Latest research in football - week 15 - 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 Attacking and defensive styles of play in soccer: analysis of Spanish and English elite teams.
Reference: J Sports Sci. 2016 Apr 7:1-10. [Epub ahead of print]
Authors: Fernandez-Navarro J, Fradua L, Zubillaga A, Ford PR, McRobert AP
Summary: The aim of this study was to define and categorise different styles of play in elite soccer and associated performance indicators by using factor analysis. Furthermore, the observed teams were categorised using all factor scores. Data were collected from 97 matches from the Spanish La Liga and the English Premier League from the seasons 2006-2007 and 2010-2011 using the Amisco® system. A total of 19 performance indicators, 14 describing aspects of attacking play and five describing aspects of defensive play, were included in the factor analysis. Six factors, representing 12 different styles of play (eight attacking and four defensive), had eigenvalues greater than 1 and explained 87.54% of the total variance. Direct and possession styles of play, defined by factor 1, were the most apparent styles. Factor analysis used the performance indicators to cluster each team's style of play. Findings showed that a team's style of play was defined by specific performance indicators and, consequently, teams can be classified to create a playing style profile. For practical implications, playing styles profiling can be used to compare different teams and prepare for opponents in competition. Moreover, teams could use specific training drills directed to improve their styles of play.

#2 Technical actions, heart rate, and locomotor activity in 7v7 and 8v8 games for female youth soccer players
Reference: J Strength Cond Res. 2016 Apr 2. [Epub ahead of print]
Authors: Ørntoft C, Nejst Larsen M, Bull Andersen T, Steentoft Rasmussen L, Póvoas SC, Bredsgaard Randers M, Krustrup P.
Summary: The purpose of this study was to evaluate technical performance, heart rate (HR), and activity profile in 7v7 and 8v8 soccer games for 9[FIGURE DASH]10-year-old girls (U11). A total of 24 female youth players participated in the study, all playing 20-min 7v7 and 8v8 games with 160 and 223 m per player, respectively. Technical actions, HR, and activity profile were measured during the games using video filming, HR monitors, and 5-Hz GPS units. The number of technical actions was higher in 7v7 than in 8v8 games (34±19 (±SD) vs. 28±14, p=0.03, d=0.37), as was the number of successful actions (25±16 vs. 20±12, p=0.01, d=0.35), with no difference in success rate for technical actions (70±13 vs. 69±14%, p=0.63, d=0.07). No differences were found between 7v7 and 8v8 in total distance covered (1574±251 and 1622±281 m, p=0.66, d=0.18), peak speed (19.5±2.6 and 20.7±1.5 km[BULLET OPERATOR]h, p=0.16, d=0.56), mean HR values (85±5 and 86±6%HRpeak, p=0.85, d=0.18), and time >90%HRpeak (37±16 and 34±16% of playing time, p=0.76, d=0.13). Distance covered at the highest running speeds of >16 km[BULLET OPERATOR]h was lower in 7v7 than in 8v8 games (34±24 vs. 63±34 m, p=0.018, d=0.98), as was number of entries into this speed zone (8±5 vs. 13±7, p=0.006, d=0.82). In conclusion, more technical actions and successful actions were observed in 7v7 than in 8v8 games, but players covered more ground with high-speed running in 8v8. This study also revealed that HR values were high in both game formats for U11 adolescent female players, with no difference between formats.

#3 Effects of high-velocity resistance training on athletic performance in prepuberal male soccer athletes
Reference: J Strength Cond Res. 2016 Mar 31. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Hammami M, Hachana Y, Granacher U.
Summary: The aim of this study was to assess the effectiveness of 12 weeks in-season low-to-moderate load high-velocity resistance training (HVRT) in addition to soccer training as compared to soccer training only on proxies of athletic performance in prepubertal soccer players. Twenty-four male soccer players performed two different protocols: 1) regular soccer training with five sessions per-week (n=11); age= 12.7±0.3 years); 2) regular soccer training with three sessions per-week and HVRT with two sessions per-week (n=13; age= 12.8±0.2 years). The outcome measures included tests for the assessment of muscle strength (e.g., 1-RM half-squat test), jump ability (e.g., countermovement jump [CMJ], squat jump [SJ] standing long jump [SLJ], and multiple 5 bounds test [MB5]), linear speed (e.g., 5-m, 10-m, 20-m, 30-m sprint test), and change of direction (e.g., T-test, Illinois change of direction test [ICODT]). Results revealed significant group×test interactions for the SJ test (p<0.05, d=0.59) and the SLJ test (p<0.01, d=0.83). Post-hoc tests illustrated significant pre post changes in the HVRT group (SJ: [INCREMENT]22%, p<0.001, d=1.26; SLJ: [INCREMENT]15%, p<0.001, d=1.30) but not in the control group. In addition, tendencies towards significant interaction effects were found for the 1-RM half squat (p=0.08, d=0.54) and the 10-m sprint test (p=0.06, d=0.57). Significant pre post changes were found for both parameters in the HVRT group only (1-RM: [INCREMENT]25%, p<0.001, d=1.23; 10-m sprint: [INCREMENT]7%, p<0.0001, d=1.47). In summary, in-season low-to-moderate load HVRT conducted in combination with regular soccer training is a safe and feasible intervention that has positive effects on maximal strength, vertical and horizontal jump and sprint performance as compared to soccer training only.

