André Seabra

Biological and socio-cultural determinants of physical activity in adolescents

A atividade fisica e um comportamento importante na promocao de saude e na prevencao de doencas. Para que se desenvolvam programas eficazes no incentivo a pratica de atividade fisica em adolescentes, torna-se necessario que se identifiquem os fatores que a determinam. Este estudo pretende rever alguns dos aspectos do estado atual do conhecimento acerca da influencia de determinantes demografico-biologicos (idade, sexo, estatuto socio-economico) e socio-culturais (familia, pares e professor de educacao fisica) na atividade fisica de adolescentes. Nesta revisao apenas foram incluidos estudos efetuados com amostras superiores a 100 adolescentes com idades entre os 10 e os 18 anos, que tenham adotado delineamentos de pesquisa transversal e que tenham utilizado questionarios. Os principais resultados e conclusoes foram que: a idade parece estar negativamente associada a atividade fisica; o sexo masculino tende a estar mais envolvido nessas atividades; o estatuto socio-economico elevado parece ser um fator protetor do risco de inatividade fisica; a participacao da familia e dos pares em atividades fisicas parece estar positivamente associada as atividades por parte dos adolescentes; o professor de educacao fisica parece nao representar um fator propiciador da atividade fisica.

Discrimination of U-14 Soccer Players by Level and Position

Adolescence is often viewed as a critical period for selection in youth soccer. The present study compared the characteristics of regionally selected and non-selected under-14 players (U-14) as a group and by position. Players were classified as local (n=69) and regional (n=45). Weight, height, skinfolds, functional capacities, soccer skills and goal orientation were measured and skeletal age was assessed with the Fels method. Factorial ANOVA was used to test the effect of selection, position and respective interaction terms, while discriminant analysis was used to identify the variables that contributed to selection. Selected players had an advanced maturity status (F=24.97, p<0.01), were heavier (F=30.67, p<0.01) and taller (F=35.07, p<0.01); performed better in explosive power (F=21.25, p<0.01), repeated sprints (F=20.04, p<0.01) and ball control (F=3.69, p<0.05); and were more ego oriented (F=13.29, p<0.01). The 2 competitive groups did not differ in agility, aerobic endurance, dribbling, shooting, passing, and task orientation. Position-related variation was negligible. The percentage of players who were correctly classified in the original groups was slightly lower when the analysis was performed for the total sample (86%) than by position (86-90%). Future research on talent identification and selection should adopt a multidimensional approach including variables related to the physiological, perceptual, cognitive and tactical demands.

Physical and Physiological Demands of Elite Team Handball

Abstract Póvoas, SCA, Seabra, AFT, Ascensão, AAMR, Magalhães, J, Soares, JMC, and Rebelo, ANC. Physical and physiological demands of elite team handball. J Strength Cond Res 26(12): 3365–3375, 2012—This study aimed to analyze elite team handball physical and physiological demands during match play. Time-motion (N = 30) and heart rate (HR; N = 60) analyses were performed throughout 10 official matches. The defined locomotor categories were standing still, walking, jogging, fast running, sprinting, backwards movement, sideways medium-intensity movement, and sideways high-intensity movement, and playing actions studied were jumps, shots, stops when preceded by high-intensity activities, changes of direction and one-on-one situations. During matches, the mean distances covered were 4,370 ± 702.0 m. Around 80% of the total time was spent standing still (43.0 ± 9.27%) and walking (35.0 ± 6.94%) and only 0.4 ± 0.31% with sprinting. The most frequent high-intensity actions were stops, changes of direction, and one-on-one situations. Effective mean HR was 157 ± 18.0 b·min−1 (82 ± 9.3% of HRmax), and total HR was 139 ± 31.9 b·min−1 (72 ± 16.7% of HRmax). The HR, time spent in high-intensity activities, frequency of stops, changes of direction, one-on-one situations, and most intense periods of the game were higher during the first half than during the second half (p ⩽ 0.05). The opposite was observed for the number of time outs and the time between each change of activity (p = 0.00). Handball is an intermittent exercise that primarily uses aerobic metabolism, interspersed by high-intensity actions that greatly tax anaerobic metabolism. Additionally, exercise intensity decreases from the first to the second half of the match, suggesting that neuromuscular fatigue may occur during the game. The training of elite handball players should comprise exercises targeting the ability to perform specific high-intensity actions throughout the game and to rapidly recover during the less intense periods.

