Male Youth Soccer Players Research Articles

Body Composition Interactions with Physical Fitness: A Cross-Sectional Study in Youth Soccer Players.

This study aimed to: (i) analyze fat mass and physical fitness variations among age-groups and playing positions, and (ii) explore the relationship between fat mass and physical fitness in youth male soccer players. A total of 66 players from under-16, under-17, and under-19 were tested. Body mass, skinfolds, countermovement jump (CMJ), single-leg triple hop jump (SLTH), bilateral triple hop jump (BTH), and yo-yo intermittent recovery Level 2 (YYIR-2) were assessed. A two- and one-way ANOVA were conducted, and the effect size was measured. Interactions were found in skin folds and fat mass. The under-19 group was taller, heavier, with a greater BMI and muscle mass than the under-16 group. They also exceeded the under-16 and under-17 in SLTH, BTH, and YYIRT-2. The under-17 group jumped higher and longer than under-16 group. Goalkeepers were taller and heavier than the midfielders. Central defenders were taller and had more muscle mass than midfielders and were heavier than the midfielders and wingers. The wingers jumped higher than the midfielders and showed better YYIRT-2. BMI was small correlated with YYIRT-2 and moderately with CMJ. Fat mass had a moderate negative correlation with CMJ and YYIRT-2. Muscle mass largely correlated with CMJ, UTH, very large with BTH and moderate with YYIRT-2. Summarily, with increasing age, better performances and body compositions were registered. Muscle mass better influences performance than body fat. Body composition can distinguish players positions.

Weekly Variations of Well-Being and Interactions with Training and Match Intensities: A Descriptive Case Study in Youth Male Soccer Players.

The aim of this study was two-fold: (i) analyze the weekly variations of well-being and training/match intensity measures in youth soccer players, and (ii) test relations between well-being and training intensity outcomes. The study followed a descriptive case study design. Twenty-seven under-17 male soccer players were monitored for well-being and training intensity parameters over seventeen consecutive weeks. An adjusted version of the Hooper questionnaire was used to monitor the perceptive sleep quality, readiness, fatigue, and delayed onset muscle soreness (DOMS) early in the morning. The CR-10 Borg’s scale was also used for monitoring the rate of perceived exertion (RPE) of players after training sessions. Repeated-measures analysis of variance was executed to test the between-week variations of both well-being and training intensity outcomes. Moreover, Pearson product moment correlation was used to test the relations between well-being and training intensity outcomes. Repeated measures ANOVA revealed significant differences between weeks in the sleep quality (F = 0.422; p < 0.001; = 0.140), readiness (F = 0.8.734; p < 0.001; = 0.251), fatigue (F = 4.484; p < 0.001; = 0.147), DOMS (F = 3.775; p = 0.001; = 0.127), RPE (F = 7.301; p < 0.001; = 0.219), and session-RPE (F = 17.708; p < 0.001; = 0.405). Correlations between well-being and training intensity outcomes in the same week revealed moderate correlations between fatigue and session-RPE (r = 0.325). As conclusions, it was found that well-being and training intensity fluctuates over the season, while well-being outcomes seems to be related with training intensity, although with a small magnitude.

Maximal Aerobic Power Using the Modified Heck Protocol: Prediction Models.

The purpose of this study was to develop prediction models based on an incremental treadmill test to volitional exhaustion utilizing the modified Heck protocol. A total of 598 professional and youth athletes participating in different sports were recruited for this study. Specifically, the study enrolled professional male soccer players (n=380), professional male futsal players (n=24), elite male basketball players (n=27), professional male soccer referees (n=50), elite female soccer players (n=19), youth male basketball players (13-14 yrs n=15, 15-17 yrs n=20) and youth male soccer players (15 yrs n=28, 16-17 yrs n=35). Anthropometric measurements included stature, body mass, and body fat. Furthermore, all participants performed incremental cardiopulmonary exercise testing on a treadmill using the modified Heck protocol. Through multiple regression analysis, a separate prediction model was developed for each of the athletic populations. Results demonstrated that a significant (p=0.001) proportion of the variation observed in VO2max was explained by the variation in running time. The generated VO2max regression equations would allow athletes and coaches to predict VO2max in a relatively short time without the need for expensive and sophisticated equipment. To our knowledge, this is the first study that provides regression models for different athletic populations using the modified Heck protocol.

