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World Conference on Science and Soccer - Presentations Day 3 Part I

Day 3 of the World Conference on Science and Soccer started with some Talent Identification. Below are some slides from the first session.

Paul Larkin

Maxime Hertzog

Ermanno Rampininni





Latest research in football - week 21 - 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 Hamstring Injury Prevention in Soccer: Before or After Training?
Reference: Scand J Med Sci Sports. 2017 May 24. doi: 10.1111/sms.12925. [Epub ahead of print]
Authors: Lovell R, Knox M, Weston M, Siegler JC, Brennan S, Marshall PWM
Summary: We examined the effects of a 12-week program of Nordic hamstring exercises (NHE), administered before or after football training, upon eccentric hamstring strength, muscle activity, and architectural adaptations. Amateur soccer players were randomized into 3 groups. The control group (CON; n=11) undertook core stability exercises, whereas a periodized NHE program was delivered either before (NHEBEF ; n=10) or after (NHEAFT ; n=14) bi-weekly training sessions. Outcome measures included peak torque and concomitant normalized peak surface electromyography signals (sEMG) of the biceps femoris (BF) and medial hamstring (MH) muscles during knee flexor maximal eccentric contractions, performed at 30°·s-1 . Ultrasonography was used to determine BF muscle thickness, muscle fiber pennation angle, and fascicle length. Performing the NHE derived likely moderate peak torque increases in both NHEBEF (+11.9%; 90% confidence interval: 3.6% to 20.9%) and NHEAFT (+11.6%; 2.6% to 21.5%) versus CON. Maximum sEMG increases were moderately greater in the BF of both NHE training groups versus CON. There were likely moderate increases in BF muscle thickness (+0.17 cm; 0.05 cm to 0.29 cm) and likely small pennation angle increases (+1.03°; -0.08° to 2.14°) in NHEAFT versus CON and NHEBEF . BF fascicle length increases were likely greater in NHEBEF (+1.58 cm; 0.48 cm to 2.68 cm; small effect) versus CON and NHEAFT . A 12-week eccentric hamstring-strengthening program increased strength and sEMG to a similar magnitude irrespective of its scheduling relative to the football training session. However, architectural adaptations to support the strength gains differed according to the timing of the injury prevention program.

#2 Heart Rate Variability Discriminates Competitive Levels in Professional Soccer Players
Reference: J Strength Cond Res. 2017 Jun;31(6):1719-1725. doi: 10.1519/JSC.0000000000001795.
Authors: Proietti R, di Fronso S, Pereira LA, Bortoli L, Robazza C, Nakamura FY, Bertollo M.
Summary: Heart rate variability (HRV) has been increasingly used to monitor team sports athletes. Besides the traditional time domain indices (i.e., the SD of successive RR intervals [SDNN] and the root mean square difference of successive normal RR intervals [RMSSD]), recently the use of the stress score (SS), which is an inverse function of the SD2 index derived from the Poincaré plot, and the sympathetic/parasympathetic ratio (S/PS) to monitor soccer players has been proposed. However, the reliability of these new indices and the ability of HRV to differentiate between soccer competitive levels are unknown. The aim of this study was to analyze the reliability of the different HRV-derived indices in professional soccer players during the competitive period and to compare HRV of professional soccer players from 3 teams of distinct competitive levels (i.e., Italian Second Division [2D], European League [EL], and Champions League [CL]). Fifty-four male professional soccer players from 3 different teams of 2 European countries (Italy and Germany) participated in the study. The intraclass correlation coefficient values of the HRV indices varied from 0.78 (very large) to 0.90 (near perfect). The coefficient of variation (CV) values for RMSSD and SDNN were all <5.00%, although the CV for SS was 6.13% and for S/PS, it was 21.33%. Both the CL and EL groups, assumed to be internationally qualified, presented higher lnRMSSD and lnSDNN and lower lnSS and S/PS than the 2D. Therefore, the HRV can be considered reliable in professional soccer players and is able to differentiate between international- and national-level players.

#3 Maximal Sprinting Speed of Elite Soccer Players During Training and Matches
Reference: J Strength Cond Res. 2017 Jun;31(6):1509-1517. doi: 10.1519/JSC.0000000000001642.
Authors: Djaoui L, Chamari K, Owen AL, Dellal A
Summary: The aim of the present study was to compare (a) the maximal sprinting speed (MSS) attained by soccer players during matches (MSSmatch) according to their level of play (professional first French division vs. elite amateur fourth French division) and the playing positions and (b) the MSS attained by professional soccer players during 14 different types of small-sided games (SSG, MSSSSG) and match-play. All players monitored through the study performed a 40-m sprint test to assess individual MSS (MSStest) and compare it to the training and match activity, with the calculation of the percentage of MSStest (%MSStest) reached. No differences were found according to the level of play; however, positional wide players achieved a higher MSSmatch, %MSStest, and MSSSSG than central players (both defenders and midfielders) during matches and SSG. MSSmatch were higher than all MSSSSG, and MSSSSG were positively correlated with the area of the pitch (0.45, p < 0.001), its length (0.53, p < 0.001), and the number of players involved (0.38, p < 0.001). The closer SSG was to match situation in terms of rules, the higher the MSSSSG. Wide players reached higher MSS in match and SSG than central players, confirming the relevance of using SSG close to match situation to specifically prepare elite players to the maximal running speed demand of the match.

#4 Quantifying the High-Speed Running and Sprinting Profiles of Elite Female Soccer Players During Competitive Matches Using an Optical Player Tracking System
Reference: J Strength Cond Res. 2017 Jun;31(6):1500-1508. doi: 10.1519/JSC.0000000000001629.
Authors: Mara JK, Thompson KG, Pumpa KL, Morgan S.
Summary: Quantifying the high-speed running and sprinting profiles of elite female soccer players during competitive matches using an optical player tracking system. J Strength Cond Res 31(6): 1500-1508, 2017-The aim of this study was to determine the high-speed running and sprinting profiles of elite female soccer players during competitive matches using a new Optical Player Tracking system. Eight stationary video cameras were positioned at vantage points surrounding the soccer field so that when each camera view was combined, the entire field could be viewed simultaneously. After each match, an optical player tracking system detected the coordinates (x, y) of each player for every video frame. Algorithms applied to the x and y coordinates were used to determine activity variables for 12 elite female players across 7 competitive matches. Players covered 9,220-10,581 m of total distance, 1,772-2,917 m of high-speed running (3.4-5.3 m·s) distance, and 417-850 m of sprinting (>5.4 m·s) distance, with variations between positional groups (p < 0.001; partial η = 0.444-0.488). Similarly, the number of high-speed runs differed between positional groups (p = 0.002; partial η = 0.342), and a large proportion of high-speed runs (81-84%) and sprints (71-78%) were performed over distances less than 10 m. Mean time between high-speed runs (13.9 ± 4.4 seconds) and sprints (86.5 ± 38.0 seconds) varied according to playing position (p < 0.001; partial η = 0.409) and time of the match (p < 0.001; partial η = 0.113-0.310). The results of this study can be used to design match-specific conditioning drills and shows that coaches should take an individualized approach to training load monitoring according to position.

#5 Exercise Intensity and Technical Demands of Small-Sided Soccer Games for Under-12 and Under-14 Players: Effect of Area per Player
Reference: J Strength Cond Res. 2017 Jun;31(6):1486-1492. doi: 10.1519/JSC.0000000000001615.
Authors: Martone D, Giacobbe M, Capobianco A, Imperlini E, Mancini A, Capasso M, Buono P, Orru S
Summary: The aim of this study was to evaluate the effects of 6 different areas per player (AP) on exercise intensity (EI) measured during small-sided games (SSGs) and expressed as percentage of maximal heart rate (%MHR) and technical actions (TAs) involvement with the ball, crosses, headers, tackles, shots on goal, dribbling, passing, and target passing-in U-12 and U-14 soccer players during SSGs. Seventeen male U-12 soccer players (age 10.0 ± 0.5 years, body mass 39.3 ± 5.3 kg, and height 143.8 ± 4.6 cm) and 16 male U-14 soccer players (age 13.2 ± 0.3 years, body mass 46.6 ± 11.9 kg, and height 154.8 ± 8.5 cm) performed SSGs with different AP: 40, 50, 66.7, 90, 112.5, and 150 m. Our results indicate that at larger AP, the U-12 group's mean EI values were significantly higher than those at smaller AP (p ≤ 0.05); in addition, intergroup comparison showed that EI was higher in U-12 than that in U-14 players when AP of 112.5 and 150 m were considered (p ≤ 0.05). Technical action analysis evidenced that moving from smaller to larger AP, U-14 players adapted better to AP changes. In conclusion, these results suggest that AP influences differently EI and TAs in U-12 and U-14 players. Our results could be taken into account by conditioning coaches to better tailor the physiological and technical training in young players through the modulation of AP.

#6 Relationship Between Internal Load Indicators and Changes on Intermittent Performance After the Preseason in Professional Soccer Players
Reference: J Strength Cond Res. 2017 Jun;31(6):1477-1485. doi: 10.1519/JSC.0000000000001613.
Authors: Campos-Vazquez MA, Toscano-Bendala FJ, Mora-Ferrera JC, Suarez-Arrones LJ
Summary: The aim of this study was to examine the effects of accumulated internal training load (ITL) during the preseason (4 weeks) on changes in the intermittent performance, in a professional soccer team. Twelve professionals soccer players (Mean ± SD age: 27.7 ± 4.3 years; height: 177.1 ± 6.2 cm; body mass: 73.1 ± 5.2 kg; % body fat [Faulkner]: 10.2 ± 1.2) belonging to a Spanish second division team (2013-2014) participated in this study. The 30-15 intermittent fitness test was performed before and after the preseason, and the speed for the last period completed by each player was recorded (VIFT). During the preseason, the team alternated practice of training sessions (TRNs) with friendly matches (FMs). Session rating of perceived exertion (sRPE), heart rate (HR), and HR reserve were analyzed every TRN and FM to calculate ITL (ITL: sRPE-TL, Edward's-TL and Edward's-TLres). The players' VIFT substantially increased after the preseason period (20.1 ± 0.8 vs. 21.1 ± 0.8 km·h; effect size [ES] = 1.15 ± 0.25; almost certainly). The average value of sRPE throughout FMs was substantially greater than the value of the TRNs (7.4 ± 0.9 vs. 5.25 ± 0.2; ES = 2.31 ± 2.45; almost certainly). sRPE-TL, practice volume, and sum of RPE during the preseason were positively and largely correlated (r = 0.70-0.75) with changes on intermittent performance. No relationships were found between HR-derived measures of exercise load and changes on intermittent fitness. The present results suggest that practice volume and subjective measures of TL, related better than HR-based TL methods to changes on intermittent performance after the preseason, in professional soccer players.

#7 Effects of Different Combinations of Strength, Power, and Plyometric Training on the Physical Performance of Elite Young Soccer Players
Reference: J Strength Cond Res. 2017 Jun;31(6):1468-1476. doi: 10.1519/JSC.0000000000001609.
Authors: Kobal R, Loturco I, Barroso R, Gil S, Cuniyochi R, Ugrinowitsch C, Roschel H, Tricoli V
Summary: Effects of different combinations of strength, power, and plyometric training on the physical performance of elite young soccer players. J Strength Cond Res 31(6): 1468-1476, 2017-The combination of strength (ST) and plyometric training (PT) has been shown to be effective for improving sport-specific performance. However, there is no consensus about the most effective way to combine these methods in the same training session to produce greater improvements in neuromuscular performance of soccer players. Thus, the purpose of this study was to compare the effects of different combinations of ST and PT sequences on strength, jump, speed, and agility capacities of elite young soccer players. Twenty-seven soccer players (age: 18.9 ± 0.6 years) participated in an 8-week resistance training program and were divided into 3 groups: complex training (CP) (ST before PT), traditional training (TD) (PT before ST), and contrast training (CT) (ST and PT performed alternately, set by set). The experimental design took place during the competitive period of the season. The ST composed of half-squat exercises performed at 60-80% of 1 repetition maximum (1RM); the PT composed of drop jump exercises executed in a range from 30 to 45 cm. After the experimental period, the maximum dynamic strength (half-squat 1RM) and vertical jump ability (countermovement jump height) increased similarly and significantly in the CP, TD, and CT (48.6, 46.3, and 53% and 13, 14.2, and 14.7%, respectively). Importantly, whereas the TD group presented a significant decrease in sprinting speed in 10 (7%) and 20 m (6%), the other groups did not show this response. Furthermore, no significant alterations were observed in agility performance in any experimental group. In conclusion, in young soccer players, different combinations and sequences of ST and PT sets result in similar performance improvements in muscle strength and jump ability. However, it is suggested that the use of the CP and CT methods is more indicated to maintain/maximize the sprint performance of these athletes.

#8 Immediate effect of ankle balance taping on dynamic and static balance of soccer players with acute ankle sprain
Reference: J Phys Ther Sci. 2017 Apr;29(4):622-624. doi: 10.1589/jpts.29.622. Epub 2017 Apr 20.
Authors: Shin YJ, Kim MK
Download link:
Summary: This study aimed to evaluate the immediate effect of ankle balance taping on balance ability of soccer players with acute ankle sprain. This study was conducted with 16 subjects who were diagnosed with ankle sprain. A cross-over randomized design was used. Each subject performed three interventions in a random order. Subjects were randomly assigned to an ankle balance taping, placebo taping, and no taping. For dynamic and static balance, ability was measured using BIORescue (RM Ingenierie, Rodes, France). Limit of stability, sway length and sway speed for one minute were measured. The Limit of Stability, Sway length and Sway speed differed significantly among the three different taping methods. In this study, we found that ankle balance taping was effective in terms of improving balance ability of soccer players with an ankle sprain.

#9 A cross-sectional study on the relationship between nutritional knowledge and physical fitness in soccer players
Reference: Clin Nutr ESPEN. 2016 Jun;13:e70. doi: 10.1016/j.clnesp.2016.03.063. Epub 2016 May 20.
Authors: Nikolaidis PT, Theodoropoulou E

American Football
#1 Relationship between proxies for Type II fiber type and resting blood pressure in Division I American Football Athletes
Reference: Int J Health Sci (Qassim). 2017 Apr-Jun;11(2):16-20.
Authors: DiCesare CA, Adams JR, Claytor RP, Ward RM, Cox RH
Summary: The risk for cardiovascular disease is well-documented. Perhaps surprisingly, specific athletic populations, including American football players, exhibit increased risk for cardiovascular disease as presented by elevated blood pressure. There is evidence suggesting a link between muscle fiber type distribution and resting blood pressure. Acknowledging this association, it becomes important to clarify an individual's risk for developing cardiovascular disease later in adulthood. The purpose of this study was to assess football performance measures-in particular proxies for muscular power-and their effect on resting blood pressure in football athletes. A total of 80 collegiate-level football players participated in this study. Each participant's body fat %, body mass index, waist circumference, and mean arterial pressure (MAP) were measured. Participants performed one-repetition maximums of bench press, back squat, 40-yard dash, and vertical leap, and a power index (PI) defined as the product of vertical leap and mass. Linear regressions were run between body composition variables and performance measures for all players and a subset of skill players only. The PI was found to be positively, significantly correlated with MAP in all players (r = 0.269; P = 0.035) and the skill players subset (r = 0.425; P = 0.004). The results of the present study indicate an association between muscle fiber type distribution, as indicated by muscular power capacity, and resting blood pressure.

#2 Nutrition practices and knowledge among NCAA Division III football players
Reference: J Int Soc Sports Nutr. 2017 May 19;14:13. doi: 10.1186/s12970-017-0170-2. eCollection 2017.
Authors: Abbey EL, Wright CJ, Kirkpatrick CM
Download link:
Summary: Participation in collegiate American football is physically demanding and may have long-term health implications, particularly in relation to cardiovascular and neurological health. National Collegiate Athletic Association (NCAA) Division III (DIII) football players are a relatively unstudied population, particularly in terms of their dietary habits and knowledge. The aim of the present study was to descriptively evaluate the dietary intake of DIII football players including a subset of linemen and assess the nutritional knowledge and sources of information of these athletes. The study sample was 88 DIII football players including a subset of nine linemen. All participants completed a food frequency questionnaire, and a nutritional knowledge questionnaire that included a quiz and questions about their main sources of nutrition information. Heights and body masses were also recorded. The linemen submitted written 3-day diet records for assessment of their dietary intake. Of the 88 participants, >50% reported consuming starches/grains, meat and dairy daily, but <50% reported consuming fruits and vegetables daily. Protein powders were the most commonly used supplements (33% reported daily use). Compared to dietary recommendations, linemen consumed high amounts of total fat, saturated fat, dietary cholesterol, sodium, and potassium, but were low in carbohydrates, fiber, and essential fats. The mean nutrition knowledge quiz score for the 88 participants was 55.2%. Those who had taken a nutrition or health course in college scored significantly higher on the quiz than those who had not. Participants reported relying primarily on coaches, websites, and athletic trainers (ATs) for nutritional guidance; ATs were the most trusted source. DIII football players had dietary habits that may both mitigate and increase their risk of chronic diseases. These athletes have room to improve their nutrition knowledge. Their reliance on athletic team staff for nutrition guidance highlights the importance of nutrition education for both athletes and staff and the potential role of a registered dietitian nutritionist.

Australian Football
#1 Australian football players experiencing groin pain exhibit reduced subscale scores of Activities of Daily Living and Sport and Recreation on the HAGOS questionnaire: A case-control study
Reference: Phys Ther Sport. 2017 Apr 20;26:7-12. doi: 10.1016/j.ptsp.2017.04.004. [Epub ahead of print]
Authors: Drew MK, Lovell G, Palsson TS, Chiarelli PE, Osmotherly PG
Summary: The objective was to report normative responses to the HAGOS questionnaire for Australian football players and to determine whether any of the HAGOS questionnaire sub scales can differentiate players with and without groin pain. Professional (n = 66) and semi-professional (n = 9) Australian football (AF) players with current groin pain (n = 16) and controls (n = 57) without current groin pain. The HAGOS subscales were compared between players with and without groin pain using the Wilcoxon rank-sum test with effect sizes (ES) calculated. Floor and ceiling effects were examined. A post-hoc factor analysis was undertaken. Participants with current groin pain showed lower Physical Function of Daily Living (PFDL) and Physical Function in Sport and Recreation (PFSR) subscale scores (p < 0.05, ES: 0.77 and 0.90 respectively). Any groin pain (current and/or historical) lowered the Pain and Quality of Life (QOL) subscale scores (p < 0.05, ES: 0.38 and 0.72 respectively). Factor analysis showed 8 significant factors with one main factor identified representing items describing forceful activities (Eigenvalue = 18.02, Proportion = 0.49). The HAGOS can distinguish AF players with current groin pain in the PFDL and PFSR subscales but not in the other four subscales. Any current or historical groin pain lowers scores on the QOL and Pain sub scales.

