Latest research in football - week 34 - 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 specificity of the Loughborough Intermittent Shuttle Test for recreational soccer players is independent of their intermittent running ability
Reference: Res Sports Med. 2016 Aug 22:1-12. [Epub ahead of print]
Authors: Coratella G, Beato M, Schena F
Summary: The aim of the present study was to evaluate whether or not recreational soccer players (SP) and non-soccer players (non-SP) with similar intermittent-running ability had similar physiological responses to a soccer match-simulation protocol. Twenty-two recreational SP and 19 fitness-matched non-SP participated. Yo-Yo level 1 assessed intermittent-running ability, while the Loughborough Intermittent Shuttle Test served as soccer match-simulation protocol. Heart rate (HR), blood lactate concentration [La-] and rating of perceived exertion (RPE) were recorded after each bout (1-5, plus an exhaustive task). SP had lower HR after the third, fourth and fifth bout, compared to non-SP. Similarly, SP had lower [La-] after the third, fourth and the fifth bout. SP also had lower RPE after the third, fourth and fifth bout. The appropriateness of intermittent-running ability as the main determinant of physical performance in SP was questioned.

#2 Effects of horizontal plyometric training volume on soccer players' performance
Reference: Res Sports Med. 2016 Aug 22:1-12. [Epub ahead of print]
Authors: Yanci J, Los Arcos A, Camara J, Castillo D, García A, Castagna C
Summary: The aim of this study was to examine the dose response effect of strength and conditioning programmes, involving horizontally oriented plyometric exercises, on relevant soccer performance variables. Sixteen soccer players were randomly allocated to two 6-week plyometric training groups (G1 and G2) differing by imposed (twice a week) training volume. Post-training G1 (4.13%; d = 0.43) and G2 (2.45%; d = 0.53) moderately improved their horizontal countermovement jump performance. Significant between-group differences (p < 0.01) in the vertical countermovement jump for force production time (T2) were detected post-training. No significant and practical (p > 0.05, d = trivial or small) post-training improvements in sprint, change of direction ability (CODA) and horizontal arm swing countermovement jump were reported in either group. Horizontal plyometric training was effective in promoting improvement in injury prevention variables. Doubling the volume of a horizontal plyometric training protocol was shown to have no additional effect over functional aspects of soccer players' performance.

#3 Periodontal status and serum creatine kinase levels among young soccer players: A preliminary report
Reference: Niger J Clin Pract. 2016 Sep-Oct;19(5):655-8. doi: 10.4103/1119-3077.188708.
Authors: Alshail F, Aljohar A, Alshehri M
Summary: It is hypothesized that soccer players with periodontal disease exhibit raised serum creatine kinase (CK) levels as compared to those without periodontal disease. We assessed the clinical gingival status and serum CK levels among young soccer players. Demographic data were collected through a structured questionnaire. Full mouth bleeding on probing (BOP) and probing pocket depth (PPD) were assessed. Blood samples (4 mL) were collected for measurement of serum CK levels. All blood samples were collected from a vein in the antecubital region. Total CK activities in serum were determined with an optimized spectrophotometric method. Statistical analysis was performed using one-way analysis of variance, and P< 0.05 was considered statistically significant. Twenty-seven male soccer players volunteered to participate in the present study. The mean age of the participants in Groups 1 (n = 14) and 2 (n = 13) were 18.2 ± 2.3 years and 19.1 ± 0.6 years, respectively. Mean scores of BOP were significantly higher among individuals in Group 2 (56.8%) compared with individuals in Group 1 (19.4%) (P < 0.001). Mean scores of PPD ≥4 mm were significantly higher among subjects in Group 2 (12.1%) as compared to individuals in Group 1 (0.8%) (P < 0.001). Levels of CK were significantly higher among individuals in Group 2 (292.7 U/L) as compared to those in Group 1 (52.3 U/L) (P < 0.01).

