Helen E. Parker

The relationship among physical activity, motor competence and health-related fitness in 14-year-old adolescents

Physical activity, physical fitness and motor competence are important health‐related constructs. However, the relationship among them, particularly for children and adolescents, is still unclear. In this study, motor competence (measured by the McCarron Assessment of Neuromuscular Development), pedometer‐determined physical activity and physical fitness (aerobic fitness, muscle strength, muscle endurance, flexibility and body composition) were examined in a cohort of 1585 adolescents (771 girls, 814 boys) of mean age 14.06 years. Significant gender differences were observed for all measures except motor competence. Apart from hip and shoulder flexibility, males outperformed females. For both males and females, motor competence was associated with all fitness measures, physical activity was associated only with aerobic fitness and aerobic fitness was associated with physical activity, motor competence, BMI and chest pass. Among males, aerobic fitness was also associated with all other fitness tests. The correlations were, in general, moderate to weak. The results challenge the current focus on physical activity rather than physical fitness as the preferred intervention.

Body mass index, adiposity rebound and early feeding in a longitudinal cohort (Raine Study).

Objective:This study examined the influence of type and duration of infant feeding on adiposity rebound and the tracking of body mass index (BMI) from birth to 14 years of age.Methods:A sample of 1330 individuals over eight follows-ups was drawn from the Western Australian Pregnancy Cohort (Raine) Study. Trajectories of BMI from birth to adolescence using linear mixed model analysis investigated the influence of age at which breastfeeding was stopped and the age at which other milk was introduced (binomial 4-month cutoff point). A subsample of linear mixed model-predicted BMI was used to determine BMI and age at nadir for early infant feeding groups.Results:Chi-square analysis between early feeding and weight status (normal weight, overweight and obese) groups found a significant difference between thee age at which breastfeeding was stopped (P<0.001) and the age at which other milk was introduced (P=0.011), with a higher proportion of overweight and obese in the ⩽4-month group, even after controlling for maternal education. Using the linear mixed model, the BMI determined was higher over time for the group that was breastfed for ⩽4 months (P=0.015), with a significant interaction effect with the group in which other milk was introduced at ⩽4 months (P=0.011). Using predicted BMI from the linear mixed model, significant differences for nadirs of adiposity rebound between early feeding groups were found (P<0.005).Conclusions:Early infant feeding was important in the timing of, and BMI at, adiposity rebound. The relationship between infant feeding and BMI remained up to the age of 14 years. Although confounding factors cannot be excluded, these findings support the importance of exclusive breastfeeding for longer than 4 months as a protective behaviour against the development of adolescent obesity.

The associations between physical activity, screen time and weight from 6 to 14 yrs: the Raine Study.

To examine the strength and direction of the relationship between physical activity level, screen use and BMI in a cohort at ages 6, 8, 10 and 14 yrs as part of a prospective longitudinal cohort study. The sample comprised 1403 males and females who participated in the follow-up survey at 14 yrs of age between 2003 and 2005. Exploratory structural equation modelling was used to examine the interrelationships between physical activity level, BMI and screen time at 6, 8, 10 and 14 yrs. Predictors of BMI at 6, 8, 10 and 14 yrs explained 1.3, 76.1, 80.1 and 73.1 percent of the variances, respectively, with previous BMI the largest predictor [χ(2)=43.082, df=36, p=194]. Increased screen time predicted higher BMI and lower physical activity at 8 and 10 yrs but not 14 yrs. At 14 yrs, physical activity predicted BMI. Sedentary patterns of behaviour in early childhood were predictive of later and concurrent obesity, whereas physical activity was predictive of obesity in adolescence. Different intervention targets are required for children and adolescents.

Physical activity measurement methods for young children: A comparative study

Many behavior patterns that impact on physical activity experiences are established in early childhood, therefore it is important that valid, reliable, and feasible measures are constructed to identify children who are not developing appropriate and healthy activity habits. In this study, measures of physical activity derived by accelerometry and pedometry are compared with direct observation of 5- and 6-year-old children (N = 24). The children were monitored for 30 min over 5 consecutive days during a free play session in their preprimary setting. The results for all measures were significantly correlated. When compared to direct observation, the coefficient of determination indicated that the pedometer (R2 = .81) was able to more accurately predict all levels of physical activity compared to the accelerometer (R2 = .59). When the children were grouped into low, moderate, wand high activity levels using observation, the pedometer data were better able to separate the groups than the accelerometer data. These findings indicate that the pedometer is a better measure of free play physical activity in 5- and 6-year-old children compared to the accelerometer.

Longitudinal Modelling of Body Mass Index from Birth to 14 Years

Background: To examine the tracking of BMI from birth to age 14 years. Participants and Methods: Linear mixed model (LMM) analysis was used to model the trajectories of BMI (n = 1,403). Adiposity rebound was investigated for a subset of individuals (n = 173). Results: Adolescents who were overweight or obese at 14 years followed a different BMI trajectory from birth compared to those of normal weight. There was a difference between weight status groups for the timing of adiposity rebound (p < 0.001) and BMI at nadir (p < 0.001). The LMM depicted a significant difference in rate of change of BMI over time for males and females (p < 0.001), with female BMI increasing at a faster rate, and for weight status groups (p < 0.005), with the obese cohort having the faster increase in BMI over time. BMI at birth was significantly lower for the normal weight cohort compared to the overweight (p = 0.029) and obese (p = 0.019) cohorts. Conclusion: This study introduces a powerful analytic tool, LMM, to model BMI and shows that weight status at 14 years is the result of a distinct path in earlier years. Compared to their normal weight peers, overweight and obese adolescents experience an earlier adiposity rebound, with a higher BMI at rebound.