#2 Optimising Pre-Season Training Loads in Australian Football
Reference: Int J Sports Physiol Perform. 2017 May 22:1-19. doi: 10.1123/ijspp.2016-0695. [Epub ahead of print]
Authors: Carey DL, Crow J, Ong KL, Blanch P, Morris ME, Dascombe BJ, Crossley KM
Summary: The purpose was to investigate whether pre-season training plans for Australian football can be computer generated using current training load guidelines to optimise injury risk reduction and performance improvement. A constrained optimisation problem was defined for daily total and sprint distance, using the pre-season schedule of an elite Australian football team as a template. Maximising total training volume and maximising Banister model projected performance were both considered as optimisation objectives. Cumulative workload and acute:chronic workload ratio constraints were placed on training programs to reflect current guidelines on relative and absolute training loads for injury risk reduction. Optimisation software was then used to generate pre-season training plans. The optimisation framework was able to generate training plans that satisfied relative and absolute workload constraints. Increasing the off-season chronic training loads enabled the optimisation algorithm to prescribe higher amounts of 'safe' training and attain higher projected performance levels. Simulations showed that using a Banister model objective led to plans that included a taper in training load prior to competition in order to minimise fatigue and maximise projected performance. In contrast, when the objective was to maximise total training volume, more frequent training were prescribed in order to accumulate as much load as possible. Feasible training plans that maximise projected performance and satisfy injury risk constraints can be automatically generated by an optimisation problem for Australian football. The optimisation methods allow for individualised training plan design and the ability to adapt to changing training objectives and different training load metrics.





World Conference on Science and Soccer - Presentations Day 2

The following slides will display some of the content of the second day of the World Conference on Science and Soccer that I have visited.


Filipe Manuel Clemente

Maickel Padilha

Alan McCall

George Nassis

Bruno Grueninger





World Conference on Science and Soccer - Presentations Day 1

As mentioned in previous post, I have attended the World Conference on Science and Soccer.

Beside presenting myself I visited a couple of session/presentations, of which I took some pictures.


Brian Dawson

Barry Drust

Aaron Coutts

Arne Jaspers

Maurizio Fanchini

Matthew Walan

Robert McCunn

At the end of the first day, the Conference Gala Dinner Reception was held at the Roazhon Park, the home (stadium) of Rennes FC.






Latest research in football - week 20 - 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 Body Size of Male Youth Soccer Players: 1978-2015
Reference: Sports Med. 2017 May 18. doi: 10.1007/s40279-017-0743-x. [Epub ahead of print]
Authors: Malina RM, Figueiredo AJ, Coelho-E-Silva MJ
Summary: Studies of the body size and proportions of athletes have a long history. Comparisons of athletes within specific sports across time, though not extensive, indicate both positive and negative trends. The objective of the study was to evaluate secular variation in heights and weights of male youth soccer players reported in studies between 1978 and 2015. Reported mean ages, heights, and weights of male soccer players 9-18 years of age were extracted from the literature and grouped into two intervals: 1978-99 and 2000-15. A third-order polynomial was fitted to the mean heights and weights across the age range for each interval, while the Preece-Baines model 1 was fitted to the grand means of mean heights and mean weights within each chronological year to estimate ages at peak height velocity and peak weight velocity for each time interval. Third-order polynomials applied to all data points and estimates based on the Preece-Baines model applied to grand means for each age group provided similar fits. Both indicated secular changes in body size between the two intervals. Secular increases in height and weight between 1978-99 and 2000-15 were especially apparent between 13 and 16 years of age, but estimated ages at peak height velocity (13.01 and 12.91 years) and peak weight velocity (13.86 and 13.77 years) did not differ between the time intervals. Although the body size of youth soccer players increased between 1978-99 and 2000-15, estimated ages at peak height velocity and peak weight velocity did not change. The increase in height and weight likely reflected improved health and nutritional conditions, in addition to the selectivity of soccer reflected in systematic selection and retention of players advanced in maturity status, and exclusion of late maturing players beginning at about 12-13 years of age. Enhanced training programs aimed at the development of strength and power are probably an additional factor contributing to secular increases in body weight.

#2 A Study of Relationships among Technical, Tactical, Physical Parameters and Final Outcomes in Elite Soccer Matches as Analyzed by a Semiautomatic Video Tracking System
Reference: Percept Mot Skills. 2017 Jun;124(3):601-620. doi: 10.1177/0031512517692904. Epub 2017 Jan 1.
Authors: Filetti C, Ruscello B, D'Ottavio S, Fanelli V
Summary: The performance of a soccer team depends on many factors such as decision-making, cognitive and physical skills, and dynamic ever-changing space-time interactions between teammate and opponents in relation to the ball. Seventy ( n = 70) matches of the Italian SERIE A season 2013-2014 were investigated to analyze the mean performance of 360 players in terms of physical (physical efficiency index; PEI) and technical-tactical (technical efficiency index; TEI) standpoints. Using a semiautomatic video analysis system that has incorporated new parameters able to measure technical-tactical and physical efficiency (Patent IB2010/002593, 2011-ISA), the correlation between these new variables and how much it relates to the likelihood of winning were verified. Correlations between TEI and PEI were significant ( n = 140, r = .60, p < .001), and TEI showed a higher likelihood of winning than PEI factors ( p < .0001 vs. .0001, CI 95% [1.64, 3.00] vs. [1.28, 2.07]). Higher TEI and TEI + PEI differences between the teams were associated with a greater likelihood of winning, but PEI differences were not. Key performance indicators and this performance assessment method might be useful to better understand what determines winning and to assist the overall training process and match management.

#3 Postactivation potentiation in elite young soccer players
Reference: J Exerc Rehabil. 2017 Apr 30;13(2):153-159. doi: 10.12965/jer.1734912.456. eCollection 2017 Apr.
Authors: Titton A, Franchini E
Download link:
Summary: The aim of this study was to investigate the acute effects of 16 different combinations to cause the postactivation potentiation (PAP) in elite young soccer players. Squat exercise in 4 different intensities (40%, 60%, 80%, and 100% one-repetition maximum [1RM]) was performed and its effects were evaluated in the performance of countermovement jump (CMJ), after 4 different recovery times (1, 3, 5, and 10 min). For this purpose, 25 young soccer players, underwent five experimental sessions. At the first session the control to determine 1RM in half-squat was carried out. The following four experimental sessions were comprised of four intensity combinations with four different recovery intervals in order to perform the CMJ test later, randomly determined and with 30-min interval between each combination. The conditions were compared using an analysis of variance with repeated measurements, followed by Bonferroni test, using 5% significance level (P<0.05). The different intensities investigated did not provide significant increases in CMJ height, but significant differences were noted in recovery time, where, at CMJ maximum height, 1-min interval was better than after 3 min (P<0.05), 5, and 10 min (P<0.001). On the average jump performances, 1-min interval resulted in better results (P<0.001) compared to other intervals. The 10-min recovery resulted in poorer performances compared to the other intervals (P<0.001). Our results indicate that regardless the intensity used in the half-squat exercise with elite young soccer players, the 1-min recovery time was more appropriate to promote an increase in vertical jump.

#4 Assessing long-term return to play after hip arthroscopy in football players evaluating risk factors for good prognosis
Reference: Knee Surg Sports Traumatol Arthrosc. 2017 May 17. doi: 10.1007/s00167-017-4573-z. [Epub ahead of print]
Authors: Barastegui D, Seijas R, Alvarez-Diaz P, Rivera E, Alentorn-Geli E, Steinbacher G, Cusco X, Cugat R
Summary: Groin pain is the third most common disease in football players and has often been associated with hip pathology such as femoroacetabular impingement and labral lesions. Hip arthroscopy offers possibilities of function restoration via minimally invasive procedures. The aim of this study is to evaluate professional football player's injuries and their return to play after hip arthroscopy for FAI and labral injuries. Patients that underwent hip arthroscopy between 2009 and 2014 were selected retrospectively. From this population, only professional soccer players competing at national level were included (Tegner 10). Arthroscopic surgery was proposed in patients with persistent pain. All patients were assessed for VAS score preoperatively and at 3, 6, 12 and 24 months post-op. HOS (sport and DLA) and mHHS tests were performed at the same time periods. All patients were men with a mean age of 26.5 ± 7.1 years old. Preoperative VAS (7.4 ± 1.3), HOS ADL (67.7 ± 5.5), HOS sport (37.6 ± 18.7) and mHHS (72.5 ± 8.8) showed improved scores during long-term follow-up. Time to return to play was 10.8 months (SD ± 4.3), with range between 4 and 20 months. Mean follow-up was 45.4 ± 15.6 months (range from 26 to 72 months). No differences were observed between non-active and active patients at final follow-up with respect to chondral lesions, but significant differences were observed with reference to management of the labrum (p = 0.031), where a higher rate of labrectomies existed among inactive patients and a higher rate of suture among active patients. Hip arthroscopy is a safe procedure with very good return to play results, but for optimized return to football one should consider patient age at the time of surgery, the condition of the labrum and low scores on the Harris Hip Score (mHHS) and HOS (sport version) as predictive factors for poor prognosis. Level of evidence IV.

#5 A football player with an evident knee trauma
Reference: Ned Tijdschr Geneeskd. 2017;161(0):D1068. [Article in Dutch]
Authors: Goudriaan WA, Huis In 't Veld R, Hoogeslag RAG
Summary: A 22-year-old male presented with medial sided instability of the right knee three days after shooting a blocked ball. Physical examination, which is usually feasible in the acute phase, showed grade 3 laxity of the superficial medial collateral ligament. MRI confirmed a distal rupture, which needs repair within 2 weeks after onset.

#6 The functional movement test 9+ is a poor screening test for lower extremity injuries in professional male football players: a 2-year prospective cohort study
Reference: Br J Sports Med. 2017 May 16. pii: bjsports-2016-097307. doi: 10.1136/bjsports-2016-097307. [Epub ahead of print]
Authors: Bakken A, Targett S, Bere T, Eirale C, Farooq A, Tol JL, Whiteley R, Khan KM, Bahr R
Summary: The 9+ screening battery test consists of 11 tests to assess limitations in functional movement. The aim was to examine the association of the 9+ with lower extremity injuries and to identify a cut-off point to predict injury risk. Professional male football players in Qatar from 14 teams completed the 9+ at the beginning of the 2013/2014 and 2014/2015 seasons. Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff during these seasons. Univariate and multivariate Cox regression analyses were used to calculate HR and 95% CI. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity and identify the optimal cut-off point for risk assessment. 362 players completed the 9+ and had injury and exposure registration. There were 526 injuries among 203 players (56.1%) during the two seasons; injuries to the thigh were the most frequent. There was no association between 9+ total score and the risk of lower extremity injuries (HR 1.02, 95% CI 0.99 to 1.05, p=0.13), even after adjusting for other risk factors in a multivariate analysis (HR 1.01, 95% CI 0.98 to 1.04, p=0.37). ROC curve analysis revealed an area under the curve of 0.48, and there was no cut-off point that distinguished injured from non-injured players. The 9+ was not associated with lower extremity injury, and it was no better than chance for distinguishing between injured and uninjured players. Therefore, the 9+ test cannot be recommended as an injury prediction tool in this population.

#7 Community-level football injury epidemiology: traumatic injuries treated at Swedish emergency medical facilities
Reference: Eur J Public Health. 2017 May 16. doi: 10.1093/eurpub/ckx053. [Epub ahead of print]
Authors: Timpka T, Schyllander J, Stark Ekman D, Ekman R, Dahlstrom O, Hagglund M, Kristenson K, Jacobsson J
Summary: Despite the popularity of the sport, few studies have investigated community-level football injury patterns. This study examines football injuries treated at emergency medical facilities using data from three Swedish counties. An open-cohort design was used based on residents aged 0-59 years in three Swedish counties (pop. 645 520). Data were collected from emergency medical facilities in the study counties between 1 January 2007 and 31 December 2010. Injury frequencies and proportions for age groups stratified by sex were calculated with 95% confidence intervals (95% CIs) and displayed per diagnostic group and body location. Each year, more than 1/200 person aged 0-59 years sustained at least one injury during football play that required emergency medical care. The highest injury incidence was observed among adolescent boys [2009 injuries per 100 000 population years (95% CI 1914-2108)] and adolescent girls [1413 injuries per 100 000 population years (95% CI 1333-1498)]. For female adolescents and adults, knee joint/ligament injury was the outstanding injury type (20% in ages 13-17 years and 34% in ages 18-29 years). For children aged 7-12 years, more than half of the treated injuries involved the upper extremity; fractures constituted about one-third of these injuries. One of every 200 residents aged 0-59 years in typical Swedish counties each year sustained a traumatic football injury that required treatment in emergency healthcare. Further research on community-level patterns of overuse syndromes sustained by participation in football play is warranted.

#8 Determination of clinically relevant differences in frontal plane hop tests in women’s collegiate Basketball and soccer players
Reference: Int J Sports Phys Ther. 2017 Apr;12(2):182-189.
Authors: Hardesty K, Hegedus EJ, Ford KR, Nguyen AD, Taylor JB
Summary: ACL injury prevention programs are less successful in female basketball players than in soccer players. Previous authors have identified anthropometric and biomechanical differences between the athletes and different sport-specific demands, including a higher frequency of frontal plane activities in basketball. Current injury risk screening and preventive training practices do not place a strong emphasis on frontal plane activities. The medial and lateral triple hop for distance tests may be beneficial for use in the basketball population. The hypothesis is to 1) establish normative values for the medial and lateral triple hop tests in healthy female collegiate athletes, and 2) analyze differences in test scores between female basketball and soccer players. It was hypothesized that due to the frequent frontal plane demands of their sport, basketball players would exhibit greater performance during these frontal plane performance tests. Thirty-two NCAA Division-1 female athletes (20 soccer, 12 basketball) performed three trials each of a medial and lateral triple hop for distance test. Distances were normalized to height and mass in order to account for anthropometric differences. Repeated measures ANOVAs were performed to identify statistically significant main effects of sport (basketball vs. soccer), and side (right vs. left), and sport x side interactions. After accounting for anthropometric differences, soccer players exhibited significantly better performance than basketball players in the medial and lateral triple hop tests (p < 0.05). Significant side differences (p  = 0.02) were identified in the entire population for the medial triple hop test, such that participants jumped farther on their left (400.3 ± 41.5 cm) than right (387.9 ± 43.4 cm) limbs, but no side differences were identified in the lateral triple hop. No significant side x sport interactions were identified. Women's basketball players exhibit decreased performance of frontal plane hop tests when compared to women's soccer players. Additionally, the medial triple hop for distance test may be effective at identifying side-to-side asymmetries.

American Football
#1 Environmental and Physiological Factors Affect Football Head Impact Biomechanics
Reference: Med Sci Sports Exerc. 2017 May 15. doi: 10.1249/MSS.0000000000001325. [Epub ahead of print]
Authors: Mihalik JP, Sumrall AZ, Yeargin SW, Guskiewicz KM, King KB, Trulock SC, Shields EW
Summary: Recent anecdotal trends suggest a disproportionate number of head injuries in collegiate football players occur during preseason football camp. In warmer climates, this season also represents the highest risk for heat-related illness among collegiate football players. Since concussion and heat illnesses share many common symptoms, we need 1) to understand if environmental conditions, body temperature, and hydration status affect head impact biomechanics; and 2) to determine if an in-helmet thermistor could provide a valid measure of gastrointestinal temperature. A prospective cohort of 18 Division I college football players (age = 21.1 ± 1.4 yrs; height = 187.7 ± 6.6 cm; mass = 114.5 ± 23.4 kg). Data were collected during three experimental and one control session. During each session, the Head Impact Telemetry System recorded head impact biomechanics (linear acceleration, rotational acceleration, and severity profile) and in-helmet temperature. A wet bulb globe device recorded environmental conditions, and CorTemp Ingestible Core Body Temperature Sensor recorded gastrointestinal temperature. Our findings suggest that linear acceleration (P = 0.57), rotational acceleration (P = 0.16), and HITsp (P =0.33) are not influenced by environmental or physiological conditions. We did not find any single or combination of predictors for impact severity. Rotational acceleration was approaching significance between our early experimental sessions when compared to our control session. More research should be conducted to better understand if rotational accelerations are a component of impact magnitudes that are affected due to changes in environmental conditions, body temperature, and hydration status.





World Conference on Science and Soccer - Posters

Since Wednesday I have been at the World Conference on Science and Soccer at Rennes (France).

As part of every conference, delegates can submit their research as a poster that are hang up in a separate room for visitors.

Below are (nearly) all poster of the conference.






Latest research in football - week 19 - 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 The Effects of Sleep Deprivation on Soccer Skills
Reference: Percept Mot Skills. 2017 Jan 1:31512517707412. doi: 10.1177/0031512517707412. [Epub ahead of print]
Authors: Pallesen S, Gundersen HS, Kristoffersen M, Bjorvatn B, Thun E, Harris A
Summary: Many athletes sleep poorly due to stress, travel, and competition anxiety. In the present study, we investigated the effects of sleep deprivation on soccer skills (juggling, dribbling, ball control, continuous kicking, 20 and 40 m sprint, and 30 m sprint with changes of direction). In all, 19 male junior soccer players (14-19 years old) were recruited and participated in a cross-balanced experimental study comprising two conditions; habitual sleep and 24 hours sleep deprivation. In both conditions, testing took place between 8 a.m. and 10 a.m. Order of tests was counterbalanced. Each test was conducted once or twice in a sequence repeated three times. The results revealed a negative effect of sleep deprivation on the continuous kicking test. On one test, 30 meter sprint with directional changes, a significant condition × test repetition interaction was found, indicating a steeper learning curve in the sleep deprived condition from Test 1 to Test 2 and a steeper learning curve in the rested condition from Test 2 to Test 3. The results are discussed in terms of limitations and strengths, and recommendations for future studies are outlined.

#2 The influence of a 12% carbohydrate-electrolyte beverage on self-paced soccer-specific exercise performance
Reference: J Sci Med Sport. 2017 Apr 21. pii: S1440-2440(17)30399-7. doi: 10.1016/j.jsams.2017.04.015. [Epub ahead of print]
Authors: Harper LD, Stevenson EJ, Rollo I, Russell M
Summary: The purpose was to assess the physiological and performance effects of a 12% carbohydrate-electrolyte beverage consumed at practically applicable time-points (i.e., before each half) throughout simulated soccer match-play. Fed players (n=15) performed 90-min of soccer-specific exercise (including self-paced exercise at the end of each half). Players consumed carbohydrate-electrolyte (CHO; 60g×500ml-1, Na+ 205mg×500ml-1), placebo-electrolyte (PL) or water (Wat) beverages at the end of the warm-up (250ml) and half-time (250ml plus ad-libitum water). Blood was drawn before each half and every 15-min during exercise. Physical (15-m sprinting, countermovement jumps, self-paced distance, acceleration/deceleration count), technical (dribbling) and cognitive (memory, attention, decision-making) performance was assessed. Ratings of perceived exertion (RPE) and abdominal discomfort were measured. Against Wat and PL, CHO increased (all p<0.05) mean accelerations >1.5m·s-2 during self-paced exercise (>+25%) and dribbling speed from 60-min onwards (>+3%). Mean sprinting speed improved (+2.7%) in CHO versus Wat. Blood glucose increased before and during each half in CHO versus PL and Wat (all p<0.05). A 27% decline in glycaemia occurred at 60-min in CHO. RPE was comparable between trials. Cognition reduced post-exercise (p<0.05); this decline was not attenuated by CHO. Abdominal discomfort increased during exercise but was similar between trials. Using more realistic fluid ingestion timings than have been examined previously, consuming a 12% carbohydrate-electrolyte beverage increased blood glucose, self-paced exercise performance, and improved dribbling speed in the final 30-min of exercise compared to water and placebo. Carbohydrates did not attenuate post-exercise reductions in cognition.