Age and sex differences in physical activity of Portuguese adolescents

PURPOSE This study sought to examine sex- and age-associated variations in physical activity (PA) among Portuguese adolescents aged 10-18 yr. METHODS A total of 12,577 males and females at the primary or secondary education level were sampled across four regions of Portugal. PA was assessed by a questionnaire, producing four different indexes: work/school (WSI), sport (SI), leisure time (LI), and total physical activity index (PAI). We examined sex and age differences by using two-way analysis of variance. RESULTS Males had higher mean values of PA than did females. In both sexes, mean values for all four PA indexes increased from ages 10 to 16 yr. After age 16, females decreased their mean values, whereas males continued to increase their values (except for LI). In both sexes, the average annual rate of change for the mean values of all four PA indexes correspond to three sensitive age periods (10-13, 13-16, and 16-18 yr). Until age 16, average mean changes for females ranged from +0.7 to +1.6% per year, except for SI in the youngest group (a modest decrease). For males under 16 yr, the pattern was similar, with increases ranging from 0.4 to 1.9% per year. After age 16, females experienced decreases of 1-2.1% per year for the four PA indexes, whereas males showed an increase for three indexes and an average decrease of 1.3% per year for LI. CONCLUSIONS These results suggest that it is important to consider sex differences in PA levels among Portuguese adolescents. Unlike their male counterparts, Portuguese females may reduce much of their PA during late adolescence.

Anthropometric Characteristics, Physical Fitness and Technical Performance of Under-19 Soccer Players by Competitive Level and Field Position

Anthropometric characteristics, physical fitness and technical skills of under-19 (U19) soccer players were compared by competitive level (elite, n=95; non-elite, n=85) and playing position (goalkeeper, central defender, fullback, midfield, forward). Fitness tests included 5- and 30-m sprints, agility, squat jump (SJ) and countermovement jump (CMJ), strength and Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2). Soccer-specific skills included ball control and dribbling. Independent of position, elite players presented more hours of training per year than non-elite players (d>1.2). Stature and body mass discriminated elite from non-elite players among goalkeepers and central defenders (d>0.6). Major differences were noted between elite and non-elite goalkeepers for SJ, CMJ, Yo-Yo IE2, and ball control (d>1.2). Elite central defenders performed better than their non-elite counterparts in SJ and ball control tests (d>1.2). Elite players presented better agility and Yo-Yo IE2 performances than non-elite players within all positional roles (d>0.6). In conclusion, U19 players differed in anthropometric characteristics, physical fitness and technical skills by competitive level within field positions.

Influence of Relative Age Effects and Quality of Tactical Behaviour in the Performance of Youth Soccer Players

The present study examines the associations between tactical performance indexes with quality of tactical behaviours and birth-date quarters of youth Soccer players. The sample comprised a total of 534 youth players classified into four seasons of 3 months (January-March; April-June; July-September; October-December). A system of tactical assessment in Soccer (FUT-SAT) was used to collect data. Descriptive statistics and multinomial logistic regression were applied. The tactical performance indexes were divided into tercis (low, moderate and high) in order to evaluate the influences of relative age effects and quality of tactical behaviours. The quality in the “penetration” and “offensive coverage” principles were positively related to moderate performance indexes. Players with the highest quality in the “depth mobility” and “unity defensive” principles were more likely to present higher performance indexes. Regarding the defensive phase, those with better qualities in the “delay”, “concentration” and “defensive unity” principles were more likely to have moderate performance index. Additionally, better quality in the “defensive coverage” and “balance” principles corresponded to a higher likelihood of having a superior performance index. Relative age effects were observed only in high defensive performance index. The present results revealed a positive correlation between tactical performance indexes and quality of tactical behaviours.

