Latest research in football - week 11 - 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 Double layer repair of tibialis anterior muscle hernia in a soccer player: a case report and review of the literature.
Reference: Muscles Ligaments Tendons J. 2016 Feb 13;5(4):331-4. doi: 10.11138/mltj/2015.5.4.331.
Authors: Dönmez G, Evrenos MK, Cereb M, Karanfil Y, Doral MN
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4762648/pdf/331-334.pdf
Summary: Muscle herniations usually present in athletes especially in the lower legs; occurring through defects in the deep fascial layer of the muscles and typically seen following local blunt trauma or muscle hypertrophy after strenuous exercise. Management of muscle hernias varies from conservative therapy to surgical repair and usually needs multidisciplinary collaboration for differential diagnosis. Herein tibialis anterior muscle hernia in 17-year-old male soccer player was presented. The diagnosis was confirmed with dynamic ultrasonographic views changing with the different movements of the ankle. Since the symptoms were not relieved with conservative methods, surgical repair of the defect was offered. we preferred to repair fascial defect with double layer and Mesh graft that were placed over primary suture repair. No complications were reported such as wound or mesh infection postoperatively. The patient was clinically satisfied and returned his previous activity level after 3 months of surgery. After 2 years of follow-up the feature of the bulge was dissolved and player was satisfied with the operation. Knowledge of the lower extremity muscle herniation is essential for both proper management and/or surgical referral. The importance of protective devices in prevention, dynamic ultrasonography in diagnosis and double layer repair of the fascial defect with Mesh graft in treatment of muscle herniations were highlighted.

#2 Use of Ultrasound to Monitor Biceps Femoris Mechanical Adaptations after Injury in a Professional Soccer Player
Reference: J Sports Sci Med. 2016 Feb 23;15(1):75-9. eCollection 2016.
Authors: Kellis E, Galanis N, Chrysanthou C, Kofotolis N
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763849/pdf/jssm-15-75.pdf
Summary: This study examined the use of ultrasound to monitor changes in the long head of the biceps femoris (BF) architecture of aprofessional soccer player with acute first-time hamstring strain. The player followed a 14 session physiotherapy treatment until return to sport. The pennation angle and aponeurosis strain of the long head of the biceps femoris (BF) were monitored at 6 occasions (up until 1 year) after injury. The size of the scar / hematoma was reduced by 63.56% (length) and 67.9% (width) after the intervention and it was almost non-traceable one year after injury. The pennation angle of the fascicles underneath the scar showed a decline of 51.4% at the end of the intervention while an increase of 109.2% of the fascicles which were closer to deep aponeurosis was observed. In contrast, pennation angle of fascicles located away from the injury site were relatively unaffected. The treatment intervention resulted in a 57.9% to 77.3% decline of maximum strain per unit of MVC moment and remained similar one year after the intervention. This study provided an example of the potential use of ultrasound-based parameters to link the mechanical adaptations of the injured muscle to specific therapeutic intervention. Key pointsChanges in fascicle orientation after biceps femoris mild tear were reduced after a 28 day intervention and remained similar one year after injury.Tendon/aponeurosis strain per unit of moment of force decreased during the course of the therapeutic intervention.Future studies could utilize ultrasonography to monitor mechanical responses after various types of hamstring injury and interventions in order to improve criteria for a safe return to sport.