#4 The effect of slope on repeated sprint ability in young soccer players
Reference: Res Sports Med. 2016 Aug 18:1-11. [Epub ahead of print]
Authors: Padulo J, Ardigò LP, Attene G, Cava C, Wong DP, Chamari K, Migliaccio GM
Summary: This study aimed to describe a gradient repeated sprint ability (RSA) test in comparison with a standard level one by investigating performance, metabolic demand and muscular jumping performance as a proxy for running mechanics. Eighteen athletes performed two level RSA tests (40 m × 6) - for reliability evaluation - and one ±5% gradient RSA test, second leg downhill (RSAgrad). Rating of perceived exertion (RPE), blood lactate concentration (BLa) concentration, vertical jump heights were assessed as well. Level test measures resulted highly reliable (Intra-class correlation coefficient (ICC) ≥0.96). RSAgrad worsened only first sprints' performance (-2%) but not overall test performance (~45 s). RSAgrad resulted to be less deteriorating in terms of fatigue index (FI) (-36%), BLa (-23%), RPE (-11%), jumping performance (RSAgrad post-/pre-squat jump, countermovement jump heights (CMJh): -3%, -6%, respectively). RSAgrad could be used to diversify common training protocol without stressing excessively athletes' current metabolic-anaerobic capacity. Such physical conditioning procedures could improve acceleration/braking capability.

#5 Risk assessment of back pain in youth soccer players
Reference: Res Sports Med. 2016 Aug 18:1-12. [Epub ahead of print]
Authors: Haag TB, Mayer HM, Schneider AS, Rumpf MC, Handel M, Schneider C
Summary: The purpose of this study is to identify several responsible parameters for back pain (BP) in youth soccer players to create a risk assessment tool for early prevention. An iPad-based survey was used to screen for parameters in a cross-sectional study. This questionnaire includes items regarding anthropometric data, training habits and sports injuries and was put into practice with 1110 athletes. Sex (odds ratio (OR): 1.84), age group (1.48) and playing surface (1.56) were significantly associated with BP. A history of injuries especially to the spine and hip/groin increased the likelihood for evolving recurrent BP (1.74/1.40). Overall 15 factors seem to influence the appearance of pain and were integrated into a feasible nomogram. The nomogram provides a practical tool to identify the risks of developing BP for youth soccer players. Although most factors we identified are non-modifiable, this method allows to rank the importance of factors and especially their prevention treatments for athletes.

#6 High-intensity efforts in elite soccer matches and associated movement patterns, technical skills and tactical actions. Information for position-specific training drills
Reference: J Sports Sci. 2016 Aug 18:1-10. [Epub ahead of print]
Authors: Ade J, Fitzpatrick J, Bradley PS
Summary: This study aimed to translate movement patterns, technical skills and tactical actions associated with high-intensity efforts into metrics that could potentially be used to construct position-specific conditioning drills. A total of 20 individual English Premier League players' high-intensity running profiles were observed multiple times (n = 100) using a computerised tracking system. Data were analysed using a novel high-intensity movement programme across five positions (centre back [CB], full-back [FB], central midfielder [CM], wide midfielder [WM] and centre forward [CF]). High-intensity efforts in contact with the ball and the average speed of efforts were greater in WMs than CBs, CMs and CFs (effect sizes [ES]: 0.9-2.1, P < 0.05). WMs produced more repeated efforts than CBs and CMs (ES: 0.6-1.3, P < 0.05). In possession, WMs executed more tricks post effort than CBs and CMs (ES: 1.2-1.3, P < 0.01). FBs and WMs performed more crosses post effort than other positions (ES: 1.1-2.0, P < 0.01). Out of possession, CFs completed more efforts closing down the opposition (ES: 1.4-5.0, P < 0.01) but less tracking opposition runners than other positions (ES: 1.5-1.8, P < 0.01). CFs performed more arc runs before efforts compared to CBs, FBs and WMs (ES: 0.9-1.4, P < 0.05), however, CBs completed more 0-90° turns compared to FBs, CMs and WMs (ES: 0.9-1.1, P < 0.01). The data demonstrate unique high-intensity trends in and out of possession that could assist practitioners when devising position-specific drills.

