Latest research in football - week 16 - 2017

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 Relationships between fitness test and kicking velocity in young soccer players
Reference: J Sports Med Phys Fitness. 2017 Apr 13. doi: 10.23736/S0022-4707.17.07084-0. [Epub ahead of print]
Authors: Torreblanca-Martinez V, Gonzalez-Jurado JA, Otero-Saborido FM
Summary: The purpose was to study the relation between fitness test and kicking velocity in young soccer players, which has not been previously studied in this group of age. Ninety eight Under-11 soccer players who belonged to two professional Spanish clubs and two amateur clubs were subjected to sprint test (15 and 30 meters), CMJ (Countermovement Jump), estimation of maximal oxygen intake (VO2max), kicking velocity test, fatigue index of jump height and anthropometrical measures. Kicking velocity was significantly correlated (p < 0.05) with 15m sprint (r =-0.554) and 30m sprint (r = -0.587), CMJ height (r = 0.479), VO2max (r = 0.475), body mass (r = 0.311) and height (r = 0.529), but not with body mass index (BMI) (r = -0.011) and fatigue index of jump height (r = -0.05). This study provides new data about correlations between kicking velocity and fitness test, establishing greater correlations between kicking velocity and other variables compared to other groups of age previously studied, suggesting high transferences between results in fitness test and kicking velocity.

#2 Effects of Sesame (Sesamum indicum L.) Supplementation on Creatine Kinase, Lactate Dehydrogenase, Oxidative Stress Markers, and Aerobic Capacity in Semi-Professional Soccer Players
Reference: Front Physiol. 2017 Mar 31;8:196. doi: 10.3389/fphys.2017.00196. eCollection 2017.
Authors: Barbosa CV, Silva AS, de Oliveira CV, Massa NM, de Sousa YR, da Costa WK, Silva AC, Delatorre P, Carvalho R, Braga VA, Magnani M
Summary: Nutritional intervention with antioxidants rich foods has been considered a strategy to minimize the effects of overtraining in athletes. This experimental, randomized, and placebo-controlled study evaluated the effects of consumption of sesame (Sesamum indicum L.) on muscle damage markers, oxidative stress, systemic inflammation, and aerobic performance in male semi-professional soccer players. Twenty athletes were randomly assigned to groups that received 40 g (two tablespoons) per day of sesame or a placebo during 28 days of regular training (exposed to routine training that includes loads of heavy training in the final half of the season). Before and after intervention, creatine kinase (CK), lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), C-reactive protein (hs-CRP), and aerobic capacity were evaluated. Before intervention, a physiologic imbalance was noted in both groups related to CK and LDH levels. Sesame intake caused a reduction of CK (19%, p < 0.05), LDH (37%, p < 0.05), MDA (55%, p < 0.05) and hs-CRP (53%, p < 0.05) and increased SOD (14%, p < 0.05), vitamin A (25%, p < 0.05), and vitamin E (65%, p < 0.05) in the experimental group. These phenomena were accompanied by increased aerobic capacity (17%, p < 0.05). The placebo group showed an increase in CK (5%, p < 0.05) and no significant change in LDH, SOD or vitamin A. MDA levels decreased (21%, p < 0.05) and vitamin E increased (14%, p < 0.05) in the placebo group, but to a much lesser extent than in the experimental group. These results show that sesame consumption may reduce muscle damage and oxidative stress while improving the aerobic capacity in soccer players.

#3 Kinesiology tape mediates soccer-simulated and local peroneal fatigue in soccer players
Reference: Res Sports Med. 2017 Apr 12:1-9. doi: 10.1080/15438627.2017.1314294. [Epub ahead of print]
Authors: Farquharson C, Greig M
Summary: The purpose was to investigate the efficacy of kinesiology taping in mediating the influence of fatigue on ankle sprain risk, 12 male soccer players completed single-leg dynamic balance trials pre- and post-exercise (soccer-specific protocol, isokinetic ankle inversion/eversion protocol) in each of three counter-balanced taping conditions (no tape, zinc oxide tape ZO, kinesiology tape KT). Balance was quantified as the overall stability index (OSI) and directional stability indices of platform deflection. Soccer-specific fatigue only increased OSI in the no tape condition (p = 0.03), with ZO and KT trials negating a fatigue affect. Localized fatigue increased OSI in the no tape (p = 0.01) and ZO (p = 0.05) trials, with no increase in the KT trial. A similar pattern was observed in medio-lateral and anterio-posterior balance indices. KT mediates soccer-simulated and local peroneal fatigue, with practical implications for epidemiological observations of increased injury risk during the latter stages of match play.