#3 Professional Soccer Player Neuromuscular Responses and Perceptions to Acute Whole Body Vibration Differ from Amateur Counterparts.
Reference: J Sports Sci Med. 2016 Feb 23;15(1):57-64. eCollection 2016.
Authors: Cloak R, Lane A, Wyon M
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763847/pdf/jssm-15-57.pdf
Summary: Acute whole body vibration (WBV) is an increasingly popular training technique amongst athletes immediately prior to performance and during scheduled breaks in play. Despite its growing popularity, evidence to demonstrate its effectiveness on acute neuromuscular responses is unclear, and suggestions that athlete ability impacts effectiveness warrant further investigation. The purpose of this study was to compare the neuromuscular effects of acute WBV and perceptions of whether WBV is an effective intervention between amateur and professional soccer players. Participants were 44 male soccer players (22 professional and 22 amateur; age: 23.1 ± 3.7 years, body mass: 75.6 ± 8.8 kg and height: 1.77 ± 0.05 m). Participants in each group were randomly assigned to either an intervention of 3 x 60 s of WBV at 40 Hz (8mm peak-to-peak displacement) or control group. Peak knee isometric force, muscle activation and post activation potentiation (PAP) of the knee extensors along with self-report questionnaire of the perceived benefits of using the intervention were collected. A three-way ANOVA with repeated measures revealed professional players demonstrated a significant 10.6% increase (p < 0.01, Partial Eta(2) = 0.22) in peak knee isometric force following acute WBV with no significant differences among amateur players. A significant difference (p < 0.01, Partial Eta(2) = 0.16) in PAP amongst professional players following acute WBVT was also reported. No significant differences amongst amateur players were reported across measurements. Results also indicated professional players reported significantly stronger positive beliefs in the effectiveness of the WBV intervention (p < 0.01, Partial Eta(2) = 0.27) compared to amateur players. Acute WBV elicited a positive neuromuscular response amongst professional players identified by PAP and improvements in knee isometric peak force as well as perceived benefits of the intervention, benefits not found among amateur players. Key pointsAcute WBV improves knee extensor peak isometric force output and PAP amongst professional and not amateur soccer playersProfessional players perceived acute WBV as more beneficial to performance than amateur playersIsometric strength,vibration intensity and duration appear to influence results amongst players of different playing levels.

#4 Effect of respiratory muscle training on pulmonary function and aerobic endurance in soccer players.
Reference: J Sports Med Phys Fitness. 2016 Feb 12. [Epub ahead of print]
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 min endurance training of respiratory muscles twice a week for 5 weeks. The CON group did not recieve RMT during this period. All participants were evaluated for aerobic endurance using 20-meter Shuttle Run Test (20-MST), pulmomary 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 = .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 > .05). Similarly, there was no difference in 20-MST in the RMT group compared to CON group (p > .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 Support leg action can contribute to maximal instep soccer kick performance: an intervention study
Reference: J Sports Sci. 2016 Mar 8:1-10. [Epub ahead of print]
Authors: Augustus S, Mundy P, Smith N.
Summary: This investigation assessed whether a Technique Refinement Intervention designed to produce pronounced vertical hip displacement during the kicking stride could improve maximal instep kick performance. Nine skilled players (age 23.7 ± 3.8 years, height 1.82 ± 0.06 m, body mass 78.5 ± 6.1 kg, experience 14.7 ± 3.8 years; mean ± SD) performed 10 kicking trials prior to (NORM) and following the intervention (INT). Ground reaction force (1000 Hz) and three-dimensional motion analysis (250 Hz) data were used to calculate lower limb kinetic and kinematic variables. Paired t-tests and statistical parametric mapping examined differences between the two kicking techniques across the entire kicking motion. Peak ball velocities (26.3 ± 2.1 m · s-1 vs 25.1 ± 1.5 m · s-1) and vertical displacements of the kicking leg hip joint centre (0.041 ± 0.012 m vs 0.028 ± 0.011 m) were significantly larger (P < 0.025) when performed following INT. Further, various significant changes in support and kicking leg dynamics contributed to a significantly faster kicking knee extension angular velocity through ball contact following INT (70-100% of total kicking motion, P < 0.003). Maximal instep kick performance was enhanced following INT, and the mechanisms presented are indicative of greater passive power flow to the kicking limb during the kicking stride.

#6 Head Impact Exposure During a Weekend Youth Soccer Tournament.
Reference: J Child Neurol. 2016 Mar 6. pii: 0883073816634857. [Epub ahead of print]
Authors: Chrisman SP, Mac Donald CL, Friedman S, Andre J, Rowhani-Rahbar A, Drescher S, Stein E, Holm M, Evans N, Poliakov AV, Ching RP, Schwien CC, Vavilala MS, Rivara FP
Summary: Concussion is a known risk in youth soccer, but little is known about subconcussive head impacts. The authors provided a prospective cohort study measuring frequency and magnitude of subconcussive head impacts using accelerometry in a middle school-age soccer tournament, and association between head impacts and changes in (1) symptoms, (2) cognitive testing, and (3) advanced neuroimaging. A total of 17 youth completed the study (41% female, mean 12.6 years). There were 73 head impacts >15g measured (45% headers) and only 2 had a maximum peak linear acceleration >50g. No youth reported symptoms consistent with concussion. After correction for multiple comparisons and a sensitivity analysis excluding clear outliers, no significant associations were found between head impact exposure and neuropsychological testing or advanced neuroimaging. The authors conclude that head impacts were relatively uncommon and low in acceleration in youth playing a weekend soccer tournament. This study adds to the limited data regarding head impacts in youth soccer.