Intra-individual variation in children's physical activity patterns: Implications for measurement

Childrens physical activity (PA) patterns change from day to day. This intra-individual variability affects precision when measuring key physical activity and sedentary behaviour variables. This paper discusses strategies used to reduce the random error associated with intra-individual variability and demonstrates the implications for assessing PA when varying number of days are sampled. Self-reported data collected on two hundred and ninety eight 13-14-year-olds were used to compare estimates of PA and sedentary behaviour derived from between 1 and 7 days of recall data. Large intra-individual coefficients of variation were calculated for physical activity level (14.5%), moderate-to-vigorous physical activity (83.4%), screen time (60.8%) and sleep (12.2%). While the magnitude of error associated with estimating means decreased as more days were sampled, the paper notes that depending on the nature of the research question being asked, sampling fewer days may yield sufficiently precise estimates. Therefore, researchers should conduct power analyses based on estimated inter- and intra-individual variability and sample size to determine how many days to sample when assessing childrens PA patterns.

Evidence for the validity of the Children's Attraction to Physical Activity questionnaire (CAPA) with young children

Attraction to physical activity is important to an individuals intrinsic motivation to engage in play, games and sports. While there are instruments designed to measure attraction to physical activity in middle childhood years, the lack of authentic measures in young children has impeded research in this area. In this study we sought to address the validity of a scale to tap young childrens attraction to physical activity. Evidence for validity was based on internal consistency, content analysis, and factor structure. Australian school children (180 boys and 154 girls) from school year two, aged 6-8 years, were individually administered a modified version of the Childrens Attraction to Physical Activity Scale (CAPA) [Brustad RJ. Who will go out to play? Parental and psychological influences on childrens attraction to physical activity. Pediatr Exerc Sci 1993;5:210-23; Brustad RJ. Attraction to physical activity in urban school children: parental socialization and gender influences. Res Q Exerc Sport 1996;67:316-23]. The results indicated that internal consistency was acceptable for most of the subscales when negative statements were excluded from the analyses. Factor analysis revealed that the liking of games and sports, liking of physical exertion and exercise, and the importance of exercise subscales were more robust. Second order factor analysis indicated that the overall construct of attraction to physical activity was viable in this age group. With some modifications, the scale appears to provide a valid approach to the measurement of attraction to physical activity in young children.

Stability and change in children's skill

SummaryThis paper explores age-related performance variability, both within trials and between sessions, in repetitive hopping. The mean, the standard deviation (SD), and the coefficient of variation (CV) of several timing and ground-reaction-force variables of hopping were analysed by repeated-measures ANOVA for age-related effects across test sessions and foot used. Forty-five subjects in five age groups (3–4 years, 4–5 years, 6–7 years, 8–9 years, or Adult) performed self-paced, one-footed hopping on three occasions within one week. As was expected, the results showed main effects for Age in all force and time variables, with the exception of CV of medio-lateral force. No significant main effects for Feet were revealed. However, significant Feet x Session interactions were found in flight-time measures, with higher flight-time SD and lower CV for the non-preferred foot in Session 1, a reversal in Session 2, and a negligible difference in Session 3. Across sessions, decreased SD and CV for both vertical and medio-lateral force and shorter flight time indicated more efficient hopping. Overall, it was concluded that SD and CV measures were more sensitive measures of childrens performance across repeated sessions than were mean scores and that the order of testing the limbs is an important consideration in experimental protocols when lateralized tasks are measured.

Symmetrical and asymmetrical motor control in children: Bipedal and unipedal hopping

Abstract The purpose of this study was to compare the temporal and kinetic features of symmetrical and asymmetrical hopping in children of different ages. If the two hopping tasks become increasingly similar with age then one might hypothesise convergence of coordinative structures for repetitive hopping, encompassing unipedal and bipedal modes. Four groups of female children ( N = 35), aged from 3.5 years to 9.5 years, were recruited. Temporal and kinetic variables were extracted from the ground reaction forces collected on a force plate sampling at 300 Hz. An Age × Task (repeated) ANOVA revealed a significant difference in unipedal and bipedal hopping in all timing and kinetic variables. Age groups differed in frequency, air duration, ground/air ratios and weight-normalised vertical impulses. Although task differences in kinetic parameters remained across age, some temporal variables became more alike. The temporal data appeared to provide tentative support for the hypothesis of convergence.

Parental and early childhood influences on adolescent obesity: A longitudinal study

The influence of parental and early childhood factors on adolescent obesity was investigated using a longitudinal model of body mass index (BMI) from birth to 14 years. Trajectories of BMI using linear mixed model (LMM) analysis were used to investigate the influence of early parental and childhood factors on BMI at 14 years in the Raine birth cohort study over eight follow-ups (n = 1403). An inverse relationship between parental education attainment and BMI was found (mothers χ 2 = 21.75, p = 0.016; LMM p = 0.043; fathers χ 2 = 21.19, p = 0.020; LMM p > 0.05). More overweight adolescents had mothers who smoked during pregnancy (χ 2 = 12.60, p = 0.002). Parental birth weight and BMI across years (p < 0.001) were strongly associated with adolescent obesity (LMM p < 0.05). Obese adolescents visited the park or playground infrequently as toddlers (p < 0.05). Results for early home environment factors were mixed. Maternal education, parental birth weight, and parental BMI were the strongest influences on their childs BMI from birth to adolescence.