Maria Paula Santos

Physical activity and school recess time: differences between the sexes and the relationship between children's playground physical activity and habitual physical activity.

The aims of this study were: (1) to observe participation in moderate-to-vigorous physical activity (MVPA) during school recess periods; (2) to determine the relative importance of physical activity during recesses to overall daily physical activity; and (3) to examine differences in physical activity between the sexes during unstructured recess periods. The participants were 22 school children (10 boys, 12 girls) aged 8 – 10 years (mean  =  8.9, s  =  0.7) in the third and fourth grades. Daily totals for the physical activity variables were calculated by summing the values for each hour of 14 h of physical activity measurements (08:00 to 22:00 h). Recess times (minutes) were as follows: morning 10:30 to 11:00 h and afternoon 15:30 to 16:00 h. We did not differences between boys and girls in daily total accelerometer counts or the overall time spent in MVPA. However, girls were significantly (P  < 0.05) more involved (38%) in MVPA during recess time than boys (31%). Participation in MVPA during recess contributes significantly more (P  < 0.05) for girls (19%) than boys (15%) to the total amount of physical activity suggested by international health-related physical activity guidelines, while the percentage of time engaged in MVPA during recess time at school accounts for a small amount of the daily MVPA (6% for boys and 8% for girls). The results of this study suggest that school recess time is an important setting to promote MVPA and contributes to daily physical activity in young children, especially in girls.

Relationships between physical activity, obesity and meal frequency in adolescents.

Objective: The purpose of this study was to assess the associations and impact of increased meal frequency, physical activity and ‘skipping’ breakfast on obesity levels in a sample of urban adolescents, aged 13–17 years old, from Porto, Portugal. Methods: Overweight and obesity were defined according to age- and sex-specific BMI cut-points. Daily meal frequency was assessed by questionnaire. Self-reported physical activity was recalled. Results: The proportion of overweight/obese girls (p ≤ 0.05) and boys (p ≤ 0.001) that consumed fewer than three meals was significantly higher than those reported from normal-weight counterparts. While no statistically significant differences were reported in girls, obese boys skipped breakfast significantly more (13% vs 5.6%; p ≤ 0.05) than normal-weight counterparts did. Normal-weight boys but not girls were significantly more active (p ≤ 0.01) than obese peers. An additional meal in boys (OR: 2.75; p ≤ 0.05) and girls (OR: 1.97; p ≤ 0.05) reduced the risk of being overweight/obese. Regardless of gender, breakfast skipping is not seen as a predictor of being overweight/obese. However, boys (OR: 2.10; p < 0.003), but not girls, who were moderately active were more likely to be of normal weight. Conclusion: The data indicate that increased meal frequency may have a beneficial effect on a reduced BMI. Physical activity and breakfast skipping may be candidate targets for prevention programmes aimed at reducing overweight/obesity among adolescents.

Active versus passive transportation to school - differences in screen time, socio-economic position and perceived environmental characteristics in adolescent girls

Objective: The aims of this study were (1) to assess the relationships between transport to and from school (active vs. passive), sedentary behaviours, measures of socio-economic position and perceived environmental variables, and (2) to determine which, if any, variables were predictors of active transportation. Methods: The sample comprised 705 girls with mean age of 14.7 (SD = 1.6) years old. Questionnaires were used to describe travel mode to school and to estimate weekly television and computer use (screen time). Girls were assigned to active transportation (AT) or passive transportation (PT) groups depending on whether they walked or bicycled (AT) to and from school or travelled by car or bus (PT). Screen time was determined by the number of hours they reported watching television and using computers in the week preceding the examination, including weekends. Socio-economic position was established by parental occupation and educational level. A questionnaire assessed Perceived Neighbourhood Environments. Results: No statistically significant differences were seen for screen time between travel groups. Occupational status of both mother (r = −0.17) and father (r = −0.15) and fathers educational level (r = −0.10) were significantly and negatively associated with AT, while street connectivity (r = 0.10) was positively and significantly associated with AT. Logistic regression analysis showed that the likelihood of active commuting decreased by around 50% with increasing fathers occupation (odds ratio (OR) = 0.51; p ≤ 0.05) and fathers education (OR = 0.52; p ≤ 0.05) from low to middle socio-economic position groups. Further, the data showed that girls who agreed that ‘there are many four-way intersections in my neighbourhood’ were more likely to be active (OR = 1.63; p ≤ 0.05). Conclusion: The data of this study showed that lower socio-economic position is associated with active commuting to school and that street connectivity is a predictor of active transportation in adolescent girls.