#7 Physical and technical performances are not associated with tactical prominence in U14 soccer matches
Reference: Res Sports Med. 2016 Aug 17:1-11. [Epub ahead of print]
Authors: Clemente FM, Figueiredo AJ, Martins FM, Mendes RS, Wong DP
Summary: The aim of this study was to analyse the association between physical/technical variables and the tactical prominence variables in U14 soccer matches. Twenty-two young amateur soccer players (13.5 [Formula: see text] 0.5 years old, 5.4 [Formula: see text] 0.5 years of practice, 163.3 [Formula: see text] 9.8 cm in body height) from two teams of the Portuguese regional league volunteered for the study. Our results showed positive and moderate correlation between dribbling test and betweenness centrality (r = 0.324; p = 0.142), and negative moderate correlation between %fatigue index and betweenness centrality (r = -0.390; p = 0.073). Physical and technical variables had no statistical differences among tactical positions. Nevertheless, when tactical prominence of players from four tactical positions were compared, significant differences were found in terms of degree prestige (p = 0.001) and degree centrality (p = 0.002). This pilot study did not find strong correlations between physical/technical levels and tactical prominence in soccer matches.

#8 Time Trends in Incidence and Severity of Injury Among Collegiate Soccer Players in the United States: NCAA Injury Surveillance System, 1990-1996 and 2004-2009
Reference: Am J Sports Med. 2016 Aug 15. pii: 0363546516659879. [Epub ahead of print]
Authors: Chandran A, Barron MJ, Westerman BJ, DiPietro L
Summary: A number of sociocultural and environmental changes have occurred over the past several decades that may affect the risk of injury among young athletes playing soccer. The purpose of the study was to identify trends in injury incidence and severity between 2 time periods (1990-1996 and 2004-2009) in both male and female National Collegiate Athletic Association (NCAA) soccer players in the United States. Data were analyzed from the NCAA Injury Surveillance System. The rate ratio (RR), along with the 95% Wald CI, compared incidence density in 2004-2009 relative to that in 1990-1996. Overall sex-pooled injury rates were significantly lower in the 2004-2009 cohort compared with the 1990-1996 cohort (RR = 0.88; 95% CI = 0.86-0.91), and this was true for almost every category of injury studied. We observed only 1 significant sex difference between the time periods with regard to noncontact injuries, as men experienced a significant increase in rate of noncontact injuries between 1990-1996 and 2004-2009 (RR = 1.09; 95% CI = 1.02-1.17), whereas women experienced a significant decrease (RR = 0.70; 95% CI = 0.67-0.75). These surveillance data show decreasing trends in collegiate soccer injuries. Whether these decreases are attributable to greater resources being allocated toward athlete health, injury management, or the safety of the playing environment cannot be determined. Given the prominence of soccer play in the United States, public health efforts should promote the use of this surveillance system to better inform and evaluate injury prevention practices and policies directed toward player safety.

#9 Kicking Velocity and Effect on Match Performance When using a Smaller, Lighter Ball in Women's Football
Reference: Int J Sports Med. 2016 Aug 23. [Epub ahead of print]
Authors: Andersen TB, Krustrup P, Bendiksen M, Orntoft CO, Randers MB, Pettersen SA
Summary: The present study evaluated the effect of a smaller, lighter ball on kicking speed and technical-tactical and physical match performance in high-level adult female footballers. In the laboratory test setting, the peak ball velocity was 6% higher with the new ball (NB) than the standard ball (SB) (26.5±0.5 vs. 25.1±0.5 m·s-1, p<0.05). However, during match-play, no differences were observed in mean heart rate (87±5 vs. 87±5%HRmax; p>0.05), blood lactate (90 min: 4.7±1.7 and 4.0±1.7 mmol·l-1; p>0.05), total distance covered (10.6±0.9 and 10.4±0.8 km; p>0.05), intense running (>16 km/h) (2.08±0.42 and 1.94±0.38 km; p>0.05) and match-induced decrement in Yo-Yo IR1 performance (28 vs. 31%, respectively, p<0.05) using NB compared to SB. Likewise, no difference was observed in the number of short, medium-range or long passes during matches played with the 2 ball types, and there was no difference in passing success rate (NB: 68±1% and SB: 68±1%, p>0.05). In conclusion, high-level adult female footballers had a higher kicking speed when using a smaller, lighter ball, but no differences were observed during match-play with the 2 ball types in respect of technical-tactical and physical match performance. The physical loading was high for the players when playing with both ball types.

