Latest research in football - week 36 - 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 Bone Turnover Markers and Lean Mass in Pubescent Boys: Comparison Between Elite Soccer Players and Controls
Reference: Pediatr Exerc Sci. 2017 Sep 5:1-20. doi: 10.1123/pes.2017-0090. [Epub ahead of print]
Authors: Nebigh A, Abed ME, Borji R, Sahli S, Sellami S, Tabka Z, Rebai H
Summary: The aim of this study was to examine the relationship between bone mass and bone turnover markers with lean mass in pubescent soccer players. Two groups participated in this study 65 elite young soccer players that trained from 6 to 8 hours per week and 60 controls. Bone mineral density (BMD), bone mineral content (BMC) in the whole body, lower limbs, lumbar spine, and femoral neck, biochemical markers of osteocalcin (OC), bone-specific alkaline phosphatase (BAP), C-telopeptide type I collagen (CTX) and total lean mass were assessed. Young soccer players showed higher BMD and BMC in the whole body and weight-bearing sites (p<0.001). Indeed, total lean mass correlated with whole body BMD and BMC (p<0.001). There were significant differences within the bone formation markers and OC (formation) / CTX (resorption) ratio between young soccer players compared to the control group; but no significant difference in (CTX) between the two groups was observed. The study showed a significant positive correlation between (BAP), (OC) and total lean mass (r = 0.29; r = 0.31; p<0.05, respectively) only for the young soccer players. Findings of this study highlight the importance of soccer practice for bone mineral parameters and bone turnover markers during the puberty stage.

#2 Neuromuscular Responses to Conditioned Soccer Sessions Assessed Via GPS-Embedded Accelerometers: Insights Into Tactical Periodization
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-21. doi: 10.1123/ijspp.2017-0045. [Epub ahead of print]
Authors: Buchheit M, Lacome M, Cholley Y, Simpson BM
Summary: The purpose was to 1) examine the reliability of field-based running-specific measures of neuromuscular function assessed via GPS-embedded accelerometers and 2) examine their responses to three typical conditioned sessions (i.e., Strength, Endurance and Speed) in elite soccer players. Before and immediately after each session, vertical jump (CMJ) and adductors squeeze strength (Groin) performances were recorded. Players also performed a 4-min run at 12 km/h followed by 4 ~60-m runs (run =12 s, r =33 s). GPS (15-Hz) and accelerometer (100 Hz) data collected during the four runs + the recovery periods excluding the last recovery period were used to derive vertical stiffness (K), peak loading force (peak force over all the foot-strikes, Fpeak) and propulsion efficiency (i.e., ratio between velocity and force loads, Vl/Fl). Typical errors were small (CMJ, Groin, K and Vl/Fl) and moderate (Fpeak), with moderate (Fpeak), high (K and Vl/Fl) and very high ICC (CMJ and Groin). After all sessions, there were small decreases in Groin and increases in K, while changes in F were all unclear. In contrast, the CMJ and Vl/Fl ratio responses were session-dependent: small increase in CMJ after Speed and Endurance, but unclear changes after Strength; the Vl/Fl ratio increased largely after Strength, while there was a small and a moderate decrease after the Endurance and Speed, respectively. Running-specific measures of neuromuscular function assessed in the field via GPS-embedded accelerometers show acceptable levels of reliability. While the three sessions examined may be associated with limited neuromuscular fatigue, changes in neuromuscular performance and propulsion-efficiency are likely session objective-dependent.

