Benjamin C. Guinhouya

Level of physical activity among children and adolescents in Europe: a review of physical activity assessed objectively by accelerometry

This study explored the proportion of European youth who are sufficiently active according to physical activity (PA) recommendations, based exclusively on objective assessment through accelerometers. A systematic electronic search of studies published up to March 2012 was conducted. PubMed was used to identify accelerometry-assessed PA studies that involved European youth. Within the 131 European studies, only 35 clearly reported the proportion of youth meeting the PA recommendations. Different thresholds lying between 1000 and 4000 counts/min (cpm) were used to define moderate-to-vigorous PA (MVPA). Overall, up to 100% of youth may be sufficiently active when using a threshold of approximately >1000-1500 cpm. With the most cited cut-off point (i.e. >2000 cpm), up to 87% of European youth might be considered physically active with reference to the current recommendations. Alternatively, with a cut-off point >3000 cpm, no more than 3-5% of them appeared to achieve these recommendations. The large discrepancy in outcomes released by accelerometer data is mainly due to the variety of cut-off points for MVPA among youth, hindering the definition of a clear goal towards PA promotion in Europe. Standardization of methods is urgently required.

Evidence of the influence of physical activity on the metabolic syndrome and/or on insulin resistance in pediatric populations: a systematic review

This study is aimed at updating the relationships between physical activity (PA) and the metabolic syndrome (MetS) and/or insulin resistance (IR) in youth. Cross-sectional, prospective cohort and intervention studies, which examined the effect of PA on MetS, its components and IR in children and adolescents (<18 yrs), were searched by applying a combination of criteria in the PubMed database. The electronic search of studies published from 2000-2010 yielded >150 references. Of these, 37 studies were included. Twenty-six studies (70%) were cross-sectional observation studies, and two studies (8%) were prospective cohort studies. The remaining eight studies (22%) were interventions, of which three (<10% of all included studies) were randomized controlled trials. Commonly, higher PA levels were consistently associated with an improved metabolic profile and a reduced risk for MetS and/or IR in these populations. The impact of PA on MetS and/or IR appeared to be either independent of other factors, or alternatively or simultaneously mediated by the physical fitness and adiposity of youth. However, more-robustly designed interventions (i.e., some mega-randomized controlled trials based on lifestyle interventions) and additional cohort studies are required to make definitive inference about the magnitude and role of PA as a single genuine preventive and treatment strategy for the metabolic and cardiovascular risk of youth in the current obesogenic context.

Physical Activity in the Prevention of Childhood Obesity

The current high prevalence of childhood obesity and its co-morbidities is concomitant with a low level of physical activity and an abundance of sedentary pastimes for Westernised children. To increase the participation of a majority of children in a sustained physical activity, interventions require a fair understanding and consideration of the influences of this behaviour, especially as children are overweight or obese. Basically, the physical activity behaviour of children depends on biological, sociocultural and psychosocial factors and their interplay. The recent literature lends support to the fact that some psychosocial factors such as self-efficacy and physical competence may be solid anchor points upon which to improve the participation of overweight and obese children in free-living physical activity. Thus, interventionists should first concentrate on improving these personal dimensions around which physiological and environmental factors might revolve. The development of motor skills may be a good means for enhancing the self-image of obese children.

Compliance of children in northern France with physical activity recommendations

Aims: This study examined the compliance of French children with physical activity (PA) guidelines, using objective assessments of PA. Methods: The study involved 252 children aged 9.9 ± 0.9 years, with mean height and weight of 1.39 ± 0.08 m and 35.8 ± 8.8 kg, respectively. Their usual PA was evaluated during a week using an Actigraph accelerometer. Results: The time spent in a moderate-to-vigorous PA (MVPA) ranged from 142 ± 44 min.d-1 to 25 ± 18 min/day according to the cut-offs used. Boys were significantly more active than girls (p ≤ .001). Overweight/obese children spent significantly less time in MVPA as determined with cut-off points at 3200 cpm (-26%) or 3600 cpm (-35%) (p < .01). Between 5% (8% of boys vs 1% of girls, p < .0001) and 9% (14% of boys vs 3% of girls, p < .0001) of children probably met the PA guidelines. No relationships were found with socioeconomic status. Conclusions: This high proportion of insufficiently active children (> 90%), together with the relatively high proportion of overweight children in this area, advocates a more aggressive PA promotion project, which should target all children whatever their social origins.

Maturity negates the gender-related difference in physical activity among youth. Is this equally justified whatever the accelerometer cut-off point used?

OBJECTIVES To examine the consistency in findings about the influence of maturity on the gender-difference in moderate-to-vigorous physical activity (MVPA) of children using different cut-off points for MVPA. DESIGN Cross-sectional observation study. METHODS The sample involved 253 children (139 boys) of 9.9±0.9 years. Their physical activity was evaluated using an Actigraph accelerometer. The biological age of children was determined with their estimated age at the peak height velocity, and maturity categories were gender-specific defined. RESULTS Boys spent more time in MVPA than girls (P<0.0001), and no maturity-related differences were obtained on the whole sample. It was only among boys that differences were found between maturity groups with cut-off points of 3000 cpm (P=0.034), 3200 cpm (P=0.024), and 3600 cpm (P=0.011). At a given maturity level, boys spent significantly more time in MVPA than girls, except with the cut-off point of 1000 cpm (P=0.07). There were higher proportions of sufficiently active boys, but significances were reached only with cut-off points above 3000 cpm. There were no maturity-related differences in the proportion of sufficiently active children as MVPA was computed using cut-off points of 1000 cpm, 2000 cpm or 3000 cpm. CONCLUSIONS The role of maturity in the gender-difference in MVPA seems unclear as one another cut-off point is used among children. Even if a relatively greater consistency was found with the three cut-off points above 3000 cpm, data comparison may require a conversion system until a consensus is reached about the exact value to be used among children.