Perceptions of the built environment in relation to physical activity in Portuguese adolescents

In this study, we investigated the association between perceptions of the built environment and physical activity among Portuguese boys and girls. Participants were 1124 adolescents (592 girls and 532 boys) 12- to 18-years-old. Physical activity and perceptions of environmental characteristics were assessed by self-report questionnaires. Significantly more girls (p<0.01) were classified as low-active (61.5%) compared to boys (22.9%). Logistic regression analyses (adjusted for age) showed a significant association between girls physical activity and availability of free- or low-cost recreational facilities in the neighbourhood (OR=1.44; 95% CI 0.99-2.11). Among boys, the presence of people being active in the neighbourhood was associated with higher levels of physical activity (OR=1.59; 95% CI 1.05-2.40). Perceptions of some aspects of neighbourhood environment may relate differently to participation in physical activity for boys compared to girls.

Is walking to school associated with improved metabolic health

BackgroundActive commuting to/from school is an important source of physical activity that has been declining over the past years. Although it is an affordable and simple way of increasing physical activity levels it is still unclear whether it has enough potential to improve health. Therefore, the aim of this cross sectional study was to examine the relationship between active commuting to/from school and metabolic risk factors in 10 to 12 year old children.MethodsParticipants were 229 adolescents, selected through consecutive sampling, (121 girls) with mean age of 11.65 (±0.73) years old from Porto, Portugal. Means of transport to/from school was accessed by asking: ”How do you usually travel to school?” and “How do you usually travel from school?”. Active commuting was considered if children reported at least one of the trips (to or from school) by active means. Total physical activity was obtained with Actigraph accelerometer for 7 consecutive days. Lipid profile measurements were conducted with Cholestech LDX® analyser. Waist circumference and blood pressure were measured by standard methods. The criteria for metabolic syndrome defined by International Diabetes Federation for children and adolescents were used.ResultsAdjusted binary logistic regression analysis suggested that walkers have higher odds to have a better waist circumference (OR = 2.64, 95% CI = 1.63-6.01) and better high density lipoprotein cholesterol (OR = 2.14, 95% CI = 1.01-4.52) profiles than non-active commuters, independent of moderate-to-vigorous physical activity. No associations were found for other metabolic risk factors.ConclusionsExertions to increase and maintain walking to school may be particularly relevant as it is likely to have a positive impact on children’s health and eventually decrease metabolic and cardiovascular diseases.

Associations between body mass index, waist circumference and body shape index with resting blood pressure in Portuguese adolescents

Background: Elevated blood pressure (BP) in childhood and adolescence is associated with overweight and obesity. Recently a body shape index (ABSI) has been suggested as superior to body mass index (BMI, kg/m2) and waist circumference (WC) as a measure of disease risk. Objective: To examine the association between ABSI, BMI, WC and BP in Portuguese adolescents and to consider the role of ABSI, BMI and WC when examining this issue in adolescents. Methods and procedures: Height, body mass, WC and resting blood pressure were assessed in 445 Portuguese adolescents (252 girls and 193 boys) aged 10–17 years. Results: ABSI, BMI and WC were all significantly related to both SBP and DBP (all p = 0.001 or better). ABSI, BMI and WC were all significant predictors of SBP and DBP for the whole sample and when analysed in separate gender groups (p = 0.001 or better in all cases). However, in all cases ABSI was a better predictor of BP than BMI or WC. Conclusions: Although BMI and WC significantly predict resting BP in adolescents, the use of ABSI explained a greater amount of the variance in BP in this population. When examining the effect of weight status on BP, researchers should consider use of ABSI alongside BMI.

Active travel to school, BMI and participation in organised and non-organised physical activity among Portuguese adolescents.