#4 Effect of respiratory muscle training on pulmonary function and aerobic endurance in soccer players
Reference: J Sports Med Phys Fitness. 2017 May;57(5):507-513. doi: 10.23736/S0022-4707.16.06283-6.
Authors: Ozmen T, Gunes GY, Ucar I, Dogan H, Gafuroglu TU
Summary: Few studies investigated the effects of the respiratory muscle training (RMT) in soccer although exhaustive high intensity exercise is known to lead to muscle fatigue in respiratory muscles. The purpose of this study was to investigate the effect of RMT on pulmonary function and aerobic endurance in soccer players. Eighteen male soccer players (mean age 22.2±1.4 years) participated in this study. Participants were assigned randomly to either an RMT or a control (CON) group. The RMT group performed a 15-minute endurance training of respiratory muscles twice a week for 5 weeks. The CON group did not receive RMT during this period. All participants were evaluated for aerobic endurance using 20-meter shuttle run test (20-MST), pulmonary function, maximal inspiratory mouth pressure (MIP), and maximal expiratory mouth pressure (MEP) using spirometry. There was a significant improvement in RMT group (14%) as compared to CON group (4%) in MIP measurement (P=0.04). No significant differences were observed in forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), maximum voluntary ventilation (MVV), and MEP after a five week of RMT (P>0.05). Similarly, there was no difference in 20-MST in the RMT group compared to CON group (P>0.05). We concluded that a five week of RMT increased MIP, but FVC, FEV1, MVV, MEP and aerobic endurance did not improve in soccer players. The RMT in addition to soccer training may improve MIP but not the tolerance to high intensity exercise.

#5 Acute effect of stretching modalities on global coordination and kicking accuracy in 12-13year-old soccer players
Reference: Hum Mov Sci. 2017 Apr 7;54:63-72. doi: 10.1016/j.humov.2017.03.008. [Epub ahead of print]
Authors: Frikha M, Derbel MS, Chaari N, Gharbi A, Chamari K
Summary: The aim of the study was to compare the effect of stretching procedures on global coordination and accuracy in instep soccer kicks achieved in different stress conditions. Twenty male young soccer players completed the global coordination test (GC), the instep kicking accuracy test in free (FKA) and in time-pressure (TPKA) conditions, either after static (SS), dynamic (DS), ballistic (BS) or no-stretching (CTR) protocols, on nonconsecutive days and in a randomized order. After performing a 5min standardized intensity jogging (70% of MAV), followed by stretching exercises for 10min, each participant completed, successively, the GC, FKA and TPKA tests. Accuracy data, heart-rate, rating of perceived exertion and task difficulty perception were recorded and analyzed using a two-way ANOVA. GC scores were analyzed using one way ANOVA with repeated measures. The results showed higher GC and TPKA performances after DS and BS procedures. However, there was no effect of the stretching procedures on FKA. The GC scores increased by 10.8% and 7.2% after DS and BS, respectively, but were not affected by SS. Compared to FKA, the TPKA accuracy significantly decreased by 20.2% after CTR (p<0.01) and 30.7% SS (p<0.001) with no significant difference after DS (10.1%; p>0.05) and BS (11.0%; p>0.05). The use of dynamic and ballistic stretching yielded to better GC scores and helped reducing the adverse effect of time-pressure on instep kicking accuracy. Consequently, dynamic and ballistic exercises can be recommended before practicing activities requiring coordination and lower limbs speed and accuracy.

#6 Progression in youth soccer: selection and identification in youth soccer players aged 13-15 years
Reference: J Strength Cond Res. 2017 Apr 7. doi: 10.1519/JSC.0000000000001924. [Epub ahead of print]
Authors: Bidaurrazaga-Letona I, Lekue JA, Amado M, Gil SM
Summary: The aim of this study was to identify the factors which are important for the identification and selection of young soccer players. Ninety four adolescent soccer players from the Under-13 (U13; age=12.3 ± 0.3 years; n=50) and Under-15 (U15; age=14.0 ± 0.2 years; n=44) categories belonging to a professional club participated in the study. Anthropometric measurements, physical tests (sprint, agility, endurance and jump) and maturity status (age at peak height velocity) were recorded over four seasons. Comparisons were performed amongst new players joining the club (Enter players, n=15), players progressing to the next age category (Club players, n=54) and players leaving the club (Deselected players, n=25). A two-way repeated measures analysis of variance (ANOVA) was performed to determine if significant differences existed between groups and testing time. Better physical performance and improvements observed during the season in performance were found to be one of the main factors for U13 players to continue in the club (p < 0.05 - 0.001). In the U15 group, although body size, maturation and physical performance appeared to be the most important characteristics for being identified to play in the club (p < 0.05), Club players demonstrated better improvements during the season (p < 0.05). Overall, these results indicate that the identification or promotion of players by coaches depends on indicators which are age-dependent. Therefore, this study has shown that the talent identification program was more a selection process than a promotion process, selecting and indentifying a posteriori rather than a priori.