#4 Incidence of ankle sprains in soccer players with joint hypermobility syndrome
Reference: Rev Bras Ortop. 2015 Nov 4;47(6):710-3. doi: 10.1016/S2255-4971(15)30026-4. eCollection 2012.
Authors: Vieira RB, Bertolini FM, Vieira TC, Aguiar RM, Pinheiro GB, Lasmar RC
Download link:
Summary: Eighty-three soccer players aged between 14 and 19 years, in the basic category of a professional soccer club in the city of Belo Horizonte, were followed up during the 2009 season. A prospective observational cohort study was conducted, in which these soccer players were divided randomly into two groups. The first consisted of individuals with joint hypermobility syndrome (JHS), totaling 22 players, and the second was a control group with 61 players without this syndrome, determined through a physical examinati. Both groups were studied with regard to incidence of ankle sprains. At the end of this period, the data were compiled and statistical analysis was performed. A total of 43 cases of ankle injury due to sprains were recorded, of which nine episodes were in players with JHS, thus making p = 0.106. The significance level was 5%. We were able to conclude that in our study there was insufficient evidence to assert that there is an association with increased incidence of ankle sprains among patients with JHS.

#5 Determination of the effects of playing soccer on physical fitness in individuals with transtibial amputation
Reference: J Sports Med Phys Fitness. 2016 Apr 7. [Epub ahead of print]
Authors: Guchan Z, Bayramlar K, Ergun N.
Summary: The aim of this paper is to determine the effects of playing soccer on various components of physical performance such as body composition, muscular endurance, anaerobic power, flexibility, balance, and speed of individuals with transtibial amputation. Twelve amputee football players aged 26.67±7.76 years and twelve sedentary individuals aged 33±6.7 years were involved in the study. Body composition, isotonic and isometric endurance of trunk muscles were assessed. Vertical jump test, Sit-and-reach test, Modified Thomas test, Berg Balance Scale, L test and Figure-of-8 Walk were used to assess other physical fitness parameters. The body mass index, waist circumference and body fat percentages of the amputee soccer players were significantly lower than the sedentary amputees (p<0.05). The endurance of back extensors was significantly higher in the soccer group (119.33±47.15sec) than the endurance in the control group (26.25±15.96sec) (p<0.001). Subjects belonging to the soccer group had significantly higher anaerobic power than those in the control group(p<0.05). Flexibility, as assessed by the Sit and Reach test was significantly higher for the soccer group (p=0.002), whereas the Modified Thomas test, which is also used to measure flexibility, indicated no significant difference among both groups (p>0.05). Balance was higher in the soccer group (p=0.023). The completion period of Figure-of-8 Walk (F8W) test was significantly lower in the soccer group (4.54±0.9sec) than the control group (7.71±2.25sec) (p<0.001). No significant difference was observed in the numbers of steps measured during the F8W test (p=0.231). This is the first paper which investigates the effects of sports on the physical fitness of individuals with transtibial amputation with the inclusion of a control group. Overall findings present the benefits of participating in playing soccer on physical fitness parameters of amputees, but further studies with randomised controlled trials, with larger populations, and with other sport branches should be conducted to motivate all amputees to participate in sports.

