Pediatric Exercise Science

Published by Human Kinetics
Online ISSN: 1543-2920
Print ISSN: 0899-8493
Running speed for each 400-m segment of the 10,000 m time-trial for the normal, high, and low CHO diet. Values are reported as the means ± SEM. Error bars represent one SEM over (High CHO) or under (Low CHO) the mean values. The Normal CHO SEM is not shown for visual clarity. 
Mean running speeds in the first 400 m (0-400 m), middle 9,200 m (400-9,600 m), and final 400 m (9,600-10,000 m) segments for the normal, high, and low CHO diets. Values are means ± SEM. Segment effects are given as p values. *-Low CHO significantly slower than high CHO in the final segment. 
Mean RPE for each 2,000-m segment under each of the dietary regimens. Values are means ± SEM. For clarity, time effects are not shown. Error bars represent one SEM over (Normal CHO) or under (Low CHO) the mean values. The high CHO error bars are not shown for visual clarity. 
This study analyzed the pacing employed by young runners in 10,000 m time-trials under three dietary regimens of different carbohydrate (CHO) intakes. Nineteen boys (13-18 years-old) ate either their normal-CHO diet (56% CHO), high- (70% CHO), or low- (25% CHO) CHO diets for 48 h; the boys then performed a 10,000 m run (crossover design). The high-CHO diet led to faster final sprint (14.4 ± 2.2 km·h-1) and a better performance (50.0 ± 7.0 min) compared with the low-CHO diet (13.3 ± 2.4 km·h-1 and 51.9 ± 8.3 min, respectively, p < 0.05). However, the final sprint and performance time in the high-CHO or low-CHO diets were statistically not significantly different from the normal-CHO diet (13.8 ± 2.2 km·h-1 and 50.9 ± 7.4 min; p > 0.05). CHO oxidation rate during the constant load exercise at 65% of VO2max was elevated in high-CHO diet (1.05 ± 0.38 g·min-1) compared with low-CHO diet (0.63 ± 0.36 g·min-1). The rating of perceived exertion increased linearly throughout the trial, independently of the dietary regimen. In conclusion, the high-CHO diet induced higher CHO oxidation rates, increased running speed in the final 400 m and enhanced overall running performance, compared with low-CHO.
Adjusted mean (plus standard error) 20mSRT performance by RA Group for 9-10yr old participants 
Adjusted mean (plus standard error) 20mSRT performance by RA group for 11-12yr old participants 
The aims of this study were firstly to examine whether there was an observed relative age effect in the cardiorespiratory fitness scores of 9-10 and 11-12 year old children, and secondly whether any observed effect was maintained after controlling for somatic maturity. Cardiorespiratory fitness data from 11,404 children aged 9-10 years and 3,911 children aged 11-12 years were obtained from a large cross-sectional field-based fitness testing program. A one-way ANOVA revealed a statistically significant relative age effect (p < .01) existed in the 20mSRT scores across all the age groups. Furthermore, ANCOVA analyses identified a statistically significant relative age effect was maintained after controlling for somatic maturation (p < .05). From a public health perspective these results confirm the existence of relative age effects for the first time and consequently may hold implications for relatively younger children in the accurate assessment of their cardiorespiratory fitness scores.
Discussions of growth and motor performance of children are often set in the context of physical fitness. Although there is a clear theoretical concept or definition of fitness comprising motor coordination, the latter is not systematically considered. This study determined to what extent the variance in motor coordination might be explained by morphological and fitness characteristics. To postulate understanding of this association during childhood, 613 boys aged 7-11 years completed the morphological measurements, the Körperkoordinationstest für Kinder (KTK) and different fitness tests. The results demonstrated a substantial interrelationship among morphology, fitness and motor coordination in elementary school boys. The magnitude of explained variance and the loadings of the canonical correlation between the several constructs are strongly pronounced during childhood indicating that these constructs should be well considered given their contribution to a child's general development.
— Development of the functional (panel a) and skill z-scores (panel b) in young soccer players aligned by chronological age. Functional and skill z-scores were determined using the mean and standard deviation for the total sample. 
— Predicted functional (panel a) and skill composite scores (panel b) from the multilevel regressions (Table 2) by skeletal maturity and playing position groups, respectively. 
This study evaluates the contributions of age, growth, skeletal maturation, playing position and training to longitudinal changes in functional and skill performance in male youth soccer. Players were annually followed over 5 years (n = 83, 4.4 measurements per player). Composite scores for functional and skill domains were calculated to provide an overall estimate of performance. Players were also classified by maturity status and playing position at baseline. After testing for multicollinearity, two-level multilevel (longitudinal) regression models were obtained for functional and skill composite scores. The scores improved with age and training. Body mass was an additional predictor in both models [functional (late maturing): 13.48 + 1.05 × centered on chronological age (CA)-0.01 × centered CA2-0.19 × fat mass (FM) + 0.004 × annual volume training-1.04 × dribbling speed; skills (defenders): 7.62 + 0.62 × centered CA-0.06 × centered CA2 + 0.04 × fat-free mass-0.03 x FM + 0.005 × annual volume training-0.19 × repeated-sprint ability + 0.02 × aerobic endurance]. Skeletal maturity status was a significant predictor of functional capacities and playing position of skill performance. Sound accuracy of each multilevel model was demonstrated on an independent cross-sectional sample (n = 52).