#7 Does the FIFA 11+ Injury Prevention Program Reduce the Incidence of ACL Injury in Male Soccer Players?
Reference: Clin Orthop Relat Res. 2017 Apr 7. doi: 10.1007/s11999-017-5342-5. [Epub ahead of print]
Authors: Silvers-Granelli HJ, Bizzini M, Arundale A, Mandelbaum BR, Snyder-Mackler L
Summary: The FIFA 11+ injury prevention program has been shown to decrease the risk of soccer injuries in men and women. The program has also been shown to decrease time loss resulting from injury. However, previous studies have not specifically investigated how the program might impact the rate of anterior cruciate ligament (ACL) injury in male soccer players. The purpose of this study was to examine if the FIFA 11+ injury prevention program can (1) reduce the overall number of ACL injuries in men who play competitive college soccer and whether any potential reduction in rate of ACL injuries differed based on (2) game versus practice setting; (3) player position; (4) level of play (Division I or II); or (5) field type. This study was a prospective cluster randomized controlled trial, which was conducted in 61 Division I and Division II National Collegiate Athletic Association men's soccer teams over the course of one competitive soccer season. The FIFA 11+ is a 15- to 20-minute on-the-field dynamic warm-up program used before training and games and was utilized as the intervention throughout the entire competitive season. Sixty-five teams were randomized: 34 to the control group (850 players) and 31 to the intervention group (675 players). Four intervention teams did not complete the study and did not submit their data, noting insufficient time to complete the program, reducing the number for per-protocol analysis to 61. Compliance to the FIFA 11+ program, athletic exposures, specific injuries, ACL injuries, and time loss resulting from injury were collected and recorded using a secure Internet-based system. At the end of the season, the data in the injury surveillance system were crosshatched with each individual institution's internal database. At that time, the certified athletic trainer signed off on the injury collection data to confirm their accuracy and completeness. A lower proportion of athletes in the intervention group experienced knee injuries (25% [34 of 136]) compared with the control group (75% [102 of 136]; relative risk [RR], 0.42; 95% confidence interval [CI], 0.29-0.61; p < 0.001). When the data were stratified for ACL injury, fewer ACL injuries were reported in the intervention group (16% [three of 19]) compared with the control group (84% [16 of 19]), accounting for a 4.25-fold reduction in the likelihood of incurring ACL injury (RR, 0.236; 95% CI, 0.193-0.93; number needed to treat = 70; p < 0.001). With the numbers available, there was no difference between the ACL injury rate within the FIFA 11+ group and the control group with respect to game and practice sessions (games-intervention: 1.055% [three of 15] versus control: 1.80% [12 of 15]; RR, 0.31; 95% CI, 0.09-1.11; p = 0.073 and practices-intervention: 0% [zero of four] versus control: 0.60% [four of four]; RR, 0.14; 95% CI, 0.01-2.59; p = 0.186). With the data that were available, there were no differences in incidence rate (IR) or injury by player position for forwards (IR control = 0.339 versus IR intervention = 0), midfielders (IR control = 0.54 versus IR intervention = 0.227), defenders (IR control = 0.339 versus IR intervention = 0.085), and goalkeepers (IR control = 0.0 versus IR intervention = 0.0) (p = 0.327). There were no differences in the number of ACL injuries for the Division I intervention group (0.70% [two of nine]) compared with the control group (1.05% [seven of nine]; RR, 0.30; CI, 0.06-1.45; p = 0.136). However, there were fewer ACL injuries incurred in the Division II intervention group (0.35% [one of 10]) compared with the control group (1.35% [nine of 10]; RR, 0.12; CI, 0.02-0.93; p = 0.042). There was no difference between the number of ACL injuries in the control group versus in the intervention group that occurred on grass versus turf (Wald chi square [1] = 0.473, b = 0.147, SE = 0.21, p = 0.492). However, there were more ACL injuries that occurred on artificial turf identified in the control group (1.35% [nine of 10]) versus the intervention group (0.35% [one of 10]; RR, 0.14; 95% CI, 0.02-1.10; p = 0.049). This program, if implemented correctly, has the potential to decrease the rate of ACL injury in competitive soccer players. In addition, this may also enhance the development and dissemination of injury prevention protocols and may mitigate risk to athletes who utilize the program consistently. Further studies are necessary to analyze the cost-effectiveness of the program implementation and to analyze the efficacy of the FIFA 11+ in the female collegiate soccer cohort.

