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Pedro Silva, Ryan Lott, Jorge Mota and Greg Welk

Social support (SS) from parents and peers are key reinforcing factors in the Youth Physical Activity Promotion (YPAP) model. This study aims to identify the relative contribution of parental and peer SS on youth participation in moderate to vigorous physical activity (MVPA). Participants included 203 high school students (n = 125 girls; mean age 14.99 ± 1.55 years). MVPA was assessed by accelerometry. SS influences were evaluated using a well-established scale. Structural equation modeling measured (AMOS, Version 19) the relative fit of the YPAP models using both parental and peer SS. Parental SS had significant associations with both predisposing factors, enjoyment (β = .62, p < .01), and self-efficacy (β= .32, p < .01), as well a direct effect on MVPA (β = .30, p < .01). Peer SS had direct effect on MVPA (β = .33, p < .05), also significantly influenced levels of enjoyment (β = .47, p < .01) and self-efficacy (β = .67, p < .01). In both models self-efficacy mediated the influence on MVPA. The direct effects for parents and peers were similar. This demonstrates that both parental and peer social support exert a strong influence on adolescent MVPA.

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Pedro F. Saint-Maurice, Gregory J. Welk, Pedro Silva, Mohammad Siahpush and Jennifer Huberty

To better understand and promote youth physical activity (PA) it is important to determine settings and characteristics that promote or influence behavior. This study evaluated the utility of a multi-method approach (accelerometers plus direct observation) to better understand youth PA at recess. A total of 100 third through fifth grade children (52 males and 48 females) wore an Actigraph accelerometer during school recess for five consecutive days in both Fall and Spring. Trained observers coded PA behaviors at the same recess periods using the System for Observing Play and Leisure Activities (SOPLAY). Overall, gender comparisons based on both instruments indicated that boys were more active than girls. MVPA levels were higher during climbing/sliding activities (40–50%) and when the activity setting was supervised and equipped (30%). Both assessments indicated that boys were more active but the contextual data from the SOPLAY indicate that differences may vary according to the environmental context.

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Luisa Aires, Pedro Silva, Gustavo Silva, Maria Paula Santos, José Carlos Ribeiro and Jorge Mota

Background:

The purpose of this study was to analyze the relation between body mass index (BMI), Cardiorespiratory Fitness (CRF), and levels of physical activity (PA) from sedentary to very vigorous intensities, measured by accelerometry, in students from a middle and high school.

Methods:

This cross-sectional study included 111 children and adolescents, age 11 to 18 years. PA was assessed with an accelerometer for 7 consecutive days (1 minute epoch) using specific cut-points. PA components were derived using special written software (MAHUffe). CRF was assessed by maximal multistage 20m shuttle run. T-test was used to test differences between BMI groups, Pearson’s correlation, to analyze correlations between all variables and multinomial logistic regression, and to predict the value of BMI categories.

Results:

This paper provides evidence that BMI was inversely and significantly correlated with CRF. Only CRF was correlated with Vigorous and Very Vigorous PA levels and total amount of PA. Children with Overweight/Obesity were less likely to perform more laps than normal weight counterparts. The total amount or intensity level of PA did not show any influence on BMI level.

Conclusions:

Low CRF is strongly associated with obesity, which highlights the importance of increasing CRF for a protective effect even in youth. No associations were found for PA and BMI.

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Pedro Silva, Luisa Aires, Rute Marina Santos, Susana Vale, Greg Welk and Jorge Mota

Background:

The purpose of the study is to evaluate age and gender differences in objectively measured levels of physical activity (PA) in a large and diverse sample of residents from an urban area in Porto, Portugal.

Methods:

Participants included 822 residents, 334 males (41%), and 488 females (59%), aged 6 to 90 years. GT1M accelerometer was used to assess daily PA over 7 consecutive days, and the measurement was from October (2007) to June (2008).

Results:

Males were more active than females. This difference was attenuated in the 2 oldest age groups (40−59 and 60+ yrs). An accentuated declined in all PA variables occurred between the youngster group (6−11 yrs) and adolescents group (12−19 yrs). Surprisingly, young adults (20−39 yrs) engaged in more moderate-to-vigorous PA (MVPA) than adolescents. Further, females also had higher MVPA in the fourth group (40−59 yrs) compared with the second group (12−19 yrs). Males had higher compliance rates of PA guidelines than females regardless the age group considered. Adolescents had very low compliance rates (females = 18.18%; males = 33.50%).

Conclusions:

Porto metropolitan area residents had low rates of compliance with current PA guidelines. A low level of PA in Porto adolescents is a matter of concern and suggests that interventions are needed.

