Latest research in football - week 21 - 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 Goal Scoring in Soccer: A Polar Coordinate Analysis of Motor Skills Used by Lionel Messi
Reference: Front Psychol. 2016 May 27;7:806. doi: 10.3389/fpsyg.2016.00806. eCollection 2016.
Authors: Castañer M, Barreira D, Camerino O, Anguera MT, Canton A, Hileno R
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Summary: Soccer research has traditionally focused on technical and tactical aspects of team play, but few studies have analyzed motor skills in individual actions, such as goal scoring. The objective of this study was to investigate how Lionel Messi, one of the world's top soccer players, uses his motor skills and laterality in individual attacking actions resulting in a goal. We analyzed 103 goals scored by Messi between over a decade in three competitions: La Liga (n = 74), Copa del Rey (n = 8), and the UEFA Champions League (n = 21). We used an ad-hoc observation instrument (OSMOS-soccer player) comprising 10 criteria and 50 categories; polar coordinate analysis, a powerful data reduction technique, revealed significant associations for body part and orientation, foot contact zone, turn direction, and locomotion. No significant associations were observed for pitch area or interaction with opponents. Our analysis confirms significant associations between different aspects of motor skill use by Messi immediately before scoring, namely use of lower limbs, foot contact zones, turn direction, use of wings, and orientation of body to move toward the goal. Studies of motor skills in soccer could shed light on the qualities that make certain players unique.

#2 Eccentric Exercises Reduce Hamstring Strains in Elite Adult Male Soccer Players: A Critically Appraised Topic
Reference: J Sport Rehabil. 2016 Jun 14. [Epub ahead of print]
Authors: Shadle IB, Cacolice PA
Summary: Hamstring strains are a common sport-related injury, which may limit athletic performance for an extended period of time. These injuries are common in the soccer setting.1 As such, it is important to determine an appropriate prevention program to minimize the risk of such an injury for these athletes. Hamstring strains occur when external loads exceed the strength of the tissue. Development of eccentric muscle control has been shown to be an effective and inexpensive intervention to improve strength. Eccentric hamstring training then, may provide an effective and practical hamstring strain prevention strategy.

#3 Congenital Pseudoarthrosis of Medial Malleolus in A Young Soccer Player - Diagnosis in Clinical setting of Ankle Sprain
Reference: J Orthop Case Rep. 2014 Jan-Mar;4(1):11-4. doi: 10.13107/jocr.2250-0685.139.
Authors: Cerulli G, Fabiano F, Gabriele P, Giacomo P, Enrico S
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Summary: We report a case of a young female soccer player affected by congenital medial bilateral malleolus pseudoarthrosis and os subfibulare. Congenital pseudoarthrosis is the failure of the bones to fuse prior or at birth. The etiology is still unknown, although frequency is high in subjects affected by neurofibromatosis or correlated syndromes, so it has been suggested that these congenital disorders may be the cause of congenital pseudoarthrosis. Our patient, a 16-year-old female, high level soccer player, was referred to us following a right ankle sprain during a match. She reported no medical history of tibia-tarsus joint injuries or disease. Pain, swelling and functional impairment were noted immediately after the accident. Standard radiographs in the emergency department revealed a displaced fracture of the medial malleolus and the presence of os subfibularis. The patient was transferred to our Traumatology and Orthopaedic Department to undergo malleolus ostheosynthesis. Before surgery swelling, functional impairment and intense pain at the medial malleolus level were confirmed. However, there was no radiological opening of ankle, instability or pronation pain; furthermore the flexion-extension was preserved with slight pain. Twenty-four hours later a considerable remission of symptoms was evident with increased range of motion and reduction in the swelling and post-traumatic edema. A radiograph on the left ankle to compare with that of the right ankle was necessary to overcome the discrepancy between the radiological diagnosis and the clinical examination. The radiographic results of both medial malleoli were comparable although on the left the os subfibularis was absent. Since the diagnosis of fracture by the association between the radiographs and the symptomatology was doubtful, a bilateral CT was performed. The scan revealed a medial bilateral malleolus pseudoarthrosis and an accessory right subfibularis nucleus. The patient was discharged from hospital with the diagnosis of "second degree right ankle sprain in patient affected by congenital medial bilateral malleolus pseudoarthrosis". A therapeutic- rehabilitative program was prescribed for the ankle sprain and unnecessary surgery was avoided. After 30 days there was an almost complete remission of pain. At a follow-up of six months the patient was completely asymptomatic and gradually began competitive activity. An accurate history and an objective examination should be performed and correlated with the results of diagnostic procedures in order to avoid the incorrect diagnosis of a fracture needing surgery. The rarity of this ailment and the absence of consequences on long-term function, show that this disease does not justify sports activity cessation. Traumatic events at this site must be assessed properly in order to avoid being confused with malleolus fractures leading to over treatment.