#8 Differences in game reading between selected and non-selected youth soccer players
Reference: J Sports Sci. 2017 Apr 21:1-7. doi: 10.1080/02640414.2017.1313442. [Epub ahead of print]
Authors: Den Hartigh RJR, Van Der Steen S, Hakvoort B, Frencken WGP, Lemmink KAPM
Summary: Applying an established theory of cognitive development-Skill Theory-the current study compares the game-reading skills of youth players selected for a soccer school of a professional soccer club (n = 49) and their non-selected peers (n = 38). Participants described the actions taking place in videos of soccer game plays, and their verbalisations were coded using Skill Theory. Compared to the non-selected players, the selected players generally demonstrated higher levels of complexity in their game-reading, and structured the information of game elements-primarily the player, teammate and field-at higher complexity levels. These results demonstrate how Skill Theory can be used to assess, and distinguish game-reading of youth players with different expertise, a skill important for soccer, but also for other sports.

#9 Soccer Match-Play Represents an Important Component of the Power Training Stimulus in Premier League Players
Reference: Int J Sports Physiol Perform. 2017 Apr 19:1-12. doi: 10.1123/ijspp.2016-0412. [Epub ahead of print]
Authors: Morgans R, Di Michele R, Drust B
Summary: Competitive match-play is a dominant component of the physical load completed by soccer players within a training micro-cycle. Characterising the temporal disruption in homeostasis that follows exercise may provide some insight into the potential for match-play to elicit an adaptive response. Countermovement jump (CMJ) performance was characterised 3 days post-match for 15 outfield players from an English Premier League soccer team (age: 25.8 ± 4.1 yrs; stature: 1.78 ± 0.08 m; mass: 71.7 ± 9.1 kg) across a season. These players were classified as either starters (n=9), or non-starters (n=6), according to the average individual playing time (higher/lower than 60 min/match). Linear mixed models were used to investigate the influence of indicators of match-activity (total distance covered (TD), and high-intensity running distance (HI)) on CMJ height and peak power (PP) values. Starting players covered largely greater TD (ES=1.5) and HI (ES=1.4) than non-starters. Furthermore, there was a possible positive effect of HI on CMJ height and PP. This relationship suggests that an additional 0.6 km high-intensity distance covered would increase CMJ height and PP by slightly more than the smallest worthwhile change values of 0.6 cm and 1.0 W/kg, respectively. This small yet practically relevant increase in performance may suggest that match-play, more specifically the intense activities that are associated with the match, provides a physiological stimulus for neuromuscular adaptation. This data may have implications for the management of preparation of soccer squads, especially the training requirements of starting and non-starting players.

#10 Straight-Line and Change of Direction Intermittent Running in Professional Soccer Players
Reference: Int J Sports Physiol Perform. 2017 Apr 19:1-22. doi: 10.1123/ijspp.2016-0318. [Epub ahead of print]
Authors: Fessi MS, Farhat F, Dellal A, Malone JJ, Moalla W
Summary: The present study aimed to investigate the difference between straight-line (STL) and change of direction (COD) intermittent running exercises in soccer players. Seventeen male professional soccer players performed the agility T-test and 6 intermittent running exercises: 10s at 130% of maximal aerobic speed (MAS) alternated with 10s of rest (10-10), 15s at 120% of MAS alternated with 15s of rest (15-15) and 30s at 110% of MAS alternated with 30s of rest (30-30) both in STL and with COD. All exercises were monitored using a global positioning system. Heart rate was measured during exercises and the rate of perceived exertion (RPE) was collected post-exercise. Delta (Δ) between covered distance in STL and COD exercises at a similar load was calculated and relationships between T-test and Δ distance were analysed. COD intermittent exercises showed a significantly decreased distance covered and an increased number of accelerations, heart rate peak and RPE value compared to STL intermittent exercises at a similar load. High relationships were observed between T-test performance and Δ distance in 10-10 (r = 0.72, P < 0.01) and 15-15 (r = 0.77, P < 0.01) whereas no significant relationships were observed between T-test performance and Δ distance in 30-30 (r = -0.37, P = 0.2). Intermittent COD exercises were associated with higher acceleration, heart rate peak and RPE compared to STL during 10-10 and 15-15 exercises. The ability to rapidly change direction is a crucial quality to perform intense sport-specific running in professional soccer players.