#3 How Game Location Affects Soccer Performance: T-Pattern Analysis of Attack Actions in Home and Away Matches
Reference: Front Psychol. 2017 Aug 21;8:1415. doi: 10.3389/fpsyg.2017.01415. eCollection 2017.
Authors: Diana B, Zurloni V, Elia M, Cavalera CM, Jonsson GK, Anguera MT
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Summary: The influence of game location on performance has been widely examined in sport contexts. Concerning soccer, game-location affects positively the secondary and tertiary level of performance; however, there are fewer evidences about its effect on game structure (primary level of performance). This study aimed to detect the effect of game location on a primary level of performance in soccer. In particular, the objective was to reveal the hidden structures underlying the attack actions, in both home and away matches played by a top club (Serie A 2012/2013-First Leg). The methodological approach was based on systematic observation, supported by digital recordings and T-pattern analysis. Data were analyzed with THEME 6.0 software. A quantitative analysis, with nonparametric Mann-Whitney test and descriptive statistics, was carried out to test the hypotheses. A qualitative analysis on complex patterns was performed to get in-depth information on the game structure. This study showed that game tactics were significantly different, with home matches characterized by a more structured and varied game than away matches. In particular, a higher number of different patterns, with a higher level of complexity and including more unique behaviors was detected in home matches than in the away ones. No significant differences were found in the number of events coded per game between the two conditions. THEME software, and the corresponding T-pattern detection algorithm, enhance research opportunities by going further than frequency-based analyses, making this method an effective tool in supporting sport performance analysis and training.

#4 Prevalence of FAI radiographic hip abnormalities in elite soccer players: are there differences related to skeletal maturity?
Reference: BMJ Open Sport Exerc Med. 2017 Feb 21;2(1):e000162. doi: 10.1136/bmjsem-2016-000162. eCollection 2016.
Authors: Monckeberg J, Amenabar T, Rafols C, Garcia N, Yañez R
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Summary: Femoroacetabular impingement (FAI) can be a source of hip pain in young adults. Some reports have revealed that participation in high-impact sports may play a role in the development of cam deformity, and there is a higher prevalence of signs of cam impingement in asymptomatic adolescents who participate in soccer and basketball than in non-athlete controls; however, current evidence is scarce regarding the initiation and development of deformities. The aim of this study was to evaluate the prevalence of radiographic hip abnormalities related to FAI in young elite soccer players and compare this with findings in a group of adult elite soccer players. Anteroposterior pelvic and cross-table hip radiographs were obtained for 75 young elite soccer players with skeletal immaturity (group 1) and for 75 adult elite soccer players (group 2), all of whom were previously asymptomatic and had no history of hip disease. After exclusion, group 1 included 72 patients, and group 2 included 70 patients. Radiological signs of FAI were evaluated. 34 subjects in groups 1 and 2 demonstrated cam morphology. The prevalence of pincer morphology was 30 in group 1 and 36 in group 2. However, these differences were not statistically significant. We found no differences in the prevalence of FAI radiological signs between soccer players in their late adolescence and adult soccer players.

#5 Comparison of physical activities of female football players in junior high school and high school
Reference: J Phys Ther Sci. 2017 Aug;29(8):1352-1356. doi: 10.1589/jpts.29.1352. Epub 2017 Aug 10.
Authors: Inoue Y, Otani Y, Takemasa S
Summary: This study aimed to compare physical activities between junior high school and high school female football players in order to explain the factors that predispose to a higher incidence of sports injuries in high school female football players. Twenty-nine female football players participated. Finger floor distance, the center of pressure during single limb stance with eyes open and closed, the 40-m linear sprint time, hip abduction and extension muscle strength and isokinetic knee flexion and extension peak torque were measured. The modified Star Excursion Balance Test, the three-steps bounding test and three-steps hopping tests, agility test 1 (Step 50), agility test 2 (Forward run), curl-up test for 30 seconds and the Yo-Yo intermittent recovery test were performed. The high school group was only significantly faster than the junior high school group in the 40-m linear sprint time and in the agility tests. The distance of the bounding test in the high school group was longer than that in the junior high school group. Agility and speed increase with growth; however, muscle strength and balance do not develop alongside. This unbalanced development may cause a higher incidence of sports injuries in high school football players.