Correlates of changes in BMI of children from the Azores islands

Objective:To model changes in body mass index (BMI), including its stability, and to investigate the association between physical activity, 1-mile run/walk and levels of gross motor coordination and BMI during 5 consecutive years.Design:A longitudinal study of children 6 years of age at baseline followed at annual intervals over 5 years.Subjects:A total of 285 children (143 boys and 142 girls) were enrolled in grade 1 (age 6 years) and followed through grade 5 (age 10 years).Measurements:BMI was recorded and physical activity was assessed by questionnaire, aerobic fitness was evaluated with the 1-mile run/walk and gross motor coordination was measured with the KTK test battery (Körperkoordination test für Kinder). Multilevel modelling techniques were for the primary analysis.Results:Changes in BMI showed similar curvilinear trends in boys and girls, with ample inter-individual crossing trajectories that is, low tracking. Longitudinal changes in physical activity (PA) and aerobic fitness were not significantly associated with BMI-changes during the 5 years. Children who were more proficient in their motor coordination showed lower values of BMI during the 5 years.Conclusions:BMI trajectories of both boys and girls show low tracking of BMI-values. Considerable inter-individual variation exists both in baseline BMI-values and changes (velocity and acceleration) over time. PA and fitness were not associated with BMI-changes, but gross motor function was negatively associated with BMI-changes. No gender-specific associations were found. If confirmed in other populations these observations could be translated in the promotion of physical activities that improve gross motor function in children aged 6–10 years. This seems to be of major importance for the physical education curriculum of primary school children.

Gender, weight status and socioeconomic differences in psychosocial correlates of physical activity in schoolchildren

OBJECTIVES This study sought to assess differences in attraction to physical activity, perceived physical competence and parental socialization influences across gender, body mass index and socioeconomic status in Portuguese children. DESIGN Cross-sectional study. METHODS 683 children, aged 8-10 years, from elementary schools were participants. Attraction to physical activity, perceived physical competence, parental socialization influences and socioeconomic status were assessed via standardized questionnaires. The prevalence of overweight and obesity was calculated using body mass index, based on the international cut-off points. MANOVA and ANOVA models were conducted. RESULTS Boys reported greater enjoyment of games and sports participation than did girls. Boys and normal-weight children perceived themselves as being more successful and physically competent than did girls and obese children. Normal-weight girls enjoyed participation in vigorous physical activity more than did overweight and obese girls. Obese children felt less accepted by their peers in games and sports than did normal-weight and overweight children. High and medium socioeconomic status children perceived physical activity participation as of greater importance than did low-socioeconomic status children. High-socioeconomic status girls reported greater liking of the exertional aspects of physical activity compared to low socioeconomic status girls. High socioeconomic status children were more likely to perceive their parents as positive role models and perceived that they had greater enjoyment of physical activity than did lower socioeconomic status children. CONCLUSIONS These results suggest that physical activity promotion interventions should focus on girls, obese children and lower socioeconomic status children as these individuals tend to have lower levels of attraction to physical activity, lower perceived physical competence and less parent physical activity support, which puts them at greater risk of being physically inactive.