#3 Profile of match performance and heart rate response in Japanese amputee soccer
Reference: J Sports Med Phys Fitness. 2017 May 5. doi: 10.23736/S0022-4707.17.07246-2. [Epub ahead of print]
Authors: Maehana H, Miyamoto A, Koshiyama K, Tanaka Yanagiya T, Yoshimura M
Summary: The purpose of this study was to profile the match performance and heart rate response in Japanese amputee soccer. Twelve amputee soccer players participated in this study. Match data were collected 20 samples in 4 matches. Match performances data such as total distance, high-intensity running (HIR: ≥13km·h-1) were collected using a global positioning systems technology. Heart rate (HR) was recorded using short-range radio telemetry. In addition, the rating of perceived exertion (RPE) was assessed immediately using Borg's original after the first half and the second half. This study showed that the distance covered over the 50 minutes of the match was 2984.2±56.1m, and it was significantly shorter in the second half than the first half (p<0.05). The distance covered by HIR was 205.3±100.5m, and there was no significant difference between the first half and the second half. Moreover, the mean HR during match was 176.8±7.9beats·min-1, which corresponded to 96.3% of HRmax. RPE was a high value of more 15 in both of the first half and the second half. This study was the first to evaluate competitive performance during matches in amputee soccer. Results of this study indicated that the exercise intensity was high in amputee soccer. It would be considered that causes were amputee soccer own rules and exercise style. These findings would serve as the reference when advance the future studies of amputee soccer.

#4 Reliability of concentric and eccentric strength of hip abductor and adductor muscles in young soccer players
Reference: Biol Sport. 2015 Dec;32(4):351-356. doi: 10.5604/20831862.1189202. Epub 2015 Dec 29.
Authors: Gerodimos V, Karatrantou K, Paschalis V, Zafeiridis A, Katsareli E, Bilios P, Kellis S
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Summary: The concentric and eccentric strength profile and muscular balance of the hip joint are important parameters for success in soccer. This study evaluated the reliability for the assessment of hip abduction and adduction isokinetic strength over a range of angular velocities (30 and 90°/s) and types of muscular actions (concentric and eccentric) in young soccer players. The reliability for the assessment of reciprocal (conventional and functional) and bilateral torque ratios was also examined. Fifteen male soccer players (15±1 years) performed two sessions, separated by three days. The testing protocol consisted of five maximal concentric and eccentric hip abductions and adductions of both legs at angular velocities of 30°/s and 90°/s. The peak torque was evaluated in young soccer players using an isokinetic dynamometer (Cybex Norm), and the reciprocal strength ratios (conventional and functional) and bilateral ratios (non-preferred to preferred leg ratios) were calculated. The test-retest reliability for the assessment of peak torque (ICC = 0.71-0.92) and of reciprocal muscle group ratios (ICC = 0.44-0.87) was found to be moderate to high. Bilateral torque ratios exhibited low to moderate reliability (ICC = 0.11-0.64). In conclusion, isokinetic strength of hip abductor and adductor muscles and the conventional and functional strength ratios can be reliably assessed in young soccer players, especially at low angular velocities. The assessment, however, of bilateral strength ratios for hip abductor/adductor muscles should be interpreted with more caution.

#5 Implication of dynamic balance in change of direction performance in young elite soccer players is angle dependent?
Reference: J Sports Med Phys Fitness. 2017 Apr 26. doi: 10.23736/S0022-4707.17.06752-4. [Epub ahead of print]
Authors: Rouissi M, Haddad M, Bragazzi NL, Owen AL, Moalla W, Chtara M, Chamari K
Summary: Team sports require rapid whole body change of direction (COD) in order to regain, maintain possession of the ball or to avoid opponent. These actions are often performed through unilateral process, with the contralateral leg incurring no ground contact. As a result, maintaining unilateral dynamic balance remains important. The aim of this study was to examine the relationship between dynamic balance (DB) and (COD) performance in young elite soccer players. 20 right-footed young elite soccer players (age=16.42±0.55 year, height=176±2.5cm; leg length=95.70±3.34cm, body-mass=67.03±5.20kg) participated in this study. All players performed star excursion balance test (SEBT) with dominant (DL) and nondominant leg (NDL). 10m sprint with COD of 45°, 90°, 135° or 180° after 5m were also assessed with COD on both right and left sides. Correlations analysis showed significant negative relationships (moderate to high) between COD tests (with DL and NDL) and some selected reaching directions of the SEBT. Stepwise multiple regression analysis showed that DB performance explained between 20% and 75% of the variance of COD tests. Likewise, dynamic balance contribution was dependent upon the angle of COD and the leg used to turn. Some selected reaching directions of the SEBT were significantly correlated with COD's performance in young elite soccer players which, possibly due to similarities in movement demands and muscle recruitment. Furthermore, the contribution of dynamic balance on COD performance was angle dependent and individualized specific dynamic stability exercises may be required to compensate players' deficit in each COD angle.

#6 Effect of a specialized injury prevention program on static balance, dynamic balance and kicking accuracy of young soccer players
Reference: World J Orthop. 2017 Apr 18;8(4):317-321. doi: 10.5312/wjo.v8.i4.317. eCollection 2017 Apr 18.
Authors: Dunsky A, Barzilay I, Fox O
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Summary: The purpose was to study the effect of balance intervention program using the "FIFA 11+" program on static and dynamic balance and kicking accuracy of young soccer players. Twenty young soccer players were allocated to experimental (n = 10) or control (n = 10) groups. The experimental group performed the "FIFA 11+" program three times a week for six weeks. The control group performed their normal warm-up routine. The primary outcomes were measured pre and post intervention, and assessed kicking accuracy, static balance and dynamic balance. No differences were found in kicking accuracy following intervention, for both groups, however, static balance improved significantly among the experimental group with significant interaction with the control group, and with high effect size. In addition, the dynamic balance of the left leg of the experimental group, with medium effect size for interaction between groups. The large effect size of balance improvement that was observed following six weeks of intervention sessions, implies that soccer trainers and coaches should consider the inclusion of "FIFA 11+" as components of programs aimed at improving balance ability/control in young soccer players, as improvement in balance abilities may prevent injuries.

#7 In Place But Not Always Used: Automated External Defibrillators in Amateur Football
Reference: Curr Sports Med Rep. 2017 May/Jun;16(3):126-128. doi: 10.1249/JSR.0000000000000352.
Authors: Vernooij RWM, Goedhart E, Pardo-Hernandez H.

#8 Thunderstorm Asthma, Relative Anemia, and Football Carnage
Reference: Curr Sports Med Rep. 2017 May/Jun;16(3):116-117. doi: 10.1249/JSR.0000000000000349.
Authors: Eichner ER.

#9 Incidence of injury and illness in South African professional male football players: a prospective cohort study
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07452-7. [Epub ahead of print]
Authors: Bayne H, Schwellnus M, Janse Van Rensburg D, Botha J, Pillay L
Summary: Medical illnesses and sports-related injuries both have an effect on athlete health and performance. Epidemiology of injury and illness has been extensively researched during international football tournaments and the European football season. Reports on injury location and severity differ across geographical regions, and there is limited information on injury epidemiology in African football leagues. No studies have investigated the illness burden in football in Africa. This was a prospective cohort study involving two football teams over the 10- month duration of the 2015/16 Premier Soccer League in South Africa. Team medical staff recorded daily football exposure, illness and injuries. Team-based match and training exposure was calculated and used to determine injury and illness incidence and burden over the football season. Overall injury incidence was 2.2 / 1000 h, with match injury incidence of 24.8 / 1000 h and training injury incidence of 0.9 / 1000 h. Time loss injuries accounted for 33 of the 44 injuries recorded. The most common time loss injury location was the knee (14 injuries, 42%). There were 7 minimal, 4 mild, 12 moderate and 10 severe injuries. Sprain/ligament injury (8 injuries) was the most common type, followed by meniscus/cartilage injury (7 injuries). Eleven illnesses were reported during the season, with an incidence of 0.7 / 1000 player days, and most were minimal in severity (8/11). The illness burden was 1.7 / 1000 player days. The respiratory (46%) and gastrointestinal (36%) systems were most commonly affected. The incidence of injury was comparable with data reported internationally and mirrors the increased risk of injury during matches versus training. The nature of injury differed in that the knee was more frequently affected than the ankle or thigh, joint injuries were more common than muscle injuries, and there was a larger proportion of severe injuries. The illness burden was very low.

#10 Intra-system reliability of SICS: video-tracking system (Digital.Stadium®) for performance analysis in football
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07267-X. [Epub ahead of print]
Authors: Beato M, Jamil M
Summary: The correct evaluation of external load parameters is a key factor in professional football. The instrumentations usually utilised to quantify the external load parameters during official matches are Video-Tracking Systems (VTS). VTS is a technology that records two- dimensional position data (x and y) at high sampling rates (over 25 Hz). The aim of this study was to evaluate the intra-system reliability of Digital.Stadium® VTS. 28 professional male football players taking part in the Italian Serie A (age 24 ± 6 years, body mass 79.5 ± 7.8 kg, stature 1.83 ± 0.05 m) during the 2015/16 season were enrolled in this study (Team A and Team B). Video-analysis was done during an official match and data analysis was performed immediately after the game ended and then replicated a week later. This study reported a near perfect relationship between the initial analysis (analysis 1) and the replicated analysis undertaken a week later (analysis 2). R2 coefficients were highly significant for each of the performance parameters, p < 0.001. This study reported a mean TD = 8095 ± 3271 and 8073 ± 3263 m in analysis 1 and analysis 2, respectively. Players reported a mean distance covered over 25 w kg-1 equivalent to 1304 ± 673 m and 1294 ± 672 m, and they reported a mean metabolic power of 9.65 ± 1.64 w kg-1 and 9.58 ± 1.61 w kg-1, in analysis 1 and analysis 2, respectively. The findings reported in this study underlined that all data reported by Digital.Stadium® VTS showed high levels of absolute and relative reliability.

#11 Quantitative T2 * relaxation time analysis of articular cartilage of the tibiotalar joint in professional football players and healthy volunteers at 3T MRI
Reference: J Magn Reson Imaging. 2017 May 9. doi: 10.1002/jmri.25757. [Epub ahead of print]
Authors: Behzadi C, Maas KJ, Welsch G, Kaul M, Schoen G, Laqmani A, Adam G, Regier M
Summary: The purpose was to compare T2 * relaxation times of the tibiotalar cartilage between professional football players and matched healthy male volunteers. Twenty-two ankles of professional football players (24.3 ± 3.8 years) and 20 age- and body mass index-matched healthy individuals (25.6 ± 2.4 years) were investigated. The study protocol consisted of multiplanar T1 -weighted, fat-saturated proton-density weighted (Pdw) and a 3D multiecho T2 * sequence with 22 echo times (4.6-53.6 msec). The articular cartilage was subdivided into six segments. Regions of interest were manually drawn in three zones (lateral, central, medial). Differences and confidence intervals were estimated applying a random effects models. Fixed effects were professional football players versus healthy individuals and areas. The random effect was defined as the person cluster of the different individuals. T2 * values were significantly prolonged in football players compared to male volunteers in all predefined cartilage segments (mean, 17.5 vs. 15.5 msec; P < 0.001). In both groups, the highest relaxation times were found in the lateral zone, with statistically higher relaxation times in professional football players (18.5 vs. 16.5 msec, P = 0.003). Separate evaluation revealed the longest relaxation times in the posterior tibiotalar cartilage, with 21.0 msec for professional football players compared to 19.4 msec for healthy volunteers (P = 0.064). Based on these initial results, T2 * values of the tibiotalar cartilage seem to be elevated in professional football players compared to healthy volunteers. Prospective longitudinal studies should be encouraged to show if these results represent early subtle cartilage lesions prior to clinical manifestation or rather temporary adaptation related to daily high-level loading.

#12 Public opinion on alcohol consumption and intoxication at Swedish professional football events

Reference: Subst Abuse Treat Prev Policy. 2017 May 8;12(1):21. doi: 10.1186/s13011-017-0103-8.
Authors: Skoglund C, Durbeej N, Elgan TH, Gripenberg J
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Summary: Alcohol-related problems at professional sporting events are of increasing concern and alarming reports are often reported in international media. Although alcohol consumption increases the risk for interpersonal violence, it is viewed as a focal element of large football events. Sweden has a long tradition of high public support for strict alcohol-control policies. However, little is known about public opinions on alcohol intoxication and the support for interventions to decrease intoxication at football events. The current study explored the public opinion towards alcohol use, intoxication and alcohol policies at professional football matches in Sweden. A cross-sectional design was utilized and a random general population sample of 3503 adult Swedish residents was asked to participate in a web survey during 2016 (response rate 68%). In total, 26% of the respondents supported alcohol sales at football events. Over 90% reported that obviously intoxicated spectators should be denied entrance or evicted from arenas. The support for regulations limiting alcohol availability varied with background factors such as gender, alcohol use and frequency of football event attendance.There is a strong public consensus for strategies and policies to reduce alcohol sales and intoxication levels at football matches. This public support has implications for our preventive efforts and will facilitate the implementation of strategies and policy changes.

American Football
#1 The Effect of the Number of Carries Among College Running Backs on Future Injury Risk and Performance in the National Football League

Reference: Orthop J Sports Med. 2017 Apr 21;5(4):2325967117703054. doi: 10.1177/2325967117703054. eCollection 2017 Apr.
Authors: Kraeutler MJ1, Belk JW1, McCarty EC1.
Download link: link
Summary: There has been speculation that running backs with an excessive number of carries in college are less likely to be successful in the National Football League (NFL). The purpose was to determine whether there is a correlation between number of carries by college running backs and future performance and injury risk in the NFL. Using the ESPN archives of National Collegiate Athletic Association and NFL running backs, the following inclusion criteria were used: running backs who played their last college season from 1999 through 2012 and who were drafted in the first 4 rounds of the NFL draft following their college career. Players were grouped by number of carries during their final college season (group A, 100-200 carries; group B, 250+ carries). Performance and injury risk were compared between groups during the first 3 eligible seasons in the NFL. Groups were compared based on total number of carries, mean yards per carry, number of games missed due to injury, and the specific injuries resulting in missed playing time. During the seasons studied, a total of 103 running backs were included (group A, n = 42; group B, n = 61). There was a trend toward a significantly greater mean total number of carries through 3 NFL seasons in group B (group A, n = 276 carries; group B, n = 376 carries; P = .058). Mean yards per carry did not differ between groups (group A, n = 3.9 yards/carry; group B, n = 4.0 yards/carry; P = .67). Groups A and B missed a mean 5.8 and 5.7 games, respectively, due to injury during their first 3 NFL seasons (P = .98). A significantly greater proportion of players in group A suffered a concussion compared with group B (P = .014). There is no correlation between the number of carries by college running backs and future injury risk or performance during their early NFL career.

#2 Concussion mechanisms and activities in youth, high school, and college football
Reference: J Neurotrauma. 2017 May 10. doi: 10.1089/neu.2017.5032. [Epub ahead of print]
Authors: Lynall RC, Campbell KR, Wasserman EB, Dompier TP, Kerr Z
Summary: Our purpose was to determine concussion mechanism and activity differences between 3 cohorts of football players; youth, high school, and college. Participants in this prospective cohort study included youth (ages 5-14, 118 teams, 310 team-seasons), high school (96 teams, 184 team-seasons), and college (34 teams, 71 team-seasons) football players. Athletic trainers collected athlete-exposure (AE) and concussion data during the 2012-2014 seasons. Injury mechanism referred to the object that made contact with the concussed player, resulting in the concussion. Injury activity referred to the type of football specific activity the player was involved in when the concussion was sustained. Injury proportion ratios (IPR) compared distributions of concussion mechanisms and activities among age levels. 1,429 concussions were reported over 1,981,284 AE across all levels (Rate: 0.72/1000AE). Overall, most concussions were due to player contact (84.7%). During games, a greater proportion of youth football concussions (14.7%) were due to surface contact than high school (7.3%, IPR=2.02; 95% CI: 1.10-3.72) and college (7.1%, IPR=2.07, 95% CI:1.02-4.23) football. Compared to college football concussions (90.2%), a smaller proportion of youth (80.0%, IPR=0.89, 95%CI: 0.79-0.99) and high school (83.2%, IPR=0.92, 95%CI: 0.86-0.99) football concussions were due to player contact. A greater proportion of game youth football concussions (42.1%) occurred while being tackled than high school (23.2%, IPR=1.81, 95%CI: 1.34-2.45) and college (23.0%, IPR=1.83, 95%CI: 1.29-2.62) football. Findings were similar during practices. Compared to college football game concussions (15.8%), a smaller proportion of youth (6.3%, IPR=0.40, 95%CI: 0.17-0.93) and high school (9.5%, IPR=0.60, 95%CI: 0.38-0.95) football game concussions occurred while being blocked. Concussion mechanism and activity differences should be considered when developing concussion prevention and sport-safety methods specific to different age levels in order to maximize effectiveness.

#3 Consequences of Traumatic Brain Injury in Professional American Football Players: A Systematic Review of the Literature
Reference: Clin J Sport Med. 2017 May 9. doi: 10.1097/JSM.0000000000000432. [Epub ahead of print]
Authors: Vos BC, Nieuwenhuijsen K, Sluiter JK
Summary: The purpose of this study was to systematically review the literature for the consequences Traumatic brain injury (TBI) has on cognitive, psychological, physical, and sports-related functioning in professional American Football players. We performed a systematic search in 2 databases, PubMed and SPORTDiscus, to obtain literature from January 1990 to January 2015. To be eligible for inclusion, a study had to examine the relationship between TBI and the consequences for several aspects of functioning in professional American football players older than 18 years. Methodological quality was assessed using a 5-item checklist which assessed selection bias, information bias, and correct reporting of the population and exposure characteristics. The search yielded 21 studies that met our inclusion criteria. An evidence synthesis was performed on the extracted data and resulted in 5 levels of evidence. The evidence synthesis revealed that there is strong evidence that concussions are associated with late-life depression and short-term physical dysfunctions. Evidence for the relationship between concussion and impaired sports-related function, prolonged reaction time, memory impairment, and visual-motor speed was inconclusive. Moderate evidence was found for the association between TBI and mild cognitive impairment (MCI), and limited evidence was found for the association between TBI and executive dysfunction. There is strong evidence that a history of concussion in American football players is associated with depression later in life and short-term physical dysfunctions. Also cognitive dysfunctions such as MCI are seen in older players with a history of TBI. These results provide input for actions to prevent TBI and their consequences in (retired) American football players

#4 Relationship between Pre-Training Subjective Wellness Measures, Player Load and Rating of Perceived Exertion Training Load in American College Football
Reference: Int J Sports Physiol Perform. 2017 May 10:1-19. doi: 10.1123/ijspp.2016-0714. [Epub ahead of print]
Authors: Govus AD, Coutts A, Duffield R, Murray A, Fullagar H
Summary: The relationship between pre-training subjective wellness, external and internal training load in American College football is unclear. This study examined the relationship between pre-training subjective wellness (sleep quality, muscle soreness, energy, wellness Z score) on 1) player load and 2) session rating of perceived exertion (s-RPE-TL) in American College footballers. Subjective wellness (measured using 5-point, Likert scale questionnaires); external load (derived from global position systems [GPS] and accelerometry) and s-RPE-TL were collected during three typical training sessions per week for the second half of an American collegiate football season (eight weeks). The relationship between pre-training subjective wellness and 1) player load and 2) s-RPE training load were analysed using linear mixed models with a random intercept for athlete and a random slope for training session. Standardised mean differences (SMD) denote the effect magnitude. A one unit increase in wellness Z score and energy were associated with a trivial 2.3% (90% confidence interval (CI): 0.5, 4.2; SMD: 0.12) and 2.6% (90% CI: 0.1, 5.2; SMD: 0.13) increase in player load. A one unit increase in muscle soreness (players felt less sore) corresponded to a trivial 4.4% (90% CI: -8.4, -0.3; SMD: -0.05) decrease in s-RPE training load. Measuring pre-training subjective wellness may provide information about players' capacity to perform within a training session and could be a key determinant of their response to the imposed training demands American College football. Hence, monitoring subjective wellness may assist the individualisation of training prescription in American College footballers.