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Susana Vale, Rute Santos, Pedro Silva, Luísa Soares-Miranda and Jorge Mota

The purpose of this study was twofold: first to document the gender differences in Moderate to Vigorous Physical Activity (MVPA) according to two epoch systems (5 vs. 60 s) in preschoolers, and, second to document the differences in physical activity (PA) patterns according to two different epoch choices. The sample comprised 59 preschoolers (31 girls) aged 2–5 years old. PA was assessed by accelerometer during school hours. The time spent in MVPA was significantly higher (p < .001) when a 5-s epoch was considered compared to the 60-s epoch, regardless gender. Further, it was found a difference of ?17 min difference between the 2 epoch systems for MVPA. Different epoch times might affect the time spent in MVPA among preschool children.

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Pedro Figueiredo, Ana Silva, António Sampaio, João Paulo Vilas-Boas and Ricardo J. Fernandes

The aim of this study was to evaluate the determinants of front crawl sprint performance of young swimmers using a cluster analysis. 103 swimmers, aged 11- to 13-years old, performed 25-m front crawl swimming at 50-m pace, recorded by two underwater cameras. Swimmers analysis included biomechanics, energetics, coordinative, and anthropometric characteristics. The organization of subjects in meaningful clusters, originated three groups (1.52 ± 0.16, 1.47 ± 0.17 and 1.40 ± 0.15 m/s, for Clusters 1, 2 and 3, respectively) with differences in velocity between Cluster 1 and 2 compared with Cluster 3 (p = .003). Anthropometric variables were the most determinants for clusters solution. Stroke length and stroke index were also considered relevant. In addition, differences between Cluster 1 and the others were also found for critical velocity, stroke rate and intracycle velocity variation (p < .05). It can be concluded that anthropometrics, technique and energetics (swimming efficiency) are determinant domains to young swimmers sprint performance.

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Pedro Galoza, Felipe Sampaio-Jorge, Marco Machado, Ricardo Fonseca and Pierre A. V. Silva

Purpose:

To compare the effect of inter-set cooling and no cooling during resistance exercise (RE) on the total repetitions and select muscle damage biomarker responses.

Methods:

Sixteen healthy men volunteered to participate in this study and were randomly assigned to Cooling (n = 8) or Control (n = 8) groups. They performed a RE protocol consisting of four sets of biceps curl at 80% of 1RM. The cooling group received the application of wet bags of ice during each inter-set rest interval (Cooling), while the Control realized the same protocol without ice application. Exercise was performed to voluntary fatigue and the numbers of repetitions per set were recorded. Subjects provided blood samples before and at 24, 48, and 72 h following RE to evaluate serum CK activity and myoglobin concentration.

Results:

The Cooling group produced a greater number of repetitions (approx. 21%) than did the Control, but there were no differences in serum CK activity and myoglobin responses between the groups.

Conclusion:

Incorporating inter-set external cooling augments the number of repetitions per set during RE without inducing an additional muscle damage biomarker response.

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Ana Silva, Pedro Figueiredo, Susana Soares, Ludovic Seifert, João Paulo Vilas-Boas and Ricardo J. Fernandes

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.

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Jorge Mota, Rute M. Santos, Pedro Silva, Luisa Aires, Clarice Martins and Susana Vale

Background:

The main goal of this study was to analyze the associations between cardiorespiratory fitness (CRF) and body mass index (BMI) with self-rated health (SRH) of adolescent girls.

Methods:

This was a cross-sectional study of 533 adolescents girls, aged from 10 to 18 years old. CRF was predicted by maximal multistage 20-m shuttle-run test according to procedures described from FITNESSGRAM. Girls’ obesity status was classified according to International Obesity Task Force and Self-rated health (SRH) was assessed by questionnaire.

Results:

The findings showed that among adolescent girls 23.2% had negative SRH. Girls who were classified as unfit were more likely to report negative SRH in both univariate logistic (OR: 3.05; CI: 1.91−4.87; P < .05) and multivariate (OR: 2.93; CI: 1.82−4.72; P < .05) regression analyses compared with their fit peers. Obese girls were more likely to report negative SRH (OR: 2.30; CI: 1.14−4.62; P < .05) compared with their normal-weight counterparts. However such association was lost in multivariate analyses suggesting an effect of CRF.

Conclusions:

Negative perception of health was associated with lower CRF and weight status although such association it is mediated by CRF condition.

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Jorge Mota, Pedro Silva, Luísa Aires, Maria Paula Santos, José Oliveira and José C. Ribeiro

Background:

The purpose of this study was to examine whether there are differences in physical activity (PA) during specific periods of the day among active and less-active girls.

Methods:

The sample comprised 54 girls age 10 to 15 years. PA was assessed by accelerometry. Girls were grouped as less active, active, and highly active.

Results:

Total minutes of moderate-to-vigorous physical activity (MVPA) was significantly higher in more-active girls than in their less-active peers (113 and 72 min/d, respectively). The most-active groups were significantly more engaged in MVPA during the outside-of-school period than were less-active girls. Highly active girls spent a significantly higher amount of their MVPA time outside of school than did the less-active group, which spent a significantly higher proportion of MVPA time during late afternoon.

Conclusion:

Outside-of-school PA is a key point for MVPA engagement. Particularly for the less-active girls, however, schools might provide additional PA.