Follow-Up Status of the Shortest and Tallest and of the Least and Most Mature Youth Soccer Players Two Years After Initial Observations 
The purpose of the study was to compare the anthropometric, functional and sport-specific skill characteristics and goal orientations of male youth soccer players at the extremes of height and skeletal maturity in two competitive age groups, 11-12 and 13-14 years. The shortest and tallest players, and least and most skeletally mature players (n = 8 per group) within each age group were compared on chronological age; skeletal age (Fels method); pubertal status (pubic hair); size, proportions and adiposity; four functional capacities; four soccer-specific skills; and task and ego orientation. The tallest players were older chronologically, advanced in maturity (skeletal, pubertal) and heavier, and had relatively longer legs than the shortest players in each age group. At 11-12 years, the most mature players were chronologically younger but advanced in pubertal status, taller and heavier with more adiposity. At 13-14 years, the most mature players were taller, heavier and advanced in pubertal status but did not differ in chronological age compared with the least mature players. Players at the extremes of height and skeletal maturity differed in speed and power (tallest > shortest; most mature > least mature), but did not differ consistently in aerobic endurance and in soccer-specific skills. Results suggested that size and strength discrepancies among youth players were not a major advantage or disadvantage to performance. By inference, coaches and sport administrators may need to provide opportunities for or perhaps protect smaller, skilled players during the adolescent years.
Frequency and Percentages of Swimmers in the Different Tanner Maturation Stages 
Mean ± SD Values of the Swimmers' Anthropometric, Sexual Maturation Status and Training Frequency Characteristics 
Mean ± SD Values of the Parameters Related to Velocity, Stroke Rate, Stroke Length, Arms Synchronization, Entry and Catch, Pull, Push and Recovery Phases, Propulsive Phases and Nonpropulsive Phases, According to Genders and Maturation 
Our aim was to characterize front crawl swimming performed at very high intensity by young practitioners. 114 swimmers 11-13 years old performed 25 m front crawl swimming at 50 m pace. Two underwater cameras was used to assess general biomechanical parameters (velocity, stroke rate, stroke length and stroke index) and interarm coordination (Index of Coordination), being also identified each front crawl stroke phase. Swimmers presented lower values in all biomechanical parameters than data presented in studies conducted with older swimmers, having the postpubertal group closest values to adult literature due to their superior anthropometric and maturational characteristics. Boys showed higher velocity and stroke index than girls (as reported for elite swimmers), but higher stroke rate than girls (in opposition to what is described for adults). In addition, when considering the total sample, a higher relationship was observed between velocity and stroke length (than with stroke rate), indicating that improving stroke length is a fundamental skill to develop in these ages. Furthermore, only catch-up coordination mode was adopted (being evident a lag time between propulsion of the arms), and the catch and the pull phases presented the highest and smallest durations, respectively.
The relationship between 20mSRT performance and peak HR in 208 schoolchildren age 11-16 years. 
The aim of this study was to determine if maximal effort, evidenced by peak HR was attained during the 20m shuttle-run test in a naturalistic setting. Shuttle-run test performance and peak HR were measured in 208 volunteers (11-16 years). Peak HR was 196 (95% confidence interval (C.I.) 194-198 bpm). The relationship between test performance and peak HR was assessed by regression. There was a weak, but statistically significant relationship between test performance and peak HR (R2 = .029, p = .029) but with such a low coefficient of determination (less than 5% criterion), poor performances were not associated with low peak HR values or underestimation of maximal performance. Peak HR values (196 bpm) were higher than cited criterion values (185 bpm) for maximal effort in laboratory studies. In a naturalistic setting, the 20m shuttle-run test elicits a maximal effort in most children.
— Time of day effect in oral temperature. Mean values (± SE) are shown (n = 20).* Significantly different from 18:00 h. *: p < .05; ***: p < .001.  
— Time of day effect in a) grip strength, b) 5-Jump test, c) Squat jump test, d, e, and f Wingate performances: d) P peak , e) P mean and f) Wd. Mean values (± SE) are shown (n = 20).* Significant difference from 08:00 h. *: p < .05; **: p < .01; ***: p < .001.  
The purpose of this study was to examine the time-of-day effects on short-term performances in boys. In a balanced and randomized study design, 20 boys performed four anaerobic tests of strength and power (grip strength, Squat-Jump, Five-jump and cycle Wingate tests) at 08:00, 14:00 and 18:00 hr on separate days. The results showed a time-of-day effect on oral temperature. Analysis of variance revealed a significant time-of-day effect for short-term performances for strength, cycle, and jump tests. The post hoc analysis revealed that performances improved significantly from morning to afternoon but no significant differences were noticed between 14:00 and 18:00 hr. The differences between the morning and the afternoon (the highest value measured either at 14:00 or at 18:00 hr) reached 5.9% for grip strength, 3.5% for the squat jump test, 5% for the five jump test, and 5.5% for P(peak) and 6% for P(mean) during the Wingate test. A significant positive correlation was found between temperature and short-term performances. In conclusion, a time-of-day effect in the child's maximal short-term exercise performances exists in relation with core temperature. Such variations would have pronounced effects when expressed in training programs and competitions.
— Mean and SD of oral temperature (n = 24) in the morning and the evening tests at T0 and T1 for all groups. *** Significant differences between the time points at the level p < .001.  
Anthropometric parameters (mean ± SD) of the MTG, ETG and CG recorded in T0 and T1.
Performances (mean ± SD) on Vertical Jump Tests (SJ (cm) and CMJ (cm)) and MVC (N) Recorded at the Two Times of Day in T0 and T1.
The aim of this study was to assess the effect of time-of-day-specific training on the diurnal variations of short-term performances in boys. Twenty-four boys were randomized into a morning-training-group (07:00-08:00h; MTG), an evening-training-group (17:00-18:00h; ETG) and a control-group (CG). They performed four tests of strength and power (unilateral isometric maximal voluntary contraction of the knee extensor muscles, Squat-Jump, Counter-Movement-Jump and Wingate tests) at 07:00 and 17:00h just before (T0) and after 6 weeks of resistance training (T1). In T0, the results revealed that short-term performances improved and oral temperature increased significantly from morning to afternoon (amplitudes between 2.36 and 17.5% for both oral temperature and performances) for all subjects. In T1, the diurnal variations of performances were blunted in the MTG and persisted in the ETG and CG. Moreover, the training program increase muscle strength and power especially after training in the morning hours and the magnitude of gains was greater at the time-of-day-specific training than at other times. In conclusion, these results suggest that time-of-day-specific training increases the child's anaerobic performances specifically at this time-of-day. Moreover, the improvement of these performances was greater after morning than evening training.