Combined Plyometric and Short Sprint Training in U-15 Male Soccer Players: Effects on Measures of Jump, Speed, Change of Direction, Repeated Sprint, and Balance.

This study examined the effect of 8 weeks of biweekly combined plyometric and short sprint training into the typical within-season training schedule of youth male soccer players. Participants were allocated at random to an experimental group (EG; n = 17, age: 14.6 ± 0.5 years, body mass: 60.5 ± 7.1 kg, height: 1.64 ± 0.08 m, body fat: 11.3 ± 1.4%) and a control group (CG; n = 17, age: 14.6 ± 0.4 years, body mass: 61.0 ± 3.9 kg, height: 1.67 ± 0.05 m, body fat: 11.8 ± 1.4%). Measures obtained pre- and post-intervention included vertical and horizontal jump performances (i.e., squat jump (SJ), countermovement jump with aimed arms (CMJA), and five-jump test (FJT)) and sprint performances (i.e., 10 and 30 m sprint). In addition, change-of-direction ability (sprint with 90° Turns (S90°) and sprint 9–3–6–3–9 m with backward and forward running (SBF)), repeated shuttle sprint ability (RSSA), and dynamic balance performance (Y balance test) were measured pre- and post-intervention. The EG experienced higher jump (all p < 0.05; d ≥ 0.71), sprint (all p < 0.05; d ≥ 0.64), change-of-direction ability (all p < 0.05; d ≥ 0.66), RSSA (all parameters except the fatigue index p < 0.01; d ≥ 0.71), and dynamic balance (all p ≤ 0.05; d ≥ 0.50) improvement compared to the CG. Adding biweekly combined plyometric and short sprint training to standard training improves the athletic performance of youth male soccer players (under 15 (U15)).

Ultrasound Shear Modulus and Thickness of Lateral Abdominal Muscles in Different Contractile States in Relation To Self- Reported Hip/Groin Problems in Youth Soccer Players.

To date, no studies have assessed lateral abdominal muscles’ (LAM) elasticity and thickness in relation to hip and groin symptoms in any population. The objectives were to a) assess the relationship between LAM ultrasound measurements (elasticity and thickness) and self-reported subscales of the Copenhagen Hip and Groin Outcome Score (HAGOS) and b) compare LAM elasticity and thickness between asymptomatic and symptomatic sides. Shear modulus and thickness of the oblique external (OE), internal (OI) and transversus abdominis (TrA) muscles in 25 young soccer players were assessed at rest and during isometric contraction using ultrasound shear wave elastography. HAGOS subscales were used to assess self-reported hip/groin problems. There was a significant (p < 0.05) moderate correlation between allometric-scaled OI resting thickness (mean of right and left) and the Activities of Daily Living (r = 0.40), Sport (r = 0.57) and Quality of Life (QOL) (r = 0.41) HAGOS subscales. Also, a moderate significant correlation was found between allometric-scaled TrA resting thickness and the QOL subscale (r = 0.47). Moderate correlations were found between resting OI shear modulus and the QOL (r = 0.44), between right TrA shear modulus during contraction and Symptoms (r = 0.57), and between the left TrA shear modulus during contraction and Physical Activity (r = 0.41) subscales. No differences were found between the symptomatic and asymptomatic side in thickness and elasticity measurements among soccer players with unilateral symptoms (p > 0.05). The relationships found between LAM and hip/groin problems in youth male soccer players indicate that muscles are thinner and more elastic (less stiff) in more symptomatic athletes.

The effects of repeated sprint training with versus without change of direction on measures of physical fitness in youth male soccer players.