Physical match performance of youth football players in relation to physical capacity

Abstract The aims of the study were to (1) analyse the activity profile of youth football players during competitive matches, and (2) examine the relationship between physical match performance and intermittent exercise performance as well as . Thirty youth male football players, aged 14–17 years, carried out a laboratory treadmill test for determination of as well as the Yo-Yo intermittent recovery level 1 (Yo-Yo IR1) and Yo-Yo intermittent endurance level 2 (Yo-Yo IE2) tests. Time–motion analysis and heart rate (HR) recordings were performed during two competitive matches per player. Distance covered during the match was 6311±948 (range: 4435–8098) m, of which 12% were high-intensity activities (HIA; 759±437 [374–2062] m), and 5% was backwards running (309±205 [12–776] m). Mean match HR was 168±12 (140–187) bpm, corresponding to 85% (69–91) of maximum HR. The total distance covered in the last 13.3-min period of the match was 40%, 26% and 17% lower than in the first, second and fourth 13.3-min periods of the match, respectively (P<0.05). The distance covered in backwards running decreased by 31% and 37% from the first to the last 13.3-min periods of the first and second half, respectively (P<0.05). The Yo-Yo IR1 was significantly associated with the time spent with sprinting during the match (r=0.63; P=0.002) and during the last 13.3-min period (r=0.63; P=0.022). Both Yo-Yo IR1 and Yo-Yo IE2 were correlated with the time spent with match HIA (r=0.56 and r=0.57, respectively; P<0.05). No significant relationship was observed between and match time–motion variables (r=−0.13–0.25; P>0.05) or Yo-Yo test performances (r=0.09–0.26; P>0.05). In conclusion, youth football players have a high heart-rate loading during match play and a decreased running performance towards the end of the game. The intermittent exercise capacity, as determined in the Yo-Yo IR1 test, appears to be a valid indicator of high-intensity exercise performance in youth matches.

Injuries in Portuguese Youth Soccer Players During Training and Match Play

CONTEXT Epidemiologic information on the incidence of youth soccer injuries in southern Europe is limited. OBJECTIVE To compare the incidence, type, location, and severity of injuries sustained by male subelite youth soccer players over the 2008-2009 season. DESIGN Descriptive epidemiology study. SETTING Twenty-eight Portuguese male youth soccer teams. PATIENTS OR OTHER PARTICIPANTS A total of 674 youth male subelite soccer players in 4 age groups: 179 U-13 (age range, 11-12 years), 169 U-15 (age range, 13-14 years), 165 U-17 (age range, 15-16 years), and 161 U-19 (age range, 17-18 years). MAIN OUTCOME MEASURE(S) Injuries that led to participation time missed from training and match play prospectively reported by medical or coaching staff of the clubs. RESULTS In total, 199 injuries reported in 191 players accounted for 14.6 ± 13.0 days of absence from practice. The incidence was 1.2 injuries per 1000 hours of exposure to soccer (95% confidence interval [CI] = 0.8, 1.6), with a 4.2-fold higher incidence during match play (4.7 injuries per 1000 hours of exposure; 95% CI = 3.0, 6.5) than during training (0.9 injuries per 1000 hours of exposure; 95% CI = 0.6, 1.3) (F₁,₆₇₃ = 17.592, P < .001). The overall incidence of injury did not increase with age (F₁,₆₇₃ = 1.299,P = .30), and the incidence of injury during matches (F₁,₆₇₃ = 2.037, P = .14) and training (F₁,₆₇₃ = 0.927, P = .44) did not differ among age groups. Collisions accounted for 57% (n = 113) of all injuries, but participation time missed due to traumatic injury did not differ among age groups (F₃,₁₁₀ = 1.044, P = .38). Most injuries (86%, n = 172) involved the lower extremity. The thigh was the most affected region (30%, n = 60) in all age groups. Muscle strains were the most common injuries among the U-19 (34%, n = 26), U-17 (30%, n = 17), and U-15 (34%, n = 14) age groups, whereas contusions and tendon injuries were the most common injuries in U-13 players (both 32%, n = 8). The relative risk of injury slightly increased with the age of the competitors. CONCLUSIONS The higher incidence of injury during matches than training highlights the need for education and prevention programs in youth soccer. These programs should focus on coach education aimed at improving skills, techniques, and fair play during competitions with the goal of reducing injuries.