Latest research in football - week 31 - 2016

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Motor Subsystem as a Predictor of Success in Young Football Talents: A Person-Oriented Study
Reference: PLoS One. 2016 Aug 10;11(8):e0161049. doi: 10.1371/journal.pone.0161049. eCollection 2016.
Authors: Zibung M, Zuber C, Conzelmann A
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Summary: Motor tests play a key role in talent selection in football. However, individual motor tests only focus on specific areas of a player's complex performance. To evaluate his or her overall performance during a game, the current study takes a holistic perspective and uses a person-oriented approach. In this approach, several factors are viewed together as a system, whose state is analysed longitudinally. Based on this idea, six motor tests were aggregated to form the Motor Function subsystem. 104 young, top-level, male football talents were tested three times (2011, 2012, 2013; Mage, t2011 = 12.26, SD = 0.29), and their overall level of performance was determined one year later (2014). The data were analysed using the LICUR method, a pattern-analytical procedure for person-oriented approaches. At all three measuring points, four patterns could be identified, which remained stable over time. One of the patterns found at the third measuring point identified more subsequently successful players than random selection would. This pattern is characterised by above-average, but not necessarily the best, performance on the tests. Developmental paths along structurally stable patterns that occur more often than predicted by chance indicate that the Motor Function subsystem is a viable means of forecasting in the age range of 12-15 years. Above-average, though not necessary outstanding, performance both on fitness and technical tests appears to be particularly promising. These findings underscore the view that a holistic perspective may be profitable in talent selection.

#2 Extra-articular tenodesis combined with an anterior cruciate ligament reconstruction in acute anterior cruciate ligament tear in elite female football players
Reference: Int Orthop. 2016 Aug 10. [Epub ahead of print]
Authors: Guzzini M, Mazza D, Fabbri M, Lanzetti R, Redler A, Iorio C, Monaco E, Ferretti A
Summary: The growing popularity of elite soccer among female participants has led to increased incidents of anterior cruciate ligament (ACL) ruptures. Many authors underline a positive glide after ACL reconstruction (ACLR), especially in women. In fact, an isolated intra-articular ACLR may be inadequate to control rotational instability after a combined injury of the ACL and the peripheral structures of the knee. Extra-articular procedures are sometimes used in primary cases displaying excessive antero-lateral rotatory instability. The purpose of this case series was to report subjective and objective outcomes after combined ACL and lateral extra-articular tenodesis (LET) with a minimum 4-year follow-up in a selected high-risk population of elite female football players. Between January 2007 and December 2010, 16 elite Italian female football players were included in the study. All patients underwent the same surgical technique: anatomical ACLR with autogenous semitendinosus and gracilis tendons. After the intra-articular reconstruction was performed, an additional extra-articular MacIntosh modified Coker-Arnold procedure was carried out. Patients were assessed pre- and post-operatively with the subjective and objective International Knee Documentation Committee (IKDC) evaluation form, Tegner activity scale (TAS) and Lysholm score. Joint laxity was assessed with KT-1000 by measuring the side-to-side (S/S) differences in displacement at manual maximum (mm) testing. At a mean follow-up of 72.6 ± 8.1 months, two independent examiners reviewed all players. All of the patients had a fully recovered range of motion. Lachman test was negative in all patients (100 %). The evaluation of joint laxity and clinical evaluation showed a statistically significant improvement. No patients experienced complication or a re-rupture. The rationale of combining extra-articular procedures with ACLR is to restrict the internal rotation of the reconstructed knee, taking advantage of its long lever arm and thus providing more stability in the rotational axis and preventing the ACL graft from undergoing further excessive strain. The combination of an LET with ACLR in elite female football players demonstrated excellent results in terms of subjective scales, post-operative residual laxity and re-rupture rate with no complication, and a complete return to sport activity.