Fitness characteristics such as linear sprinting, repeated sprint ability, and change of direction (CoD) are important for male youth soccer players to maximize training safety and physical performance. We aimed to compare the effects of a 9-week repeated sprint training (RST) program, with and without CoD movements, on repeated sprint ability (RSA total time [RSA<inf>total</inf>], RSA best time [RSA<inf>best</inf>]), CoD speed (505 CoD test), linear sprint speed (10-m and 20-m linear sprint), and aerobic endurance (AE; Yo-Yo intermittent endurance test level 1) in male youth soccer players. During the in-season period, 20 soccer players were randomly assigned to a RST with CoD (RST<inf>CoD</inf>) group (N.=10, age 15.4±0.4 years) or a repeated linear sprint training group (N.=10, age 15.6±0.3 years). Both training groups completed approximately two 15 minutes RST sessions per week, with the only difference between training programs being the inclusion of one CoD movement during sprint repetitions for the RST<inf>CoD</inf> group. The two-way ANOVA with repeated measures revealed a significant, moderate effect of time for RSA<inf>best</inf> and RSA<inf>total</inf> (effect size [d] 0.69 and 0.67, respectively). Likewise, significant, moderate-to-large effects of time were found for CoD (d=0.83), 10-m and 20-m sprint (d=0.68 and d=0.67, respectively), and AE (d=0.66). No significant group × time interactions were observed for any measure of physical fitness (d=0.00 to d=0.16). RST with and without CoD movements is equally effective in improving RSA total and best time, CoD speed, linear sprint speed, and AE in youth male soccer players.

Impact of Prolonged Absence of Organized Training on Body Composition, Neuromuscular Performance, and Aerobic Capacity: A Study in Youth Male Soccer Players Exposed to COVID-19 Lockdown.

The aim of this study is to examine how physical performance has changed after 15 weeks (109 days) long-term absence of organized training in youth soccer players imposed by the stay at home orders. A total of sixty-eight young male soccer players from different age categories (U15, U16, U17 and U19) voluntarily participated in the prospective cohort study. Body fat percentage (BF%), counter-movement jump (CMJ), 30 m sprint, change-of-direction (COD) and yo-yo intermittent recovery test level-1 (YYIRTL-1) were evaluated twice (before and after the detraining period). Subsequently, 2 × 2 repeated measures ANOVA was used to investigate group and time differences in repeated measurements. A significance level of p < 0.05 was implemented. CV and SWC values were calculated to test the reliability of the tests performed at different times. Statistical analysis was performed using the IBM SPSS statistics software (v.25, IBM, New York, NY, USA). Significant increments in BF%, 30 m sprint, and COD (left and right), and also significant decrements in CMJ and YYIRTL-1, were found after the detraining period. A long-term detraining period due to the stay at home orders has a detrimental effect on body composition, neuromuscular performances, and aerobic capacity in youth soccer players.

Coaches' Criteria for Talent Identification of Youth Male Soccer Players.

Introduction: The main aim of this study was to examine which criteria coaches considered in the talent identification of youth male soccer players aged 13–16. The second aim was to describe how the coaches considered these criteria when identifying players for their club or regional teams and how these criteria take the impact of the relative age effect into consideration. Methods: We conducted qualitative, semi-structured interviews with six male coaches from a professional club academy or a regional team within the Norwegian Football Federation. Results: In line with earlier research, the results showed that the coaches considered the technical, tactical, and mental factors as the most important in talent identification. Further in line with earlier research, they considered that the physiological and sociological factors were of secondary importance, while anthropometric measures were considered the least important. Regarding the relative age effect, the coaches were aware of the effect and its consequences, while few of them had ways to reduce the effect and its impact on their talent identification process. Even so, the coaches highlighted the importance of considering a holistic approach to talent identification. Conclusion: The results show similarities with earlier research, but there is still a need for more longitudinal studies that investigate criteria for talent identification in youth football.