Australian Football
#1 Factors Affecting Match Outcome in Elite Australian Football: A 14-Year Analysis
Reference: Int J Sports Physiol Perform. 2017 May 10:1-16. doi: 10.1123/ijspp.2016-0450. [Epub ahead of print]
Authors: Lazarus BH, Hopkins WG, Stewart AM, Aughey RJ
Summary: Effects of fixture and team-characteristics on match outcome in elite Australian football were quantified using data accessed at for 5109 matches for seasons 2000-2013. Aspects of each match included days-break between matches (≤7 d vs ≥8 d), location (home vs away), travel-status (travel vs no travel), and differences between opposing teams' mean age, body mass and height (expressed as quintiles). A logistic-regression version of the generalised mixed linear model estimated each effect, which was assessed with magnitude-based inference using one extra win or loss in every 10 matches as the smallest important change. For every 10 matches played, the effects were: days break, 0.1 ±0.3 (90% CL) wins; playing away, 1.5 ±0.6 losses; travelling, 0.7 ±0.6 losses; and being in the oldest, heaviest or shortest, quintile, 1.9 ±0.4, 1.3 ±0.4 and 0.4 ±0.4 wins respectively. The effects of age and body mass difference were not reduced substantially when adjusted for each other. All effects were clear, mostly at the 99% level. The effects of playing away, travel and age difference were not unexpected, but the trivial effect of days break and the advantage of a heavier team will challenge current notions about balancing training with recovery and about team selection.

Gaelic Football
#1 Duration specific Running performance in Elite Gaelic Football
Reference: J Strength Cond Res. 2017 Apr 25. doi: 10.1519/JSC.0000000000001972. [Epub ahead of print]
Authors: Malone S, Solan B, Hughes B, Collins K
Summary: The aim of the current investigation was to determine the position and duration specific running performance of elite Gaelic football players through the use of a moving average method. Global positioning system data (4-Hz, VX Sport, New-Zealand) were collected from thirty-five (n = 35) elite Gaelic football players across a two season period. A total of 32 competitive matches were analysed with 300 full match play data samples obtained for final analysis. Players were categorised based on positional groups; full-back, half-back, midfield, half- forward and full-forward. The velocity-time curve was analysed for each position using a rolling average method, where maximal values were calculated for ten different time durations (1-10 min) using total distance (m·min), high-speed (m·min) and sprint distance (m·min) across each match. There were large differences between the 1 and 2 min rolling averages and all other rolling average durations. Smaller differences were observed for rolling averages of a greater duration. Midfielders covered significantly more relative total, high speed and sprint distance than other positions across all time periods (p < 0.05; ES: 0.84-1.33), with half-backs (p < 0.05; ES: 0.74 - 1.22) and half-forwards (p < 0.05; ES: 0.99-1.45) covering more relative distance than full-backs and full-forwards. The results of the current investigation suggest that running performance within Gaelic football fluctuates across match-play. These data provide further knowledge of the running requirements of Gaelic football competition and this information can be used to aide coaches and practitioners in adequately preparing athletes for the most demanding periods of play.





FC Schalke & Eintracht Frankfurt Goalkeeper Pre-Match Warm-Up

I was able to visit my one and only Bundesliga game for the closed 2016/2017 season.


Obviously, I brought my camera and took some footage of the goalkeeper warm-up of both teams.


Unfortunately it is not the entire warm-up as I focused on the teams later on. However, please enjoy the two videos below, the first one shows the FC Schalke and the second one the Eintracht Frankfurt goalkeeper warm-up.



Unfortunately, there will be a short part of the team warm-up inside the following video of the Eintracht Frankfurt goalkeeper. During these seconds, the goalkeepers are visible in the upper(-right) part of the screen. I apologize for inconvenience.






Latest research in football - week 18 - 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 Perceptions of football players regarding injury risk factors and prevention strategies
Reference: PLoS One. 2017 May 1;12(5):e0176829. doi: 10.1371/journal.pone.0176829. eCollection 2017.
Authors: Zech A, Wellmann K
Download link:
Summary: Current approaches regarding injury prevention focus on the transfer of evidence into daily practice. One promising approach is to influence attitudes and beliefs of players. The objective of this study was to record player's perceptions on injury prevention. A survey was performed among players of one German high-level football (soccer) club. 139 professional and youth players between age 13 and 35 years completed a standardized questionnaire (response rate = 98%). It included categories with (1) history of lower extremity injuries, (2) perceptions regarding risk factors and (3) regularly used prevention strategies. The majority of players (84.2%) had a previous injury. 47.5% of respondents believe that contact with other players is a risk factor, followed by fatigue (38.1%) and environmental factors (25.9%). The relevance of previous injuries as a risk factor is differently perceived between injured (25%) and uninjured players (0.0%). Nearly all players (91.5%) perform stretching to prevent injuries, followed by neuromuscular warm up exercises (54.0%). Taping is used by 40.2% of previously injured players and 13.6% of players without a history of injuries. In conclusion, the perception of risk factors and performed preventive strategies are inconsistent with scientific evidence. Future transfer strategies should incorporate the players beliefs and attitudes.

#2 A unique opportunity to use football to improve birth registration awareness and completeness in Nigeria
Reference: Br J Sports Med. 2017 Apr 28. pii: bjsports-2016-097404. doi: 10.1136/bjsports-2016-097404. [Epub ahead of print]
Authors: Makinde OA, Odimegwu CO, OlaOlorun FM
Download link:

#3 More Than the Win: The Relation between Appetitive Competition Motivation, Socialization, and Gender Role Orientation in Women's Football
Reference: Front Psychol. 2017 Apr 13;8:547. doi: 10.3389/fpsyg.2017.00547. eCollection 2017.
Authors: Meyer-Parlapanis D, Siefert S, Weierstall R
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Summary: The ability to produce peak performance plays a decisive role in the success of athletes in competitive contest situations. Levels of appetitive competition motivation (ACM), i.e., the desire to defeat an opponent independent of secondary reinforcing factors, were assessed in professional female football/soccer players in the premier and regional leagues, using club level as the measurement of sport success. Furthermore, the influence of social environments predominantly encouraging masculine and competitive play behavior and the players' perceptions of their own gender role orientations were investigated. Ninety female football players from the German premier league (44) and regional leagues (46) participated (age: M = 24, SD = 5 years). Questionnaires ascertaining ACM and self-perceptions of gender via gender-role stereotypes, childhood play behavior and style of upbringing were utilized. Premier league athletes showed a significantly greater inclination toward direct sporting confrontations. Almost 50% of the variance in ACM between the premier and regional league athletes was determined by modern upbringing style and the development of gender roles not corresponding to classic female gender stereotypes. The results emphasize the significance of ACM as an important facet in competitive sports and illustrate the influence of socialization on athletic performance.

#4 The influence of successive matches on match-running performance during an under-23 international soccer tournament: The necessity of individual analysis
Reference: J Sports Sci. 2017 May 12:1-7. doi: 10.1080/02640414.2017.1325511. [Epub ahead of print]
Authors: Varley MC, Di Salvo V, Modonutti M, Gregson W, Mendez-Villanueva A
Summary: This study investigated the effects of successive matches on match-running in elite under-23 soccer players during an international tournament. Match-running data was collected using a semi-automated multi-camera tracking system during an international under-23 tournament from all participating outfield players. Players who played 100% of all group stage matches were included (3 matches separated by 72 h, n = 44). Differences in match-running performance between matches were identified using a generalised linear mixed model. There were no clear effects for total, walking, jogging, running, high-speed running and sprinting distance between matches 1 and 3 (effect size (ES); -0.32 to 0.05). Positional analysis found that sprint distance was largely maintained from matches 1 to 3 across all positions. Attackers had a moderate decrease in total, jogging and running distance between matches 1 and 3 (ES; -0.72 to -0.66). Classifying players as increasers or decreasers in match-running revealed that match-running changes are susceptible to individual differences. Sprint performance appears to be maintained over successive matches regardless of playing position. However, reductions in other match-running categories vary between positions. Changes in match-running over successive matches affect individuals differently; thus, players should be monitored on an individual basis.


#5 Effects of Sex and Event Type on Head Impact in Collegiate Soccer
Reference: Orthop J Sports Med. 2017 Apr 24;5(4):2325967117701708. doi: 10.1177/2325967117701708. eCollection 2017 Apr.
Authors: Reynolds BB, Patrie J, Henry EJ, Goodkin HP, Broshek DK, Wintermark M, Druzgal TJ
Download link:
Summary: The effects of head impact in sports are of growing interest for clinicians, scientists, and athletes. Soccer is the most popular sport worldwide, but the burden of head impact in collegiate soccer is still unknown. The purpose of the study was to quantify head impact associated with practicing and playing collegiate soccer using wearable accelerometers. Mastoid patch accelerometers were used to quantify head impact in soccer, examining differences in head impact as a function of sex and event type (practice vs game). Seven female and 14 male collegiate soccer players wore mastoid patch accelerometers that measured head impacts during team events. Data were summarized for each athletic exposure, and statistical analyses evaluated the mean number of impacts, mean peak linear acceleration, mean peak rotational acceleration, and cumulative linear and rotational acceleration, each grouped by sex and event type. There were no differences in the frequency or severity of head impacts between men's and women's soccer practices. For men's soccer, games resulted in 285% more head impacts than practices, but there were no event-type differences in mean impact severity. Men's soccer games resulted in more head impacts than practices across nearly all measured impact severities, which also resulted in men's soccer games producing a greater cumulative impact burden. Similar to other sports, men's soccer games have a greater impact burden when compared with practices, and this effect is driven by the quantity rather than severity of head impacts. In contrast, there were no differences in the quantity or severity of head impacts in men's and women's soccer practices. These data could prompt discussions of practical concern to collegiate soccer, such as understanding sex differences in head impact and whether games disproportionately contribute to an athlete's head impact burden.

#6 Prognostic factors for musculoskeletal injury identified through medical screening and training load monitoring in professional football (soccer): a systematic review
Reference: Br J Sports Med. 2017 May 10. pii: bjsports-2017-097827.1. doi: 10.1136/bjsports-2017-097827.1. [Epub ahead of print]
Authors: Hughes T, Sergeant JC, Parkes M, Callaghan M
Summary: The purpose was to identify prognostic factors and models for spinal and lower extremity injuries in adult professional/elite football players from medical screening and training load monitoring processes. The MEDLINE, AMED, EMBASE, CINAHL Plus, SPORTDiscus electronic bibliographic databases and the Cochrane Database of Systematic Reviews were searched from inception to July 2016. Searches were limited to original research, published in peer reviewed journals of any language. The Quality in Prognostic Studies (QUIPS) tool was used for appraisal and the modified GRADE approach was used for synthesis. Prospective and retrospective cohort study designs of spinal and lower extremity injury incidence were found from populations of adult professional/elite football players, between 16 and 40 years. Non-football or mixed sports were excluded. 858 manuscripts were identified. Removing duplications left 551 studies, which were screened for eligibility by title and abstract. Of these, 531 studies were not eligible and were excluded. The full text of the remaining 20 studies were obtained; a further 10 studies were excluded. 10 studies were included for appraisal and analysis, for 3344 participants. Due to the paucity and heterogeneity of the literature, and shortcomings in methodology and reporting, the evidence is of very low or low quality and therefore cannot be deemed robust enough to suggest conclusive prognostic factors for all lower limb musculoskeletal injury outcomes identified. No studies were identified that examined spinal injury outcomes or prognostic models.


#7 Solid Organ Laceration in an Adolescent Soccer Player: A Case Report
Reference: Med Sci Sports Exerc. 2017 May 9. doi: 10.1249/MSS.0000000000001316. [Epub ahead of print]
Authors: Visenio M, Buesing K, Moffatt K
Summary: Pediatric solid organ lacerations are a relatively uncommon but potentially dangerous injury that must be addressed urgently once recognized. Seen most often during recreational or team sports, they usually occur after a blunt deceleration mechanism to the abdomen or flank. Depending on the severity of injury, solid organ laceration may not be immediately apparent clinically. This emphasizes the importance of sideline witnessing and evaluation, acting quickly once symptoms develop, and placing importance on safe sporting technique. Additionally, management has changed over time to favor medical management for minor injuries, with laparotomy reserved for high-grade or hemodynamically unstable lacerations. Awareness of solid organ laceration in pediatric populations is more important than ever as they are beginning to appear in younger adolescents. Here we present a case of a 14-year-old girl sustaining a grade IV liver laceration while playing contact team sports.

#8 Modulation of isometric quadriceps strength in soccer players with transcranial direct current stimulation: a crossover study
Reference: J Strength Cond Res. 2017 May 9. doi: 10.1519/JSC.0000000000001985. [Epub ahead of print]
Authors: Vargas VZ, Baptista AF, Pereira GOC, Pochini AC, Ejnisman B, Santos MB, Joao SMA, Hazime FA
Summary: The aim of this study was to evaluate the effect of transcranial direct current stimulation (tDCS) on the maximum isometric muscle contraction (MVIC) of the knee extensors in soccer players at the pre-professional level. Twenty female soccer players aged 15 to 17 years (mean = 16.1; SD = 0.9) with 5.2 ± 2.6 years of training were randomly divided into two groups to receive either active or sham tDCS in a single session (2 mA; 0.057mA/cm). The MVIC of the knee extensors was evaluated in both lower limbs by manual dynamometry in five sets of contractions divided into four blocks: (0) pre-stimulation, (1) during tDCS, (2) 30 minutes post-tDCS, and (3) 60 minutes post-tDCS. After an interval of seven days, the groups were evaluated again, and the type of initial stimulation was inverted between participants. The MVIC of the knee extensors increased significantly during active tDCS (MD = 0.4; IC = 0.1 to 0.8 N/Kg), 30 minutes post-active tDCS (MD = 0.9; IC 0.4 to 1.4 N/Kg), and 60 minutes post-active tDCS (MD = 1.0; IC 0.3 to 1.6 N/Kg) but not for sham tDCS. Our conclusion was that tDCS temporarily increases isometric quadriceps strength in adolescent female soccer players, which may be useful for both strength training and rehabilitation.

#9 Match outcome and sprinting activities in match play by elite German soccer players
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07352-2. [Epub ahead of print]
Authors: Andrzejewski M, Chmura P, Konefal M, Kowalczuk E, Chmura J
Summary: The aim of the study was to examine the ways playing positions and match outcome (i.e. win, draw, loss) affect the sprint distance covered and the number of sprints performed by German Bundesliga soccer players. Match performance data were collected from 350 soccer players competing in the German Bundesliga during the 2014/2015 domestic season. A total of 4393 individual match observations were undertaken on outfield players. The analysis was carried using the Impire AG motion analysis system with records of all movements of players in all the 306 matches. The recorded variables included total sprint distance covered and the total number of sprints in offensive and defensive play. The conformity assessment was carried out with the Shapiro-Wilk test (p ≤ 0.01). To compare mean values of the examined variables a two-way ANOVA was used. The differences between pairs of means were verified with Fisher's LSD. The analysis of the covered sprint distance and the number of performed sprints showed that central defenders and full-backs covered shorter distances in won matches than in lost matches (p ≤ 0.05). Furthermore, forwards and wide midfielders covered significantly longer sprint distances in won matches than in lost matches (p ≤ 0.05). The match outcome may be viewed as a measure of performance accomplishment and, hence, it may influence the sprinting efforts made by players.

#10 Soccer training: high-intensity interval training is mood disturbing while small sided games ensure mood balance
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07292-9. [Epub ahead of print]
Authors: Selmi O, Haddad M, Majed L, Ben Khalifa W, Hamza M, Chamari K
Summary: The aim of the study was to compare the effects of high-intensity intermittent training (HIIT) versus small-sided games (SSG) in soccer on both the physiological responses and the mood state of players. Sixteen professional soccer players took part in the study (age: 24.1±0.9 years). Testing of players was conducted on separate days in a randomized and counter-balanced order (each training session: 28-min: 4x4 minutes work with 3-min of passive recovery in-between). Effort: HIIT: intermittent 15-s runs at 110% maximal aerobic speed with 15-s of passive recovery in-between. SSG: 4 versus 4 players on a 25x35m pitch size with full-involvement play. Psychological responses before- and after- each training-session were assessed using the profile of mood-state (POMS: Tension, Depression, Anger, Vigor, Fatigue, and Confusion). The players' heart rate (HR) was continuously measured, whereas ratings of perceived exertion (RPE) and blood lactate concentration ([La]) were collected ~3-min after each training-session. HIIT and SSG showed no significant difference in HR, RPE and [La] responses. The HIIT compared with SSG resulted in: an increased total mood disturbance (p<0.001), tension (p<0.05), fatigue (p<0.01) and a decreased vigor (p<0.001). Both HIIT and SSG sessions induced similar physiological responses, in contrast, HIIT produced a mood disturbance while SSG ensured mood balance. Practitioners could choose between these two exercises according to the objective of their training, keeping in mind the mood-related advantages of the SSG shown in the present study.

American Football
#1 Return to Play and Decreased Performance After Anterior Cruciate Ligament Reconstruction in National Football League Defensive Players
Reference: Am J Sports Med. 2017 May 1:363546517703361. doi: 10.1177/0363546517703361. [Epub ahead of print]
Authors: Read CR, Aune KT, Cain EL Jr, Fleisig GS
Summary: Anterior cruciate ligament (ACL) injuries occur commonly in football. Recent work has reported ACL reconstruction (ACLR) as one of several orthopaedic procedures with unfavorable outcomes for professional athletes. The performance impact to defensive players after surgery has not been quantified. The purpose was to quantify the effect of ACLR on the performance of defensive players by comparing them to a cohort of matched controls as well as to measure the effect of ACLR on athletes' career length in the National Football League (NFL). Thirty-eight NFL defensive players with a history of ACLR from 2006 to 2012 were identified. For each injured player, a matched control player was identified. Demographic and performance statistics were collected from the online NFL player database. Players who returned after ACLR (n = 23) were compared with players who did not return (n = 15) using t tests and chi-squared analyses. Similarly, players who returned after ACLR (n = 23) were compared with their matched controls with t tests and chi-squared analyses. Two-way repeated-measures analysis of variance was utilized to test for significant differences between performance before and after the season of the injury for the players in the ACLR group who returned (n = 23) and for their matched controls. Kaplan-Meier analysis was performed to test for differences in the rate of retirement between the groups. For all analyses, P values <.05 were considered significant. Approximately 74% (28/38) of athletes who underwent ACLR returned to play at least 1 NFL game, and 61% (23/38) successfully returned to play at least half a season (ie, 8 games). Athletes in the ACLR group who returned retired from the NFL significantly sooner and more often after surgery than their matched controls. In the seasons leading up to their injury, athletes who successfully returned to play started a greater percentage of their games (81%) and made more solo tackles per game (3.44 ± 1.47) compared with athletes in the ACLR group who did not return to play (54% and 1.82 ± 1.17, respectively) and compared with healthy control players (52% and 1.77 ± 1.19, respectively). After the season of surgery, athletes in the ACLR group who returned to play decreased to 57% games started and 2.38 ± 1.24 solo tackles per game, while their matched controls suffered no significant decreases. Players who successfully returned were above-average NFL players before their injury but comparatively average after their return.

