Vasco Vaz

Network analysis and intra-team activity in attacking phases of professional football

In this study we sought to verify whether network analyses could be used to identify key players in attacking phases of a professional football match and establish the main interactions and preferential linkages between attacking teammates during competitive performance. For this purpose, we examined circulation of the ball on field during randomly selected attacking phases of play in a video-taped Portuguese Premier League match. We observed six matches and notated 1488 collective attacking actions, including: passes completed, passes received, and crosses involving a total of 4126 intra-team interactions (eg., 2063 passes and crosses performed and 2063 passes and crosses received). We used Amisco® software to perform quantitative and qualitative analyses of the attacking actions. Results indicated how key individual players are instrumental in orchestrating team performance, exerting a powerful influence in creating attacking patterns of play. Our findings may help coaches and sports scientists quantify the contributions and interactions of individual team members through analysis of their relevant actions in team sports like football.

Allometric scaling of peak oxygen uptake in male roller hockey players under 17 years old

Peak oxygen uptake (V̇O2peak) is routinely expressed in litres per minute and by unit of body mass (mL·kg(-1)·min(-1)) despite the theoretical and statistical limitations of using ratios. Allometric modeling is an effective approach for partitioning body-size effects in a performance variable. The current study examined the relationships among chronological age (CA), skeletal age (SA), total body and appendicular size descriptors, and V̇O2peak in male adolescent roller hockey players. Seventy-three Portuguese, highly trained male athletes (CA, 15.4 ± 0.6 years; SA, 16.4 ± 1.5 years; stature, 169.9 ± 6.9 cm; body mass, 63.7 ± 10.7 kg; thigh volume, 4.8 ± 1.0 L) performed an incremental maximal test on a motorized treadmill. Exponents for body size descriptors were 2.15 for stature (R(2) = 0.30, p < 0.01) and 0.55 for thigh volume (R(2) = 0.46, p < 0.01). The combination of stature or thigh volume and CA or SA, and CA(2) or SA(2), increased the explained variance in V̇O2peak (R(2) ranged from 0.30 to 0.55). The findings of the allometric model combining more than 1 body size descriptor (i.e., stature and thigh volume) in addition to SA and CA(2) were not significant. Results suggest that thigh volume and SA are the main contributors to interindividual variability in aerobic fitness.

Ventricular mass in relation to body size, composition, and skeletal age in adolescent athletes.

Objective:To examine the contribution of chronological age (CA), skeletal age (SA), stature, sitting stature, fat-free mass (FFM), and fat mass (FM) to interindividual variability in left ventricular mass (LVM) in male adolescent roller hockey players using allometric models. Design:Cross sectional. Setting:Training and competitive sport during adolescence. Participants:Seventy-three Portuguese male roller hockey players aged 14.5 to 16.5 years. Independent Variables:Stature, sitting stature, body mass, estimated FM and FFM, and SA assessed by the Fels method. Main Outcome Measures:Allometric modeling of LVM assessed in accordance with recommendations of the American Society of Echocardiography. Results:Hockey players (CA: 15.4 ± 0.6 years; SA: 16.4 ± 1.5 years) showed an eccentric remodeling of LV structure within the reference range (ie, 0.24-0.42), a dilated LV chamber, but no LVM increase. Exponents for body size descriptors were 2.69 for stature (R2 = 27%; P < 0.001), 2.49 for sitting stature (R2 = 37%; P < 0.001), 0.76 for FFM (R2 = 31%; P < 0.001), and 0.22 for FM (R2 = 26%; P < 0.001). The combination of size descriptors with CA and SA increased the explained variance in LVM slightly (26%-45%). Conclusions:When stature and FM are used for indexing LVM in a sample of adolescent athletes, biological maturity status should also be considered.

Sport selection in under-17 male roller hockey

Abstract Characteristics of 32 international and 41 local under-17 (U-17) (14.5–16.5 years) roller hockey players were considered in the context of discrimination by competitive level using training history, anthropometry, skeletal maturation, and several laboratory and field performance tests. More international (42%) than local (22%) players were advanced in maturity status. International players had slightly less hockey experience (years), but had more practice sessions and match time (minutes) during the season. Local players were shorter and attained better performance in the 25-m dash, while international players performed better in sit-ups, ball throw and 20-m shuttle run. The fatigue index derived from the Wingate anaerobic test was higher among local players, while peak torques of knee extension and flexion were greater in international players. Stepwise discriminant function correctly classified 85% of players by competitive level based on grip strength, ratio of eccentric and concentric knee extension, number of training sessions, playing time and fatigue index. The results suggested an interaction among strength, anaerobic fitness and training plus game time as factors in discriminating international from local level players and by inference in the selection and development of youth roller hockey players.