#4 Association between Foot Posture Index and Ankle Sprain in Indoor Football Players
Reference: Glob J Health Sci. 2016 Feb 25;8(10):51426. doi: 10.5539/gjhs.v8n10p160.
Authors: Cherati AS, Dousti M, Younespour S
Summary: This study investigated the relationship between foot type and ankle sprain incidence. In a prospective cohort study using the FPI, 68 adult male and female indoor football (Futsal) players were measured and their feet were classified according to foot posture index (FPI) as neutral, supinated and pronated. They were followed over 6 month as a one competition season and at the end, any injuries at the ankle during this period were detected. There was no significant association between FPI score (considering the total FPI score and its six components) and occurrence of ankle sprain. Also, no association was existed between gender, age, height, weight, BMI, duration of professional exercise, dominant foot and occurrence of ankle sprain. In this study, the history of previous ankle sprain was the only significant predictor of the occurrence of ankle sprain in the follow-up period. Participants with the positive history of previous ankle sprain were at higher risk of developing new ankle sprain (OR=6.02, 95% CI: (1.93, 18.84), p=0.002). There was no significant association between FPI score and occurrence of ankle sprain. There was scarce of supinated foot in the study so evaluation of relationship between supinated feet and ankle sprain was not applicable.

#5 Attention towards the goalkeeper and distraction during penalty shootouts in association football: a retrospective analysis of penalty shootouts from 1984 to 2012
Reference: J Sports Sci. 2016 Jun 13:1-7. [Epub ahead of print]
Authors: Furley P, Noël B, Memmert D
Summary: In the present study, we tested the consequences of attention towards goalkeepers in association football penalty shootouts that have exclusively been derived from laboratory experiments. We conducted a retrospective analysis of all penalty shootouts during FIFA World Cups (1986-2010) and UEFA European Football Championships (1984-2012). We linked key variables of previous laboratory research to observable behaviour in the field that was coded by two independent coders. The following hypotheses were tested: first, attention towards goalkeepers results in more saves/better goalkeeper performance; second, goalkeepers can deliberately distract penalty takers by drawing attention towards themselves which results in less accurate penalty kicks/better goalkeeper performance. Results were in line with previous laboratory analyses as they showed that attention towards goalkeepers resulted in more saves/better goalkeeping performance. Further, if goalkeepers distracted penalty takers this also resulted in better goalkeeping performance. The applied implications of these findings are discussed for both goalkeepers and penalty takers in association football.

#6 Heart rate variability in the standing position reflects training adaptation in professional soccer players
Reference: Eur J Appl Physiol. 2016 Jun 15. [Epub ahead of print]
Authors: Ravé G, Fortrat JO
Summary: The purpose of the study was to show that heart rate variability (HRV) in the standing position better reflects the way in which athletes adapt to training in so-called intermittent sports than the indicator of resting parasympathetic tone usually employed in endurance sports. Twenty professional soccer players (intermittent sport) took part in a 5-week training session divided into three successive periods: "Warm-up", "Intensive training" and "Tapering". At the beginning and end of each of the three periods, a stand test was carried out and the heart rate was recorded, beat by beat (Polar Team 2). We analysed HRV to determine the indicator mostly used to demonstrate training adaptation in endurance sports (lnRMSSD supine, natural logarithm of root mean square of the successive differences) as well as indicators obtained by means of spectral analysis in both supine and standing position. A decrease in heart rate was observed in the supine position at rest during training (-5.2 ± 1.3 bpm) while lnRMSSD and spectral analysis indicators remained unchanged. The "Warm-up" caused an increase in spectral analysis total power in standing position which was further highlighted by "Tapering" (3.39 ± 0.09, 3.61 ± 0.08 and 3.65 ± 0.09 log ms2, respectively). However, the autonomic changes are probably more complex than a change in autonomic activity or balance since spectral analysis autonomic indicators remained unchanged. HRV in the standing position could monitor training adaptation in intermittent sports contrary to the indicator usually employed in endurance sports. However, the significance of the HRV change in the standing position during training remains unclear.