#6 Descriptive analysis of objectively assessed physical activity among talented soccer players: a study of three Norwegian professional football clubs
Reference: BMJ Open Sport Exerc Med. 2017 Feb 21;2(1):e000178. doi: 10.1136/bmjsem-2016-000178. eCollection 2016.
Authors: Saether SA, Aspvik NP
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Summary: Talented football players are expected to overcome large training and match loads, indicating a high weekly level of physical activity (PA). With the use of accelerometers, the aim of this study was to objectively describe the players' total time spent in moderate-to-vigorous PA (MVPA), vigorous PA (VPA) and very vigorous PA (VVPA) per day in 1 week. Since high-intensity PA has been highlighted as important in terms of overall PA load, we also included 2 and 4 min bouts of VPA. Data were collected in three junior teams in professional football clubs in March (club 1: 2014, club 2: 2012 and club 3: 2011). A one-way analysis of variance was applied to analyse differences between the three respective clubs. The players averaged 77.2-86.2 min in MVPA, 14.9-18.5 min in VPA and 1.0-3.1 in VVPA per day. While there were no differences in total time spent in MVPA and VPA per day, VVPA was significantly higher in club 1 (p<0.01) compared with clubs 2 and 3. Moreover, when using the VPA bouts, club 3 (p<0.01) achieved significantly more time in this intensity compared with clubs 1 and 2. This study acknowledges the importance of including both club-related and non-club-related PA when analysing talented football players' PA level. We suggest that future studies examining players' PA with accelerometers should emphasise time spent in high-intensity PA and how this is associated with physical overload, psychological burnout and risk of injury.

#7 Cryotherapy Re-Invented: Application of Phase Change Material for Recovery in Elite Soccer
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-21. doi: 10.1123/ijspp.2017-0334. [Epub ahead of print]
Authors: Clifford T, Abbott W, Kwiecien SY, Howatson G, McHugh MP
Summary: This study examined whether donning lower body garments fitted with cooled phase change material (PCM) would enhance recovery after a soccer match. In a randomized, crossover design, eleven elite-soccer players from the reserve squad of a team in the 2nd highest league in England wore PCM cooled to 15°C (PCMcold) or left at ambient temperature (PCMamb; sham control) for 3 h after a soccer match. To assess recovery, countermovement jump (CMJ) height, maximal isometric voluntary contraction (MIVC), muscle soreness (MS), and the adapted Brief Assessment of Mood Questionnaire (BAM+) were measured before, 12, 36 and 60 h after each match. Pre and post intervention, a belief questionnaire (BFQ) was completed to determine perceived effectiveness of each garment. Results are comparisons between the two conditions at each time point post-match. MIVC at 36 h post was greater with PCMcold vs. PCMwarm (P =0.005; ES=1.59; 95% CI=3.9 to 17.1%). MIVC also tended to be higher at 60 h post (P =0.051; ES=0.85; 95% CI= -0.4 to 11.1%). MS was 26.5% lower in PCMcold vs. PCMwarm at 36 h (P =0.02; ES=1.7; 95% CI= -50.4 mm to -16.1 mm) and 24.3% lower at 60 h (P =0.039; ES=1.1; 95% CI= -26.9 mm to -0.874 mm). There were no between condition differences in post-match CMJ height or BAM+ (P >0.05). The BFQ revealed that players felt the PCMcold was more effective than the PCMamb after the intervention (P =0.004). PCM cooling garments provide a practical means of delivering prolonged post-exercise cooling and thereby accelerating recovery in elite soccer players.