Reproducibility of peak power output during a 10-s cycling maximal effort using different sampling rates

The study was aimed to investigate the reproducibility of performance parameters obtained from 10-s maximal cycling effort against different braking forces in young adult athletes. The sample (n = 48) included male athletes aged 18.9-29.9 years (175.5 ± 6.9 cm, 76.2 ± 10.1 kg). The exercise protocol was performed in a cycle-ergometer against a random braking force (4% to 11% of body mass). Intra-individual variation was examined from repeated tests within one week. Descriptive statistics were computed and differences between sessions were tested using paired t-test. The coefficient of correlation between repeated measures, technical error of measurement (TEM), coefficient of variation and ICC were calculated. Agreement between trials was examined using the Bland-Altman procedure. Mean values of peak power were relatively stable when obtained from sampling rates of 50 Hz and ranged between 1068 watt and 1082 watt (t(47) = 1.149, p = 0.256, ES-r = 0.165) or while corresponding to a sampling rate of 1 Hz (t(47) = 0.742, p = 0.462, ES-r = 0.107). Correlations between repeated measures were high (+0.907, 95% CI: +0.839 to +0.947) and TEM about 59.3 watt (%CV = 5.52%; ICC = 0.951, 95% CI: 0.912 to 0.972). The present study suggests that reproducibility of peak power in male adult athletes tended to be acceptable and within individual error appeared unrelated to braking force.

Reproducibility of estimated optimal peak output using a force-velocity test on a cycle ergometer

The current study aimed to examine the reproducibility of estimated peak power and estimated pedal velocity in a multi-trial 10-s all-out cycling test among adult athletes (n = 22; aged 23.50±4.73 years). Stature, sitting height and body mass were measured. Leg length was estimated as stature minus sitting height. Body volume was obtained from air displacement plethysmography and was subsequently used to calculate body density. Fat mass and fat-free mass were derived. The short-term power outputs were assessed from the force-velocity test (FVT), using a friction-braked ergometer on two separated occasions. Differences between repeated measurements were examined with paired t-test and effect sizes calculated. No significant differences were found between session 1 (898 W, 142 rpm) and session 2 (906 W, 142 rpm). Test-retest procedure showed acceptable reliability for estimated peak power output [technical error of measurement (TEM) = 31.9 W; % coefficient of variation (CV) = 3.5; intra-class correlation coefficient (ICC) = 0.986] and pedal velocity (TEM = 5.4 rpm, %CV = 3.8, ICC = 0.924). The current study demonstrated a reasonable reproducibility of estimated peak power and pedal velocity outputs in non-elite male athletes and supports that a familiarization session including a complete FVT protocol is not required.

Cardiac remodeling indicators in adolescent athletes

Objective: The idea that different sports and physical training type results in different cardiac adaptations has been widely accepted. However, this remodelling process among different sport modalities is still not fully understood. Thus, the current study aims to investigate the heart morphology variation associated with a set of different modalities characterized by distinct models of preparation and different methods and demands of training and completion. Method: The sample comprises 42 basketball players, 73 roller hockey players, 28 judo athletes and 21 swimmers. Anthropometry was assessed by a single and experienced anthropometrist and the same technician performed the echocardiographic exams. Analysis of variance was used to study age, body size and echocardiograph parameters as well as different sport athletes comparison. Results: Basketball players are taller (F=23.448; p<0.001; ES-r=0.553), heavier (F=6.702; p<0.001; ES-r=0.334) and have a greater body surface area (F=11.896; p<0.001; ES-r=0.427). Basketball and hockey players have larger left auricle diameters compared with judo athletes (F=3.865; p=0.011; ES-r=0.316). Interventricular end-diastolic septal thickness (F=7.287; p<0.001; ES-r=0.347) and left ventricular posterior wall thickness (F=8.038; p<0.001; ES-r=0.362) of the judokas are smaller compared to the mean values of other sports participants. In addition, relative left parietal ventricular wall thickness is lower among swimmers compared with judokas (F=4.127; p=0.008; ES-r=0.268). Conclusion: The major contributors to changes in heart morphology are for the most part associated with sport-specific training and competition and the specific dynamics and adaptive mechanisms imposed by each sport.