The relationship between executive functions and sports experience, relative age effect, as well as physical maturity in youth soccer players of different ages

ABSTRACT Sports psychology and kinesiology research focused on executive functions in the last ten years as cognitive functions could be one of the smallest adjustments possible in high-level athletes. We examined the connection of sports experience, (relative-) age effects, and physical maturity on the executive functions in male youth soccer players (N = 110). Working memory was assessed using the 3-back task, inhibition was measured using the flanker task, and cognitive flexibility was measured using the number-letter task. We hypothesised that sports experience, (relative-) age effects and physical maturity are positively correlated with executive functions. However, the linear regression model MANOVA test statistics revealed only an impact of calendar age on executive functions. The results demonstrate that athletes attain a certain level in executive functions and gain specific cognitive skills in their sports. Nevertheless, questions about the transfer of executive functions on sport-specific cognitive skills remain unclear.

Change of Direction Speed in Youth Male Soccer Players: The Predictive Value of Anthropometrics and Biological Maturity.

This study aimed to develop the optimal allometric body size/shape and a biological maturity model that predicted the change of direction (CoD) mean speed performance in youth male soccer players. One-hundred and fifteen youth soccer players (age: 12.4 [1.3]y) participated in this study. The 505 test was used to assess CoD mean speed performance. Anthropometric measurements comprised body height (cm), sitting height (cm), body mass (kg), fat mass (kg), lower limb length (cm), thigh length (cm), leg length (cm), foot length (cm), thigh girth (cm), and calf girth (cm). The maturity status was determined based on the maturity offset method. To identify size/shape and maturity characteristics associated with CoD speed performance, we computed a multiplicative allometric log-linear regression model, which was refined using backward elimination. The multiplicative allometric model exploring the association between 505 CoD mean speed performance and the different anthropometric characteristics in youth soccer players estimated that fat mass (P < .001), sitting height (P = .02), and maturity offset (P = .004) are the key predictors. More specifically, youths who are more mature and have a lower fat mass and a shorter trunk length, are likely to achieve a better CoD mean speed performance. These findings highlight the relevance of considering anthropometric and maturity characteristics in youth soccer players to support talent identification.

Apophysitis Among Male Youth Soccer Players at an Elite Soccer Academy Over 7 Seasons.

Background:Apophyseal injuries are common in children and adolescent athletes. These injuries are believed to be caused by repetitive overloading, which can create inflammatory and degenerative conditions in growing bone prominences. However, their prevalence, diagnosis, and treatment in young soccer players have been understudied.Purpose:To evaluate characteristics of apophyseal injuries in adolescent athletes at an elite soccer academy.Study Design:Case series; Level of evidence, 4.Methods:All apophyseal injuries between July 2008 and June 2015 were evaluated. For each injury, the authors recorded the type and location, age of the player, injury date, imaging modalities, and time absent from training/competition.Results:Over the 7 seasons of this study, 210 apophyseal injuries were documented, including 172 simple apophyseal injuries and 38 apophyseal avulsion fractures. The rate of apophyseal injuries was 0.35 per 1000 hours of training exposure. A total of 196 (93.3%) cases were primary injuries, and the rest (6.7%) were reinjuries. Ultrasonography was the most commonly used imaging modality for diagnosis (172 cases; 81.9%). The most common location of apophyseal injuries was the anterior inferior iliac spine (AIIS). Return to sport was faster in athletes with apophyseal injury at the ischiopubic ramus, those with simple apophyseal injuries, and younger athletes.Conclusion:The most common location for apophyseal injury among soccer players was the AIIS. Return to training and competition differed according to injury location, type of apophyseal injury, and age.

Associations between differing magnitudes of inter-limb asymmetry and linear and change of direction speed performance in male youth soccer players

Abstract Study aim: This study examines the relationship between different magnitudes of asymmetry and their effects on speed performance. Material and methods: Forty-two sub-elite male youth soccer players performed a 30-m sprint, change of direction, single leg countermovement jump and single leg hop. Subjects were divided into groups with vertical and horizontal asymmetry, and both groups were then divided into three groups according to magnitudes of inter-limb asymmetry (&lt;5%, 5–10%, and &gt;10%). Results: The results showed no significant correlation between different jump asymmetry magnitudes and the mentioned outcomes of speed performance (p &gt; 0.05). In addition, larger asymmetries resulted in faster linear speed, even if small differences (g range = 0.00 to 0.57; p &gt; 0.05). But this was not similar for change of direction speed (g range = –0.42 to 0.34; p &gt; 0.05). Conclusions: There are inconsistent findings for the effects of inter-limb asymmetries on speed performance. The results of the present study indicate that the magnitude of asymmetry had no meaningful association with independent measures of performance in soccer players. Therefore, it seems more likely to explain the effects of individual asymmetries on performance rather than the idea that asymmetry negatively affects performance.