#8 Adding Fish Oil to Whey Protein, Leucine and Carbohydrate Over a 6 Week Supplementation Period Attenuates Muscle Soreness Following Eccentric Exercise in Competitive Soccer Players
Reference: Int J Sport Nutr Exerc Metab. 2017 Sep 5:1-28. doi: 10.1123/ijsnem.2017-0161. [Epub ahead of print]
Authors: Philpott JD, Donnelly C, Walshe IH, Dick J, Galloway SDR, Tipton KD, Witard OC
Summary: Soccer players often experience eccentric exercise-induced muscle damage given the physical demands of soccer match-play. Since long chain n-3 polyunsaturated fatty acids (n-3PUFA) enhance muscle sensitivity to protein supplementation, dietary supplementation with a combination of fish oil-derived n-3PUFA, protein and carbohydrate may promote exercise recovery. This study examined the influence of adding n-3PUFA to a whey protein, leucine and carbohydrate containing beverage over a 6 week supplementation period on physiological markers of recovery measured over 3 days following eccentric exercise. Competitive soccer players were assigned to one of three conditions (2 × 200mL): FO (n=10) contained n-3PUFA (1100mg DHA/EPA - approx. 550mg DHA, 550mg EPA), whey protein (15g), leucine (1.8g) and carbohydrate (20g); PRO (n=10) contained whey protein (15g), leucine (1.8g) and carbohydrate (20g) and CHO (n=10) contained carbohydrate (24g). Eccentric exercise consisted of unilateral knee extension/flexion contractions on both legs separately. Maximal force production was impaired by 22% during the 72 hour recovery period following eccentric exercise (p<0.05). Muscle soreness, expressed as AUC during 72 hour recovery, was less in FO (1948±1091 mm×72 h) than PRO (4640±2654 mm×72h, p<0.05) and CHO (4495±1853 mm×72h p=0.10). Blood concentrations of creatine kinase, expressed as AUC, were ~60% lower in FO compared to CHO (p<0.05) and tended to be lower (~39%, p = 0.07) than PRO. No differences in muscle function, soccer performance or blood c-reactive protein concentrations were observed between groups. In conclusion, the addition of n-3PUFA to a beverage containing whey protein, leucine and carbohydrate ameliorates the increase in muscle soreness and blood concentrations of creatine kinase following eccentric exercise in competitive soccer players.

#9 Movement Patterns of a U-20 National Women's Soccer Team during Competitive Matches: Influence of Playing Position and Performance in the First Half
Reference: Int J Sports Med. 2017 Sep;38(10):747-754. doi: 10.1055/s-0043-110767. Epub 2017 Aug 7.
Authors: Ramos GP, Nakamura FY, Pereira LA, Junior WB, Mahseredjian F, Wilke CF, Garcia ES, Coimbra CC
Summary: The aim of this study was to determine the match locomotor characteristics of a sample of U-20 Brazilian female soccer players. Seven international matches were analyzed during the 2015 U-20 South American Championship, using global positioning technology. During a typical match, fullbacks and forwards covered greater distances in high-intensity running and sprinting than central defenders and midfielders (effect size [ES]=1.42-3.69). In the final 15 min of a game, total and high-intensity running distance and player load were ≈20 to 35% (ES=0.41-3.86) lower than in the first 15 min period for midfielders, fullbacks, forwards, and central defenders. Sprinting, and high-intensity running distances, and the frequency of accelerations >2 m.s-2 immediately after the most intense 5-min period declined in forwards (ES=1.78-2.67), fullbacks (ES=1.96-5.25), midfielders (ES=1.66-3.77), and central defenders (ES=1.50-4.22). Maintaining 'high' levels of activity in the first half resulted in ≈19% reductions in the second half for sprinting distance and frequency of accelerations >2 m.s-2 (ES=0.43 and 0.88), while increases in these locomotor activities were observed in situations with 'low' levels of activity (ES=0.64 and 1.12, for sprinting and accelerations >2 m.s-2, respectively) (within-subject analysis). The data demonstrate that high-intensity efforts are reduced during various phases of international matches and overall activity patterns vary among playing positions. This information could be useful in the development and prescription of sex- and age-specific training regimes.

#10 Sudden Cardiac Death in Professional Soccer Players

Reference: J Am Coll Cardiol. 2017 Sep 12;70(11):1420-1421. doi: 10.1016/j.jacc.2017.07.738.

Authors: Santos-Lozano A, Martin-Hernandez J, Baladron C, Turrado-Sevilla MA, Arraras-Flores A, Villacastin JP, Boraita A, Bueno H, Lucia A.