#2 Return to Play After Revision Anterior Cruciate Ligament Reconstruction in National Football League Players
Reference: Orthop J Sports Med. 2017 Apr 4;5(4):2325967117698788. doi: 10.1177/2325967117698788. eCollection 2017.
Authors: Okoroha KR, Kadri O, Keller RA, Marshall N, Cizmic Z, Moutzouros V
Download link:
Summary: National Football League (NFL) players who undergo anterior cruciate ligament (ACL) reconstruction have been shown to have a lower return to play (RTP) than previously expected. However, RTP in the NFL after revision ACL reconstruction (RACLR) is not well defined. The purpose of this study is to determine the RTP of NFL players after RACLR and evaluate factors that predict RTP. Our hypothesis was that more experienced and established players would be more likely to RTP after RACLR. A total of 24 NFL players who underwent RACLR between 2007 and 2014 were reviewed and evaluated. Return to NFL play, time to return, seasons and games played prior to and after revision surgery, draft status, and demographic data were collected. Overall RTP was determined, and players who did RTP were compared with those unable to RTP. Data were also compared with control players matched for age, position, size, and experience. After RACLR, 79% (19/24) of NFL players returned to NFL regular-season play at an average of 12.6 months. All players who were drafted in the first 4 rounds, played in at least 55 games, or played 4 seasons of NFL play prior to injury were able to RTP. Players drafted in the first 4 rounds of the NFL draft were more likely to RTP than those who were not (odds ratio, 0.1; 95% CI, 0.01-1.00; P = .05). Those who returned to NFL play played in significantly less games and seasons after their injury than before (P = .01 and P = .01, respectively). However, these values did not differ when compared with matched controls (P = .67 and P = .33). NFL players who RTP after RACLR do so at a similar rate but prolonged time period compared with after primary ACL reconstruction. Athletes who were drafted in earlier rounds were more likely to RTP than those who were not. Additionally, player experience prior to injury is an important factor when predicting RTP after RACLR.

#3 The Effect of Subcritical Bone Loss and Exposure on Recurrent Instability After Arthroscopic Bankart Repair in Intercollegiate American Football
Reference: Am J Sports Med. 2017 May 1:363546517704184. doi: 10.1177/0363546517704184. [Epub ahead of print]
Authors: Dickens JF, Owens BD, Cameron KL, DeBerardino TM, Masini BD, Peck KY, Svoboda SJ
Summary: There is no consensus on the optimal method of stabilization (arthroscopic or open) in collision athletes with anterior shoulder instability. The purpose was to examine the effect of "subcritical" bone loss and football-specific exposure on the rate of recurrent shoulder instability after arthroscopic stabilization in an intercollegiate American football population. Fifty intercollegiate football players underwent primary arthroscopic stabilization for anterior shoulder instability and returned to football for at least a single season. Preoperatively, 32 patients experienced recurrent subluxations, and 18 patients experienced a single or recurrent dislocation. Shoulders with glenoid bone loss >20%, an engaging Hill-Sachs lesion, an off-track lesion, and concomitant rotator cuff repair were excluded from the study. The primary outcome of interest was the ability to return to football without subsequent instability. Patients were followed for time to a subsequent instability event after return to play using days of exposure to football and total follow-up time after arthroscopic stabilization. Fifty consecutive patients returned to American football for a mean 1.5 seasons (range, 1-3) after arthroscopic stabilization. Three of 50 (6%; 95% CI, 1.3%-16.5%) patients experienced recurrent instability. There were no subsequent instability events after a mean 3.2 years of military service. All shoulders with glenoid bone loss >13.5% (n = 3) that underwent arthroscopic stabilization experienced recurrent instability upon returning to sport, while none of the shoulders with <13.5% glenoid bone loss (n = 47) sustained a recurrent instability event during football ( X2 = 15.80, P < .001). Shoulders with >13.5% glenoid bone loss had an incidence rate of 5.31 cases of recurrent instability per 1000 athlete-exposures of football. In 72,000 athlete-exposures to football with <13.5% glenoid bone loss, there was no recurrent instability. Significantly more anchors were used during the primary arthroscopic stabilization procedure in patients who experienced multiple preoperative instability events ( P = .005), and lesions spanned significantly more extensive portions along the circumference of the glenoid ( P = .001) compared with shoulders having a single preoperative instability event before surgical stabilization. Arthroscopic stabilization of anterior shoulder instability in American football players with <13.5% glenoid bone loss provides reliable outcomes and low recurrence rates.





Looking for football specific data?

Dear coaches,

I was approached by some of you with regards to testing data of goalkeepers (and field players). As some of you might know, there is not a lot of data on goalkeepers in the current literature.


Therefore I would like to offer different things.

  1. If there are coaches that collect (what ever) data, I would like to have them. I will sort (for different tests) and group (for different Division for example) them and finally make them available for coaches that have sent some data. Naturally (and before posting the data) I will make them anonymous before, meaning if Coach Michael Rumpf has sent me goalkeeping (or fieldplayer) data from FC Takatuka, the data will be shown as Coach 34 from Division 4 school.

  2. If there are coaches that are interested in putting a scientific turn to their training and testing, I will assist with regards to different questions of reliability, validity and analysis.

  3. If there are coaches that have already figured out everything, however, are looking to have a different opinion on the efficacy of their training, I would suggest a project that will be a win/win/win for you, your team and me.


Depending on the response there will be a timely post.

If there are any question with regards to the points above, and or if you would like to participate - I would be happy if you sent me an email to






Eintracht Frankfurt Pre-Match Warm-up

The video below shows the pre-match warm-up of the german Bunesliga team Eintracht Frankfurt.



The game was played at home two weeks ago and I was able to visit the game and take some footage.






Latest research in football - week 17 - 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 Talent identification and recruitment in youth soccer: Recruiter's perceptions of the key attributes for player recruitment
Reference: PLoS One. 2017 Apr 18;12(4):e0175716. doi: 10.1371/journal.pone.0175716. eCollection 2017.
Authors: Larkin P, O'Connor D
Download link:
Summary: Using the modified Delphi method, we aimed to understand the attributes youth coaches and recruiters perceive as important when identifying skilled youth performance at the entry level of representative soccer in Australia (i.e., Under 13 years). Furthermore, we also aimed to describe the current methods youth coaches and recruiters use to assess and identify these attributes in youth players. Australian regional youth technical directors and coaches (n = 20) completed a three stage process, including an initial interview and two subsequent questionnaires, whereby attributes and qualities associated with talent identification were rated and justified according to the importance for youth player performance and talent identification. Results indicate a hierarchy of attributes recruiters perceive as important for Under 13 soccer performance, including technical (i.e., first touch, striking the ball, one-versus-one ability, and technical ability under pressure), tactical (i.e., decision-making ability) and psychological attributes (i.e., coachability and positive attitude). In addition, the findings indicated attributes and qualities not emphasised within the talent identification process including, physiological, anthropometrical, sociological and several psychological attributes. It is suggested talent recruiters apply a holistic multidisciplinary approach to talent identification, with the current findings potentially providing initial evidence to suggest recruiters do consider numerous attributes when selecting and identifying youth players.

#2 Unilateral jumps in different directions: a novel assessment of soccer-associated power?
Reference: J Sci Med Sport. 2017 Mar 29. pii: S1440-2440(17)30348-1. doi: 10.1016/j.jsams.2017.03.016. [Epub ahead of print]
Authors: Murtagh CF, Vanrenterghem J, O'Boyle A, Morgans R, Drust B, Erskine RM
Summary: We aimed to determine whether countermovement jumps (CMJs; unilateral and bilateral) performed in different directions assessed independent lower-limb power qualities, and if unilateral CMJs would better differentiate between elite and non-elite soccer players than the bilateral vertical (BV) CMJ. Elite (n=23; age, 18.1±1.0years) and non-elite (n=20; age, 22.3±2.7years) soccer players performed three BV, unilateral vertical (UV), unilateral horizontal-forward (UH) and unilateral medial (UM) CMJs. Jump performance (height and projectile range), kinetic and kinematic variables from ground reaction forces, and peak activation levels of the vastus lateralis and biceps femoris (BF) muscles from surface electromyography, were compared between jumps and groups of players. Peak vertical power (V-power) was greater in BV (220.2±30.1W/kg) compared to UV (144.1±16.2W/kg), which was greater than UH (86.7±18.3W/kg) and UM (85.5±13.5W/kg) (all, p<0.05) but there was no difference between UH and UM (p=1.000). Peak BF EMG was greater in UH compared to all other CMJs (p≤0.001). V-power was greater in elite than non-elite for all CMJs (p≤0.032) except for BV (p=0.197). Elite achieved greater UH projectile range than non-elite (51.6±15.4 vs. 40.4±10.4cm, p=0.009). We have shown that UH, UV and UM CMJs assess distinct lower-limb muscular power capabilities in soccer players. Furthermore, as elite players outperformed non-elite players during unilateral but not BV CMJs, unilateral CMJs in different directions should be included in soccer-specific muscular power assessment and talent identification protocols, rather than the BV CMJ.

#3 Range limitation in hip internal rotation and fifth metatarsal stress fractures (Jones fracture) in professional football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2017 Apr 25. doi: 10.1007/s00167-017-4552-4. [Epub ahead of print]
Authors: Saita Y, Nagao M, Kawasaki T, Kobayashi Y, Kobayashi K, Nakajima H, Takazawa Y, Kaneko K, Ikeda H
Summary: The purpose of the study was to identify unknown risk factors associated with fifth metatarsal stress fracture (Jones fracture). A case-controlled study was conducted among male Japanese professional football (soccer) players with (N = 20) and without (N = 40) a history of Jones fracture. Injury history and physical examination data were reviewed, and the two groups were compared. Univariate and multivariate logistic regression controlling for age, leg dominance and body mass index were used to obtain odds ratios (ORs) and 95% confidence intervals (CIs) to describe the association between physical examination data and the presence or absence of Jones fractures. From 2000 to 2014, among 162 professional football club players, 22 (13.6%; 21 Asians and one Caucasian) had a history of Jones fracture. Thirteen out of 22 (60%) had a Jones fracture in their non-dominant leg. The mean range of hip internal rotation (HIR) was restricted in players with a history of Jones fracture [25.9° ± 7.5°, mean ± standard deviation (SD)] compared to those without (40.4° ± 11.1°, P < 0.0001). Logistic regression analyses demonstrated that HIR limitation increased the risk of a Jones fracture (OR = 3.03, 95% CI 1.45-6.33, P = 0.003). Subgroup analysis using data prior to Jones fracture revealed a causal relationship, such that players with a restriction of HIR were at high risk of developing a Jones fracture [Crude OR (95% CI) = 6.66 (1.90-23.29), P = 0.003, Adjusted OR = 9.91 (2.28-43.10), P = 0.002]. In addition, right HIR range limitation increased the risks of developing a Jones fracture in the ipsilateral and the contralateral feet [OR = 3.11 (1.35-7.16) and 2.24 (1.22-4.12), respectively]. Similarly, left HIR range limitation increased the risks in the ipsilateral or the contralateral feet [OR (95% CI) = 4.88 (1.56-15.28) and 2.77 (1.08-7.08), respectively]. The restriction of HIR was associated with an increased risk of developing a Jones fracture. Since the HIR range is a modifiable factor, monitoring and improving the HIR range can lead to prevent reducing the occurrence of this fracture.

#4 Testosterone and cortisol responses in male soccer players: The effect of home and away venues
Reference: Physiol Behav. 2017 Apr 21. pii: S0031-9384(16)30994-5. doi: 10.1016/j.physbeh.2017.04.021. [Epub ahead of print]
Authors: Fothergill M, Wolfson S, Neave N
Summary: The present studies examined the influence of playing venue on psychobiological responses in male soccer players. Many studies have demonstrated the existence of a home advantage, wherein teams perform better at home than away. A recent focus has attempted to explain this advantage from a psychobiological perspective, with studies showing hormonal differences with regard to venue, game outcome, dominance and perceived stress. Two studies investigated testosterone and cortisol responses in relation to home and away venues. In an initial study of 18 male elite Premier League academy soccer players (age, 17.47, SD, 64), salivary cortisol levels were monitored in two competitive matches, both at home and away. Higher post-game cortisol levels were observed at home (p=0.002), with the team winning all its games. In a second study involving a 12 semi-professional group of players (age, 23.17, SD, 3.8), the same post-game cortisol findings at home were replicated (p=0.001), with this team losing all its games. No effects were observed for testosterone in either study. The results extend earlier research findings on the complex relationship which surrounds the psychobiological impact on the home advantage. The findings suggest that higher levels of stress are experienced by home players in their home matches.

#5 Wellbeing perception and the impact on external training output among elite soccer players
Reference: J Sci Med Sport. 2017 Apr 13. pii: S1440-2440(17)30360-2. doi: 10.1016/j.jsams.2017.03.019. [Epub ahead of print]
Authors: Malone S, Owen A, Newton M, Mendes B, Tiernan L, Hughes B, Collins K
Summary: The objective of the investigation was to observe the impact of player wellbeing on the training output of elite soccer players. Forty-eight soccer players (age: 25.3±3.1years; height: 183±7cm; mass: 72±7kg) were involved in this single season observational study across two teams. Each morning, pre-training, players completed customised perceived wellbeing questionnaires. Global positioning technology devices were used to measure external load (total distance, total high-speed running distance, high speed running, player load, player load slow, maximal velocity, maximal velocity exposures). Players reported ratings of perceived exertion using the modified Borg CR-10 scale. Integrated training load ratios were also analysed for total distance:RPE, total high speed distance:RPE player load:RPE and player load slow:RPE respectively. Mixed-effect linear models revealed significant effects of wellbeing Z-score on external and integrated training load measures. A wellbeing Z-score of -1 corresponded to a -18±2m (-3.5±1.1%), 4±1m (-4.9±2.1%,) 0.9±0.1kmh-1 (-3.1±2.1%), 1±1 (-4.6±2.9%), 25±3AU (-4.9±3.1%) and 11±0.5AU (-8.9±2.9%) reduction in total high speed distance, high speed distance, maximal velocity, maximal velocity exposures, player load and player load slow respectively. A reduction in wellbeing impacted external:internal training load ratios and resulted in -0.49±0.12mmin-1, -1.20±0.08mmin-1,-0.02±0.01AUmin-1 in total distance:RPE, total high speed distance:RPE and player load slow:RPE respectively. The results suggest that systematic monitoring of player wellbeing within soccer cohorts can provide coaches with information about the training output that can be expected from individual players during a training session.

#6 Reliability and Validity of a New Test of Agility and Skill for Female Amateur Soccer Players
Reference: J Hum Kinet. 2017 Mar 12;56:219-227. doi: 10.1515/hukin-2017-0039. eCollection 2017.
Authors: Kutlu M, Yapici H, Yilmaz A
Summary: The aim of this study was to evaluate the Agility and Skill Test, which had been recently developed to assess agility and skill in female athletes. Following a 10 min warm-up, two trials to test the reliability and validity of the test were conducted one week apart. Measurements were collected to compare soccer players' physical performance in a 20 m sprint, a T-Drill test, the Illinois Agility Run Test, change-of-direction and acceleration, as well as agility and skill. All tests were completed following the same order. Thirty-four amateur female soccer players were recruited (age = 20.8 ± 1.9 years; body height = 166 ± 6.9 cm; body mass = 55.5 ± 5.8 kg). To determine the reliability and usefulness of these tests, paired sample t-tests, intra-class correlation coefficients, typical error, coefficient of variation, and differences between the typical error and smallest worthwhile change statistics were computed. Test results showed no significant differences between the two sessions (p > 0.01). There were higher intra-class correlations between the test and retest values (r = 0.94-0.99) for all tests. Typical error values were below the smallest worthwhile change, indicating 'good' usefulness for these tests. A near perfect Pearson correlation between the Agility and Skill Test (r = 0.98) was found, and there were moderate-to-large levels of correlation between the Agility and Skill Test and other measures (r = 0.37 to r = 0.56). The results of this study suggest that the Agility and Skill Test is a reliable and valid test for female soccer players and has significant value for assessing the integrative agility and skill capability of soccer players.

#7 Analysis of Motor Activities of Professional Soccer Players during the 2014 World Cup in Brazil
Reference: J Hum Kinet. 2017 Mar 12;56:187-195. doi: 10.1515/hukin-2017-0036. eCollection 2017.
Authors: Chmura P, Andrzejewski M, Konefał M, Mroczek D, Rokita A, Chmura J
Summary: The aim of the present study was to analyze motor activities of soccer players in seven consecutive rounds of matches of the 2014 World Cup in Brazil and to compare the performance of the world champions, the German national team with other participating teams. The study sample comprised 905 observations of 340 soccer players, who played full-time matches in all seven rounds of the tournament. The study was conducted using data collected from the Castrol Performance Index, a kinematic game analysis system that records movements of players with semi-automatic cameras. The following variables were analyzed: total distance covered, the percentage of total distance covered at high intensity, the number of sprints, frequency of sprints and peak running speed. A statistically significant increase (p ≤ 0.01) was noted in total distance covered, the percentage of distance covered at high intensity and total number of sprints, between the quarter-finals and semi-finals of the World Cup tournament in Brazil. The German national team covered a significantly longer total distance (p ≤ 0.05) and had a greater percentage of distance covered at high intensity (p ≤ 0.001) than players from other teams. The obtained results point to the necessity of development of players' aerobic endurance and speed-endurance abilities while preparing for top-level soccer tournaments. Winning a soccer championship requires players to run longer mean total distances and longer distances at high intensity during a single match.

#8 Effects of the off-Season Period on Field and Assistant Soccer Referees `Physical Performance
Reference: J Hum Kinet. 2017 Mar 12;56:159-166. doi: 10.1515/hukin-2017-0033. eCollection 2017.
Authors: Castillo D, Cámara J, Castagna C, Yanci J
Summary: The evolution of referees' physical fitness has been studied over one or several seasons, however, the variation of the physical performance between the end of the competitive season (T1) and the start of the following pre-season (T2) has not been ascertained. Therefore, the aim of this study was to analyze the effects of the transition period on physical performance variables (i.e. linear straight sprint, change of direction ability and endurance) in National Soccer Division referees. Forty-five Spanish referees volunteered to participate in this study. Participants were classified according to competitive status, field referees (FR, n = 23) and assistant referees (AR, n = 22). A loss of performance (p < 0.05) was observed in the 20 and 30 m linear straight sprint between T1 and T2 in both FR (1.64-1.56%, d = 0.29 to 0.32) and AR (2.01-3.41%, d = 0.33 to 0.60). In T2 the FR significantly improved the distance covered (p < 0.05, 13.11%, d = 0.39) in the Yo-Yo Intermittent Recovery test (YYIR1). Besides, significant differences were observed between FR and AR in the distance covered (p < 0.05, -23.55%, d = -0.97) in the YYIR1 test in T2. More research may be necessary to focus on the off-season period in order to implement specific training programs and consequently reduce the loss of sprint ability in field and assistant referees and the decrease in cardiovascular fitness in assistant referees.