#7 Test-retest reliability of physiological and performance responses to 120 minutes of simulated soccer match-play.
Reference: J Strength Cond Res. 2016 Mar 3. [Epub ahead of print]
Authors: Harper LD, Hunter R, Parker P, Goodall S, Thomas K, Howatson G, West DJ, Stevenson E, Russell M.
Summary: This study investigated the test-retest reliability of physiological and performance responses to 120 min (90 min plus 30 min extra-time; ET) of the Soccer Match Simulation (SMS). Ten university-standard soccer players completed the SMS on two occasions under standardized conditions. Capillary and venous blood was taken pre-exercise, at half-time, at 90 and 120 min, with further capillary samples taken every 15 min throughout exercise. Core temperature (Tcore), physical (20-m and 15-m sprint speeds, and countermovement jump height), and technical (soccer dribbling) performance was also assessed during each trial. All variables except blood lactate demonstrated no systematic bias between trials (p > 0.05). During the last 15 min of ET, test-rest reliability (CV% and Pearson's r, respectively) was moderate to strong for 20-m sprint speed (3.5%, 0.71), countermovement jump height (4.9%, 0.90), dribble speed (2.8%, 0.90) and blood glucose (7.1%, 0.93), and very strong for Tcore (1.2%, 0.99). Moderate reliability was demonstrated for 15-m sprint speed (4.6%, 0.36), dribble precision (11.5%, 0.30), plasma insulin (10.3%, 0.96), Creatine Kinase (CK; 28.1%, 0.38), interleukin-6 (24%, 0.99), non-esterified fatty acids (NEFA; 13.2%, 0.73), glycerol (12.5%, 0.86), and blood lactate (18.6%, 0.79). In the last 15 min of ET, concentrations of blood glucose and lactate, and sprint and jump performances were reduced while Tcore, NEFA, glycerol and CK concentrations were elevated (p < 0.05). The SMS is a reliable protocol for measuring responses across a full 120 min of soccer-specific exercise. Deleterious effects on performance and physiological responses occur during ET.

#8 Mental fatigue impairs soccer-specific decision-making skill.
Reference: J Sports Sci. 2016 Mar 7:1-8. [Epub ahead of print]
Authors: Smith MR, Zeuwts L, Lenoir M, Hens N, De Jong LM, Coutts AJ
Summary: This study aimed to investigate the impact of mental fatigue on soccer-specific decision-making. Twelve well-trained male soccer players performed a soccer-specific decision-making task on two occasions, separated by at least 72 h. The decision-making task was preceded in a randomised order by 30 min of the Stroop task (mental fatigue) or 30 min of reading from magazines (control). Subjective ratings of mental fatigue were measured before and after treatment, and mental effort (referring to treatment) and motivation (referring to the decision-making task) were measured after treatment. Performance on the soccer-specific decision-making task was assessed using response accuracy and time. Visual search behaviour was also assessed throughout the decision-making task. Subjective ratings of mental fatigue and effort were almost certainly higher following the Stroop task compared to the magazines. Motivation for the upcoming decision-making task was possibly higher following the Stroop task. Decision-making accuracy was very likely lower and response time likely higher in the mental fatigue condition. Mental fatigue had unclear effects on most visual search behaviour variables. The results suggest that mental fatigue impairs accuracy and speed of soccer-specific decision-making. These impairments are not likely related to changes in visual search behaviour.

#9 Effects of 10-week eccentric overload training on kinetic parameters during change of direction in football players.
Reference: J Sports Sci. 2016 Mar 10:1-8. [Epub ahead of print]
Authors: de Hoyo M, Sañudo B, Carrasco L, Mateo-Cortes J, Domínguez-Cobo S, Fernandes O, Del Ojo JJ, Gonzalo-Skok O
Summary: The aim of the current study was to analyse the effect of 10-week eccentric overload training on kinetic parameters during change of direction (COD) in U-19 football players. The outcome measured included relative peak braking (rPB) and propulsive force (rPF), contact time (CT), time spent during braking (BT) and propulsive phase (PT), relative total (rTOT_IMP), braking (rB_IMP) and propulsive (rP_IMP) impulses. Between-group results showed a substantial better improvement (likely) in CT (ES: 0.72) and BT (ES: 0.74) during side-step cutting, and in rPB (ES: 0.84) and rB_IMP (ES: 0.72) during crossover cutting, in the experimental group (EXP) in comparison to control group (CON). Within-group analysis showed a substantially better performance (likely to almost certain) in CT (ES: 1.19), BT (ES: 1.24), PT (ES: 0.70), rPB (ES: 0.75), rPF (ES: 0.68), rTOT_IMP (ES: 0.48) and rB_IMP (ES: 0.50) in EXP during side-step cutting. Regarding crossover cutting, within-group analysis showed a substantial better performance (likely to almost certain) in CT (ES: 0.75), rPB (ES: 0.75), rPF (ES: 1.34), rTOT_IMP (ES: 0.61), rB_IMP (ES: 0.76) and rP_IMP (ES: 0.46) in EXP. In conclusion, the eccentric overload-based programme led to an improvement in kinetic parameters during COD football tasks.