Descriptive Characteristics of Normal-Weight and Overweight/Obese Boys and Girls (M ± SD) Boys Girls
Associations Between Boys' and Girls' Physical Activity, Physical Self-Perceptions and Normal Weight Status 
The study examined associations between children’s weight status, physical activity intensity, and physical self-perceptions. Data were obtained from 409 children (224 girls) aged 10–11 years categorized as normal-weight or overweight/obese. Physical activity was assessed using accelerometry, and children completed the Physical Self-Perception Profile. After controlling for the effects of age, maturation, and socioeconomic status vigorous physical activity was significantly associated with normal-weight status among boys (OR = 1.13, p = .01) and girls (OR = 1.13, p = .03). Normal-weight status was significantly associated with perceived Physical Condition (Boys: OR = 5.05, p = .008; Girls: OR = 2.50, p = .08), and Body Attractiveness (Boys: OR = 4.44, p = .007; Girls: OR = 2.56, p = .02). Weight status of 10–11 year old children was significantly associated with time spent in vigorous physical activity and self-perceptions of Body Attractiveness and Physical Condition. <br /
— Distribution of average pedometer steps/day among boys (a) and girls (b). 
The age-related decline in physical activity during adolescence is well documented; however, little is known about differences in physical activity among early, average, and late maturing adolescents. The purpose of this study was to examine the relationship between maturity status and physical activity among 167 adolescents who were 13-14 years old. The maturity offset was derived and biological maturity groups were created. Habitual physical activity was determined with a pedometer over a 7-day period. No significant maturity-group differences were found for physical activity. The results of this study did not demonstrate significant differences in physical activity as determined by a pedometer among early, average, and late maturing 13- to 14-year-olds.
The purpose of this study was to examine relationships between aerobic fitness (AF), fatness, and coronary-heart-disease (CHD) risk factors in 12- to 13-year-olds. The data were obtained from 208 schoolchildren (100 boys; 108 girls) ages 12.9 +/- 0.3 years. Measurements included AF, indices of obesity, blood pressure, blood lipids and lipoproteins, fibrinogen, homocysteine, and C-reactive protein. An inverse relationship was found between AF and fatness (p <or= .05). Fatness was related to a greater number of CHD risk factors than fitness was (p <or= .05). Further analysis revealed fatness to be an independent predictor of triglyceride and blood-pressure levels (p <or= .05). Our findings indicate that, for young people, fatness rather than fitness is independently related to CHD risk factors.
This study aimed to identify characteristics of match performance and physical ability that discriminate between elite and sub-elite under-14 soccer players. Players were assessed for closed performance and movement, physiological responses and technical actions during matches. Elite players covered more total m·min-1 (115.7 ± 6.6 cf. 105.4 ± 7.7 m·min-1) and high intensity m·min-1 (elite = 14.5 ± 2.3 cf. 11.5 ± 3.7 m·min-1) compared to sub-elite players. Elite players also attempted more successful (0.41 ± 0.11 cf. 0.18 ± 0.02) and unsuccessful ball retentions·min-1 (0.14 ± 0.04 cf. 0.06 ± 0.02) compared to sub-elite players. Elite players were faster over 10 m (1.9 ± 0.1 cf. 2.3 ± 0.2 s) and faster dribblers (16.4 ± 1.4 cf. 18.2 ± 1.1 s) compared to sub-elite players. Speed (10 m) and successful ball retention·min-1 contributed to a predictive model, explaining 96.8% of the between-group variance. The analysis of match performance provides a more thorough understanding of the factors underlying talent among youth soccer players.
— Schematic of the p VO  ̇ 2 response in a representative participant to a step change in exercise work rate, on each test occasion. The single exponential fit defining the predicted O 2 cost of exercise is extended to demonstrate the magnitude of the p VO  ̇ 2 slow component. The phase 1 portion of the p VO  ̇ 2 response is removed for clarity. 
— Mean temporal profile of the gain of the p VO  ̇ 2 response to heavy-intensity exer- cise on each test occasion. The phase 1 portion of the p VO  ̇ 2 response is removed for clarity. 
p ˙ VO 2 Kinetic Response Parameters on Two Separate Visits Over a 2-Year Interval Test Occasion 1 Test Occasion 2 P value (ω 2 )
This study examined longitudinal changes in the pulmonary oxygen uptake (pVO(2)) kinetic response to heavy-intensity exercise in 14-16 yr old boys. Fourteen healthy boys (age 14.1 +/- 0.2 yr) completed exercise testing on two occasions with a 2-yr interval. Each participant completed a minimum of three 'step' exercise transitions, from unloaded pedalling to a constant work rate corresponding to 40% of the difference between the pVO(2) at the gas exchange threshold and peak pVO(2) (40% Delta). Over the 2-yr period a significant increase in the phase II time constant (25 +/- 5 vs. 30 +/- 5 s; p = .002, omega(2) = 0.34), the relative amplitude of the pVO(2) slow component (9 +/- 5 vs. 13 +/- 4%; p = .036, omega(2) = 0.14) and the pVO(2) gain at end-exercise (11.6 +/- 0.6 vs. 12.4 +/- 0.7 mL x min(-1) x W(-1); p < .001, omega(2) = 0.42) were observed. These data indicate that the control of oxidative phosphorylation in response to heavy-intensity cycling exercise is age-dependent in teenage boys.