OBJECTIVES To assess the relationship between participation in organised (OPA) and non-organised physical activity (NOPA), commuting to school and BMI. METHODS Questionnaire assessing participation in OPA, NOPA, and travel behavior submitted in spring 2006 to 721 Portuguese secondary school students. Active travellers walked or biked (AT). Passive travellers drove or took the bus (PT). Height and weight were measured. RESULTS AT was related to NOPA among boys (odds ratio (OR)=1.8, p < or = 0.05) but not among girls. AT was unrelated to OPA. BMI was weakly associated with OPA (boys: OR=0.56, p < or = 0.05; girls: OR=0.54, p < or = 0.05) and not with NOPA. CONCLUSION After-school organised and non-organised physical activities do not predict active travelling to school among Portuguese adolescents.

Associations of Cardiorespiratory Fitness in Children and Adolescents with Physical Activity, Active Commuting to School, and Screen Time

BACKGROUND The objective of this study was to analyze associations of cardiorespiratory fitness (CRF) with physical activity, time spent watching television and using computer, mode of commuting to school (CS), and adiposity, by gender. METHODS Participants were 1708 students (53.8% girls), aged 11 to 19 years. CRF was evaluated with a 20-meter shuttle-run test using VO2max by previously published equation. Maturation stages determined by Tanners criteria, body mass index, and skinfolds were measured, and a questionnaire used to assess socioeconomic status, PA, television and computer time, and mode of CS. We conducted a regression analysis using CRF as the dependent variable. RESULTS CRF was independent and positively associated with physical activity [β = 0.338 (95% CI = 0.119; 0.188); P < .001] and with maturation [β = -0.876 (95% CI = 0.666; 1.087); P < .001]; independent and negatively associated with television time [β = -0.003 (95% CI = -0.005; -0.002); P < .001] and adiposity [β = -0.068 (95% CI = -0.076; -0.060); P < .001]. CRF was positively associated with CS [β = 0.337; (95% CI = 0.014; 0.741); P = .014]. No associations were found for computer time. CONCLUSIONS These findings suggest that increasing overall physical activity levels through interventions in different domains such as active CS, reducing sedentary activities, such as television time, might be effective strategies for improving CRF in youth.

Accelerometer cut-points and youth physical activity prevalence

The purpose of this study was twofold: first, to examine the effects of specific cut-off scoring points (on the estimated prevalence of meeting health-related guidelines for physical activity in youth) and, second, to document the differences in gender physical activity patterns according to two different cut-off points. The sample comprised 62 children (boys n = 23; girls n = 39) aged 8—16 years old. Children wore accelerometers for three consecutive weekdays. The daily time spent in moderate-to-vigorous physical activity (MVPA) was calculated using an equation regression developed for youth according to different cut-points. The data analysis from Freedsons cut points showed that both sexes engaged in significantly (p ≤ .01) more MVPA when compared with Puyaus cut points. Boys engaged in significantly (p ≤ .01) more MVPA activities than girls regardless of the cut-off point used. Our data also showed that the percentage of students that reach the physical activity/health related guidelines was significantly higher in both boys (77.3 vs 6.9 percent; p < .001) and girls (60 vs 2.3 percent; p < .001) when Freedsons cut-off point was used. Our data showed that for preventive strategies youth specific cut-off points still need to be refined and, as a result, health-related criteria for young people need to be based on further research evidence.

Cardiorespiratory fitness status and body mass index change over time: a 2-year longitudinal study in elementary school children.

OBJECTIVE This study aimed to examine the prospective relationship of baseline body mass index (BMI) and performance in a cardiorespiratory fitness (CRF) field test with a change in BMI (DeltaBMI) over a 2-year period in a sample of rural children from elementary school in Fundão, Portugal. METHODS Obesity status was obtained by the age- and sex-specific BMI cut-off points and CRF by a 9-minute run test. RESULTS BMI stratification at baseline showed that overweight/obese children were over 11 times (OR=11.31; p=0.007) more likely to be DeltaBMI gainers than their normal weight peers. Those who were classified as unfit were 3.9 times more likely to be DeltaBMI gainers than those classified as fit at baseline. Both BMI at time 1 and CRF change (DeltaCRF) were not significantly associated with DeltaBMI over time. CONCLUSION The findings of this study suggest that children who have higher BMI and lower CRF are likely to have greater BMI gain over time.