#9 Determination of Aerobic Performance in Youth Soccer Players: Effect of Direct And Indirect Methods
Reference: J Hum Kinet. 2017 Mar 11;56:109-118. doi: 10.1515/hukin-2017-0028. eCollection 2017.
Authors: Higino WP, Sorroche AS, de Mattos Falqueiro PG, Suzuki Lima YC, Higa CL
Summary: This study was conducted to correlate and compare values for variables determined in indirect tests with the values determined directly in youth soccer players. The study subjects were 27 youth soccer players (age 16.77 ± 0.75 years; body mass 63.29 ± 7.37 kg; body height 174.14 ± 8.46 cm) playing in the basic categories of a first division team at the regional level of Brazilian soccer. Each subject was evaluated with the following tests: a) a treadmill test to directly determine values of VO2max and Vamax (Treadmill); b) an indirect Shuttle Run Test (SRT); c) an indirect Carminatti's test (TCar). VO2max showed significantly different values in the Treadmill and the SRT (59.21 ± 5.88 and 50.67 ± 3.58 ml⋅kg-1⋅min-1, respectively). Similarly, values obtained for VPeak in the treadmill test and for Vamax in TCar were different from values for SRT VPeak (15.01 ± 1.10, 14.92 ± 0.87 and 12.64 ± 0.62 km⋅h-1, respectively). A correlation analysis showed a moderate relationship between values for VPeak TCar and VO2max determined on a treadmill (r = 0.46) and Vamax determined on a treadmill (r = 0.54). The analysis also showed a high correlation between values of VO2max determined on the treadmill and VO2max evaluated in the SRT (r = 0.69), as well as VPeak determined in the SRT and VO2max tested on the treadmill (r = 0.71), as well as between VPeak determined in the SRT and VO2max evaluated on the treadmill (r = 0.77). We concluded that the SRT underestimated values of VO2max and Vamax. Additionally, VPeak TCar showed no difference compared to Vamax, although it did show a low correlation with it. In addition the SRT, even with high correlations, did not seem to be a great predictor of aerobic fitness in youth soccer players.

#10 Effects of environmental temperature on physiological responses during submaximal and maximal exercises in soccer players
Reference: Integr Med Res. 2016 Sep;5(3):216-222. doi: 10.1016/j.imr.2016.06.002. Epub 2016 Jun 16.
Authors: No M, Kwak HB
Download link:
Summary: Although thermoregulation is effective in regulating body temperature under normal conditions, exercise or physical activity in extreme cold or heat exerts heavy stress on the mechanisms that regulate body temperature. The purpose of this study was to investigate the effects of environmental temperature on physiological responses and endurance exercise capacity during submaximal and maximal exercises in healthy adults. Nine male soccer players participated in this study. In this study, three environmental temperatures were set at 10 ± 1°C, 22 ± 1°C, and 35 ± 1°C with the same humidity (60 ± 10%). The participants cycled for 20 minutes at 60% maximum oxygen uptake (60% VO2max), and then exercise intensity was increased at a rate of 0.5 kp/2 min until exhaustion at three different environmental conditions. Oxygen uptake and heart rate were lower in a moderate environment (22 ± 1°C) than in a cool (10 ± 1°C) or hot (35 ± 1°C) environment at rest and during submaximal exercise, and were higher during maximal exercise (p < 0.05). Minute ventilation was lower at 22 ± 1°C than at 10 ± 1°C or 35 ± 1°C at rest and during submaximal exercise, and no significant differences were observed in minute ventilation during maximal exercise (p < 0.05). Blood lactate concentrations were lower at 22 ± 1 °C than at 10 ± 1°C or 35 ± 1°C at rest and during submaximal exercise, and were higher during maximal exercise (p < 0.05). Time to exhaustion during exercise was longer at 22 ± 1°C than at 10 ± 1°C or 35 ± 1°C (p < 0.05). It is concluded that physiological responses and endurance exercise capacity are impaired under cool or hot conditions compared with moderate conditions, suggesting that environmental temperature conditions play an important role for exercise performance.

#11 Enhancing the implementation of injury prevention exercise programmes in professional football
Reference: Br J Sports Med. 2017 May 3. pii: bjsports-2017-097539. doi: 10.1136/bjsports-2017-097539. [Epub ahead of print]
Authors: O'Brien J

American Football
#1 Game Times and Higher Winning Percentages of West Coast Teams of the National Football League Correspond With Reduced Prevalence of Regular Season Injury: Erratum.
Reference: J Strength Cond Res. 2017 May;31(5):e72. doi: 10.1519/JSC.0000000000001851.
Authors: no authors listed

#2 Acute Effect of Biomechanical Muscle Stimulation on the Counter-Movement Vertical Jump Power and Velocity in Division I Football Players
Reference: J Strength Cond Res. 2017 May;31(5):1259-1264. doi: 10.1519/JSC.0000000000001136.
Authors: Jacobson BH, Monaghan TP, Sellers JH, Conchola EC, Pope ZK, Glass RG
Summary: Research regarding whole body vibration (WBV) largely supports such training augmentation in attempts to increase muscle strength and power. However, localized biomechanical vibration has not received the same attention. The purpose of this study was to assess peak and average power before and after acute vibration of selected lower-body sites in division I athletes. Twenty-one subjects were randomly assigned to 1 of 2 conditions using a cross-over design. Pretest consisted of a counter-movement vertical jump (VJ) followed by either localized vibration (30 Hz) to 4 selected lower-body areas or 4 minutes of moderately low-resistance stationary cycling (70 rpm). Vibration consisted of 1 minute bouts at each lower-leg site for a total of 4 minutes followed by an immediate post-test VJ. Repeated measures analysis of variance yielded no significant differences (p > 0.05) in either peak power or peak velocity. Similarly, no significant differences were found for average power and velocity between conditions. It should be noted that, while not significant, the vibration condition demonstrated an increase in peak power and velocity while the bike condition registered slight decreases. Comparing each of the post-VJ repetitions (1, 2, and 3) the vibration condition experienced significantly greater peak power and velocity from VJ 1 to VJ 3 compared with the bike condition which demonstrated no significant differences among the post-test VJs. These results yielded similar, although not statistically significant outcomes to previous studies using WBV. However, the novelty of selected site biomechanical vibration merits further investigation with respect to frequency, magnitude, and duration of vibration.

#3 Epidemiology of Knee Sprains in Youth, High School, and Collegiate American Football Players
Reference: J Athl Train. 2017 Apr 17. doi: 10.4085/1062-6050-52.3.09. [Epub ahead of print]
Authors: Clifton DR, Onate JA, Schussler E, Djoko A, Dompier TP, Kerr ZY
Summary: Variations in knee-sprain incidence among competition levels are unclear but may help inform prevention strategies in American football players. The purpose of the study was to describe the epidemiology of knee sprains in youth, high school, and collegiate football players. Injury and athlete-exposure (AE) data were collected from 3 injury-surveillance programs at the youth, high school, and collegiate competition levels. Data from 310 youth, 184 high school, and 71 collegiate football team-seasons were collected during the 2012 through 2014 seasons. Knee-sprain rates and risks were calculated for each competition level. Injury rate ratios (IRRs) and risk ratios (RRs) compared knee-sprain rates by competition level. Injury proportion ratios (IPRs) compared differences in surgery needs, recurrence, injury mechanism, and injury activity by competition level. Knee-sprain rates in youth, high school, and collegiate football were 0.16/1000 AEs, 0.25/1000 AEs, and 0.69/1000 AEs, respectively. Knee-sprain rates increased as the competition level increased (high school versus youth: IRR = 1.60; 95% confidence interval [CI] = 1.12, 2.30; collegiate versus high school: IRR = 2.73; 95% CI = 2.38, 3.96). Knee-sprain risk was highest in collegiate (4.3%), followed by high school (2.0%) and youth (0.5%) athletes. Knee-sprain risk increased as the competition level increased (high school versus youth: RR = 3.73; 95% CI = 2.60, 5.34; collegiate versus high school: RR = 2.14; 95% CI = 1.83, 2.51). Collegiate football had the lowest proportion of knee sprains that were noncontact injuries (collegiate versus youth: IPR = 0.54; 95% CI = 0.31, 0.95; collegiate versus high school: IPR = 0.59; 95% CI = 0.44, 0.79) and the lowest proportion that occurred while being tackled (collegiate versus youth: IPR = 0.44; 95% CI = 0.26, 0.76; collegiate versus high school: IPR = 0.71; 95% CI = 0.51, 0.98). Knee-sprain incidence was highest in collegiate football. However, level-specific variations in the distributions of knee sprains by injury activity may highlight the need to develop level-specific policies and prevention strategies that ensure safe sports play.





Borussia Dortmund - Goalkeeper Pre-Match Warm-up

As already mentioned in previous two blog posts, I was able to visit the UEFA Champions League semi-final BVB against AS Monaco. Furthermore, I have posted the two pre-match warm-up of Dortmund HERE and of Monaco HERE.


Nevertheless, I was able to take some footage from the goalkeepers warm-up as well. If interested, please check out the video below.





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.






Special edition - Research in football

The following articles were (originally) conference presentations at the "2nd Aspire Sport Science Conference on Monitoring Athlete Training Loads".

It was a fantastic conference and the International Journal of Sports Physiology and Performance released an open-access special-edition. HERE is the link to the publisher website and therefore ALL papers.

However, below are the one with regards to a team sports/football environment.

#1 The Influence of Changes in Acute Training Load on Daily Sensitivity of Morning-Measured Fatigue Variables in Elite Soccer Players
Reference: Int J of Sports Phys and Perf, 12, Suppl 2, 2-107
Authors: Thorpe RT, Strudwick AJ, Buchheit M, Atkinson G, Drust B, Gregson W
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Summary: The purpose of the study was to determine the sensitivity of a range of potential fatigue measures to daily training load accumulated over the previous 2, 3, and 4 d during a short in-season competitive period in elite senior soccer players (N = 10). Total highspeed-running distance, perceived ratings of wellness (fatigue, muscle soreness, sleep quality), countermovement-jump height (CMJ), submaximal heart rate (HRex), postexercise heart-rate recovery (HRR), and heart-rate variability (HRV: Ln rMSSD) were analyzed during an in-season competitive period (17 d). General linear models were used to evaluate the influence of 2-, 3-, and 4-d total high-speed-running-distance accumulation on fatigue measures. Fluctuations in perceived ratings of fatigue were correlated with fluctuations in total high-speed-running-distance accumulation covered on the previous 2 d (r = –.31; small), 3 d (r = –.42; moderate), and 4 d (r = –.28; small) (P < .05). Changes in HRex (r = .28; small; P = .02) were correlated with changes in 4-d total high-speed-running-distance accumulation only. Correlations between variability in muscle soreness, sleep quality, CMJ, HRR%, and HRV and total high-speed-running distance were negligible and not statistically significant for all accumulation training loads. Perceived ratings of fatigue and HRex were sensitive to fluctuations in acute total high-speed-running-distance accumulation, although sensitivity was not systematically influenced by the number of previous days over which the training load was accumulated. The present findings indicate that the sensitivity of morning-measured fatigue variables to changes in training load is generally not improved when compared with training loads beyond the previous day’s training.

#2 The Research Doesn’t Always Apply: Practical Solutions to Evidence-Based Training-Load Monitoring in Elite Team Sports
Reference: Int J of Sports Phys and Perf, 2017, Vol 12, Issue Suppl 2, S2-136
Author: Burgess DJ
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Summary: Research describing load-monitoring techniques for team sport is plentiful. Much of this research is conducted retrospectively and typically involves recreational or semielite teams. Load-monitoring research conducted on professional team sports is largely observational. Challenges exist for the practitioner in implementing peer-reviewed research into the applied setting. These challenges include match scheduling, player adherence, manager/coach buy-in, sport traditions, and staff availability. External-load monitoring often attracts questions surrounding technology reliability and validity, while internal-load monitoring makes some assumptions about player adherence, as well as having some uncertainty around the impact these measures have on player performance This commentary outlines examples of load-monitoring research, discusses the issues associated with the application of this research in an elite team-sport setting, and suggests practical adjustments to the existing research where necessary.

#3 Monitoring Fatigue Status in Elite Team-Sport Athletes: Implications for Practice
Reference: Int J of Sports Phys and Perf, 2017, Vol 12, Issue Suppl 2, S2-27
Authors: Thorpe RT, Atkinson G, Drust B, Gregson W
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Summary: The increase in competition demands in elite team sports over recent years has prompted much attention from researchers and practitioners to the monitoring of adaptation and fatigue in athletes. Monitoring fatigue and gaining an understanding of athlete status may also provide insights and beneficial information pertaining to player availability, injury, and illness risk. Traditional methods used to quantify recovery and fatigue in team sports, such as maximal physical-performance assessments, may not be feasible to detect variations in fatigue status throughout competitive periods. Faster, simpler, and nonexhaustive tests such as athlete self-report measures, autonomic nervous system response via heart-rate-derived indices, and to a lesser extent, jump protocols may serve as promising tools to quantify and establish fatigue status in elite team-sport athletes. The robust rationalization and precise detection of a meaningful fluctuation in these measures are of paramount importance for practitioners working alongside athletes and coaches on a daily basis. There are various methods for arriving at a minimal clinically important difference, but these have been rarely adopted by sport scientists and practitioners. The implementation of appropriate, reliable, and sensitive measures of fatigue can provide important information to key stakeholders in team-sport environments. Future research is required to investigate the sensitivity of these tools to fundamental indicators such as performance, injury, and illness.





Club wages and costs

Chapter 9 of the European club footballing landscape was about squad cost and wages

Generally, wages absorbed 63% of the club’s revenue in 2015.


A country comparison shows that the English Premier League clubs had more than double the next highest league (Italy’s Serie A) wages. Only Germany, Norway and Sweden have a wage to revenue ratio below 60%. Clubs in Turkey spend 80% of their revenue on wages.



Outside the Top 20 league, Finnland spend only 47% of revenue on wages, while clubs in Georgia spend 105%.



Making a closer look on the club inside the top 20 league you will find the usual clubs, with Barca and Real sitting at the top spending 340 and 289 mio Euros in wages, which equals 61 and 50% of the revenue and 5.5 and 4.7 times the Spanish league average respectively.


A total of 24 clubs had a wage bill in excess of 100 mio Euros and 9 clubs exceeding 200 mio.


Interestingly, an analysis of teams clustered in a) clubs ranked 1-4, b) ranked 5-8 and c) ranked 9+ indicates that due to the massive English Premier League TV deal, the English teams ranked 5-8 paid more in wages (144 mio) than clubs ranked 1-4 in France (128 mio), Russia (72 mio) and Turkey (70 mio). Furthermore, the EPL teams 9+ paid more in wages (86) than any other league teams ranked 5-8 (<74 mio in Germany).



Another interesting fact is that clubs ranked 1-4 in Portugal (42 mio) and Netherlands (39 mio) have a more than a 50% gap to the clubs ranked 5-8. There seems no doubt as to why there are (most likely) the same league winner over time.

Taking the transfer cost of squad into account, England (528 mio) showed again the greatest budget, followed by Spain (350 mio), Italy (257 mio), Germany (194) and France (183) for the teams ranked 1-4. Again, teams in England ranked 5-8 “outcost” teams ranked 1-4 in Germany, France, Russia and Turkey by more than 60 mio Euros. Interestingly, the average costs of Spains second cluster (teams 5-8 = 49 mio) seems very low compared to the equivalent to England (256 mio), Italy (129 mio), Germany (73 mio) and the third cluster (team ranked 9+) in England (91 mio). The document mentioned that the situation was driven by changes in the regulatory environment with a need to balance finances.

Outside the top 8 leagues, Portugal had the greatest squad costs with 86 mio, followed by Netherlands (37 mio) and Belgium (23 mio).



The question arises if a more precise measurement would be the squad costs to wages ratio. There seems to be a strong correlation (r=089) between wages and transfer fees. However, Barca has a relatively high wage bill, however a “low” squad spend, while Liverpool and Inter had low wage bills relative to their squad costs.



Squad affordability is a ratio of squad expenses to the clubs revenue, indicating that only the German clubs in the Top 20 are under a ratio of 1.0. Inter has the worst ratio of 1.5 having squad costs of 268 mio against wages of 120 mio. Real and ManU comfortably sitting in first and second place with 650 and 573 mio squad expenses respectively.







Latest research in football - week 15 - 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 ACTN3/ACE genotypes and mitochondrial genome in professional soccer players’ performance
Reference: J Biol Regul Homeost Agents. 2017 Jan-Mar;31(1):207-213.
Authors: Galeandro V, Notarnicola A, Bianco A, Tafuri S, Russo L, Pesce V, Moretti B, Petruzzella V
Summary: Two nuclear genes, ACTN3, encoding for the α-actinin skeletal muscle isoform 3, and ACE encoding the angiotensin-converting enzyme, have both been associated with quantitative physical performance traits in the general population. The purpose of our study was to assess the association between the two nuclear gene variants, R577X (rs1815739) in ACTN3 and I/D (rs4340) in ACE, with elite athletes’ performance and the effect of training on the mitochondrial DNA (mtDNA) content in peripheral blood. We evaluated the genotypes and frequencies of ACTN3 R577X and ACE I/D polymorphisms between soccer players (n = 43) and healthy non-athletic controls (n = 128). Total DNA was extracted from peripheral blood samples using the standard procedure. The genotypes were assessed by PCR-RFLP analysis and mtDNA cellular content by RT-PCR. The soccer players showed a tendency to a prevalence of ACTN3RR and ACEDD genotypes both independently and in co-occurrence. The effect of physical training on the mitochondrial DNA content in the athletic population was reflected strikingly in its increase in peripheral blood. Based on our results, we suggest that the analysis of ACTN3 and ACE genotypes could predict talent in the soccer field and that knowledge of the genetic variants could determine types and training times for soccer players. In addition, the novelty of this work, never before described in the sports literature, is that the increase of mitochondrial content can be correlated with the training load, suggesting that the mtDNA copy number may be considered a viable bioenergetics biomarker.

#2 Strength and endurance training reduces the loss of eccentric hamstring torque observed after soccer specific fatigue
Reference: Phys Ther Sport. 2017 Feb 2;25:39-46. doi: 10.1016/j.ptsp.2017.01.006. [Epub ahead of print]
Authors: Matthews MJ, Heron K, Todd S, Tomlinson A, Jones P, Delextrat A, Cohen DD
Summary: The purpose was to investigate the effect of two hamstring training protocols on eccentric peak torque before and after soccer specific fatigue. Twenty-two university male soccer players participated in this study. Isokinetic strength tests were performed at 60°/s pre and post fatigue, before and after 2 different training interventions. A 45-min soccer specific fatigue modified BEAST protocol (M-BEAST) was used to induce fatigue. Players were randomly assigned to a 4 week hamstrings conditioning intervention with either a maximum strength (STR) or a muscle endurance (END) emphasis. The following parameters were evaluated: Eccentric peak torque (EccPT), angle of peak torque (APT), and angle specific torques at knee joint angles of 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90°. There was a significant effect of the M-BEAST on the Eccentric torque angle profile before training as well as significant improvements in post-fatigue torque angle profile following the effects of both strength and muscle endurance interventions. Forty-five minutes of simulated soccer activity leads to reduced eccentric hamstring torque at longer muscle lengths. Short-term conditioning programs (4-weeks) with either a maximum strength or a muscular endurance emphasis can equally reduce fatigue induced loss of strength over this time period.

