Under-17 Research Articles

Validity and reliability of Gyko Sport for the measurement of barbell velocity on the bench-press exercise.

The aim of this study was to examine the validity and reliability of the novel inertial measurement unit (named: Gyko Sport) for the measurement of barbell concentric velocity on the bench-press exercise. Ten under-16 (U16) basketball players performed 2 repetitions of the bench press exercise with 6 different loads (40, 50, 60, 70, 80 and 90% of one repetition maximum [1-RM]; N.=120 repetitions). Mean velocity for each repetition was simultaneously recorded using the Gyko Sport and SmartCoach linear transducer. Results showed a very large correlation between the SmartCoach and Gyko Sport (r=0.79; standard error of estimate [SEE]=0.18 m/s). Furthermore, there was a very high agreement between both devices for the measurement of the mean velocity (intraclass correlation coefficient [ICC]=0.774; Cronbach's alpha [α]=0.872; Bland-Altman Plots [R2]=0.070). The Gyko Sport registered similar, but slightly higher values than the SmartCoach (P=0.103; mean difference 0.075±0.05 m/s). The results support the use of the Gyko Sport as an affordable, portable, and suitable wearable device to measure mean velocity on bench press exercise.

Velocity-specific knee strength between professional and under-17 female volleyball players.

BackgroundMany studies have investigated isokinetic performance in volleyball players but not through surface maps.ObjectivesThe goals of this study were to assess velocity-specific isokinetic knee extensor–flexor muscle strength and to compare the isokinetic knee extensor–flexor muscles between professional (PRO) and under-17 (U17) female volleyball players.MethodThis cross-sectional laboratory study was developed with two groups: PRO (n = 12), medianage = 21.3 years, and U17 (n = 9), medianage = 15 years. Peak torque, total work, mean power, angle of peak torque, hamstring–quadriceps torque ratio (H–Q ratio) and torque–angle–velocity surface maps were analysed from knee extension–flexion at 60, 120 and 300 degrees per second (°/s).ResultsSignificant differences were identified for extensor peak torque between PRO x = 202.3 Newton metre (N·m) (standard deviation [SD] = 24.4) and U17 x = 141.6 N·m (30.1) at 60 °/s (p < 0.001; d = 2.21) as well as flexor peak torque (PRO x = 75.7 N·m [10.3] and U17 x = 57.7 N·m [11.4]) at 120 °/s (p < 0.001; d = 1.65) for the dominant limb. There were also significant group differences for total work and mean power at all velocities for extension and flexion. Surface maps demonstrated higher torque at lower speeds for both groups with smaller torque changes across velocities for flexion.ConclusionDifferent groups of female volleyball players showed contrasting concentric knee muscle strength across isokinetic velocities.Clinical implicationsThese results demonstrate the importance of specific strength training for different age groups, even within the same sport, and provide insight into muscle strength.

Jump higher, run faster: effects of diversified sport participation on talent identification and selection in youth basketball

ABSTRACTThe aims of this study were to examine the medium-term effects of previous experiences during early stages of sport development on physical capacities of under-13 (U-13) talented basketball players and, to identify variables that discriminated under-14 (U-14) national team training camp selection. Anthropometrical and physical measurements were collected during a basketball training camp. Previous sport experiences (6–10 years), maturity offset, power outputs for jumping and sprinting were determined. A cluster analysis was used to allocate the subjects according to their different levels of sport experiences (more specialized vs. less specialized) to allow creating a dummy variable for the subsequent analysis of the physical variables. A stepwise discriminant analysis was computed to identify the construct that best classifies selected and non-selected players for U-14 national team training camp. The less specialized group outscored more specialized in all physical parameters, irrespectively of gender. The Abalakov Jump Peak Power and Predicted Adult Height (PAH) could successfully discriminate selected from non-selected players for U-14 national team training camp in boys and PAHin girls. The diversified and non-specific sport stimulus during early ages seem to be determinant to the acquisition and development of fundamental movement skills of talented basketball players.

Effects of Maturation on Lower Limb Neuromuscular Asymmetries in Elite Youth Tennis Players.