#7 Examining Young Recreational Male Soccer Players' Experience in Adult- and Peer-Led Structures
Reference: Res Q Exerc Sport. 2016 Jun 17:1-10. [Epub ahead of print]
Authors: Imtiaz F, Hancock DJ, Côté J
Summary: Youth sport has the potential to be one of the healthiest and most beneficial activities in which children can partake. Participation in a combination of adult-led and peer-led sport structures appears to lead to favorable outcomes such as enhanced physical fitness, as well as social and emotional development. The purpose of the present study was to examine the subjective and objective experiences of 27 recreational male soccer players aged 10 to 12 years old (M = 10.11 years, SD = 0.32) across adult-led and peer-led sport structures. Direct video observation and experience-rating scales were utilized in an effort to shed light on the impact of adult-led and peer-led sport structures on the same athletes. In the adult-led structures, youth experienced high levels of effort and concentration while spending more time physically or mentally engaged. Meanwhile, youth experienced high rates of prosocial behaviors, sport-related communication, and general communication during the peer-led structures. The results of the present study indicate that rather than one approach being superior to the other, both adult- and peer-led sport structures have the potential to yield unique benefits toward children's positive experiences in sport.

#8 Differences in strength and speed demands between 4v4 and 8v8 small-sided football games
Reference: J Sports Sci. 2016 Jun 9:1-9. [Epub ahead of print]
Authors: Rebelo AN, Silva P, Rago V, Barreira D, Krustrup P
Summary: The aims of this study were (i) to characterise the acceleration demands of two different formats of small-sided game (SSG), i.e., 4v4 + goalkeepers (4v4 + GK) and 8v8 + goalkeepers (8v8 + GK); (ii) to analyse the correlation between performance in power-based tests and acceleration-based physical loading during the two different SSG formats and (iii) to analyse the neuromuscular-induced fatigue. Eighteen adult male footballers participated in the study (20.7 ± 1.0 years, 178 ± 5 cm and 71.4 ± 2.1 kg). Baseline measurements were obtained from countermovement jumps, 15 s repeated jumps and 5 and 15 m sprints. A total of 36 min was analysed for each SSG (4v4 + GK: two sets of 3 × 6 min, and 8v8 + GK: 2 × 18 min). Heart rate, blood lactate, perceived exertion and movement pattern (GPS) were analysed. Distances covered by very-high-intensity activities and very-high-speed running were lower in 4v4 + GK than in 8v8 + GK (effect sizes (ES) = -0.69 ± 0.67 and -1.04 ± 0.67, respectively; very likely), while accelerations and decelerations were higher in 4v4 + GK than in 8v8 + GK (ES = 1.13-1.52; almost certainly). Blood lactate concentrations were higher (ES = 1.40 ± 0.58; almost certainly) and players perceived themselves to be more tired (ES = 0.80-2.31; almost certainly) after 4v4 + GK than after 8v8 + GK. Sprint ability in 5 and 15 m tests decreased (ES = 0.87 ± 0.58 and 0.89 ± 0.58, respectively; almost certainly) only after 4v4 + GK. This SSG format appeared more demanding in relation to repetitions and fatigue development of muscle power-based actions than 8v8 + GK. It may therefore be logical to use the former type of SSG to target development of power-related football actions.