#3 Dietary intake according to hydration status in 9-10 year-old soccer players
Reference: Nutr Hosp. 2016 Jul 13;33 Suppl 3:315. doi: 10.20960/nh.315.
Authors: Rodriguez L, Azevedp AR, Seabra A, Padrao P, Moreira P
Summary: Children have an increased risk of voluntary dehydration especially during physical activity which may increase the risk of non-compensating water losses. The aim of this study was to assess the hydration status and its relation to food intake in a children group of soccer players. A sample of 36 boys aged 9-10 years was included in this study; 30 completed a 24 h urine collection. Participants completed a 24 h urine collection; a 24 hours food recall corresponding to the day of urine collection was applied, weight and height were measured and parents/caregivers fi lled a lifestyle and socio-demographic questionnaire. The free water reserve (FWR [ml/24 h] = urine volume [ml/24 h] - obligatory urine volume [ml/24 h]) was used to assess the hydration status. Food and beverage groups were created and models of unconditional logistic regression were fi tted in order to estimate the magnitude of the association between the hydration status and diet. Forty three per cent of participants were classifi ed as at risk of hypohydration. Children who reported a high fruit and vegetables intake (above the median) were at decreased risk of hypohydration (OR = 0.19, 95% CI 0.04-0.94, p = 0.041), compared to children who reported a low fruit and vegetables intake. Almost half of the children were at risk of hypohydration. Our results suggested that water food sources such as fruit and vegetables may contribute to euhydration.

#4 Ethnic Differences in Bony Hip Morphology in a Cohort of 445 Professional Male Soccer Players
Reference: Am J Sports Med. 2016 Aug 4. pii: 0363546516656163. [Epub ahead of print]
Authors: Mosler AB, Crossley KM, Waarsing JH, Jomaah N, Weir A, Hölmich P, Agricola R
Summary: Participation in high-impact athletic activities has recently been associated with a higher prevalence of cam deformity. Bony hip morphology has also emerged as an important factor in the development of hip osteoarthritis. However, it is unknown whether bony morphology differs between ethnicities in athletes participating in high-impact sports. The purpose was to investigate whether the prevalence of specific bony hip morphological abnormalities differed between professional male soccer players of diverse ethnic backgrounds. Professional male soccer players from an entire league attending preparticipation screening were invited to participate in this study. Ethnicity was registered, and standardized radiographs of anteroposterior pelvic and Dunn views were obtained. Cam and pincer deformity, and acetabular dysplasia were quantified using the alpha angle, triangular index, and lateral center-edge angle (LCEA). Regression analyses with generalized estimating equations were used to determine prevalence differences in bony hip morphology. A total of 445 male soccer players (890 hips; mean age ± SD, 25 ± 4.9 years) participated in the study, representing the following ethnic groups: Arabic (59%), black (24%), Persian (7%), white (6%), East Asian (2%), and other (2%). The prevalence of cam deformity (alpha angle >60°) ranged from 57.5% to 71.7% across 4 of the groups, but East Asians had a significantly lower prevalence (18.8%; P ≤ .032). A large cam deformity (alpha angle >78°) was more prevalent in white (33.3%) compared with black soccer players (17.8%; P = .041) and was absent in East Asian players. Pincer deformity (LCEA >40°) was uncommon (3%) in all ethnicities. The prevalence of acetabular dysplasia (LCEA <20°) ranged from 8.0% to 16.7%, apart from the white group, in which prevalence was only 1.9% (P = .03). The prevalence of a cam deformity and acetabular dysplasia differed between ethnicities in this cohort of professional male soccer players. These findings suggest that there may be ethnic differences in both acetabular morphology and femoral bony response to athletic load

#5 Holistic Patterns as an Instrument for Predicting the Performance of Promising Young Soccer Players - A 3-Years Longitudinal Study
Reference: Front Psychol. 2016 Jul 27;7:1088. doi: 10.3389/fpsyg.2016.01088. eCollection 2016.
Authors: Zuber C, Zibung M, Conzelmann A
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Summary: Multidimensional and dynamic talent models represent the current state of the art, but these demands have hardly ever been implemented so far. One reason for this could be the methodological problems associated with these requirements. This paper will present a proposal for dealing with this, namely for examining the development of young soccer players holistically. The patterns formed by the constructs net hope, motor abilities, technical skills and biological maturity were examined, as well as the way in which these holistic patterns are related to subsequent sporting success. 119 young elite soccer players were questioned and tested three times at intervals of 1 year, beginning at the age of 12. At the age of 15, the level of performance reached by the players was determined. At all three measuring points, four patterns were identified, which displayed partial structural and high individual stability. The highly skilled players, scoring above average on all factors - but not necessarily those having the highest overall scores - were significantly more likely to advance to the highest level of performance. Failure-fearing fit players, i.e., physically strong, early developed players but with some technical weaknesses, have good chances of reaching the middle performance level. In contrast, none of the achievement-oriented, highly skilled, late-matured or late-matured, low skilled players reached the highest performance level. The results indicate the importance of holistic approaches for predicting performance among promising soccer talents in the medium-term and thus provide valuable clues for their selection and promotion.