Australian Football
#1 The Use of Relative Speed Zones in Australian Football: Are We Really Measuring What We Think We Are?
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-25. doi: 10.1123/ijspp.2017-0148. [Epub ahead of print]
Authors: Murray NB, Gabbett TJ, Townshend AD
Summary: This study aimed to examine the difference between absolute and relative workloads, injury likelihood, and the acute:chronic workload ratio (ACWR) in elite Australian football. Forty-five elite Australian football players from one club participated in this study. Running workloads of players were tracked using Global Positioning System technology, and were categorised using either; (1) absolute, pre-defined speed thresholds, or (2) relative, individualised speed thresholds. Players were divided into three equal groups based on maximum velocity; (1) faster, (2) moderate, or (3) slower. One-week and four-week workloads were calculated, along with the ACWR. Injuries were recorded if they were non-contact in nature and resulted in "time-loss". Faster players demonstrated a significant overestimation of very high-speed running when compared to their relative thresholds (p=0.01, ES=-0.73). Similarly, slower players demonstrated an underestimation of high- (p=0.06, ES=0.55) and very high-speed (p=0.01, ES=1.16) running when compared to their relative thresholds. For slower players, (1) greater amounts of relative very high-speed running had a greater risk of injury than less (RR=8.30, p=0.04), and (2) greater absolute high-speed chronic workloads demonstrated an increase in injury likelihood (RR=2.28, p=0.16), while greater relative high-speed chronic workloads offered a decrease in injury likelihood (RR=0.33, p=0.11). Faster players with a very high-speed ACWR of >2.0 had a greater risk of injury than those between 0.49-0.99 for both absolute (RR=10.31, p=0.09) and relative (RR=4.28, p=0.13) workloads. The individualisation of velocity thresholds significantly alters the amount of very high-speed running performed and should be considered in the prescription of training load.

#2 The Influence of Rotations on Match Running Performance in Female Australian Football Midfielders
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-22. doi: 10.1123/ijspp.2017-0175. [Epub ahead of print]
Authors: Black GM, Gabbett TJ, Johnston RD, Naughton G, Cole MH, Dawson B
Summary: With female Australian football (AF) gaining popularity, the understanding of match demands is becoming increasingly important. The aim of this study compare running performances of rotated and whole-quarter state level female Australian Football players during match quarters. Twenty-two state-level female AF midfielders wore global positioning system units during 14 games to evaluate activity profiles. The Yo-Yo Intermittent Recovery Test (Level 1[Yo-Yo IR1]) was used as a measure of high-intensity running ability. Each player's data were categorised into either (1) whole-quarter (2) rotation bout 1 (3) rotation bout 2 before being further divided into quartiles. Players were separated into high or low Yo-Yo IR1 groups using a median split based on their Yo-Yo IR1 performance. Short (4-6 minutes), moderate (6-12 minutes) and long (12-18 minutes) on-field bout activity profiles were compared with whole-quarter players. Rotated players covered greater relative-and high-speed distances than whole-quarter players during a number of quartiles (Effect Size: ES, ≥0.44, Likelihood ≥94%). High Yo-Yo IR1 players covered greater relative and high-speed distances than low Yo-Yo IR1 players in rotation period 1. High Yo-Yo IR1 performance allowed players to cover greater relative distances (ES range=0.57-0.88) and high-speed distances (ES range=0.57-0.86) during rotations. No differences were reported between Yo-Yo IR1 groups when players were required to play whole quarters (ES ≤0.26, Likelihood ≤64%). Players who were on-field for short and moderate durations exhibited greater activity profiles than whole-quarter players. Rotated players have greater activity profiles than whole-quarter players. Additionally, superior high-speed running ability results in a greater activity profile than players who possess lower high-speed running ability. The findings also highlight the importance of short-to-moderate (4-12 minute) rotation periods and may be used to increase high-intensity running performances within quarters in female AF players.

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