American Football
#1 Repeated mild traumatic brain injuries is not associated with volumetric differences in former high school football players
Reference: Brain Imaging Behav. 2017 Apr 22. doi: 10.1007/s11682-017-9719-6. [Epub ahead of print]
Authors: Terry DP, Miller LS
Summary: We investigated potential brain volumetric differences in a sample of former high school football players many years after these injuries. Forty community-dwelling males ages 40-65 who played high school football, but not college or professional sports, were recruited. The experimental group (n = 20) endorsed experiencing two or more mTBIs on an empirically validated mTBI assessment tool (median = 3, range = 2-15). The control group (n = 20) denied ever experiencing an mTBI. Participants completed a self-report index of current mTBI symptomatology and underwent high-resolution T1-weighted MRI scanning, which were analyzed using the Freesurfer software package. A priori regions of interest (ROIs) included total intracranial volume (ICV), total gray matter, total white matter, bilateral anterior cingulate cortex, bilateral hippocampi, and lateral ventricles. ROIs were corrected for head size using a normalization method that took ICV into account. Despite an adequate sample size and being matched on age, education, estimated premorbid IQ, current concussive symptomatology, there were no statistically significant volumetric group differences across all of the ROIs. These data suggest that multiple mTBIs from high school football may not be associated with measurable brain atrophy later in life. Accounting for the severity of injury and chronicity of sport exposure may be especially important when measuring long-term neuroanatomical differences.

#2 Neck collar with mild jugular vein compression ameliorates brain activation changes during a working memory task after a season of high school football
Reference: J Neurotrauma. 2017 Feb 18. doi: 10.1089/neu.2016.4834. [Epub ahead of print]
Authors: Yuan W, Leach J, Maloney T, Altaye M, Smith D, Gubanich P, Barber-Foss K, Thomas S, DiCesare C, Kiefer A, Myer GD
Summary: Emerging evidence indicates that repetitive head impacts, even at a sub-concussive level, may result in exacerbated or prolonged neurologic deficits in athletes. This study aimed to: 1) quantify the effect of repetitive head impacts on the alteration of neuronal activity based on fMRI of working memory after a high school football season; and 2) determine whether a neck collar that applies mild jugular vein compression to reduce brain energy absorption in head impact through slosh mitigation can ameliorate the altered fMRI activation during a working memory task. Participants were recruited from local high school football teams with 27 and 25 athletes assigned to the non-collar and collar group, respectively. A standard N-Back task was used to engage working memory in the fMRI at both pre- and post-season. The two study groups experienced similar head impact frequency and magnitude during the season (all p>0.05). fMRI BOLD signal response (a reflection of the neuronal activity level) during the working memory task increased significantly from pre to post-season in the non-collar group (corrected p<0.05), but not in the collar group. Areas displaying less activation change in the collar group (corrected p<0.05) included the precuneus, inferior parietal cortex, and dorsal lateral prefrontal cortex. Additionally, BOLD response in the non-collar group increased significantly in direct association with the total number of impacts and total g-force (p<0.05). Our data provide initial neuroimaging evidence for the effect of repetitive head impacts on the working memory related brain activity, as well as a potential protective effect that resulted from the use of the purported brain slosh reducing neck collar in contact sports.

#3 Systemic Hypothermia as Treatment for an Acute Cervical Spinal Cord Injury in a Professional Football Player: 9-Year Follow-Up
Reference: Am J Orthop (Belle Mead NJ). 2017 Mar/Apr;46(2):E79-E82.
Authors: Cappuccino A, Bisson LJ, Carpenter B, Snyder K, Cappuccino H.
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Summary: The following report provides clinical follow-up on a National Football League player who sustained a complete cervical spinal cord injury (SCI) while tackling an opposing player in 2007. He received prompt medical and surgical care based on then-current recommendations, but was also treated with systemic hypothermia soon after his injury, which was controversial at the time. Since then, smaller randomized human studies have described the tolerable safety profile, efficacy, and potential benefits of this intervention in acute SCI in humans. Now, modest systemic hypothermia can be one of many tools considered in the treatment of acute SCI. Before it can become the standard of care, however, additional larger prospective randomized studies need to be completed. The patient described in this article had long-term excellent clinical results, with residual deficits of occasional tingling in fingertips and toe tips, although the patient continues to slowly improve.


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