#6 Effects of Soccer Heading on Brain Structure and Function.
Reference: Front Neurol. 2016 Mar 21;7:38. doi: 10.3389/fneur.2016.00038. eCollection 2016.
Authors: Rodrigues AC, Lasmar RP, Caramelli P
Download link:
Summary: Soccer is the most popular sport in the world, with more than 265 million players worldwide, including professional and amateur ones. Soccer is unique in comparison to other sports, as it is the only sport in which participants purposely use their head to hit the ball. Heading is considered as an offensive or defensive move whereby the player's unprotected head is used to deliberately impact the ball and direct it during play. A soccer player can be subjected to an average of 6-12 incidents of heading the ball per competitive game, where the ball reaches high velocities. Moreover, in practice sessions, heading training, which involves heading the ball repeatedly at low velocities, is common. Although the scientific community, as well as the media, has focused on the effects of concussions in contact sports, the role of subconcussive impacts, as it can occur during heading, has recently gained attention, considering that it may represent an additional mechanism of cumulative brain injury. The purpose of this study is to review the existing literature regarding the effects of soccer heading on brain structure and function. Only in the last years, some investigations have addressed the impact of heading on brain structure, by using neuroimaging techniques. Similarly, there have been some recent studies investigating biochemical markers of brain injury in soccer players. There is evidence of association between heading and abnormal brain structure, but the data are still preliminary. Also, some studies have suggested that subconcussive head impacts, as heading, could cause cognitive impairment, whereas others have not corroborated this finding. Questions persist as to whether or not heading is deleterious to cognitive functioning. Further studies, especially with longitudinal designs, are needed to clarify the clinical significance of heading as a cause of brain injury and to identify risk factors. Such investigations might contribute to the establishment of safety guidelines that could help to minimize the risk of possible adverse effects of soccer on brain structure and function.

#7 Is muscular strength balance influenced by menstrual cycle in female soccer players?
Reference: J Sports Med Phys Fitness. 2016 Apr 5. [Epub ahead of print]
Authors: Dos Santos Andrade M, Mascarin NC, Foster R, DE Jarmy DI Bella ZI, Vancini RL, DE Lira CA.
Summary: Muscular strength imbalance is an important risk factor for ACL injury, but it is not clear the impact of menstrual cycle on muscular strength balance. Our aims were to verify whether muscular balance (hamstring-to-quadriceps peak torque strength balance ratio) during menstrual cycle (luteal and follicular phases) and compare gender differences relative to strength balance to observe possible fluctuations in strength balance ratio. Thirty-eight soccer athletes (26 women and 12 men) took part in this study. Athletes participated in two identical isokinetic strength evaluations for both knee (non-dominant: ND and dominant: D). Peak torque for quadriceps and hamstring muscles were measured in concentric mode and hamstring-to-quadriceps peak torque strength balance ratio calculated. Women had significantly lower hamstring-to-quadriceps peak torque strength balance ratio during the follicular compared to luteal phase, for the ND limb (p=0.011). However, no differences, between luteal and follicular phases, were observed in the D limb. In men, no difference in strength balance ratios was found between the ND and D limbs. These data may be useful in prevention programs for knee (ACL) injuries among soccer female athletes.

#8 Effects of Complex Versus Block Strength Training on the Athletic Performance of Elite Youth Soccer Players
Reference: Sportverletz Sportschaden. 2016 Mar;30(1):E2. doi: 10.1055/s-0035-1567084. Epub 2016 Apr 4. [Article in German]
Authors: Wallenta C, Granacher U, Lesinski M, Schünemann C, Muehlbauer T

#9 Initial Weekly HRV Response is Related to the Prospective Change in VO2max in Female Soccer Players.
Reference: Int J Sports Med. 2016 Apr 4. [Epub ahead of print]
Authors: Esco MR, Flatt AA, Nakamura FY
Summary: The aim of this study was to determine whether the early response in weekly measures of HRV, when derived from a smartphone application, were related to the eventual change in VO2max following an off-season training program in female soccer athletes. 9 female collegiate soccer players participated in an 11-week off-season conditioning program. In the week immediately before and after the training program, each participant performed a test on a treadmill to determine maximal oxygen consumption (VO2max). Daily measures of the log-transformed root mean square of successive R-R intervals (lnRMSSD) were performed by the participants throughout week 1 and week 3 of the conditioning program. The mean and coefficient of variation (CV) lnRMSSD values of week 1 showed small (r=- 0.13, p=0.74) and moderate (r=0.57, p=0.11), respectively, non-significant correlations to the change in VO2max at the end of the conditioning program (∆VO2max). Significant and near-perfect correlation was found between the change in the weekly mean lnRMSSD values from weeks 1 and 3 (∆lnRMSSDM) and ∆VO2max (r=0.90, p=0.002). The current results have identified that the initial change in weekly mean lnRMSSD from weeks 1 to 3 of a conditioning protocol was strongly associated with the eventual adaptation of VO2max.

#10 Fatigue in football: it's not a brainless task!
Reference: J Sports Sci. 2016 Apr 6:1. [Epub ahead of print]
Authors: Coutts AJ.

The Training Manager -