Does the body adiposity index (BAI) apply to paediatric populations

Abstract Objective: Validation of body adiposity index (BAI) in a paediatrics sample; and to develop, if necessary, a valid BAI for paediatrics (i.e. BAIp). Methods: A total of 1615 children (52% boys) aged 5–12 years underwent anthropometry. Their body composition was assessed using a foot-to-foot bioimpedance. The validity of BAI = (Hip circumference/Height1.5) − 18 was tested by combining correlation and agreement statistics. Then, the sample was split into two sub-samples for the construction of BAIp. A regression was used to compute the prediction equation for BAIp-based percentage of body fat (%BF). Results: The initial BAI over-estimated the %BF of children by 49% (29.6 ± 4.2% versus 19.8 ± 6.8%; p < 0.0001). The original methodology led to a BAIp = (Hip circumference/Height0.8) − 38 in children. When compared to BAI, BAIp showed both better correlation (r = 0.57; p < 0.01 versus r = 0.74; p < 0.0001) and agreement (ICC = 0.34; [95% CI = −0.19–0.65] versus ICC = 0.83; [95% CI = 0.81–0.84]). However, there were some systematic biases between the two values of %BF as exemplified by the large 95% limit of agreement [−9.1%; 8.8%] obtained. Conclusion: BAI over-estimates the %BF in children. In contrast, BAIp appears as a new index for children’s body fatness, with acceptable accuracy. In its current form, this index is valid only for large-scale studies.

Insight into physical activity in combating the infantile metabolic syndrome

Metabolic syndrome (MetS) is increasingly reported in children, mainly in the presence of overweight/obesity. From the most recent report, up to 60% of overweight and obese children can be affected by this syndrome. MetS acquired during childhood has been shown to track into adulthood, including its clinical complications, such as type 2 diabetes and cardiovascular diseases. Among the practical preventive and therapeutic measures to be taken in children, physical activity (PA) appears to be at least as efficient as the most adequate pharmacology. The current literature suggests that exercise programs based either on aerobic-or resistance-type exercises, or a combination of these 2 types of structured activity, may promote insulin sensitivity and weaken or suppress MetS in children. Furthermore, daily-living activities such as brisk walking were found to substantially reduce the risk of MetS among children. Regardless of their weight status, PA needs to be promoted among children as early as possible.

A Multi-agent Simulation: The Case of Physical Activity and Childhood Obesity

Engaging in a regular physical activity appears to be an important factor in the prevention of childhood obesity, which became one of the major public health challenges worldwide. The literature suggests that the relationship between physical activity and obesity is complex with many intervening factors that come from different aspects of the child’s life. Yet, so far, the proposed models do not include all of the identified factors. The main objective of this study is to simulate the child’s behavior within his/her social and physical environments in order to understand precisely the relationship between the PA and childhood obesity. This paper proposes a simulation model using the multi-agent paradigm.

Simulating Complex Systems - Complex System Theories, Their Behavioural Characteristics and Their Simulation

Complexity science offers many theories such as chaos theory and coevolutionary theory. These theories illustrate a large set of real life systems and help decipher their nonlinear and unpredictable behaviours. Categorizing an observed Complex System among these theories depends on the aspect that we intend to study, and it can help better understand the phenomena that occur within the system. This article aims to give an overview on Complex Systems and their modelling. Therefore, we compare these theories based on their main behavioural characteristics, e.g. emergence, adaptability, and dynamism. Then we compare the methods used in the literature to model and simulate Complex Systems, and we propose and discuss simple guidelines to help understand one’s Complex System and choose the most adequate model to simulate it.

Does biological maturity actually confound gender-related differences in physical activity in preadolescence?

AIM To examine: (i) if maturity-related gender differences in moderate-to-vigorous physical activity (MVPA) depend on how maturity status is defined and measured; and (ii) the influence of maturity level on compliance with PA recommendations. METHODS The study involved 253 children (139 boys) aged 9.9 ± 0.9 years, with mean stature and weight of 1.39 ± 0.08 m and 35.8 ± 8.8 kg respectively. Their PA was evaluated using an Actigraph accelerometer (Model 7164). Maturity was assessed using the estimated age at peak height velocity (APHV) and a standardized APHV by gender (i.e. centred APHV). RESULTS Boys engaged in significantly more MVPA than girls (P < 0.0001). There was a significant correlation between the centred APHV and MVPA in boys (r = 0.20; P = 0.016), but not in girls (r = 0.13; P = 0.155). An ancova controlling for the estimated APHV showed no significant interactions between gender and APHV, and the main effect of gender on MVPA was negated. Conversely, there was a significant main effect of APHV on MVPA (F 1,249 = 6.12; P = 0.014; η p (2) = 0.024). Only 9.1% of children met the PA recommendations, including 14.4% of boys and 2.6% of girls (P < 0.01). This observation also applies in both pre-APHV (12.7% of boys vs. 2.4% of girls, P < 0.001) and post-APHV children (23.8% of boys vs. 3.4% of girls, P < 0.0001). No differences in PA guidelines were observed between pre-APHV and post-APHV children. CONCLUSIONS Among prepubescent children, the influence of biological maturity on gender differences in PA may be a function of how maturity status is determined. The most physically active prepubescent children were those who were on time according to APHV.