Latest research in football - week 10- 2018

#1 Kicking Performance in Young U9 to U20 Soccer Players: Assessment of Velocity and Accuracy Simultaneously
Reference: Res Q Exerc Sport. 2018 Mar 7:1-11. doi: 10.1080/02701367.2018.1439569. [Epub ahead of print]
Authors: Vieira LHP, Cunha SA, Moraes R, Barbieri FA, Aquino R, Oliveira LP, Navarro M, Bedo BLS, Santiago PRP
Summary: The purpose of this study was to compare the kicking performance of young soccer players in the U9 to U20 age groups. Three hundred and sixty-six Brazilian players were evaluated on an official pitch using three-dimensional kinematics to measure (300 Hz) ball velocity (Vball), foot velocity (Vfoot), Vball/Vfoot ratio, last stride length, and distance between the support foot and the ball. Simultaneously, a two-dimensional procedure was also conducted to compute (60 Hz) the mean radial error, bivariate variable error, and accuracy. Possible age-related differences were assessed through one-way analysis of variance and magnitude-based inferences. Ball velocity increased by 103% (p < .001, η2 = .39) from the U11 age group (48.54 ± 8.31 km/hr) to the U20 age group (98.74 ± 16.35 km/hr). Foot velocity presented a 59% increase (p < .001, η2 = .32) from the U11 age group (49.08 ± 5.16 km/hr) to U20 (78.24 ± 9.49 km/hr). This finding was due to improvement in the quality of foot-ball impact (Vball/Vfoot ratio) from U11 (0.99 ± 0.13 a.u.) to U20 (1.26 ± 0.11 a.u.; p < .001, η2 = .25). Parameters such as mean radial error and accuracy appeared to be impaired during the growth spurt (U13-U15). Last stride length was correlated, low to moderately high, with Vball in all age groups (r = .36-.79). In summary, we concluded that simple biomechanical parameters of kicking performance presented distinct development. These results suggest that different training strategies specific for each age group could be applied. We provide predictive equations to aid coaches in the long-term monitoring process to develop the kick in soccer or search for talented young players.


#2 The biomechanical characteristics of elite deaf and hearing female soccer players: comparative analysis
Reference: Acta Bioeng Biomech. 2017;19(4):127-133.
Authors: Szulc AM, Busko K, Sandurska E, Kolodziejczyk M
Summary: The aim of this study was to examine the differences in body composition, strength and power of lower limbs, height of jump measured for the akimbo counter movement jumps, counter movement jump and spike jumps between deaf and hearing elite female soccer players. Twenty deaf (age: 23.7±5.0 years, hearing loss: 96±13.9 dB) and 25 hearing (age: 20.3±3.8 years) participated in the study. Their WHR and BMI were calculated. Body fat was measured using the BIA method. The maximal power and height of jump were measured by force plate. Biodex dynamometer was used to evaluate isokinetic isometric strength of the hamstrings and quadriceps. Significant differences between hearing and deaf soccer players in anthropometric values were for the waist and calf circumferences and the WHR index ( p < 0.01, effect size 0.24-0.79). Statistically significant differences were observed for flexion of the lower limb in the knee joint for the relative joint torque and relative power obtained for the angular velocity of 300 degˑs-1 for both lower limbs (p < 0.01, effect size 0.19-0.48) and for 180 degˑs-1 during flexion of the left limb (p = 0.02, effect size 0.13). The hearing female football players developed significantly greater MVC in all the cases. Statistically significant differences between deaf and hearing athletes were found for spike jump for maximal power (1828.6 ± 509.4 W and 2215.2 ± 464.5 W, respectively; p = 0.02, effect size 0.14). Hearing impairment does not limit the opportunities for development of physical fitness in the population of deaf women.