#6 Shoulder injuries in soccer goalkeepers: review and development of a FIFA 11+ shoulder injury prevention program
Reference: Open Access J Sports Med. 2016 Aug 8;7:75-80. doi: 10.2147/OAJSM.S97917. eCollection 2016.
Authors: Ejnisman B, Barbosa G, Andreoli CV, de Castro Pochini A, Lobo T, Zogaib R, Cohen M, Bizzini M, Dvorak J
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Summary: In the last years, shoulder injuries have represented an increasing health problem in soccer players. The goalkeepers are more exposed to shoulder disorders than other field players. Injury prevention exercises for upper limbs were cited in few studies involving throwing athletes, but we know that goalkeepers need a specific program. The purpose of this study is to describe the development of an adapted Fédération Internationale de Football Association (FIFA) 11+ program, namely the FIFA 11+ shoulder, which targets the prevention of shoulder injuries in soccer goalkeepers. The FIFA 11+ shoulder program is structured into three parts: general warming-up exercises, exercises to improve strength and balance of the shoulder, elbow, wrist, and finger muscles, and advanced exercises for core stability and muscle control. The exercises were selected based on recommendations from studies demonstrating high electromyographic activity.

#7 Jump Training in Youth Soccer Players: Effects of Haltere Type Handheld Loading
Reference: Int J Sports Med. 2016 Aug 24. [Epub ahead of print]
Authors: Rosas F, Ramirez-Campillo R, Diaz D, Abad-Colil F, Martinez-Salazar C, Caniuqueo A, Cañas-Jamet R, Loturco I, Nakamura FY, McKenzie C, Gonzalez-Rivera J, Sanchez-Sanchez J, Izquierdo M
Summary: The aim of this study was to compare the effects of a jump training program, with or without haltere type handheld loading, on maximal intensity exercise performance. Youth soccer players (12.1±2.2 y) were assigned to either a jump training group (JG, n=21), a jump training group plus haltere type handheld loading (LJG, n=21), or a control group following only soccer training (CG, n=21). Athletes were evaluated for maximal-intensity performance measures before and after 6 weeks of training, during an in-season training period. The CG achieved a significant change in maximal kicking velocity only (ES=0.11-0.20). Both jump training groups improved in right leg (ES=0.28-0.45) and left leg horizontal countermovement jump with arms (ES=0.32-0.47), horizontal countermovement jump with arms (ES=0.28-0.37), vertical countermovement jump with arms (ES=0.26), 20-cm drop jump reactive strength index (ES=0.20-0.37), and maximal kicking velocity (ES=0.27-0.34). Nevertheless, compared to the CG, only the LJG exhibited greater improvements in all performance tests. Therefore, haltere type handheld loading further enhances performance adaptations during jump training in youth soccer players.

#8 Gaze Control in One Versus One Defensive Situations in Soccer Players With Various Levels of Expertise
Reference: Percept Mot Skills. 2016 Aug 23. pii: 0031512516664903. [Epub ahead of print]
Authors: Krzepota J, Stępiński M, Zwierko T
Summary: Experienced and less experienced soccer players were compared in terms of their gaze behavior (number of fixations, fixation duration, number of fixation regions, and distribution of fixations across specific regions) during frontal 1 vs. 1 defensive situations. Twenty-four men (eight experienced soccer players, eight less experienced players and eight non-players) watched 20 video clips. Gaze behavior was registered with an Eye Tracking System. The video scenes were analyzed frame-by-frame. Significant main effect of the group (experience) was observed for the number of fixation regions. Experienced soccer players had a lower number of fixation regions than the non-soccer players. Moreover, the former group presented with significantly larger percentage of fixations in the ball/foot region. These findings suggest that experienced players may use a more efficient search strategy than novices, involving fixation on a lesser number of areas in specific locations.

