenopausal women, 40-50 years of age, were randomly assigned to either a resistance training (RT) and sedentary control (CON) group. The study finished with 12 women exercising and 14 in the control group. INTERVENTION: The resistance training consisted of three days per week of high-intensity weightlifting specifically designed to place strain on the spine and hips. MEASURES: Bone density of the lumbar vertebrae, femoral neck, and distal radius, were determined prior to and at the end of the exercise program using dual energy X-ray absorptiometry (DEXA). RESULTS: Resistance-training produced strength gains: overhead press = 125%, leg press = 86%, and calf raises = 91% (p < 0.001). RT tended to increased lumbar BMD 1.03%, while the CON decreased 0.36% (p = 0.072). Both groups lost radial BMD (CON = -0.45%; RT = -1.04%). Both groups gained femoral neck BMD (CON = 1.26%; RT = 1.22%). CONCLUSIONS: These results suggest that even a short-term weight training program can either maintain or improve the BMD of the femoral neck and lumbar vertebrae in premenopausal women. [ABSTRACT FROM AUTHOR]