Do conditioning focused various-sided training games prepare elite youth male soccer players for the demands of competition?

Relative metrics (i.e. distance covered per minute of match time) are regularly used to quantify soccer player movement demands. However, limited literature is available concerning the peak player demands during training. This study aimed to compare the relative and peak demands of conditioning-focused various-sided training games (VSG) to competition matches in elite youth male soccer players according to playing position. Data from twenty-nine competition matches (national) and twenty-two VSGs (small, medium, and large) were collected for twenty-three elite under-17 soccer players using 15-Hz portable global positioning system tracking devices (GPSports, Canberra, Australia). Relative player movements were reported as total distance (TD) and high-speed running distance (HSRD) (> 5.0 m/s) per minute of total playing time. Peak player movements were calculated using a 1-minute rolling epoch length, reported as the maximum TD and HSRD. Linear mixed models demonstrated interactions between VSG type and player position for relative TD (p < 0.001) and HSRD (p < 0.001), and peak TD (p = 0.010) and HSRD (p = 0.003). The relative TD of VSGs were greater than match-play for all player positions. However, only Central Defenders demonstrated similar HSRD in MSGs and LSGs compared to match-play when analysed using relative calculations. External Attackers also replicated match-play relative HSRD demands in LSGs. No VSG type was found to replicate or supersede the peak player movements of match-play across any playing position. Consequently, VSGs should be supplemented with high-speed running training to prepare players for the peak running requirements of match-play.

The effects of combined aerobic and resistance training program in Korean male youth soccer players

Background: This study analyzed the effects of short-term, off-season physical training on the core dynamic and thigh muscle function of youth soccer players. Methods: For two weeks during the off-season, middle-school soccer players (MSP, n = 75) and high-school soccer players (HSP, n = 104) participated in exercise training (five times per week). Their body composition, physical fitness, core dynamic balance, and isokinetic muscle function were compared before and after training. Results: Both groups showed significant (p &lt; 0.01) decreases in body composition, and significant (p &lt; 0.01) improvements in physical fitness (MSP, 1.02–1.15%; HSP, 1.05–3.76%). In terms of core dynamic balance, both groups showed a significant (p &lt; 0.01) increase in back strength (MSP, 1.09–1.11%; HSP, 1.06–1.16%), and a significant (p &lt; 0.05) decrease in the left-right difference (MSP, 0.70–1.43%; HSP, 1.00–1.09%) after training. For isokinetic muscle function at the knee joint, the MSP group showed significant improvement in flexors, whereas the HSP group showed significant improvements in both the extensors and flexors. The dominant vs non-dominant deficit decreased significantly in the MSP group for total work and average power per repetition of the flexors at 60 deg/sec and in the HSP group for peak torque and total work of the flexors at 60 deg/sec. The hamstring-to-quadriceps ratio increased significantly at 60 deg/sec on the dominant side in the MSP group. Conclusions: In youth soccer players, two weeks of physical training during the off-season improved both physical fitness and core dynamic balance, suggesting that this training is effective for injury prevention.