#10 Tactical expertise assessment in youth football using representative tasks
Reference: Springerplus. 2016 Aug 9;5(1):1301. doi: 10.1186/s40064-016-2955-1. eCollection 2016.
Authors: Serra-Olivares J, Clemente FM, González-Víllora S
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Summary: Specific football drills improve the development of technical/tactical and physical variables in players. Based on this principle, in recent years it has been possible to observe in daily training a growing volume of small-sided and conditioned games. These games are smaller and modified forms of formal games that augment players' perception of specific tactics. Despite this approach, the assessment of players' knowledge and tactical execution has not been well documented, due mainly to the difficulty in measuring tactical behavior. For that reason, this study aims to provide a narrative review about the tactical assessment of football training by using representative tasks to measure the tactical expertise of youth football players during small-sided and conditioned games. This study gives an overview of the ecological approach to training and the principles used for representative task design, providing relevant contribution and direction for future research into the assessment of tactical expertise in youth football.

#11 High prevalence of dysfunctional, asymmetrical, and painful movement in elite junior Australian Football players assessed using the Functional Movement Screen
Reference: J Sci Med Sport. 2016 May 21. pii: S1440-2440(16)30064-0. doi: 10.1016/j.jsams.2016.05.003. [Epub ahead of print]
Authors: Fuller JT, Chalmers S, Debenedictis TA, Townsley S, Lynagh M, Gleeson C, Zacharia A, Thomson S, Magarey M
Summary: The purpose of this study was to describe the prevalence of dysfunctional, asymmetrical, and painful movement in junior Australian Football players using the Functional Movement Screen (FMS). Elite junior male Australian Football players (n=301) aged 15-18 years completed pre-season FMS testing. The FMS consists of 7 sub-tests: deep squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, trunk stability push-up (TSPU) and rotary stability. The shoulder mobility, TSPU, and rotary stability tests were combined with an accompanying clearing test to assess pain. Each sub-test was scored on an ordinal scale from 0 to 3 and summed to give a composite score out of 21. Composite scores ≤14 were operationally defined as indicating dysfunctional movement. Players scoring differently on left and right sides were considered asymmetrical. Players reported whether they missed any games due to injury in the preceding 22 game season. Sixty percent of players (n=182) had composite scores ≤14, 65% of players (n=196) had at least one asymmetrical sub-test, and 38% of players (n=113) had at least one painful sub-test. Forty-two percent of players (n=126) missed at least one game in the previous season due to injury. Previous injury did not influence composite score (p=0.951) or asymmetry (p=0.629). Players reporting an injury during the previous season were more likely to experience pain during FMS testing (odds ratio 1.97, 95% confidence interval 1.23-3.18; p=0.005). Junior Australian Football players demonstrate a high prevalence of dysfunctional, asymmetrical, and painful movement during FMS testing.

#12 Injuries in professional male football players in Kosovo: a descriptive epidemiological study
Reference: BMC Musculoskelet Disord. 2016 Aug 12;17:338. doi: 10.1186/s12891-016-1202-9.
Authors: Shalaj I, Tishukaj F, Bachl N, Tschan H, Wessner B, Csapo R
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Summary: The incidence and severity of football-related injuries has been found to differ strongly between professional leagues from different countries. The aims of this study were to record the incidence, type and severity of injuries in Kosovarian football players and investigate the relationship between injury incidence rates (IRs), players' age and playing positions. Players' age, anthropometric characteristics and playing positions, training and match exposure as well as injury occurrences were monitored in 11 teams (143 players) of Kosovo's top division during the 2013/14 season. The exact type, severity and duration of football-related injuries were documented following International Federation of Football Associations (FIFA) recommendations. A total of 272 injuries were observed, with traumatic injuries accounting for 71 %. The overall injury IR was 7.38 (CI: 7.14, 7.63) injuries per 1,000 exposure hours and ~11x lower during training as opposed to matches. Strains and ruptures of thigh muscles, ligamentous injuries of the knee as well as meniscus or other cartilage tears represented the most frequent differential diagnoses. While no statistical differences were found between players engaged in different playing positions, injury IR was found to be higher by 10-13 % in younger (IR = 7.63; CI: 7.39, 7.87) as compared to middle-aged (IR = 6.95; CI: 6.41, 7.54) and older players (IR = 6.76; CI: 5.71, 8.00). The total injury IR in elite football in Kosovo is slightly lower than the international average, which may be related to lesser match exposure. Typical injury patterns agree well with previously reported data. Our finding that injury IR was greater in younger players is related to a higher rate of traumatic injuries and may indicate a more aggressive and risky style of play in this age group.

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