Neuromuscular asymmetries have been previously associated with reduced performance. Similarly, maturation has shown that youth athletes may experience a loss of motor control, which could also lead to compromised physical performance. The present study aimed to evaluate and quantify the level of asymmetry among chronological and maturational groups. Forty-one youth tennis players performed the single leg countermovement jump (SLCMJ), star excursion balance test (SEBT) and a change of direction speed (CODS) test. Differences were found between the strongest and weakest limbs across all tests (p < 0.001), and also for SEBT in the posteromedial direction (p = 0.02), SEBT composite score (p < 0.01) in maturation groups, and for SEBT posterolateral direction (p = 0.03) and SEBT composite score (p = 0.01) in chronological groups. The SLCMJ showed the largest inter-limb asymmetries for the circa peak height velocity (PHV) group (19.31 ± 12.19%) and under-14 (U14) group (17.55 ± 9.90%). Chronological and maturation groups followed similar trends for inter-limb asymmetries, but the biological index showed larger asymmetry scores in the jumping test at PHV compared to that found in the chronological group (U14). These results show that inter-limb differences may be heightened during PHV. Practitioners can use this information to inform the decision-making process when prescribing training interventions in youth tennis players.

Workload and injury incidence in elite football academy players

ABSTRACTThe aim of this study was to prospectively analyse the relationship between workloads and injury in elite football academy players. Elite football academy players (n = 122) from under-19 (U19) and under-21 (U21) of a professional football team competing in UEFA European Cups were followed during 5 seasons. Injuries were collected and absolute workload and workload ratios (4-weeks, 3-weeks, 2-weeks and week-to-week) calculated using a rolling days method with the help of the session Rate of Perceived Exertion. There was no association between absolute workload or workload ratio with the injury incidence in the U19. In the U21, the level of cumulative absolute workloads during 3-weeks (RR = 1.39, p = 0.026) and during 4-weeks (RR = 1.40, p = 0.019) were associated with an increase in injury. There was no association between workload ratio and injury in U21. The significant link between high cumulated 3-weeks and 4 weeks workloads and injury in U21 confirmed the requirement to monitor the internal subjective workload in U21 in order to prevent injury. Further studies exploring the relationships between workload and injury are required in football academy.

Tactical efficacy and offensive game processes adopted by Italian and Brazilian youth soccer players

Abstract Aim: To analyze success and failure of offensive sequences and the adopted offensive method in under-15 (U-15) and under-17 (U-17) soccer players. Methods: The sample was composed of 218 offensive sequences performed by U-15 and U-17 players selected from 28 matches, being 18 matches of an Italian team and 10 matches of a Brazilian team. All offensive sequences which ended in finalization were selected for the analysis. Using observational methodology, an adapted ad hoc observational instrument was built with the variables “number of players involved”, “ball touches”, “passing”, “duration”, and “corridor changes”. Next, offensive actions were classified into three offensive game methods: counter-attack, quick attack, and positional attack. Results: Results revealed that teams which use positional attack expend more time constructing an offensive play, involve extra players, and change the ball corridor more often during offensive actions when compared to counter-attack and quick attack (p<0.01). Moreover, offensive efficacy did not present an association with the offensive method employed (X2=0.47; p=0.78). Sequences that finished in success presented significantly higher values of the number of touches (p=0.02), passes (p=0.003), and duration (p=0.01) in comparison to failure. Conclusion: The findings suggest that all offensive methods adopted can be used to reach success during a game of U-15 and U-17 soccer players.

Effects of different repeated sprint-training frequencies in youth soccer players

The aim of this study was to determine the effects of 2 different repeated-sprint ability (RSA) training frequencies (2 RSA sessions per week [RSA2D] or 1 RSA session [RSA1D]) under volume-equated conditions on sprint and RSA performance in under-15 (U15) soccer players. Twenty-seven youth male soccer players (age: 12.29±0.47 years; height: 158.35±10.86 cm; weight: 45.08±8.05 kg) were randomly assigned to RSA2D (n=14) or RSA1D (n=13) groups. The players performed the same RSA training for 6 weeks, and only the training frequency differed between the groups. Before and after the training period, 5 m sprint, 10 m sprint, 20 m sprint and the RSA test were assessed. No significant time × group interactions were observed (p>0.05). Within-group analysis showed significant improvements in 20 m sprint (p=0.046, partial eta squared [ηp2] = 0.150, large) and RSA average time (p=0.001, ηp2=0.438, large), fastest time (p=0.012, ηp2=0.229, large), and total time (p=0.001, ηp2=0.438, large) from pre-test to post-test in RSA1D and RSA2D groups. However, no significant pre-post changes (p>0.05) were found in 5 m and 10 m sprint tests. In the between-group analysis, there were no significant differences between RSA1D and RSA2D groups in any variable. In conclusion, the current findings suggest that 6 weeks of RSA training 1 or 2 times per week in addition to typical soccer training produced significant and similar improvements in sprint and RSA performances. This information could be useful for coaches when planning training sessions during congested fixtures of soccer competitions or in periods when the emphasis should be placed on other physical qualities.