This study examined the efficacy of peak power estimation equations in children using force platform data and determined whether allometric modelling offers a sounder alternative to estimating peak power in pediatric samples. Ninety one boys and girls, aged 12-16 years, performed three counter movement jumps (CMJ) on a force platform. Estimated peak power (PPest) was determined using the Harman et al, Sayers-SJ, Sayers-CMJ and Canavan and Vescovi equations. All four equations were associated with actual peak power (r = .893 - .909, all P<.01). There were significant differences between PPest using the Harman et al., Sayers SJ and Sayers CMJ equations (P<.05) and actual peak power (PPactual). ANCOVA also indicated sex and age effect for PPactual (P <.01). Following a random two-thirds to one-third split of participants, an additive linear model (P = .0001) predicted PPactual (adjusted R2 = .866) from body mass and CMJ height in the two-thirds split (n=60). An allometric model using CMJ height, body mass and age was then developed with this sample which predicted 88.8% of the variance in PPactual (P < .0001, adjusted R2 = .888). The regression equations were cross-validated using the one-third split sample (n=31) evidencing a significant positive relationship (r = .910, P = .001) and no significant difference (P = .151) between PPactual and PPest using this equation. The allometric and linear models determined from this study provide accurate models to estimate peak power in children.
The study aimed to establish pedometer step cut points in relation to weight status among 2,071 5-16 year old Australians. Height, weight and waist circumference were measured, and participants wore a pedometer for seven days. Pedometer values were taken as the average number of steps per day and weighted according to the ratio of weekdays to weekends. Receiver operating characteristic (ROC) curves were used to identify the optimal pedometer counts to predict overweight. Analysis of covariance (ANCOVA) was used to compare anthropometric variables across pedometer step quintiles. The ROC model for older females was nonsignificant. Optimal cut points were 12,000 for younger males, 11,000 for older males and 10,000 for younger females. These were largely confirmed by ANCOVA. The cut points were lower than previously reported for equivalent age groups. Cultural and environmental differences may necessitate population-specific guidelines to be established.
The aims of this study were (1) to determine minutes of moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) accrued in youth sport football (also internationally referred to as soccer), and the contribution towards daily weekend MVPA and VPA for males aged 9 to 16 years, and (2) to investigate variability in these outcomes related to age and playing position. One hundred and nine male grassroots footballers (Mean age = 11.98 ± 1.75 years) wore a GT3X accelerometer for 7 days. Weekend youth sport football participation and playing position were recorded. Youth sport football MVPA (M = 51.51 ± 17.99) and VPA (M = 27.78 ± 14.55) contributed 60.27% and 70.68% towards daily weekend MVPA and VPA, respectively. Overall, 36.70% of participants accumulated ≥ 60 minutes MVPA and 69.70% accrued ≥ 20 minutes of VPA during youth sport. For participants aged 13 to16 years, youth sport football MVPA and VPA were significantly higher, and contributed a greater amount towards daily weekend MVPA and VPA than for participants aged 9 to 12 years (p = <.01). Youth sport football is an important source of MVPA and VPA at the weekend for male youth, and particularly for adolescents. Participation may offer opportunity for weekend engagement in VPA towards health enhancing levels.
Age, School-Day Steps and Proportion Who Undertook Active Transport (AT) on Previous Day by Year and Sex
School-Day and Weekend Steps According to Mode of Traveling To and From School: Walking Versus Nonactive Transport (Non-AT)
Percentage of Children Who Achieved Pedometer Cut-offs by Categorization of Whether Children Traveled To and From School by Walking Versus Nonactive Transport (Non-AT)
Objective measurement of daily steps was used to assess whether children (n = 2,076) in Years 1, 5 and 10 who reported walking to or from school were more active and more likely to reach recommended step targets than those who were driven or took public transport to school. Walking to school was associated with higher school-day steps in older children (16,238 vs 15,275 for Year 5 male p < .05, 13,521 vs 12,502 for Year 5 female p < .01, 12,109 vs 11,373 for Year 10 female p < .05). The proportion of children who met recommended step thresholds was higher in those who walked to school compared with those who took motorized transport, and this was significant for Year 5 females (71.7% vs 54.5%, p < .01). This study suggests that walking to school for older children has potential to contribute significantly to daily activity levels and increases the likelihood of attaining recommended step targets. These data should encourage public policy and those concerned with the built environment to provide and support opportunities for walking to school.
The aims were to develop and validate a VO(2peak) prediction equation from a treadmill running test in active male adolescents. Eighty-eight athletes (12-18 yrs.) performed a maximal exercise test on a treadmill to assess the actual VO2peak and a 20m Shuttle-Run-Test (20mST). A step-wise linear regression analysis was used and the following equation for estimation of VO(2peak) (mL·kg⁻¹·min⁻¹) = 35.477 + 1.832 × duration in min - 0.010 × duration × body mass in kg was developed. The cross-validation statistics were: R = .54, CE = 0.1 mL·kg⁻¹min⁻¹, SEE = 2.5 mL·kg⁻¹·min⁻¹ (4.6%), and TE = 2.6 mL·kg⁻¹·min⁻¹ (4.9%). The cross-validation values (CE, SEE, and TE) were lower compared with those of previously published equations in adolescents that estimated VO(2peak) using anthropometric data, performance in 20mST, and energy cost at submaximal speeds.
The aim of this article was to assess the oxygen-uptake efficiency slope (OUES) throughout the age span of 7 to 18 years. One hundred fourteen healthy children (58 boys and 56 girls) exercised on a treadmill by means of a modified Balke protocol. The OUES grew in a nonlinear pattern with age, and it appeared to be significantly higher in boys than in girls. There was a very strong correlation between OUES and VO2peak (r = .92), and there was a small difference between the values of OUES calculated for different exercise intensities. Stepwise-regression analysis outlined body surface area (BSA) and sex as main determinants of OUES. OUES is an objective measure of exercise capacity that does not require a maximal effort but is considerably dependent on anthropometric variables and necessitates the generation of appropriate reference values.
The aim of this study was to investigate the relationship between youth physical activity and family socioeconomic status (FSES) over 28 years. As a part of the Finnish Adolescent Health and Lifestyle Survey a random sample of 12-, 15- and 18-year-old boys and girls participated in a nation-wide survey by answering questions every second year, from 1977 to 2005, on, among other things, leisure time physical activity and sport participation. Father's education represented FSES. The results showed that there were no significant or only small differences between the high and low FSES groups in unorganised physical activity during the study period. Participation in physical activities organized by the school was not associated with FSES. Participation in youth sport organized by sport clubs was strongly associated with FSES in both sexes. The young people in the high FSES groups participated more than those in the low FSES groups. It was concluded that considerable inequality exists in youth sport participation, that this inequality has been growing during the last decade, and that it is bigger among girls than among boys.