Influence of game format and team strategy on physical and perceptual intensity in soccer small-sided games

The aim of the study was to compare internal and external load responses of different small-sided games, using balanced (5v5 Possession and small-sided games formats) and unbalanced (6v4) teams. Ten elite youth male soccer players were monitored at the start of the in-season period using global positioning system, heart rate and subjective ratings of intensity. Results showed higher physiological stress (&gt;90% HRmax) in Possession and small-sided games formats when compared to the unbalanced teams (ES = 1.3–2.3). Total and high-intensity distance in small-sided games (28 ± 25 m) and Possession (67 ± 35 m) were greater compared to teams of 6 and 4 in the unbalanced scenario. Small-sided games format and team with six players had higher proportion of distance running at sub-maximal velocities (0–5.8 m/s2). Small-sided games format and team with four players saw greater mean acceleration effort (mean acceleration intensity in small-sided games 1.91 ± 0.27 vs. Possession 1.80 ± 0.20 m/s2, ES = 0.4 and Team 4 1.56 ± 0.24 vs. Team 6 1.44 ± .0.19 m/s2, ES = 1.3). Small-sided games format and team with 6 players had lower starting velocities prior to acceleration efforts (small-sided games 0.90 ± 0.08 and Team 6 1.11 ± 0.11 m/s2, ES = 1.5 and ES = 1.8), while velocity at the end of each acceleration effort was greater in the Possession format and Team 4 compared to small-sided games and Team 6 (Possession 3.54 ± 0.23 m/s2 and Team 4 3.13 ± 0.22 m/s2) compared to the small-sided games format (ES = 0.1) and the team with six players (ES = 2.3). These data demonstrate that using unbalanced teams can provide an additional form of training prescription to facilitate player specific training within a squad environment by providing different internal and external training responses within a combined drill.

The New Generation of Professional Soccer Talent Is Born under the Bias of the RAE: Relative Age Effect in International Male Youth Soccer Championships

In 2019, numerous championships of youth categories soccer national teams were held. In the present study, we analyzed the existence of the Relative Age Effect (RAE) in four major male championships that, due to their importance and participating teams, most likely brought together the great bulk of the players who will dominate professional soccer in the next decade. Participants were professional and amateur youth male soccer players who participated in the last international championships: UEFA European Under-21 Championship (2017–2019); UEFA European Under-19 Championship (2019); South American Youth Football Championship (also known as Conmebol U-20) (2019); and FIFA U-20 World Cup (2019), with 823 players (20.25 ± 0.84 years). In the four championships analyzed, the existence of RAE was found for all players (p < 0.001). Analyzing the players when considering their position on the pitch and their championship, RAE was found, statistically significant, in 10 of the 16 classifications. New generations of elite soccer players arrive with a clear bias in the selection of talent; an unfair bias, based on unequal opportunities in early categories, which should be reviewed by sports authorities.

Effects of Three Different Combined Training Interventions on Jump, Change of Direction, Power Performance, and Inter-Limb Asymmetry in Male Youth Soccer Players.

Background: This study compared the effects of performing different unilateral combined training interventions on diverse vertical and horizontal jumping performance parameters, change of direction, concentric and eccentric mean power, and their associated inter-limb asymmetries in young soccer players. Methods: Forty-seven young male soccer players (age: 15.5 ± 0.9 years) were distributed into three groups. Two groups performed the same training volume with both legs, beginning with the weaker leg (Stronger Volume Weaker leg group (SVW), n = 14) or with the stronger leg (Stronger Volume Stronger leg group, (SVS), n = 15). The third group executed double the volume with the weaker leg and also commenced with such leg (Double Volume Weaker leg group (DVW), n = 16) during a 10-week period. Pre- and post-intervention tests included a single-leg hop, single-leg lateral hop, triple hop, bilateral and unilateral countermovement jumps, a change of direction speed test, concentric and eccentric mean power during the lateral squat test, and their corresponding asymmetries. Results: Single-leg hop weaker leg, triple hop weaker leg, and bilateral countermovement jump improvements were achieved in the SVW (ES: 0.29 to 0.46) and DVW (ES: 0.55 to 0.73) groups. Between-groups analysis showed better results in single-leg hop in the SVW and DVW compared to group SVS. The DVW group achieved better improvements in countermovement jump in comparison to groups SVS and SVW. Conclusions: Groups that started with the weaker leg seemed to achieve a greater volume of significant changes than when starting with the stronger leg. Performing a double volume on the weaker limb does not guarantee further improved performance compared to other groups.