Are regional differences in basketball already established in under-18 games?

Abstract Aims: To identify regional differences in basketball games for under-age categories, this study analyzed game-related statistics of four continental championships for under-18 (U18) men. Methods: A total of 149 games from each continental championship for U18 men held in 2016 were analyzed. A one-way analysis of variance followed by a Bonferroni post hoc test was performed to assess differences in game-related statistics between the continents (Europe, Africa, America, Asia). A discriminant analysis was performed to identify game-related statistics which discriminate among the continents. Results: The U18 African championship, which was characterized by a high number of free throws, was clearly discriminated from any other U18 continental championship. Among the other U18 continental championships excluding the African championship, the biggest difference was observed between the European and the Asian championships. The U18 European championship was characterized by a low number of possessions and a high number of assists, whereas the U18 Asian championship was characterized by a high number of possessions and a low number of assists. Both possessions and assists showed high numbers in the U18 American championship. Conclusion: This study identified regional differences in basketball games among four continental championships for U18 men held in 2016. It is suggested that basketball games for under-age categories are played in a different manner in each region of the world. The information derived from this study will help players and coaches of under-age national teams prepare for international competitions.

Evidence for a Role of ACTN3 R577X Polymorphism in Football Player's Career Progression.

The aim was to investigate a possible role of the ACTN3 R577X polymorphism in a Brazilian football player's career progression. 2 questions were formulated: 1. Does ACTN3 polymorphism affect the probability of an individual being a professional football player? 2. Does this polymorphism affect the progression of the athlete throughout his career? The study included 353 players from first division Brazilian football clubs in the following categories: under-14 (U-14), U-15, U-17, U-20, and professional (PRO). The control group (CON) was composed of 100 healthy non-athletes. The chi-squared test was used to assess differences between the allele and genotype frequencies. Comparing football categories, the XX genotype was less frequent among professional players than in the U-20 (p<0.05) or the U-15 category (p<0.05). The RX genotype also presented more frequently in the PRO category than the U-14 category (p<0.05). Moreover, a trend towards a higher frequency of the RX genotype and a lower frequency of the XX genotype was observed in the professional category compared to U-20. These results suggest that the genotype in the ACTN3 polymorphism affects the probability of a football player progressing throughout his career and becoming professional, meaning that playing football selects against the ACTN3 XX genotype.

Successful and Unsuccessful Offensive Sequences Ending in a Shot in Professional and Elite Under-16 Basketball.

Following observational methodology, we analyzed successful and unsuccessful offensive attacks by professional and elite under-16 (U16) basketball players in Spain using an adapted ad hoc observation instrument designed to study efficiency in basketball. We identified both similarities and differences between how players from both categories built their attacks. The synchronic statistical analysis based on frequency counts showed that shots were more efficient in professional basketball and that U16 basketball was less static and had a higher frequency of fast breaks. Diachronic analysis, which consisted of T-pattern detection using Theme software, allowed us to identify characteristic successful and unsuccessful offensive sequences in professional and elite U16 basketball. These results have practical implications as they can be used to design training drills and prepare for competitions in U16 and professional basketball.

Basketball Game-Related Statistics that Discriminate among Continental Championships for Under-18 Women.