In 1989 we knew that exercise, including regular prescribed physical activity, could be safely performed and described some of the physiological responses to exercise in patients with cystic fibrosis (CF). Also in 1989, the genetic defect causing cystic fibrosis (CF) was identified leading to improvements in treatment that greatly extended the life span for these patients. Increased understanding of the factors limiting exercise capacity and of the important role of regular exercise in slowing the progression of CF and in modulating some of the effects of the genetic defect on airway function has led to the consensus that regular exercise should be part of the standard of care for this disease.
The article presents the current performance capacity in 11-15 year old Dutch adolescents who participated in an incremental cycle test (n = 509) and or in a shuttle run test (N = 1,198). Cycle test results increased significantly with age in both genders, also after normalization to body weight. Shuttle run test results increased significantly with age only in boys. Compared with previous data, the absolute performance capacity in the cycle tests was comparable to data from 15 years ago, whereas the performance capacity normalized to kg body weight and the shuttle run test results seem to be fairly lower compared with the former data.
— Schematic of the P i /PCr response in muscle with a high (continuous lines) and low (broken lines) oxidative capacity (A). The intracellular thresholds for muscle P i /PCr (ο) and pH (@BULLET) are shown in B for a 9 year old boy during incremental quadriceps exercise.  
Magnetic resonance imaging scans of an adults (A) and child's (B) calf muscle. Assuming an 8 cm surface coil was used to interrogate the calf muscle for metabolic changes using 31 P-MRS (43), the sensitivity of the coil to detect 31 P changes is shown by the white contours. It is clear that for the adult calf muscle, the gastrocnemius represents a disproportionately greater volume of the 31 P-MRS signal when compared with the child.
(31)phosphorous-magnetic resonance spectroscopy ((31)P-MRS) has become an extremely valuable technique to investigate changes in muscle metabolism noninvasively and in vivo. The purpose of this article is to critically review how (31)P-MRS has contributed to current understanding of muscle metabolic function in healthy children and adolescents. In addition, an overview of the basic principles of (31)P-MRS and its application to the study of muscle metabolism is provided and discussed in relation to child-specific methodological concerns when using this technique.
— Overall 800 m performance time (s) for field-based exercise trials (Trials 1–4). Values are reported as mean ± SEM * Trials 2 and 3 were significantly faster than Trial 1 ( p < .017) 
— Split times (s) for each 200 m distance, across field-based exercise trials (Trials 1–4). Values are reported as mean ± SEM * Average split time for 200 m was significantly faster than succeeding distances (400-, 600-, & 800 m), and average split time for 800 m was significantly faster than both 400 m and 600 m, for Trials 1–3 (all p < .008). # Average split time for 200 m was significantly faster than succeeding distances (400-, 600-, & 800 m), and average split time for 800 m was significantly faster than 400 m, for Trials 3 and 4 (all p < .017). † Average split times for Trial 3 were significantly faster than for both Trial 1 and Trial 4 ( p < .017). 
— Heart rate (b·min -1 ) during each 200 m distance, across field-based exercise trials (Trials 1–4). Values are reported as mean ± SEM * Average heart rate for 200 m was significantly lower than for succeeding distances (400-, 600-, & 800 m), for Trials 1–3 (all p < .001). # Average heart rate for 200 m was significantly lower than for succeeding distances (400-, 600-, & 800 m), for Trials 3 and 4 (all p < .001). 
— Rating of perceived exertion (RPE; E-P scale) during each 200 m distance, across field-based exercise trials (Trials 1–4). Values are reported as mean ± SEM * Average RPE for 200 m was significantly lower than for succeeding distances (400-, 600-, & 800 m), average RPE for 400 m was significantly lower than 600 m and 800 m, and average RPE for 600 m was significantly lower than 800 m, for Trials 1–3 (all p < .008). # Average RPE for 200 m was significantly lower than for succeeding distances (400-, 600-, & 800 m), average RPE for 400 m was significantly lower than 600 m and 800 m, and average RPE for 600 m was significantly lower than 800 m, for Trials 3–4 (all p < .001) 
Prior experience of fatiguing tasks is considered essential to establishing an optimal pacing strategy. This study examined the pacing behavior of inexperienced children during self-paced, 800 m running, both individually and within a competitive environment. Thirteen children (aged 9-11 y) completed a graded-exercise test to volitional exhaustion on a treadmill (laboratory trial), followed by three self-paced, individual 800 m time-trials (Trials 1-3) and one self-paced, competitive 800 m time-trial (Trial 4) on an outdoor athletics track. Ratings of perceived exertion (RPE) and heart rate (HR) were measured throughout all trials. Overall performance time improved from Trial 1-3 (250.1 ± 50.4 s & 242.4 ± 51.5 s, respectively, p < .017). The difference in overall performance time between Trials 3 and 4 (260.5 ± 54.2 s) was approaching significance (p = .06). The pacing strategy employed from the outset was consistent across all trials. These findings dispute the notion that an optimal pacing strategy is learned with exercise experience or training.
Schematic of the study design. 
Mean minutes/day spent in diary recorded leisure time activities plotted against the respective time indications in the questionnaire The range of minutes covered by the time categories of the questionnaire (x-axis) is shadowed in gray. Results are shown for sedentary and active behavior and stratified by weekday and weekend. 
a. Comparison of Parent's Reported Sedentary Behavior With Accelerometer-Based SA 
Reliability of Questionnaire Reported Duration of Leisure Time Activities Two and Six Months Later 
Accurately measuring children's physical activity and their sedentary behavior is challenging. The present study compared 189 parental responses to a questionnaire surveying physical activity and sedentary behavior of children aged 6-14 years, to accelerometer outputs and time activity diaries for the same group. Responses were analyzed taking age, sex and maternal education into account. Correlation coefficients between questionnaire reports and accelerometer-based physical activity across all age groups were acceptable (up to r = .55). Yet, adjustment for age markedly attenuated these associations, suggesting concomitant influences of biological and behavioral processes linked to age. The comparisons of general time indications in the questionnaire with 24h-diary records suggested that parents tended to under- and over-report single activities, possibly due to social desirability. We conclude that physical activity questionnaires need to be designed for specific age groups and be administered in combination with objective measurements.