#10 The levels of vitamin D in relation to injury profiles of professional football players
Reference: Med Clin (Barc). 2016 Mar 5. pii: S0025-7753(16)00054-3. doi: 10.1016/j.medcli.2015.12.019. [Epub ahead of print] [Article in Spanish]
Authors: Pruna R, Bahdur K

#11 Short Duration Heat Acclimation in Australian Football Players.
Reference: J Sports Sci Med. 2016 Feb 23;15(1):118-25. eCollection 2016.
Authors: Kelly M, Gastin PB, Dwyer DB, Sostaric S, Snow RJ
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4763830/pdf/jssm-15-118.pdf
Summary: This study examined if five sessions of short duration (27 min), high intensity, interval training (HIIT) in the heat over a nine day period would induce heat acclimation in Australian football (AF) players. Fourteen professional AF players were matched for VO2peak (mL·kg(-1)·min(-1)) and randomly allocated into either a heat acclimation (Acc) (n = 7) or Control (Con) group (n = 7). The Acc completed five cycle ergometer HIIT sessions within a nine day period on a cycle ergometer in the heat (38.7 ± 0.5 °C; 34.4 ± 1.3 % RH), whereas Con trained in thermo-neutral conditions (22.3 ± 0.2 °C; 35.8 ± 0. % RH). Four days prior and two days post HIIT participants undertook a 30 min constant load cycling test at 60% V̇O2peak in the heat (37.9 ± 0.1 °C; 28.5 ± 0.7 % RH) during which VO2, blood lactate concentration ([Lac(-)]), heart rate (HR), rating of perceived exertion (RPE), thermal comfort, core and skin temperatures were measured. Heat acclimation resulted in reduced RPE, thermal comfort and [Lac(-)] (all p < 0.05) during the submaximal exercise test in the heat. Heart rate was lower (p = 0.007) after HIIT, in both groups. Heat acclimation did not influence any other measured variables. In conclusion, five short duration HIIT sessions in hot dry conditions induced limited heat acclimation responses in AF players during the in-season competition phase. In practice, the heat acclimation protocol can be implemented in a professional team environment; however the physiological adaptations resulting from such a protocol were limited. Key pointsSome minor heat acclimation adaptations can be induced in professional AF players with five 27 min non-consecutive, short duration HIIT sessions in the heat.The heat acclimation protocol employed in this study was able to be implemented in a professional team sport environment during an actual competitive season.Elevating and maintaining a high core temperature sufficient for heat acclimation likely requires a longer heat training session or some pre-heating prior to exercise.

#12 Effect of kinesio taping on the isokinetic muscle function in football athletes with a knee injury.
Reference: J Phys Ther Sci. 2016 Jan;28(1):218-22. doi: 10.1589/jpts.28.218. Epub 2016 Jan 30.
Authors: Hong S, Shim J, Kim S, Namkoong S, Roh H
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756007/pdf/jpts-28-218.pdf
Summary: The purpose of this study was to determine the difference in isokinetic muscle function in football athletes with a knee injury with and without kinesio taping. The subjects for this study were 10 football athletes (males) with a knee injury. Measurements were performed by using Cybex dynamometer under uniform motion before and after the application of kinesio tape to the quadriceps and hamstring muscle. Maximal concentric knee extension and flexion at three angular velocities (60°/s, 120°/s, and 180°/s) were measured. A significant difference was found in peak torque and total work of the flexion at 120°/s and 180°/s, as well as in the average power of extension at 180°/s. Though it is not the main therapy for muscle function in football athletes with injury, kinesio taping was an effective adjunct therapy.

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