The purposes of this study were (a) to evaluate differences in basketball game-related statistics among continental championships for under-18 (U18) women, and (b) to identify game-related statistics that discriminate among the continents. The analysis was performed on all matches (n = 136) in the four continental championships (Africa, America, Asia, Europe) of 2016. Differences in game-related statistics among the continents were analyzed by an analysis of variance (ANOVA) with effect size statistics. Game-related statistics that discriminate among the continents were assessed by discriminant analysis. The ANOVA yielded significant F-values for 13 of 16 variables and large effect size differences for 10 of 16 variables. The discriminant analysis yielded three significant functions. The Asian championship was discriminated from the other continental championships by ball possessions, defensive rebounds, assists, and fouls. The African championship was discriminated from the European championship by ball possessions, successful 3-point field goals, unsuccessful free throws, and turnovers, and from the American championship by ball possessions, unsuccessful 2-point field goals, successful 3-point field goals, successful free throws, and assists. The results of this study suggest that U18 women’s basketball games are played differently in each continent.

The number of purposeful headers female youth soccer players experience during games depends on player age but not player position

ABSTRACTPurpose: The aim of this study was to describe the frequency and characteristics of purposeful soccer heading in youth players based on age, position, and head impact location.Methods: Game video was recorded for three female youth teams [under-13 (U13), under-14 (U14), and under-15 (U15)] for an entire season. Purposeful headers were categorized for these three teams and their opposition.Results: The median number of headers experienced during games was one, and the minimum number of headers was zero. The maximum number of headers performed during a game by a U13 player was eight, and nine for U14 and U15 players. There were statistically significant differences in the number of headers performed in the different age groups (p < 0.05), but no significant differences between player position (p > 0.05). There was no significant association between head impact location and game scenario (p > 0.05).Conclusions: Our study shows that youth players frequently head the ball during games. This information may guide data-driven approaches regarding heading restrictions in youth soccer.

Differential Learning as a Key Training Approach to Improve Creative and Tactical Behavior in Soccer

ABSTRACTPurpose: The aim of this study was to identify the effects of a differential-learning program, embedded in small-sided games, on the creative and tactical behavior of youth soccer players. Forty players from under-13 (U13) and under-15 (U15) were allocated into control and experimental groups and were tested using a randomized pretest to posttest design using small-sided games situations. Method: The experimental group participated in a 5-month differential-learning program embodied in small-sided games situations, while the control group participated in a typical small-sided games training program. In-game creativity was assessed through notational analyses of the creative components, and the players’ positional data were used to compute tactical-derived variables. Results: The findings suggested that differential learning facilitated the development of creative components, mainly concerning attempts (U13, small; U15, small), versatility (U13, moderate; U15, small), and originality (U13, unclear; U15, small) of players’ actions. Likewise, the differential-learning approach provided a decrease in fails during the game in both experimental groups (moderate). Moreover, differential learning seemed to favor regularity in pitch-positioning behavior for the distance between players’ dyads (U13, small; U15, small), the distance to the team target (U13, moderate; U15, small), and the distance to the opponent target (U13, moderate; U15, small). Conclusions: The differential-learning program stressed creative and positional behavior in both age groups with a distinct magnitude of effects, with the U13 players demonstrating higher improvements over the U15 players. Overall, these findings confirmed that the technical variability promoted by differential learning nurtures regularity of positioning behavior.

Exploring how playing football with different age groups affects tactical behaviour and physical performance.

The study aimed to compare footballers’ performances when playing with teammates and opponents from the same age group with performances when playing with teammates and opponents of different age groups. Three football matches were played: i) under-15 (U15) players played with each other; ii) under-17 (U17) players played with each other; and iii) players under the age of 15 and 17 played with each other in two equivalent mixed age teams. The players’ physical performance was measured using the distances covered at different speed categories and tactical behaviour was assessed using several positioning-derived variables. The results showed that, when playing in the mixed age condition, the U15 players increased the distance covered in sprinting intensity (18.1%; ±21.1%) and the U17 players increased the distance covered in jogging zones (6.8%; ±6.5%). The intra-team movement synchronization in longitudinal and lateral displacements was higher when U15 players confronted peers of the same age, in the first half (-13.4%; ±2.0%, -20.3%; ±5.7% respectively), and when U17 players confronting the mixed group, in both halves (-16.9%; ±2.5%, 9.8%; ±4.0% and 7.9%; ±5.7%, 10.6% ±4.4%, respectively). The differences between age groups and the mixed condition may be connected with the level of players’ tactical expertise and adaptive positioning according to the dynamic environmental information. In general, these results suggest that mixing the age groups may be useful to promote a wider range of training session stimuli in these young football players.