In this study, daily step counts were recorded for 4 consecutive days in 129 four- and five-year-old children. To compare daily Yamax Digiwalker step counts with minutes of engagement in moderate to vigorous physical activity (MVPA), concurrent accelerometer data were collected in a random subsample (n = 76). The average daily step count was 9,980 (+/- 2,605). Step counts and MVPA minutes were strongly correlated (r = .73, p < .001). The daily step count of 13,874, equating to 1-hr MVPA engagement, was reached by 8% of the children. Daily step counts in preschool children give valid information on physical activity levels-daily step counts in preschoolers are low.
This study examines the association between objectively-measured physical activity (PA) intensities and sedentary behavior (SED) in a cohort of 532 children aged 8-10 y. PA and SED were assessed by accelerometer over 7-days. Television and computer/video-game use were self-reported. Associations between PA intensities and SED variables were assessed by Spearman correlations and adjusted multiple linear regression. Higher mean daily moderate-to-vigorous and vigorous PA (MVPA, VPA) were negatively associated with mean daily SED (r = -0.47 and -0.37; p < .001), and positively associated with mean daily total PA (r = .58 and 0.46; p < .001). MVPA was also positively associated with light PA (LPA; r = .26, p < .001). MVPA and VPA were not significantly associated with TV, computer/video or total screen time; accelerometer SED was only weakly associated with specific SED behaviors. On average, for each additional 10 min daily MVPA, children accumulated >14 min less SED, and for each additional 5 min VPA, 11 min less SED. Thus, over the course of a week, higher mean daily MVPA may displace SED time and is associated with higher total PA over and above the additional MVPA, due to concomitant higher levels of LPA. Public health strategies should target both MVPA and SED to improve overall PA and health in children.
This is a validation study of the RT3 accelerometer for measuring physical activities of children in simulated free-living conditions. Twenty-five children age 12-14 years completed indoor testing, and 18 of them completed outdoor testing. Activity counts from the RT3 accelerometer estimated activity energy expenditure (AEE) and the Cosmed K4b2 analyzer measured oxygen uptake. Correlations were found between activity counts and metabolic cost (r = .95, p < .001), metabolic cost and RT3 estimated AEE (r = .96, p < .001) in the indoor test, activity counts and RT3 estimated AEE (r = .97, p < .001) in the outdoor test, and activity counts and metabolic cost when all activities were combined (r = .77, p < .001). Results indicate that the RT3 accelerometer might be used to provide acceptable estimates of free-living physical activity in children.
Accelerometry is frequently used to assess physical activity in children. The number of articles in this area has increased dramatically in the last 10 years. The aim of this article is to provide a contemporary overview of accelerometry research in children. Specifically, the review addresses the choice of monitor, choice of epoch, when and for how long activity should be measured, the lack of consensus over how to define a complete day of activity data, issues of compliance, methods for the calibration of activity output, and the richness of data available from accelerometry.
The aim of this study was to assess the convergent validity of a new piezoelectric pedometer and an omnidirectional accelerometer for assessing children's time spent in moderate to vigorous physical activity (MVPA).A total of 114 children (51 boys, 63 girls) aged 5-11 years wore a sealed NL-1000 piezoelectric pedometer (New Lifestyles Inc, Lee's Summit, MO) and an Actical accelerometer (Mini Mitter, Bend, OR) over one school day. The NL-1000 pedometers were randomized to one of two manual intensity thresholds used to define MVPA (1): Level 3 = 2.9 metabolic equivalent test (MET) and (2) Level 4 = 3.6 MET. Compared with the Actical, the NL-1000 underestimated the time spent in MVPA by 37% and 45% at intensity levels 3 and 4, respectively. In addition, the 95% limits of agreement were wide at both intensity levels (level 3 = -144%, 70%; level 4 = -135%, 45%), indicating a low level of precision.
This study examined the validity of commonly used regression equations for the Actigraph and Actical accelerometers in predicting energy expenditure (EE) in children and adolescents. Sixty healthy (8-16 yrs) participants completed four treadmill (TM) and five self-paced activities of daily living (ADL). Four Actigraph (AG) and three Actical (AC) regression equations were used to estimate EE. Bias (±95% CI) and root mean squared errors were used to assess the validity of the regression equations compared with indirect calorimetry. For children, the Freedson (AG) model accurately predicted EE for all activities combined and the Treuth (AG) model accurately predicted EE for TM activities. For adolescents, the Freedson model accurately predicted EE for TM activities and the Treuth model accurately predicted EE for all activities and for TM activities. No other equation accurately estimated EE. The percent agreement for the AG and AC equations were better for light and vigorous compared with moderate intensity activities. The Trost (AG) equation most accurately classified all activity intensity categories. Overall, equations yield inconsistent point estimates of EE.
Actigraph accelerometers are hypothesized to be valid measurements for assessing children's sedentary time. However, there is considerable variation in accelerometer cut-points used. Therefore, we compared the most common accelerometer sedentary cut-points of children performing sedentary behaviors. Actigraph Actitrainer uniaxial accelerometers were used to measure children's activity intensity (29 children, 5-11 years old) during different activities, namely playing computer games, nonelectronic sedentary games, watching television and playing outdoors. A structured protocol was the criterion for assessing the validity of four common cut-points (100, 300, 800, 1100 counts/minute). The median counts during all sedentary behaviors were below the lowest comparison cut-point of 100 cpm. The 75th percentile values for the sedentary behaviors were always below the cut-point of 300 cpm. Our results suggest that the cut-point of <100 cpm is the most appropriate.