#3 Sport Nutrition Knowledge, Behaviors and Beliefs of High School Soccer Players
Reference: Nutrients. 2017 Apr 1;9(4). pii: E350. doi: 10.3390/nu9040350.
Authors: Manore MM, Patton-Lopez MM, Meng Y, Wong SS
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Summary: For adolescent athletes (14-18 years), data on sport nutrition knowledge, behaviors and beliefs are limited, especially based on sex, race/ethnicity and socioeconomic status. High school soccer players (n = 535; 55% female; 51% White, 41% Latino; 41% National School Lunch Program (NSLP) participants (80% Latino)) completed two questionnaires (demographic/health history and sport nutrition). The sport nutrition knowledge score was 45.6% with higher scores in NSLP-Whites vs. NSLP-Latinos (p < 0.01). Supplement knowledge differed by sex (16% lower in females; p = 0.047) and race/ethnicity (33% lower in Latinos; p < 0.001). Breakfast consumption was 57%; females ate breakfast less (50%) than males (60%; p < 0.001); NSLP-participants ate breakfast less (47%) than non-NSLP (62%; p < 0.001). Supplement use was 46%, with Latinos using more supplements than Whites do (p = 0.016). Overall, 30% used protein shakes, with females using less than males (p = 0.02), while use was twice as likely in Latino vs. White (p = 0.03). Overall, 45% reported their nutrient requirements were different from non-athlete peers. Latinos were less likely (p = 0.03) to report that their diet met nutritional requirements, but more than twice as likely to report that nutritional supplements were necessary for training (p < 0.001). Adolescent athletes, especially females and Latinos, would benefit from sport nutrition education that enhances food selection skills for health and sport performance.

#4 Effects of a 12-Month Complex Proprioceptive-Coordinative Training Program on Soccer Performance in Prepubertal Boys Aged 10-11 Years
Reference: J Strength Cond Res. 2017 Mar 31. doi: 10.1519/JSC.0000000000001878. [Epub ahead of print]
Authors: Boraczynski M, Sozanski H, Boraczynski T
Summary: The aim was to examine the effects of a series of on-field proprioceptive-coordinative (P-C) exercises on motor performance (MP) in prepubertal soccer players. Fifty-three male soccer players aged 10.1-11.8 years were randomized among two experimental programs receiving P-C training (P-CT; n = 26) or regular training (RT; n = 27). A control group (C; n = 22) consisted of age-matched (10.3-11.9 years) cohorts not involved in any regular physical activity. Both experimental groups completed an identical 12-month comprehensive soccer program except training in P-CT was modified to substitute small-sided conditioning games with 24 multi-mode P-C exercises with modulated exercise intensity (every 8-9 weeks based on predicted HRmax). Pre-, peri-, and post-training measures included anthropometry and five tests assessing soccer-specific MP: movement rhythm (turning the ball backwards - T1), motor adaptation (running with the ball around poles - T2), spatial orientation (running to sequentially numbered balls - T3), balance (single-leg static balance - T4), and kinesthetic differentiation of movement (landing the ball on a 2 × 2 m sector - T5). Repeated measures ANOVA revealed no significant between-group differences for age, anthropometry and BF% at baseline. Significant main effects for group (P-CT vs. RT) were found in all tests (T1-T5) and main effects for time (group P-CT) in T3-T5, while a significant group × time interaction was observed only in T4 (F = 2.98, p = 0.0204). Post-hoc tests indicated that P-CT attained significantly better results than RT at peri-training (by 26.4%; p < 0.01) and post-training (by 31.9%, p < 0.01). Modulated exercise intensity had little effect on soccer performance (T1-T3, T5). Based on the results, it is recommended that the training of young soccer players be supplemented with the bilateral balance exercises and games employed in the study. Furthermore, the suitability of monitoring HR in P-C exercises targeting the analyzed MP skills is questionable.

#5 Cut-offs of isokinetic strength ratio and hamstring strain prediction in professional soccer players
Reference: Scand J Med Sci Sports. 2017 Apr 4. doi: 10.1111/sms.12890. [Epub ahead of print]
Authors: Dauty M, Menu P, Fouasson-Chailloux A
Summary: Hamstring strain injuries frequently occur during professional soccer practice. Low hamstring strength represents an intrinsic modifiable risk factor but cut-offs of isokinetic knee strength ratios are controversial to predict hamstring strain in professional soccer players. We aimed to predict hamstring strain in accordance to cut-offs of isokinetic knee strength ratios. Bilateral, conventional and functional isokinetic strength ratios were calculated in 194 professional soccer players at the beginning of 15 consecutive seasons. 36 soccer players presented a moderate hamstring strain and 158 were not injured. The different calculated isokinetic ratios were compared with the right and left limb of the uninjured population. Different usual cut-offs were tested: at 0.85 and 0.90 for the bilateral concentric and eccentric hamstring-to-hamstring ratio, at 0.60 and 0.47 for the conventional hamstring-to-quadriceps ratio and at 0.80 and 1 for the mixed hamstring-to-quadriceps ratio. The specific ratios for the studied population were also determined by the 10th percentile and then tested. Hamstring strain prediction was established in term of odds ratios. No cut-off with bilateral, conventional or functional isokinetic strength ratio was predictive of hamstring strain after univariate analysis. Specific cut-offs determined from the studied population were not more predictive. Very few injured soccer players presented values under the cut-offs at 0.47 for the conventional ratio and at 0.80 for the mixed ratio. Regardless of their values, cut-offs of isokinetic strength ratios were not predictive of hamstring injuries. The use of isokinetic cut-offs is not recommended to predict hamstring muscle strain in professional soccer players.

#6 Case Study: Hydration Intervention Improves Pre-game Hydration Status in Female Collegiate Soccer Players
Reference: Int J Sport Nutr Exerc Metab. 2017 Apr 7:1-18. doi: 10.1123/ijsnem.2016-0209. [Epub ahead of print]
Authors: Hoerner NR, Domnik K, Koehler K, Schaenzer W, Braun H
Summary: Little is known about whether athletes follow hydration guidelines. The objective of the present study was to assess fluid status in female soccer players in a hot and humid environment, and to assess the effect of an intervention aimed at preventing players from exercising in a dehydrated state. We hypothesized that following the intervention, players would exhibit improved hydration status, as indicated by greater voluntary fluid intake and improved hydration markers. Ten female collegiate soccer players (20±1yrs., 64±9kg) participated in this seven-week study. Changes in body weight (BW), fluid intake, urine color (UC), and urine specific gravity (USG) were measured periodically over three days. Dehydration was classified as USG ≥1.020g/ml and UC >3. Following a 7- week intervention (to individualize hydration strategies), BW, fluid intake, UC, and USG were again measured on two game days to evaluate the impact of the intervention. Pre-test: five players started exercising dehydrated (USG 1.029g/ml; UC 6). Seven players were dehydrated before the next morning practice session (USG 1.029g/ml; UC 5). Five players had a mean BW loss of 2.5%.Post-test: four players were dehydrated before game 1. Despite hydration guidelines, two players experienced tiredness and cramps during the second half. Six players were dehydrated 4h before game 2 and subsequently received individual rehydration instructions. 2h before game 2, none of the players were dehydrated. No symptoms of tiredness or cramps were reported. Hydration status assessment coupled with an intervention of individualized drinking strategies, can prevent female soccer players from exercising in a dehydrated state.

#7 n-3 Fatty Acid Supplementation During 4 Weeks of Training Leads to Improved Anaerobic Endurance Capacity, But Not Maximal Strength, Speed, or Power in Soccer Players
Reference: Int J Sport Nutr Exerc Metab. 2017 Apr 7:1-25. doi: 10.1123/ijsnem.2016-0325. [Epub ahead of print]
Authors: Gravina L, Brown FF, Alexander L, Dick J, Bell G, Witard OC, Galloway SD
Summary: Omega-3 fatty acid (n-3 FA) supplementation could promote adaptation to soccer-specific training. We examined the impact of a 4 wk period of n-3 FA supplementation during training on adaptations in 1RM knee extensor strength, 20m sprint speed, vertical jump power, and anaerobic endurance capacity (Yo-Yo test) in competitive soccer players. Twenty six soccer players were randomly assigned to one of two groups: n-3 FA supplementation (n-3 FA; n=13) or placebo (n=13). Both groups performed two experimental trial days. Assessments of physical function and respiratory function were conducted pre (PRE) and post (POST) supplementation. Training session intensity, competitive games and nutritional intake were monitored during the 4 wk period. No differences were observed in respiratory measurements (FEV1, FVC) between groups. No main effect of treatment was observed for 1RM knee extensor strength, explosive leg power, or 20 m sprint performance, but strength improved as a result of the training period in both groups (p<0.05). Yo-Yo test distance improved with training in the n-3 FA group only (p<0.01). The mean difference (95% CI) in Yo-Yo test distance completed from PRE to POST was 203 (66 to 340) m for n-3 FA, and 62 (-94 to 217) m for placebo, with a moderate effect size (Cohen's d of 0.52). We conclude that 4 wk of n-3 FA supplementation does not improve strength, power or speed assessments in competitive soccer players. However, the increase in anaerobic endurance capacity evident only in the n-3 FA treatment group suggests an interaction that requires further study.

#8 Left ventricular biomechanics in professional football players
Reference: Scand J Med Sci Sports. 2017 Apr 4. doi: 10.1111/sms.12893. [Epub ahead of print]
Authors: von Lueder TG, Hodt A, Gjerdalen GF, Steine K
Summary: Chronic exercise induces adaptive changes of left ventricular (LV) ejection and filling capacities which may be detected by novel speckle-tracking echocardiography (STE) and tissue Doppler imaging (TDI)-based techniques. 103 consecutive male elite Norwegian soccer players and 46 age-matched healthy controls underwent echocardiography at rest. STE was used to assess LV torsional mechanics and LV systolic longitudinal strain (LS). Diastolic function was evaluated by trans-mitral blood flow, mitral annular velocities by TDI, and LV inflow propagation velocity by colour M-mode. Despite similar global LS, players displayed lower basal wall and higher apical wall LS values vs controls, resulting in an incremental base-to-apex gradient of LS. Colour M-mode and TDI-derived data were similar in both groups. Peak systolic twist rate (TWR) was significantly lower in players (86.4 ± 2.8 vs controls 101.9 ± 5.2 deg/s, P<0.01). Diastolic untwisting rate (UTWR) was higher in players (-124.5 ± 4.2 vs -106.9 ± 6.7 deg/s) and peaked earlier during the cardiac cycle (112.7 ± 0.8 vs 117.4 ± 2.4% of systole duration, both P<0.05). Untwisting/twisting ratio (-1.48 ± 0.05 vs -1.11 ± 0.08; P <0.001) and untwisting performance (=UTR/TW; -9.25 ± 0.34 vs -7.38 ± 0.40 s-1 , P<0.01) were increased in players. Augmented diastolic wall strain (DWS), a novel measure of LV compliance in players was associated with improved myocardial mechanical efficiency. The described myocardial biomechanics may underlie augmented exertional cardiac function in athletes and may have a potential role to characterize athlete's heart by itself or to distinguish it from hypertensive or hypertrophic cardiomyopathy.

#9 Isolated HAGL lesion after arthroscopic Bankart repair in a professional soccer player
Reference: Phys Sportsmed. 2017 Mar 29:1-4. doi: 10.1080/00913847.2017.1309955. [Epub ahead of print]
Authors: Celik H, Seckin MF, Kara A, Akman S
Summary: Post-traumatic anterior shoulder instability commonly occurs following an avulsion of capsulolabral complex from glenoid (Bankart lesion) or rarely after humeral avulsion of the glenohumeral ligaments (HAGL lesion). Arthroscopic Bankart repair offers high success rates of healing. However, trauma following the treatment may cause implant failure or re-avulsion of the treated tissue. We aim to present the diagnosis and treatment of an isolated HAGL lesion in a professional soccer player who had previously undergone arthroscopic Bankart repair.

#10 Daily Distribution of Carbohydrate, Protein and Fat Intake in Elite Youth Academy Soccer Players Over a 7-Day Training Period
Reference: Int J Sport Nutr Exerc Metab. 2016 Oct;26(5):473-480. Epub 2016 Aug 24.
Authors: Naughton RJ, Drust B, O'Boyle A, Morgans R, Abayomi J, Davies IG, Morton JP, Mahon E.
Summary: While traditional approaches to dietary analysis in athletes have focused on total daily energy and macronutrient intake, it is now thought that daily distribution of these parameters can also influence training adaptations. Using 7-day food diaries, we quantified the total daily macronutrient intake and distribution in elite youth soccer players from the English Premier League in U18 (n = 13), U15/16 (n = 25) and U13/14 squads (n = 21). Total energy (43.1 ± 10.3, 32.6 ± 7.9, 28.1 ± 6.8 kcal·kg-1·day-1), CHO (6 ± 1.2, 4.7 ± 1.4, 3.2 ± 1.3 g·kg-1·day-1) and fat (1.3 ± 0.5, 0.9 ± 0.3, 0.9 ± 0.3 g·kg-1·day-1) intake exhibited hierarchical differences (p < .05) such that U13/14 > U15/16 > U18. In addition, CHO intake in U18s was lower (p < .05) at breakfast, dinner and snacks when compared with both squads but no differences were apparent at lunch. Furthermore, the U15/16s reported lower relative daily protein intake than the U13/14s and U18s (1.6 ± 0.3 vs. 2.2 ± 0.5, 2.0 ± 0.3 g·kg-1). A skewed distribution (p < .05) of daily protein intake was observed in all squads, with a hierarchical order of dinner (~0.6 g·kg-1) > lunch (~0.5 g·kg-1) > breakfast (~0.3 g·kg-1). We conclude elite youth soccer players do not meet current CHO guidelines. Although daily protein targets are achieved, we report a skewed daily distribution in all ages such that dinner > lunch > breakfast. Our data suggest that dietary advice for elite youth players should focus on both total daily macronutrient intake and optimal daily distribution patterns.

American Football
#1 Epidemiology of Sport-Related Concussions in High School Athletes: National Athletic Treatment, Injury and Outcomes Network (NATION), 2011-2012 Through 2013-2014

Reference: J Athl Train. 2017 Mar;52(3):175-185. doi: 10.4085/1062-6050-52.1.15.

Authors: O'Connor KL, Baker MM, Dalton SL, Dompier TP, Broglio SP, Kerr ZY

Summary: Sports participation is one of the leading causes of concussions among nearly 8 million US high school student-athletes. The objective was to describe the epidemiology of sport-related concussion (SRC) in 27 high school sports during the 2011-2012 through 2013-2014 academic years. Aggregate injury and exposure data from 27 sports in 147 high schools in the National Athletic Treatment, Injury and Outcomes Network (NATION). Boy and girl high school athletes during the 2011-2012 through 2013-2014 academic years were analyzed. Sport-related concussion counts, percentages, rates per 10 000 athlete-exposures (AEs), rate ratios (RRs), and injury proportion ratios (IPRs) were reported with 95% confidence intervals (CIs). Rate ratios and IPRs with 95% CIs not containing 1.0 were considered significant. Overall, 2004 SRCs were reported among 27 high school sports, for a rate of 3.89 per 10 000 AEs. Football had the highest SRC rate (9.21/10 000 AEs), followed by boys' lacrosse (6.65/10 000 AEs) and girls' soccer (6.11/10 000 AEs). The SRC rate was higher in competition than in practice (RR = 3.30; 95% CI = 3.02, 3.60). Among sex-comparable sports, the SRC rate was higher in girls than in boys (RR = 1.56; 95% CI = 1.34, 1.81); however, the proportion of SRCs due to player-to-player contact was higher in boys than in girls (IPR = 1.48; 95% CI = 1.27, 1.73). Common symptoms reported among all athletes with SRCs were headache (94.7%), dizziness (74.8%), and difficulty concentrating (61.0%). Only 0.8% of players with SRCs returned to play within 24 hours. The majority of athletes with SRCs (65.8%) returned to play between 7 and 28 days. More players had symptoms resolve after 7 days (48.8%) than less than a week (40.7%). Our findings provide updated high school SRC incidence estimates and further evidence of sex differences in reported SRCs. Few athletes with SRCs returned to play within 24 hours or a week. Most injured players returned after 7 days, despite a smaller proportion having symptoms resolve within a week.

#2 Head-Impact-Measurement Devices: A Systematic Review

Reference: J Athl Train. 2017 Mar;52(3):206-227. doi: 10.4085/1062-6050.52.2.05.

Authors: O'Connor KL, Rowson S, Duma SM, Broglio SP

Summary: With an estimated 3.8 million sport- and recreation-related concussions occurring annually, targeted prevention and diagnostic methods are needed. Biomechanical analysis of head impacts may provide quantitative information that can inform both prevention and diagnostic strategies. The objective of the study was to assess available head-impact devices and their clinical utility. We performed a systematic search of the electronic database PubMed for peer-reviewed publications, using the following phrases: accelerometer and concussion, head impact telemetry, head impacts and concussion and sensor, head impacts and sensor, impact sensor and concussion, linear acceleration and concussion, rotational acceleration and concussion, and xpatch concussion. In addition to the literature review, a Google search for head impact monitor and concussion monitor yielded 15 more devices. Included studies were performed in vivo, used commercially available devices, and focused on sport-related concussion. One author reviewed the title and abstract of each study for inclusion and exclusion criteria and then reviewed each full-text article to confirm inclusion criteria. Controversial articles were reviewed by all authors to reach consensus. In total, 61 peer-reviewed articles involving 4 head-impact devices were included. Participants in boxing, football, ice hockey, soccer, or snow sports ranged in age from 6 to 24 years; 18% (n = 11) of the studies included female athletes. The Head Impact Telemetry System was the most widely used device (n = 53). Fourteen additional commercially available devices were presented. Measurements collected by impact monitors provided real-time data to estimate player exposure but did not have the requisite sensitivity to concussion. Proper interpretation of previously reported head-impact kinematics across age, sport, and position may inform future research and enable staff clinicians working on the sidelines to monitor athletes. However, head-impact-monitoring systems have limited clinical utility due to error rates, designs, and low specificity in predicting concussive injury.

#3 American-Style Football Players as Modern Gladiators: Could Heart Rate Provide All Answers?

Reference: JACC Cardiovasc Imaging. 2017 Apr;10(4):495-496. doi: 10.1016/j.jcmg.2016.12.015.

Authors: Tadic M, Cuspidi C, Ivanovic B.





AS Monaco UEFA Champions League Pre-Match Warm-up

As mentioned in previous post about the BVB warm-up HERE, I was also able to tape most of the pre-match warm-up of AS Monaco.


The warm-up can be seen below.


The list of football videos (warm-ups, training sessions and others) can be seen HERE.





Club revenue highlights

Chapter 8 was about the UEFA clubs and their revenue.

Generally, revenue has grown over the last year with an average of more than 9% per year. The club’s revenue are now six times the level of 1996.



Interestingly, the average English Premier League club having five times more revenue than the average Italian Serie A or French Ligue 1 club.

The average six-year club growth was the greatest in England followed by Germany, Spain and Italy. On average, every club in England extended its revenue by 99.2 mio Euros, followed by German clubs (48.1), Spanish club (27.4) and Italy (19.0).



So how much do the clubs earn on average?

According to UEFA, the ability of clubs to generate revenue varies enormously. For example a club in England generate ~220 mio, followed by Germany ~135 mio, Spain wit ~102 and Italy ~95 mio Euros.

As a consequence its not surprising that England aggregated 4.4 bn in its top division, followed by Germany (2.4 bn), Spain (2.0 bn), Italy (1.9 bn) and France (1.4 bn). In 2015 there were 46 clubs with an annual revenue of 100+ mio Euros.

The map shows where the wealth in football is concentrated.



So what are the top clubs in terms of total revenue in 2015?