Skin temperature changes of under-20 soccer players after two consecutive matches

To examine whether two consecutive soccer matches would affect skin temperature (t sk) measured via infrared thermography (IRT) in under-20 (U-20) soccer athletes, as well as verify whether the t sk changes would be different between regions of interest. A cross sectional study. Ten under-20 soccer athletes [age 19.0 ± 1.0 years; height 181.3 ± 6.6 cm; body fat percentage (BF%) 9.0 ± 1.8%, body surface area 1.9 m2 and $$\dot{V}$$ O2max 56.4 ± 3.2 ml min−1 kg−1]. Skin thermal responses obtained by IRT and creatine kinase concentration (CK) were evaluated in response to two soccer matches with 3 days of recovery between each match. The t sk increased (≅1.0 °C) 24 h after the first match in all studied regions of interest (ROIs), returning to near pre-match values 48 h after the first match. However, after playing the second match, the t sk increased even more (≅1.5 °C) 24 h after in all the considered ROIs, not returning to pre-match values 48 h after. Regarding CK analysis, its course during the experiment was similar to t sk, with high values 24 h after (first match 763.8 ± 294.5 U/L; second match 784.1 ± 298.8 U/L) and recovering 48 h after (first match 526.4 ± 289.7 U/L; second match 672.2 ± 285.0 U/L) both matches. However, when the two matches are compared, CK showed a higher value 48 h after the second match in comparison to first match (P = 0.002). The t sk and CK were moderately correlated in all ROIs analyzed, with higher correlation in the anterior right leg (r = 0.425) and anterior left leg (r = 0.428). The t sk of lower limbs as well as CK markedly change in response to two consecutive matches separated by an interval of 3 days. There is indication of the highest inflammatory response after the second match, which was preceded by just a 3-day recovery. In addition, a general increase was obtained in thighs and legs in anterior and posterior views.

Physiological Profile and Activity Pattern of Minor Gaelic Football Players.

Cullen, BD, Roantree, M, McCarren, A, Kelly, DT, O'Connor, PL, Hughes, SM, Daly, PG, and Moyna1, NM. Physiological profile and activity pattern of minor Gaelic football players. J Strength Cond Res 31(7): 1811-1820, 2017-The purpose of this study was to evaluate the physiological profile and activity pattern in club- and county-level under-18 (U-18) Gaelic football players relative to playing position. Participants (n = 85) were analyzed during 17 official 15-a-side matches using global positioning system technology (SPI Pro X II; GPSports Systems, Canberra, Australia) and heart rate (HR) telemetry. During the second part of this study, 63 participants underwent an incremental treadmill test to assess their maximal oxygen uptake (V[Combining Dot Above]o2max) and peak HR (HRmax). Players covered a mean distance of 5,774 ± 737 m during a full 60-minute match. The mean %HRmax and %V[Combining Dot Above]O2max observed during the match play were 81.6 ± 4.3% and 70.1 ± 7.75%, respectively. The playing level had no effect on the distance covered, player movement patterns, or %HRmax observed during match play. Midfield players covered significantly greater distance than defenders (p = 0.033). Playing position had no effect on %HRmax or the frequency of sprinting or high-intensity running during match play. The frequency of jogging, cruise running, striding (p = 0.000), and walking (p = 0.003) was greater in the midfield position than in the forward position. Time had a significant effect (F(1,39) = 33.512, p-value = 0.000, and (Equation is included in full-text article.)= 0.462) on distance covered and %HRmax, both of which showed a reduction between playing periods. Gaelic football is predominantly characterized by low-to-moderate intensity activity interspersed with periods of high-intensity running. The information provided may be used as a framework for coaches in the design and prescription of training strategies. Positional specific training may be warranted given the comparatively greater demands observed in the midfield playing position. Replicating the demands of match play in training may reduce the decline in distance covered and %HRmax observed during the second half of match play.

Physical characteristics of elite adolescent female basketball players and their relationship to match performance.