Establishing and maintaining healthy physical activity (PA) levels is important throughout life. The purpose of this study was to determine the extent of PA tracking between ages 3 and 7 y. Objective measures of PA (RT3, triaxial accelerometer) were collected every 4 mo from ages 3 to 7; data from 234 children with PA measures available during each year of age were analyzed. Mean PA (total, moderate/vigorous (MV), and inactivity(IA)) was calculated for each year of age and adjusted for wear time. Correlations with age 3 PA were moderate at age 4 (r=0.42-0.45) but declined by age 7 (r=0.19-0.25). After classification into sex-specific tertiles of PA at age 3, boys in the High age 3 MVPA tertile maintained significantly higher PA at all subsequent ages, while girls in the High age 3 MVPA tertile were not significantly higher at age 6 and 7. Boys and girls in the High age 3 IA tertile had significantly higher IA at multiple subsequent years of age (P<0.05 at ages 5 and 6). In conclusion, boys who were relatively more active at age 3 remained more active for several subsequent years. These findings highlight early childhood differences in physical activity patterns between boys and girls.
This study sought to assess criterion validity of the Actical monitor step-count function in children via ankle and waist placement, compared with observed video recordings. Children attending a summer program (12 boys, 7 girls, mean age = 9.6yrs, range 7-11yrs) wore two synchronized Acticals, attached at the ankle (AA) and waist (AW). Children performed treadmill walking at varying speeds, and two research assistants counted steps using observed video recordings (OVR). Results showed high correlations for AW-OVR (r = .927, p < .001) and AA-OVR (r = .854, p < .001), but AW and AA were significantly lower than OVR (t > 11.2, p < .001). AW provided better step estimates than AA for step rates above 130 steps per minute. In contrast, AA was superior to AW for slow walking, and measured more steps during the (nontreadmill) program time. Overall, the Actical monitor showed good evidence of validity as a measure of steps in children for population-based studies.
Panel A: difference between self-reported and accelerometer MVPA in boys, girls, and for the total sample (youth 15 years of age).
Descriptive Characteristics of Subjects (n = 2761)
— Panel A: difference between self-reported and measured MVPA in youth 12, 15, and 19 years of age. Panel B:  
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.
The objectives of this study were to explore whether triaxial is more accurate than uniaxial accelerometry and whether shorter sampling periods (epochs) are more accurate than longer epochs. Physical activity data from uniaxial and triaxial (RT3) devices were collected in 1-s epochs from 31 preschool children (15 males, 16 females, 4.4 ± 0.8 yrs) who were videoed while they engaged in 1-hr of free-play. Video data were coded using the Children's Activity Rating Scale (CARS). A significant difference (p < .001) in the number of minutes classified as moderate to vigorous physical activity (MVPA) was found between the RT3 and the CARS (p < .002) using the cut point of relaxed walk. No significant difference was found between the GT1M and the CARS or between the RT3 and the CARS using the cut point for light jog. Shorter epochs resulted in significantly greater overestimation of MVPA, with the bias increasing from 0.7 mins at 15-s to 3.2 mins at 60-s epochs for the GT1M and 0 mins to 1.7 mins for the RT3. Results suggest that there was no advantage of a triaxial accelerometer over a uniaxial model. Shorter epochs result in significantly higher number of minutes of MVPA with smaller bias relative to direct observation.
The purpose of this study was to determine the minimum number of days of accelerometry required to estimate accurately MVPA and total PA in 3- to 5-year-old children. The study examined these metrics for all days, weekdays, and in-school activities. Study participants were 204 children attending 22 preschools who wore accelerometers for at least 6 hr per day for up to 12 days during most waking hours. The primary analysis considered the intraclass correlation coefficient (ICC) for each metric to estimate the number of days required to attain a specified reliability. The ICC estimates are 0.81 for MVPA-all days, 0.78 for total PA-all days, 0.83 for MVPA weekdays, 0.80 for total PA-weekdays, 0.81 for in-school MVPA, and 0.84 for in-school total PA. We recommend a full seven days of measurement whenever possible, but researchers can achieve acceptable reliability with fewer days, as indicated by the Spearman-Brown prophecy: 3-4 days for any weekday measure and 5-6 days for the all-days measures.
This study examined the potential relationship between participation in physical activity (PA) assessed by triaxial accelerometry and physical fitness testing, including health-related and skill-related parameters of fitness, in 136 Japanese preschoolers (65 girls and 71 boys, 5.5 ± 0.6 years). In partial correlation analyses, grip strength and 20m shuttle run test were positively correlated with time spent in physical activity ratio (PAR) ≥ 4. Better scores on standing long jump distance and jump over and crawl under tests were associated with lower sedentary time and greater moderate-to-vigorous PA time and PAR ≥ 4 time, and increased physical activity level. Moreover, 25m run speed was positively correlated with time spent in PAR ≥ 4 and locomotive activity. These findings suggest that development of both health-related (muscle strength and aerobic fitness) and skill-related fitness (power, agility and speed) may make engagement in PA easier for preschool children, although further research on the cause-effect relationship is needed.
A: Bland-Altman plots assessing agreement of minutes of sedentary activity between the criterion measure; Children's Activity Rating Scale (CARS) with the cut points (i) Sirard et al. (Sed s); (ii) Puyau et al. (Sed pu); (iii) van Cauwenberghe et al.(Sed va); (iv) Reilly et al. (Sed r). (continued) 
Summary of the Published Actigraph Cut Points for Young Children 
Mean Minutes of Sedentary Behavior, Light Intensity and Moderate to Vigorous Activity (MVPA) ± SD for Cut Points 
This study compared accelerometry cut points for sedentary behavior, light and moderate to vigorous intensity activity (MVPA) against a criterion measure, the Children's Activity Rating Scale (CARS), in preschool children. Actigraph accelerometry data were collected from 31 children (4.4 ± 0.8 yrs) during one hour of free-play. Video data were coded using the CARS. Cut points by Pate et al., van Cauwenberghe et al., Sirard et al. and Puyau et al. were applied to calculate time spent in sedentary, light and MVPA. Repeated-measures ANOVA and paired t tests tested differences between the cut points and the CARS. Bland and Altman plots tested agreement between the cut points and the CARS. No significant difference was found between the CARS and the Puyau et al. cut points for sedentary, light and MVPA or between the CARS and the Sirard et al. cut point for MVPA. The present study suggests that the Sirard et al. and Puyau et al. cut points provide accurate group-level estimates of MVPA in preschool children.