#9 Salivary Biomarker Responses to Two Final Matches in Women's Professional Football.
Reference: J Sports Sci Med. 2016 May 23;15(2):365-71. eCollection 2016.
Authors: Maya J, Marquez P, Peñailillo L, Contreras-Ferrat A, Deldicque L, Zbinden-Foncea H
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Summary: The aim of this study was to examine the link between salivary concentrations of cortisol, testosterone, immunoglobulin A (IgA) and the rate of perceived exertion (RPE) as a measure of internal load after two final matches played 3 days apart by professional women football players. Saliva samples were taken before and after the two matches (M1, M2). RPE was used to monitor the exercise intensity after each match. Testosterone concentrations increased after each match (M1: +42%, p = 0.002; M2: +50%, p < 0.001) while cortisol increased only after M1 (+116%, p < 0.001). The testosterone-to-cortisol ratio decreased only after M1 (-32.4%, p < 0.001). IgA concentration did not change after any match. Testosterone concentrations were correlated with IgA concentrations after each match (M1: R = 0.59, p = 0.008; M2: R=0.51, p = 0.02). RPE was correlated with cortisol concentrations after M1 (R = 0.57; p = 0.01), but not after M2 (R = 0.38; p = 0.07). All these results suggest that salivary cortisol and testosterone concentrations increase especially after the first match of a final, without affecting IgA levels. We speculate that increased testosterone concentration in women after football matches may play a protecting role against immune suppression usually observed after intense exercise. Key pointsIn our sample space, IgA concentrations did not change for teams even, before and after separated match. Suggesting that salivary IgA determinations after physical activities remain under debate.Testosterone concentrations were the only one hormone showing a consequent increase in both matches after physical activity carrying.The T/C ratio decrease only after M1 according with a higher cortisol level reach after M1 get-together, suggesting a differential impact over anxiety-associated team performance. So M2 play gives a more stable psychological state.

#10 Match play demands of 11 versus 11 professional football using Global Positioning System tracking: Variations across common playing formations.
Reference: Hum Mov Sci. 2016 Jun 3;49:1-8. doi: 10.1016/j.humov.2016.05.007. [Epub ahead of print]
Authors: Tierney PJ, Young A, Clarke ND, Duncan MJ
Summary: This study aimed to examine Global Positioning System (GPS) determined movement patterns across the 5 most common playing formations (4-4-2; 4-3-3; 3-5-2; 3-4-3; 4-2-3-1) employed in 11 versus 11 football match play in England. Elite male footballers (n=46) were monitored over the course of a season; total distance (TD), high speed running (HSR), high metabolic load distance (HMLD), high speed accelerations (Acc) and decelerations (Dec) data was collected for analysis. It was found that 3-5-2 formation elicited higher TD (10528±565m, p=0.05), HSR (642±215m, p=0.001), and HMLD (2025±304m, p=0.001) than all other formations and above average Acc and Dec (34±7, p=0.036 and 57±10, p=0.006), with 4-2-3-1 eliciting the highest Acc and Dec (38±8 and 61±12). Positional data showed that CM in 4-3-3 covered >11% TD than in 4-4-2 (p=0.012). FW in 3-5-2 covered >45% HSR than in 4-2-3-1 (p=0.004). CM in 4-3-3 covered >14% HMLD than in 4-4-2 (p=0.367). FW in 4-3-3 performed >49% accelerations than in 4-2-3-1 (p=0.293). WD in 3-5-2 performed >20% more decelerations than in 4-4-2 (p=0.161). This study is important for coaches understanding, that positional physical characteristics are influenced by the demands of playing in different formations during match play.

#11 Acute neuromuscular and performance responses to Nordic hamstring exercises completed before or after football training.
Reference: J Sports Sci. 2016 Jun 6:1-9. [Epub ahead of print]
Authors: Lovell R, Siegler JC, Knox M, Brennan S, Marshall PW
Summary: The optimal scheduling of Nordic Hamstring exercises (NHEs) relative to football training sessions is unknown. We examined the acute neuromuscular and performance responses to NHE undertaken either before (BT) or after (AT) simulated football training. Twelve amateur players performed six sets of five repetitions of the NHE either before or after 60 min of standardised football-specific exercise (SAFT60). Surface electromyography signals (EMG) of the hamstring muscles were recorded during both the NHE, and maximum eccentric actions of the knee flexors (0.52 rad · s-1) performed before and after the NHE programme, and at 15 min intervals during SAFT60. Ten-metre sprint times were recorded on three occasions during each 15 min SAFT60 segment. Greater eccentric hamstring fatigue following the NHE programme was observed in BT versus AT (19.8 %; very likely small effect), which was particularly apparent in the latter range of knee flexion (0-15°; 39.6%; likely moderate effect), and synonymous with hamstring EMG declines (likely small-likely moderate effects). Performing NHE BT attenuated sprint performance declines (2.0-3.2%; likely small effects), but decreased eccentric hamstring peak torque (-14.1 to -18.9%; likely small effects) during football-specific exercise. Performing NHE prior to football training reduces eccentric hamstring strength and may exacerbate hamstring injury risk.

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