There were two aims of this study: first, to investigate physical fitness and match performance differences between under-16 (U16) and under-18 (U18) female basketball players, and second, to evaluate the relationship between physical fitness and game-related performances. Twenty-three young, female, elite Spanish basketball players (16.2 1.2 years) participated in the study. The sample was divided into two groups: U16 and U18 players. The average scores from pre- and post-season physical fitness measurements were used for subsequent analyses. Anthropometric variables were also measured. To evaluate game performance, game-related statistics, including the number of games and minutes played, points, rebounds, assists, steals and blocks per game, were recorded for every competitive match in one season. When anthropometric and physical performance variables were compared between groups, the U18 group demonstrated significantly (p<0.05) higher values in upper (+21.2%) and lower (+27.11%) limb strength compared to the U16 group. Furthermore, no significant differences between groups were observed in match performance outcomes. Only two performance variables, steals and assists per game, correlated significantly with jump capacity, speed, agility, anaerobic power, repeated sprint ability and aerobic power (p ≤ 0.005). These findings can help optimize training programs for young, elite female basketball players.

Torque-angle-velocity Relationships and Muscle Performance of Professional and Youth Soccer Players.

Soccer matches consist of a variety of different activities, including repeated sprints. Time to attain velocity (TTAV), load range (LR) and the torque-angle-velocity relationship (TAV3D) represent an important measurement of muscle performance, however there are few related studies. The aim of this study was to compare these outcomes between soccer players of different age category. 17 professional (PRO) and 17 under-17 (U17) soccer players were assessed for concentric knee flexion/extension at 60, 120 and 300°/s. For the extensor muscles, differences were found in favor of the U17 group for TTAV and LR outcomes at 120°/s, however, the PRO group maintained higher torques in both movement directions in comparison to the U17 in TAV3D evaluation. These results suggest that muscle performance of the PRO group is more efficient than the U17 group.

Peak torque and muscle balance in the knees of young U-15 and U-17 soccer athletes playing various tactical positions.

Soccer is a sport that is practiced worldwide and has been investigated in its various aspects, particularly muscle strength, which is an essential motor skill for sports performance. The objective of this study was to investigate the peak torque and muscle balance on the knee extensor and flexor of young soccer players in the tactical positions of goalkeeper, defender, full back, midfielder, defensive midfielder and striker, as well as to determine which field position has the highest peak torque. Forty-nine male players were recruited and divided into two categories during the preparatory period of the season: the Under-15 (U-15) group (N.=23, mean age 14.7±0.5 years, body mass 58.2±10.5 kg, body height 168.5±7.6 cm), and the Under-17 (U-17) group (N.=26, mean age 16.8±0.4 years, body mass 69.2±7.9 kg, body height 176.2±6.6 cm). The U-17 athletes presented a higher peak torque in all the movements of flexion and extension in the two angular velocities (i.e. 60°/s and 300°/s), but only the dominant knee extensor at 300°/s was significantly different between the two categories as well as the percentage change in peak torque compared between U-15 and U-17 was always above 20%. The peak torque variation in the U-17 category (i.e. mostly above 20%) highlights a higher peak torque compared to U-15 athletes. The muscular deficit of the two categories presented a low average of 10-15%, indicating a good muscle balance between knee extensors and flexors. Finally, goalkeepers and defenders achieved the highest peak torque amongst the field positions.

Influence of Skeletal Maturity on Size, Function and Sport-specific Technical Skills in Youth Soccer Players

This study compared variation in size, function and sport-specific technical skills of youth soccer players associated with differences in biological maturity status. 60 male soccer players of under-14 (U14) and under-17 (U17) categories were submitted to anthropometric and body composition measurements as well as motor and soccer-specific technical skill tests. Skeletal maturity was determined by skeletal age. Athletes of both categories were classified as early, on-time or late-maturing, according to the difference between chronological age and skeletal age. Body mass and height were lower in the late athletes, independent of category (P<0.01). Differences in adiposity were found only between athletes of the U14 (late<early, P<0.05). Statistically significant differences were identified on aerobic endurance in U14 (early<on time, P<0.01), upper limbs muscular strength (late<early, P<0.01) and flexibility in U17 (late<on time, P<0.05). Players in each age group of contrasting maturity status do not differ in soccer-specific skills. The results suggest that the maturational development influences body mass, height, body fat, flexibility, muscular strength of upper limbs and cardiorespiratory fitness, whereas the specific technical skills and other functional capabilities do not seem to be affected.