#9 Effects Of Different Combinations Of Strength, Power, And Plyometric Training On The Physical Performance Of Elite Young Soccer Players
Reference: J Strength Cond Res. 2016 Aug 18. [Epub ahead of print]
Authors: Kobal R, Loturco I, Barroso R, Gil S, Cuniyochi R, Ugrinowitsch C, Roschel H, Tricoli V.
Summary: The combination of strength (ST) and plyometric training (PT) has been shown to be effective for improving sport specific performance. However, there is no consensus about the most effective way to combine these methods in the same training session, in order to produce greater improvements in neuromuscular performance of soccer players. Thus, the purpose of this study was to compare the effects of different combinations of ST and PT sequences on strength, jump, speed, and agility capacities of elite young soccer players. Twenty-seven soccer players (age: 18.9±0.6 years) participated in an 8-week resistance training program and were divided into three groups: complex training-CP (ST before PT), traditional training-TD (PT before ST), and contrast training-CT (ST and PT performed alternately, set-by-set). The experimental design took place during the competitive period of the season. The ST was composed of half-squat exercises performed at from 60 to 80% of 1RM; the PT was composed of drop jump exercises executed in a range from 30 to 45 cm. After the experimental period, the maximum dynamic strength (Half-squat 1RM) and vertical jump ability (countermovement jump height) increased similarly and significantly in the CP, TD, and CT (48.6, 46.3, and 53% and 13, 14.2 and 14.7%, respectively). Importantly, whereas the TD group presented a significant decrease in sprinting speed in 10- (7%) and 20-m (6%), the other groups did not show this response. Furthermore, no significant alterations were observed in agility performance in any experimental group. In conclusion, in young soccer players, different combinations/sequences of ST and PT sets result in similar performance improvements in muscle strength and jump ability. However, it is suggested that the use of the CP and CT methods are more indicated to maintain/maximize the sprint performance of these athletes.

#10 Exercise intensity and technical demands of small-sided soccer games for under-12 and under-14 players: effect of area per player
Reference: J Strength Cond Res. 2016 Aug 18. [Epub ahead of print]
Authors: Martone D, Giacobbe M, Capobianco A, Imperlini E, Mancini A, Capasso M, Buono P, Orrù S.
Summary: The aim of the present study was to evaluate the effects of six different area per player (AP) on Exercise Intensity (EI)-measured during SSGs and expressed as percentage of maximal heart rate (%MHR)-and Technical Actions (TAs)-involvement with the ball, crosses, headers, tackles, shots on goal, dribbling, passing, and target passing-in U-12 and U-14 soccer players during Small-Sided Games (SSGs). Seventeen male U-12 soccer players (age 10.0±0.5yrs, body mass 39.3±5.3kg, and height 143.8±4.6cm) and sixteen male U-14 soccer players (age 13.2±0.3yrs, body mass 46.6±11.9kg, and height 154.8±8.5cm) performed SSGs with different AP: 40, 50, 66.7, 90, 112.5 and 150m2. Our results indicate that at larger AP the U-12 group's mean EI values were significantly higher than those at smaller AP (p<0.05); in addition inter-group comparison showed that EI was higher in U-12 than in U-14 players when AP of 112.5 and 150m2 were considered (p<0.05). TA analysis evidenced that, moving from smaller to larger AP, U-14 players adapted better to AP changes. In conclusion, these results suggest that AP influences differently EI and TAs in U-12 and U-14 players. Our results could be taken in to account by conditioning coaches in order to better tailor the physiological and/or technical training in young players through the modulation of AP.

#11 Who runs the fastest? Anthropometric and physiological correlates of 20 m sprint performance in male soccer players
Reference: Res Sports Med. 2016 Aug 22:1-11. [Epub ahead of print]
Authors: Nikolaidis PT, Ruano MA, de Oliveira NC, Portes LA, Freiwald J, Leprêtre PM, Knechtle B
Summary: The aim of the present study was to examine the relationship of 20 m sprint performance with anthropometrical and physiological parameters in male soccer players. A hundred and 81 soccer players from the region of Athens (age 23.4 ± 5.0 yrs, body mass 73.4 ± 7.7 kg, height 180.0 ± 5.9 cm, body fat (BF) 14.4 ± 3.6%), classified into quartiles according to 20 m sprint time (group A, 2.84-3.03 s; group B, 3.04-3.09 s; group C, 3.10-3.18 s; group D, 3.19-3.61 s), participated. Soccer players in group A were younger and had better performance in vertical jumps and in the Wingate anaerobic test (WAnT, p < 0.05). Sprint time correlated to age (r = 0.27), body mass (r = 0.23), body height (r = 0.20), BF (r = 0.23), vertical jumps (-0.58 ≤ r ≤ -0.50) and the WAnT (-0.45 ≤ r ≤ -0.30, p < 0.05). In summary, the magnitude of correlations of sprint time with measures of lower limbs muscle strength and power (WAnT and jumps) was larger than with anthropometric measures (body mass and BF).

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