Effects of plyometric jump training versus power training using free weights on measures of physical fitness in youth male soccer players

ABSTRACT This study aimed to contrast the effects of power training (PT) and plyometric-jump-training (PJT) programmes on measures of physical fitness in prepubertal male soccer players. Thirty-three participants were randomly allocated to PT group (n = 11), PJT group (n = 11), and an active control group (CG; n = 11). Before and after 12 weeks of training, tests were performed for the assessment of sprint-speed , change-of-direction (CoD) speed, muscular strength , and aerobic-endurance (AE). Findings indicated significant group×time interaction effects for all sprint-speed intervals, CoD speed, AE, and strength (d = 0.20–0.32). Post-hoc analyses revealed significant, moderate-to-large improvements in all sprint-speed intervals, CoD speed, AE, and muscle strength following PT (ES = 0.71 to 1.38). The PJT induced significant, moderate-to-large enhancements in 10 m, 20 m, and 30 m sprint, CoD speed, and AE (ES = 0.51 to 0.96) with no significant changes for 5 m sprint-speed and muscle strength (ES = 0.71 and 0.16, respectively). No significant pre-post changes were observed for the CG . Overall, PT and PJT are effective means to improve various measures of physical fitness in prepubertal male soccer players. Notably, to additionally improve acceleration and muscle strength, PT has an advantage over PJT.

Validation of the Athletic Identity Measurement Scale in Youth Academy Soccer Players

The Athletic Identity Measurement Scale (AIMS) is a popular measure of Athletic Identity (AI). The purpose of the present study was to investigate the factor structure (7-item single factor and 3 factor model; Social Identity, Exclusivity and Negative Affectivity) of the AIMS within youth academy soccer players. A total of 259 male youth academy soccer players aged 12-18 years completed the AIMS. A series of confirmatory factor analyses, independent cluster modelling indicated support for the 7-item single-factor (AI) and the three-factor models but not within the same analysis. The results support the use of AIMS for the measurement of AI in elite male youth soccer players. Practitioners seeking to explore AI in youth soccer populations should use the three-factor model to glean further insight from the three subscales to support the design of more specific interventions where appropriate.

A Practical Approach to Monitoring Biomarkers of Inflammation and Muscle Damage in Youth Soccer Players During a 6‐Month Training Cycle

The aim of the study was to determine the effects of a 6-month training cycle on muscle damage and inflammatory markers in youth male soccer players. Twenty-one soccer players were tested four times: at the beginning (T1) and immediately after the pre-season period (T2), in the middle (T3) and at the end of the competitive period (T4). Muscle damage and inflammatory markers were determined in blood taken 36 hours after the match. Throughout the training cycle significant increases (p < 0.05) of creatine kinase (T1: 254.4 U·L-1; T4: 304.2 U·L-1) and lactate dehydrogenase (T1: 382.8 U·L-1; T4: 453.2 U·L-1) activities were observed. Significant changes (p < 0.05) in platelet count (T1: 210.5·109·L-1; T4: 234.2·109·L-1), percentage of lymphocyte (T1: 39.80%; T4: 42.97%), monocyte (T1: 6.88%; T4: 9.99%) and granulocyte (T1: 53.32%; T4: 47.05%) as well as in granulocyte-to-lymphocyte (T1: 1.41; T4: 1.17) and lymphocyte-to-monocyte (T1: 6.21; T4: 4.46) ratios were noted. The correlation analysis revealed statistically significant relationships (p < 0.05) between: myoglobin and the percentage of leukocyte subpopulations and the granulocyte to lymphocyte ratio; lactate dehydrogenase and the percentage of monocyte; lactate and leukocyte count. In conclusion, the reported muscle damage and inflammatory markers in T3 and T4 indicate the need for fatigue status monitoring in youth soccer players, especially in the competitive period. Moreover granulocyte to lymphocyte and lymphocyte to monocyte ratios proved to be sensitive to fatigue changes and therefore can provide coaches and sport scientists with a broader perspective on the biochemical monitoring of training status in soccer players.