This study aimed to describe the location and intensity of free-living physical activity in New Zealand adolescents during weekdays and weekend days using Global Positioning Systems (GPS), accelerometry, and Geographical Information Systems (GIS). Participants (n = 79) aged 12-17 years (M = 14.5, SD 1.6) recruited from two large metropolitan high schools each wore a GPS watch and an accelerometer for four consecutive days. GPS and accelerometer data were integrated with GIS software to map the main locations of each participant's episodes of moderate-vigorous physical activity. On average participants performed 74 (SD 36) minutes of moderate and 7.5 (SD 8) minutes of vigorous activity per day, which on weekdays was most likely to occur within a 1 km radius of their school or 150 meters of their home environment. On weekends physical activity patterns were more disparate and took place outside of the home environment. Example maps were generated to display the location of moderate to vigorous activity for weekdays and weekends.
— M± SD of the total activity counts for Mozambique and Portugal by gender and age group. 
Physical activity (PA) in children/adolescents of both genders from a rural community in Mozambique was estimated by accelerometry and by questionnaire and was compared with PA of Portuguese youth. Total PA, moderate (MPA), vigorous (VPA) and very vigorous (VVPA) were evaluated. Mozambican boys were more active than girls. Intensity of PA declined significantly with age. Survival activities, such as household tasks, were the predominant mode of PA. Compared with Portuguese children/adolescents, Mozambicans had significantly higher total PA; showed less decline of PA with age and engaged in fewer minutes at higher intensity PA. Environmental factors likely explain documented differences.
The purpose of this study was to investigate the influence of jumping activities and nutrition education on bone accretion in prepubescents. Fourth-grade children were divided into four groups: jumping (n = 61), nutrition (n = 9), jumping plus nutrition (n = 14), and control (n = 28). Interventions spanned the fourth and fifth grade academic years. Assessments were gathered at 0, 8 and 20 months. Baseline BMD values were (mean +/- SD): lumbar (0.752 +/- 0.095 g/cm2), neck (0.794 +/- 0.089 g/cm2) and total (0.907 +/- 0.060 g/cm2). There was a significant increase in BMD over time. However, the interventions produced no significant effects. Twice weekly jumping and/or biweekly nutrition education did not influence bone accrual.
Most pedometers record cumulative steps, limiting ability to assess level of physical activity or nonwear periods. The SportBrain iStep X1 has potential to overcome this limitation by recording and storing step count data in 60-s epochs. We evaluated accuracy of this instrument in children and the duration of consecutive zero step count minutes that indicated nonwear time periods. Seventeen children walked or ran on a treadmill at 2, 3, 4 and 5 miles/hour and walked around a track while wearing the SportBrain and Digiwalker SW-701 pedometer. We compared percent error in step counts for each pedometers relative to observer counts. A subsample wore a SportBrain pedometer during up to 5 days of usual activity. The SportBrain pedometer performed with acceptable accuracy at all evaluated treadmill speeds and during self-paced walking, recording steps within an average of 4% of observed step counts. It outperformed the Digiwalker, especially at slower speeds and in overweight children. During normal wear only 1% of zero count periods were more than 60 min. We conclude that the SportBrain iStep X1 pedometer provides a valid measure of step counts in short averaging times useful for assessing patterns of physical activity in population studies and periods of nonwear.
The present study examined the association between the angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism, physical activity, and resting blood pressure (BP) in a sample of 132 children (48.4% female). Children attaining 60 min/day of moderate-to-vigorous physical activity (MVPA) possessed lower % body fat (29% vs 24%, p < .05). Resting BP did not significantly differ between genotypes. Furthermore, partial correlations between MVPA and BP were low and did not vary by ACE genotype. Thus, the ACE I/D genotype is not associated with BP and does not modify the relationship between physical activity and BP in this sample of children.
Relationships of academic achievement (government tests) with physical fitness (multistage run), physical activity (pedometers) and percent body fat (dual emission X-ray absorptiometry) were examined at both the aggregate school level and the individual child level using data collected from 757 children in 29 elementary schools. Statistical adjustments included gender, grade and socioeconomic status. Between-school relationships of the academic scores with fitness and physical activity were strong and positive, with some evidence of (negative) relationships with percent body fat. The between-child relationships were weaker, and nonexistent with percent body fat. Stronger between-school than between-child relationships favor the argument that variation in school cultures, characterized by concurrent attention to fitness and academic achievement, might play a more dominant role in explaining these relationships than any direct effect of fitness on academic achievement.
Descriptive Data
Means, Standard Deviations, and Z Scores for the Task and Ego Orientations by the Four Clusters
This study examined achievement goal orientation patterns and their impact on student motivation in physical education running programs. Participants included 533 fifth graders. They completed questionnaires assessing their achievement goal orientations, expectancy beliefs, task values, and intentions for future participation in running. They also completed a timed, 1-mile run. Data revealed 4 goal orientation patterns: low task/low ego, low task/high ego, high task/low ego, and high task/high ego. Students in the high-task/low-ego and high-task/high-ego groups demonstrated higher levels of motivation in running than those in the low-task/low-ego and low-task/high-ego groups.
Top-cited authors
Russell R Pate
  • University of South Carolina
Marsha Dowda
  • University of South Carolina
John Reilly
  • University of Strathclyde
Patty S Freedson
  • University of Massachusetts Amherst
Thomas L Mckenzie
  • San Diego State University