#3 Effect of Muscular Strength, Asymmetries and Fatigue on Kicking Performance in Soccer Players
Reference: Int J Sports Med. 2018 Mar 5. doi: 10.1055/s-0043-123648. [Epub ahead of print]
Authors: Maly T, Sugimoto D, Izovska J, Zahalka F, Mala L
Summary: The aim of this study was to determine the effect of muscular strength, strength asymmetries, and fatigue on the speed and accuracy of an instep kick in soccer players. We measured ball velocity (BV) and kicking accuracy (KA) in the preferred (PL) and non-preferred leg (NPL) before (PRE) and after (POST) physical load in the PL. Maximum peak muscle torque of the knee extensors and flexors in the PL and NPL as well as ipsilateral knee flexors and knee extensors ratio (H:Q ratio) for both legs were assessed. BV was significantly decreased in POST physical load (5.82%, BVPRE=30.79±1.70 m·s-1, BVPOST=29.00±1.70 m·s-1, t19=3.67, p=0.00, d=1.05). Instep kick accuracy after the physical load worsened by an average of 10% in the most accurate trials. Results revealed a significant decrease in instep kick accuracy after physical loading (KAPRE=2.74±0.70 m, KAPOST=3.85±1.24 m, t19=-3.31, p=0.00, d=1.10). We found an insignificant correlation between H:Q ratio and KA in PRE test value, whereas a lower ipsilateral ratio (higher degree of strength asymmetry) in the POST physical load significantly correlated with KA in all angular velocities (r=-0.63 up to -0.67, p=0.00).


#4 The independent effects of match location, match result and the quality of opposition on subjective wellbeing in under 23 soccer players: a case study
Reference: Res Sports Med. 2018 Mar 4:1-14. doi: 10.1080/15438627.2018.1447476. [Epub ahead of print]
Authors: Abbott W, Brownlee TE, Harper LD, Naughton RJ, Clifford T
Summary: This study examined if subjective wellbeing in soccer players was affected by match location, match result and opposition quality before a match (PRE), 1 day after (POST-1), and 3 days after a match (POST-3). Eleven professional male soccer players from the under 23 squad playing in the Premier League 2 division completed a wellbeing questionnaire before and after 17 matches. Match training load (session-rating perceived exertion) was not different, regardless of the location, result, or quality of opposition faced (P > 0.05). Subjective wellbeing was not different at PRE (P > 0.05); however, at POST-1 and POST-3, stress and mood were ≥20% lower after playing away from home or losing (P < 0.05). Stress, mood and sleep were ≥12% worse after playing against a higher-level opposition at POST-1. Coaches need to be aware that match location, match result and the quality of the opposition can influence post-match wellbeing, irrespective of match load.


#5 Childhood football play and practice in relation to self-regulation and national team selection; a study of Norwegian elite youth players
Reference: J Sports Sci. 2018 Mar 9:1-7. doi: 10.1080/02640414.2018.1449563. [Epub ahead of print]
Authors: Erikstad MK, Hoigaard R1, Johansen BT, Kandala NB, Haugen T
Summary: Childhood sport participation is argued to be important to understand differences in self-regulation and performance level in adolescence. This study sought to investigate if football-specific activities in childhood (6-12 years of age) is related to self-regulatory skills and national under 14- and 15-team selection in Norwegian elite youth football. Data of practice histories and self-regulatory skills of 515 youth football players selected at Norwegian regional level were collected and further analysed using multilevel analyses. The results revealed that high self-regulated players were more likely to be selected for national initiatives, and increased their involvement in peer-led football practice and adult-led football practice during childhood, compared to players with lower levels of self-regulation. While national level players reported higher levels of peer-led football play in childhood, the interaction effect suggest that the regional level players increased their involvement in peer-led play during childhood compared to national level players. In conclusion, the findings indicate that childhood sport participation may contribute to later differences in self-regulation, and highlights the importance of childhood engagement in football-specific play and practice in the development of Norwegian youth football players.


#6 "The Early Specialised Bird Catches the Worm!" - A Specialised Sampling Model in the Development of Football Talents
Reference: Front Psychol. 2018 Feb 21;9:188. doi: 10.3389/fpsyg.2018.00188. eCollection 2018.
Authors: Sieghartsleitner R, Zuber C, Zibung M, Conzelmann A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5826374/pdf/fpsyg-09-00188.pdf
Summary: Characteristics of learning activities in early sport participation play a key role in the development of the sporting talent. Therefore, pathways of specialisation or diversification/sampling are as well debated as the implementation of practice- or play-oriented activities. The related issues are currently perceived as a two-dimensional construct of domain specificity and performance orientation. In this context, it has been shown that early specialisation, with experiences in practice and play, has led to Swiss junior national team football players reaching higher success levels as adults. This study aimed to examine whether a similar approach improves chances of even being selected for junior national teams from a broader sample. Hence, 294 youth players answered retrospective questionnaires on their early sport participation when entering the Swiss football talent development programme. Using the person-oriented Linking of Clusters after removal of a Residue (LICUR) method, volumes of in-club practice, free play and activities besides football until 12 years of age were analysed along with age at initial club participation. According to the results, clusters of Football enthusiasts (p = 0.01) with the most free play and above average in-club practice and Club players (p = 0.02) with the most in-club practice and average free play had a greater chance of reaching junior national team level. Thus, high levels of domain-specific activities seem to increase the chances of junior national team participation. Furthermore, the most successful constellation (Football enthusiasts) may illustrate the relevance of domain-specific diversity, induced by several types of practice and play. In line with previous studies, specialising in football and sampling different experiences within this specific domain seems to be the most promising pathway. Therefore, we argue that the optimal model for the development of football talents is a specialised sampling model.