Repeated dribbling ability in young soccer players: reproducability and variation by the competitive level

Abstract The intermittent nature of match performance in youth soccer supports relevance of ability to repeatedly produce high-intensity actions with short recovery periods. This study was aimed to examine the reproducibility of a repeated dribbling ability protocol and, additionally, to estimate the contribution of concurrent tests to explain inter-individual variability in repeated dribbling output. The total sample comprised 98 players who were assessed as two independent samples: 31 players were assessed twice to examine reliability of the protocol; and 67 juveniles aged 16.1 ± 0.6 years were compared by the competitive level (local, n = 34; national, n = 33) to examine construct validity. All single measurements appeared to be reasonably reliable: total (ICC = 0.924; 95%CI: 0.841 to 0.963); ideal (ICC = 0.913; 95%CI: 0.820 to 0.958); worst (ICC = 0.813; 95%CI: 0.611 to 0.910). In addition, the percentage of the coefficient of variation was below the critical value of 5% for total (%CV = 3.84; TEM = 2.51 s); ideal (%CV = 3.90, TEM = 2.48 s). Comparisons between local and national players suggested magnitude effects as follows: moderate (d-value ranged from 0.63 to 0.89) for all repeated sprint ability scores; large for total (d = 1.87), ideal (d = 1.72), worst (d = 1.28) and moderate for composite scores: the fatigue index (d = 0.69) and the decrement score (d = 0.67). In summary, the dribbling protocol presented reasonable reproducibility properties and output extracted from the protocol seemed to be independent from biological maturation.

Morfología de lo ventrículo izquierdo en adolescentes: comparación entre atletas y no atletas

Introducao: A morfologia do ventriculo esquerdo altera-se com o crescimento e desenvolvimento, durante a infância e adolescencia. Contudo, sao escassos os estudos comparativos entre nao atletas e jovens atletas de elite.Objetivo: Analisar possiveis diferencas na morfologia do ventriculo esquerdo entre jovens atletas de elite e nao atletas, do sexo masculino.Metodos: Trinta atletas de elite (15,4±0,6 anos; 68,0±11,3 kg; 175,2±7,5 cm) e 28 adolescentes saudaveis sem experiencia com a pratica esportiva (15,2±1,3 anos; 62,9± 3,8 kg; 168,8±7,7 cm) foram submetidos a medidas antropometricas (estatura, massa corporal e espessura de dobras cutâneas) e avaliacoes ecocardiograficas.Resultados: Diferencas estatisticamente significantes foram encontradas nos diâmetros telediastolico e telesistolico do ventriculo esquerdo, na espessura do septo interventricular em diastole, na espessura da parede posterior do ventriculo esquerdo, no diâmetro do atrio esquerdo e na relacao entre o diâmetro do atrio esquerdo e o diâmetro da raiz da aorta, com os jovens atletas de elite apresentando valores superiores aos nao atletas (P<0,01), mesmo apos ajuste pela estatura. Correlacoes positivas e de moderada magnitude entre a massa do ventriculo esquerdo e a estatura foram encontradas em atletas (r=0,57) e nao atletas (r=0,40).Conclusao: Os resultados do presente estudo sugerem que os valores superiores nas medidas da cavidade e de espessura da parede ventricular esquerda, encontrados no coracao de jovens atletas de elite nao podem ser explicados pela maior estatura, destacando a importância da exploracao de modelos alometricos simples e multiplicativos que integrem medidas de maturacao biologica em futuras investigacoes.

Morfologia do ventrículo esquerdo em adolescentes: comparação entre atletas e não atletas

Introducao: A morfologia do ventriculo esquerdo altera-se com o crescimento e desenvolvimento, durante a infância e adolescencia. Contudo, sao escassos os estudos comparativos entre nao atletas e jovens atletas de elite.Objetivo: Analisar possiveis diferencas na morfologia do ventriculo esquerdo entre jovens atletas de elite e nao atletas, do sexo masculino.Metodos: Trinta atletas de elite (15,4±0,6 anos; 68,0±11,3 kg; 175,2±7,5 cm) e 28 adolescentes saudaveis sem experiencia com a pratica esportiva (15,2±1,3 anos; 62,9± 3,8 kg; 168,8±7,7 cm) foram submetidos a medidas antropometricas (estatura, massa corporal e espessura de dobras cutâneas) e avaliacoes ecocardiograficas.Resultados: Diferencas estatisticamente significantes foram encontradas nos diâmetros telediastolico e telesistolico do ventriculo esquerdo, na espessura do septo interventricular em diastole, na espessura da parede posterior do ventriculo esquerdo, no diâmetro do atrio esquerdo e na relacao entre o diâmetro do atrio esquerdo e o diâmetro da raiz da aorta, com os jovens atletas de elite apresentando valores superiores aos nao atletas (P<0,01), mesmo apos ajuste pela estatura. Correlacoes positivas e de moderada magnitude entre a massa do ventriculo esquerdo e a estatura foram encontradas em atletas (r=0,57) e nao atletas (r=0,40).Conclusao: Os resultados do presente estudo sugerem que os valores superiores nas medidas da cavidade e de espessura da parede ventricular esquerda, encontrados no coracao de jovens atletas de elite nao podem ser explicados pela maior estatura, destacando a importância da exploracao de modelos alometricos simples e multiplicativos que integrem medidas de maturacao biologica em futuras investigacoes.