#7 Muscle strength characteristics of the hamstrings and quadriceps in players from a high-level youth football (soccer) Academy
Reference: Res Sports Med. 2018 Mar 5:1-13. doi: 10.1080/15438627.2018.1447475. [Epub ahead of print]
Authors: Peek K, Gatherer D, Bennett KJM, Fransen J, Watsford M
Summary: The objective of this study was to investigate knee muscle strength characteristics in players from a high-level youth football Academy. In total, 110 players (aged 8-15 years) underwent muscle strength assessments carried out by a research physiotherapist using a computer-linked hand-held dynamometer. Results indicated that isometric hamstrings and quadriceps strength increased with age, whereas the isometric hamstring to quadriceps (H/Q) ratio decreased with age. A number of youth football players (n = 20; 18%; 95% CI: 11-27%) demonstrated isometric H/Q ratios of less than 0.60, as well as muscle strength asymmetries between limbs for the hamstrings (n = 40, 36%; 95% CI: 27-46%) and quadriceps (n = 51, 46%; 95% CI 37-56%), potentially increasing injury risk. This study provides new evidence that the isometric H/Q ratio reduces with advancing age during adolescence which may have important implications for junior athlete development and long-term injury prevention in football.


#8 Neophyte experiences of football match analysis: a multiple case study approach
Reference: Res Sports Med. 2018 Mar 5:1-17. doi: 10.1080/15438627.2018.1447473. [Epub ahead of print]
Authors: McKenna M, Cowan D, Stevenson D, Baker J
Summary: Performance analysis is extensively used in sport, but its pedagogical application is little understood. Given its expanding role across football, this study explored the experiences of neophyte performance analysts. Experiences of six analysis interns, across three professional football clubs, were investigated as multiple cases of new match analysis. Each intern was interviewed after their first season, with archival data providing background information. Four themes emerged from qualitative analysis: (1) "building of relationships" was important, along with trust and role clarity; (2) "establishing an analysis system" was difficult due to tacit coach knowledge, but analysis was established; (3) the quality of the "feedback process" hinged on coaching styles, with balance of feedback and athlete engagement considered essential; (4) "establishing effect" was complex with no statistical effects reported; yet enhanced relationships, role clarity, and improved performances were reported. Other emic accounts are required to further understand occupational culture within performance analysis.


#9 Muscle strength characteristics of the hamstrings and quadriceps in players from a high-level youth football (soccer) Academy
Reference: Res Sports Med. 2018 Mar 5:1-13. doi: 10.1080/15438627.2018.1447475. [Epub ahead of print]
Authors: Peek K, Gatherer D, Bennett KJM, Fransen J, Watsford M
Summary: The objective of this study was to investigate knee muscle strength characteristics in players from a high-level youth football Academy. In total, 110 players (aged 8-15 years) underwent muscle strength assessments carried out by a research physiotherapist using a computer-linked hand-held dynamometer. Results indicated that isometric hamstrings and quadriceps strength increased with age, whereas the isometric hamstring to quadriceps (H/Q) ratio decreased with age. A number of youth football players (n = 20; 18%; 95% CI: 11-27%) demonstrated isometric H/Q ratios of less than 0.60, as well as muscle strength asymmetries between limbs for the hamstrings (n = 40, 36%; 95% CI: 27-46%) and quadriceps (n = 51, 46%; 95% CI 37-56%), potentially increasing injury risk. This study provides new evidence that the isometric H/Q ratio reduces with advancing age during adolescence which may have important implications for junior athlete development and long-term injury prevention in football.