The greatest revenue was generated by Real Madrid (578 mio), followed by Barcelona (561 mio) and ManU (521 mio). Juventus as the first Italian club ranked 10th with 325 mio Euros. Zenit Petersburg comes in with 196 mio at 15th place and Galatasaray with 148 mio at rank 26.



The club’s revenue come from diverse income streams. Number one is domestic broadcasting (34%), followed by Sponsorships (24%), Gate receipts (16%), revenues from UEFA and commercials (both 9%) and other revenues (8%).

The picture below shows broadcast revenues for the six largest domestic leagues. Obviously, the broadcast revenues in England exceeded 100 mio per club, comfortably more than double the Italian and triple the Spanish and German average. Interestingly, the 36.1 mio per club in Germany displays 27% “only” of the total revenue, while 47.7 mio equals 50% of the total revenue in Italy.



While 17 out of the 20 top clubs by broadcast revenues are from England, the top two are Barca and Real Madrid from Spain. Both clubs receiving 3.8 – 3.9 times the league average (equaling ~142 mio Euros).


Another income source was the UEFA price money, which is determined in part by the clubs sporting performance. While the UEFA price money equals ~51% of the clubs revenue in Bulgaria (10th place), its about 4% (in England) and 10% (in Spain) leading to a club average of 10.5 mio Euros.

The top 20 clubs receiving from UEFA can be seen in the slide below.



Gate receipts as the third highest income stream for clubs in different countries are as follows in the next slide.



Real Madrid receives the greatest amount (compared to other clubs) from gate receipts having 4.9 mio per match which is about six times the Spanish league average. There seemed to big differences in the ability to generate revenue from gate receipts. Five clubs, all with 60.000+ stadium capacities generated more than 100 mio Euros with an average per home game between 4.2 and 5.1, however, Juventus in 5th place generating only half of that.



Sponsorship, as the second biggest income stream provided at least 20% (19.3 mio in Italy), but not more than 66% (2.6 mio in Azerbaijan) of the total revenue. The highest club average of 64.8 mio was received in England.



The last part of the UEFA club revenue highlights was about transfer proceeds. Sorted after the total amount of transfer proceeds, Real Madrid sat in front with 111 mio Euros, however, spending 186 mio which ends-up in a total of net transfer proceeds of -75 mio. Genoa CFC was the club that created the greatest net transfer proceeds with 68 mio Euros. However, having a closer look on the original transfer costs and the achieved revenue, FC Porto created the highest profit with 49 mio Euros.



Three English clubs ManCity, ManU and Chelsea have to be named as the top clubs selling players for “marked-down”, with -95, -74 and -42 mio Euros respectively. Interestingly, there are no “country” trend for this part, meaning that we will find clubs of different countries (England, Portugal, France, Italy, Germany, Spain, Ukrain) inside the top 20 of club transfer proceeds. Interestingly, ManU spend 198 mio in transfers resulting in a net transfer proceed of -144 mio. The top 20 clubs aggregated a net transfer proceed of -341 mio Euros.

The last two slides is about the revenue mix in (and outside) the top 20 leagues sorted after aggregate revenue. Clubs in Italy and England (on average) depend on domestic broadcasting with an average of 50 and 49%. However, transfer proceeds made up of 75% of the clubs revenue in Portugal.



Revenue mix outside the Top 20 leagues showed that transfer proceeds (relative to revenue) were the highest in Croatian (85%) and Serbian clubs (82%). Revenue from UEFA club competition is highly significant for clubs in most middle-income and lower-earning leagues.








Latest research in football - week 14 - 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 Injuries in male and female semi-professional football (soccer) players in Nigeria: prospective study of a National Tournament
Reference: BMC Res Notes. 2017 Mar 21;10(1):133. doi: 10.1186/s13104-017-2451-x.
Authors: Owoeye OB, Aiyegbusi AI, Fapojuwo OA, Badru OA, Babalola AR
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Summary: Research on the epidemiology of football injuries in Africa is very sparse despite its importance for injury prevention planning in a continent with limited sports medicine resources. The vast majority of studies available in literature were conducted in Europe and only a very few studies have prospectively reported the pattern of football injury in Africa. The purpose of this study was to evaluate the incidence and pattern of injuries in a cohort of male and female semi-professional football players in Nigeria. A prospective cohort design was conducted, in which a total of 756 players with an age range of 18-32 years (356 males and 300 females) from 22 different teams (12 male and 10 female teams), were prospectively followed in a National Football Tournament. Physiotherapists recorded team exposure and injuries. Injuries were documented using the consensus protocol for data collection in studies relating to football injury surveillance. An overall incidence of 113.4 injuries/1000 h (95% CI 93.7-136.0) equivalent to 3.7 injuries/match and time-loss incidence of 15.6 injuries/1000 h were recorded for male players and 65.9 injuries/1000 h (95% CI 48.9-86.8) equivalent to 2.2 injuries/match and time-loss incidence of 7.9 injuries/1000 h were recorded for female players. Male players had a significantly higher risk of injuries [IRR = 1.72 (95% CI 1.23-2.45)]. Injuries mostly affected the lower extremity for both genders (n = 81, 70% and n = 31, 62% for males and females respectively). Lower leg contusion (n = 22, 19%) and knee sprain (n = 9, 18%) were the most common specific injury types for male and female players respectively. Most of the injuries were as a result of contact with another player (n = 102, 88%-males; n = 48, 96%-females). Time-loss injuries were mostly estimated as minimal (n = 11, 69%) for male players and severe (n = 4, 66%) for female players. The overall incidence of injuries among Nigerian semi-professional football players is high but most of the injuries do not result in time-loss. Pattern of injuries is mostly consistent with previous studies. More prospective studies are needed to establish injury prevention initiatives among African players.

#2 Geographical Variations in the Interaction of Relative Age Effects in Youth and Adult Elite Soccer
Reference: Front Psychol. 2017 Mar 7;8:278. doi: 10.3389/fpsyg.2017.00278. eCollection 2017.
Authors: Steingrover C, Wattie N, Baker J, Helsen WF, Schorer J
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Summary: Selection biases based on the use of cut-off dates and the timing of athletes' birthdates have been termed relative age effects. These effects have been shown to differentially affect individuals involved in sport. For example, young male soccer players born early in their age group are overrepresented in elite teams while studies in adult soccer indicated potential carry-over effects from talent development systems. This two-study approach focuses on the processes within multi-year age groups in youth and adult elite soccer and on the role of players' age position within the age band with regard to players' birth year and birth month. Study 1 tests for an interaction of two different types of relative age effects among data from participants in the last five Under-17 FIFA World Cups (2007-2015). Analyses revealed a significant global within-year effect and varying birthdate distributions were found between confederations. Even stronger effects were found for constituent year effects. For the total sample, a multi-way frequency analysis (MFA) revealed an interaction with a pattern of a stronger within-year effect for the younger year group. This study highlights the need to consider interactions between different types of age effects. The main aim of Study 2 was to test for carry-over effects from previously found constituent year effects among players participating in the 2014 soccer World Cup and, therefore, to test for long-term effects of age grouping structures used during earlier stages of talent development. A secondary purpose of this study was to replicate findings on the existence of within-year effects and to test whether effects vary between continental confederations. No significant interaction between constituent year and within-year effects was shown by the MFA among the World Cup sample and previous findings on varying within-year effects were replicated. Results indicate that long-term effects of age grouping structures in earlier high-level talent development structures exist.

#3 The effects of an increased calorie breakfast consumed prior to simulated match-play in Academy soccer players
Reference: Eur J Sport Sci. 2017 Mar 21:1-9. doi: 10.1080/17461391.2017.1301560. [Epub ahead of print]
Authors: Briggs MA, Harper LD, McNamee G, Cockburn E, Rumbold PL, Stevenson EJ, Russell M
Summary: Dietary analysis of Academy soccer players highlights that total energy and carbohydrate intakes are less than optimal, especially, on match-days. As UK Academy matches predominantly kick-off at ∼11:00 h, breakfast is likely the last pre-exercise meal and thus may provide an intervention opportunity on match-day. Accordingly, the physiological and performance effects of an increased calorie breakfast consumed ∼135-min before soccer-specific exercise was investigated. English Premier League Academy soccer players (n = 7) repeated a 90-min soccer match simulation on two occasions after consumption of habitual (Bhab; ∼1100 kJ) or increased (Binc; ∼2100 kJ) energy breakfasts standardised for macronutrient contributions (∼60% carbohydrates, ∼15% proteins and ∼25% fats). Countermovement jump height, sprint velocities (15-m and 30-m), 30-m repeated sprint maintenance, gut fullness, abdominal discomfort and soccer dribbling performances were measured. Blood samples were taken at rest, pre-exercise, half-time and every 15-min during exercise. Although dribbling precision (P = .522; 29.9 ± 5.5 cm) and success (P = .505; 94 ± 8%) were unchanged throughout all time-points, mean dribbling speed was faster (4.3 ± 5.7%) in Binc relative to Bhab (P = .023; 2.84 vs 2.75 m s-1). Greater feelings of gut fullness (67 ± 17%, P = .001) were observed in Binc without changes in abdominal discomfort (P = .595). All other physical performance measures and blood lactate and glucose concentrations were comparable between trials (all P > .05). Findings demonstrate that Academy soccer players were able to increase pre-match energy intake without experiencing abdominal discomfort; thus, likely contributing to the amelioration of energy deficits on match-days. Furthermore, whilst Binc produced limited benefits to physical performance, increased dribbling speed was identified, which may be of benefit to match-play.

#4 Effects of Plyometric Training on Physical Fitness in Prepuberal Soccer Athletes
Reference: Int J Sports Med. 2017 Mar 17. doi: 10.1055/s-0042-122337. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Sammoud S, Bouguezzi R, Abbes MA, Hachana Y, Granacher U
Summary: This study aimed at examining the effects of plyometric training on stable (SPT) vs. unstable (UPT) surfaces on physical fitness in prepuberal soccer players. Male athletes were randomly assigned to SPT (n=18; age=12.7±0.2 years) or UPT (n=16; age=12.2±0.5 years). Both groups conducted 3 regular soccer training sessions per week combined with either 2 SPT or UPT sessions. Assessment of jumping ability (countermovement jump [CMJ], and standing long jump [SLJ]), speed (10-m, 20-m, 30-m sprint), agility (Illinois agility test [IAT]), and balance (stable [SSBT], unstable [USBT] stork balance test; stable [SYBT], unstable [UYBT] Y balance test) was conducted pre-and post-training. An ANCOVA model was used to test for between-group differences (SPT vs. UPT) at post-test using baseline values as covariates. No significant differences were found for CMJ height (p>0.05, d=0.54), SLJ (p>0.05; d=0.81), 10-m, 20-m, and 30-m sprint performances (p>0.05, d=0.00-0.24), IAT (p>0.05, d=0.48), and dynamic balance (SYBT and UYBT, both p>0.05, d=0.39, 0.08, respectively). Statistically significant between-group differences were detected for the USBT (p<0.01, d=1.86) and the SSBT (p<0.01, d=1.75) in favor of UPT. Following 8 weeks of SPT or UPT in prepuberal athletes, similar performance levels were observed in both groups for measures of jumping ability, speed, dynamic balance, and agility. However, if the goal is to additionally enhance static balance, UPT has an advantage over SPT.

#5 Interrelationships among Jumping Power, Sprinting Power and Pubertal Status after Controlling for Size in Young Male Soccer Players
Reference: Percept Mot Skills. 2017 Apr;124(2):329-350. doi: 10.1177/0031512516686720. Epub 2017 Jan 16.
Authors: Cunha GS, Cumming SP, Valente-Dos-Santos J, Duarte JP, Silva G, Dourado AC, Leites GT, Gaya AC, Reischak-Oliveira A, Coelho-E-Silva M
Summary: This study examined power output on jumping and sprinting tests in young soccer players of differing pubertal status, while controlling for body size with allometric scaling exponents. A total of 46 males aged 12-18 years (14.17 years) were divided into three groups: pre-pubescent ( n = 12), pubescent ( n = 22), and post-pubescent ( n = 12). Participants performed a series of tests, including the squat jump (SJ), countermovement jump (CMJ), and 10-meter and 30-meter sprint test protocols. The Post-PUB group was older ( F = 112.411, p < 0.001), more experienced in competitive soccer ( F = 8.055, p = 0.001), taller ( F = 28.940, p < 0.001), and heavier ( F = 20.618, p < 0.001), when compared to peers in the other groups. Mean differences in jumping and sprinting performances suggested a significant effect for pubertal status on performance in the 10-meter sprint (large effect size, F = 8.191, p < 0.001) and 30-meter sprint (large effect size, F = 8.093, p < 0.001) after allometric scaling. Power output derived from SJ (small effect size, F = 0.536, p = 0.001) and CMJ (small effect size, F = 1.058, p = 0.356) showed no significant differences across players of varying pubertal status. Biological maturation showed a large effect on maximal power output for sprints, but not for jumps, when the effect of body size was adjusted by statistically derived allometric exponents in young male soccer players.

#6 Redox status alterations during the competitive season in élite soccer players: focus on peripheral leukocyte-derived ROS
Reference: Intern Emerg Med. 2017 Mar 30. doi: 10.1007/s11739-017-1653-5. [Epub ahead of print]
Authors: Becatti M, Mannucci A, Barygina V, Mascherini G, Emmi G, Silvestri E, Wright D, Taddei N, Galanti G, Fiorillo C
Summary: It is well known that exercise training can deeply affect redox homeostasis by enhancing antioxidant defenses. However, exhaustive exercise can induce excessive reactive oxygen species (ROS) production, leading to oxidative stress-related tissue injury and impaired muscle contractility. Hence, ROS represent important signaling molecules whose level has to be maintained to preserve normal cellular function, but which can also accumulate in response to repetitive muscle contraction. In fact, low levels of oxidants have been suggested to be essential for muscle contraction. Both aerobic and anaerobic exercise induce ROS production from several sources (mitochondria, NADPH oxidases and xanthine oxidases); however, the exact mechanisms underlying exercise-induced oxidative stress remain undefined. Professional athletes show a high risk for oxidative stress, and consequently muscle injury or decreased performance. Based on this background, we investigated leukocyte redox homeostasis alterations during the soccer season in élite soccer players. Overall blood redox status was investigated in twenty-seven male soccer players from primary division (Italian "Serie A" team) at four critical time points during the soccer season: T0: just before the first team training session; T1: at the beginning of the season; T2: in the middle of the season and T3: at the end of the season. The main markers of muscular damage (CK, myoglobin, LDH), assessed by standard routine methods, are significantly altered at the considered time points (T0 vs T1 P < 0.01). In peripheral leukocyte subpopulations, ROS production shows significant alterations at the considered time points during the soccer season, and strictly and significantly correlates with CK values at every considered time point. Our experimental data indicate that deep redox homeostasis alterations are evident during the soccer season in élite soccer players, and that oxidative stress can be easily monitored, besides using the standard plasma biochemical parameters, by leukocyte ROS production analysis.

#7 Return to play after hamstring injuries in football (soccer): a worldwide Delphi procedure regarding definition, medical criteria and decision-making
Reference: Br J Sports Med. 2017 Mar 30. pii: bjsports-2016-097206. doi: 10.1136/bjsports-2016-097206. [Epub ahead of print]
Authors: van der Horst N, Backx F, Goedhart EA, Huisstede BM; HIPS-Delphi Group
Summary: There are three major questions about return to play (RTP) after hamstring injuries: How should RTP be defined? Which medical criteria should support the RTP decision? And who should make the RTP decision? The study aimed to provide a clear RTP definition and medical criteria for RTP and to clarify RTP consultation and responsibilities after hamstring injury. The study used the Delphi procedure. The results of a systematic review were used as a starting point for the Delphi procedure. Fifty-eight experts in the field of hamstring injury management selected by 28 FIFA Medical Centres of Excellence worldwide participated. Each Delphi round consisted of a questionnaire, an analysis and an anonymised feedback report. After four Delphi rounds, with more than 83% response for each round, consensus was achieved that RTP should be defined as 'the moment a player has received criteria-based medical clearance and is mentally ready for full availability for match selection and/or full training'. The experts reached consensus on the following criteria to support the RTP decision: medical staff clearance, absence of pain on palpation, absence of pain during strength and flexibility testing, absence of pain during/after functional testing, similar hamstring flexibility, performance on field testing, and psychological readiness. It was also agreed that RTP decisions should be based on shared decision-making, primarily via consultation with the athlete, sports physician, physiotherapist, fitness trainer and team coach. The consensus regarding aspects of RTP should provide clarity and facilitate the assessment of when RTP is appropriate after hamstring injury, so as to avoid or reduce the risk of injury recurrence because of a premature RTP.

#8 Repeated sprint ability is not enhanced by caffeine, arginine, and branched-chain amino acids in moderately trained soccer players
Reference: J Exerc Rehabil. 2017 Feb 28;13(1):55-61. doi: 10.12965/jer.1732722.361. eCollection 2017.
Authors: Ermolao A, Zanotto T, Carraro N, Fornasier T, Zaccaria M, Neunhaeuserer D, Bergamin M
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Summary: The aim was to investigate the effect of a dietary supplementation on the repeated sprint ability (RSA) performance in recreationally trained team sports athletes. Twelve young men underwent a RSA exercise protocol in five trials, in which participants ingested carbohydrates (CHO) plus caffeine (Caf), CHO plus arginine (Arg), CHO plus branched-chain amino acids (BCAA), CHO plus Caf, Arg, and BCAA (ALL), and CHO only. Heart rate, oxygen saturation, hematic lactate, ratings of perceived exertion, average sprint time, total time, best sprint time, peak power, and average power were taken. Data revealed no significant effects neither on physiological nor performance parameters with any of the supplements.

#9 Within Session Sequence of Balance and Plyometric Exercises Does Not Affect Training Adaptations with Youth Soccer Athletes
Reference: J Sports Sci Med. 2017 Mar 1;16(1):125-136. eCollection 2017.
Authors: Chaouachi M, Granacher U, Makhlouf I, Hammami R, Behm DG, Chaouachi A
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Summary: The integration of balance and plyometric training has been shown to provide significant improvements in sprint, jump, agility, and other performance measures in young athletes. It is not known if a specific within session balance and plyometric exercise sequence provides more effective training adaptations. The objective of the present study was to investigate the effects of using a sequence of alternating pairs of exercises versus a block (series) of all balance exercises followed by a block of plyometric exercises on components of physical fitness such as muscle strength, power, speed, agility, and balance. Twenty-six male adolescent soccer players (13.9 ± 0.3 years) participated in an 8-week training program that either alternated individual balance (e.g., exercises on unstable surfaces) and plyometric (e.g., jumps, hops, rebounds) exercises or performed a block of balance exercises prior to a block of plyometric exercises within each training session. Pre- and post-training measures included proxies of strength, power, agility, sprint, and balance such as countermovement jumps, isometric back and knee extension strength, standing long jump, 10 and 30-m sprints, agility, standing stork, and Y-balance tests. Both groups exhibited significant, generally large magnitude (effect sizes) training improvements for all measures with mean performance increases of approximately >30%. There were no significant differences between the training groups over time. The results demonstrate the effectiveness of combining balance and plyometric exercises within a training session on components of physical fitness with young adolescents. The improved performance outcomes were not significantly influenced by the within session exercise sequence.

#10 Comparison of Skillful vs. Less Skilled Young Soccer Players on Anthropometric, Maturation, Physical Fitness and Time of Practice
Reference: Int J Sports Med. 2017 Mar 24. doi: 10.1055/s-0042-122815. [Epub ahead of print]
Authors: Gouvea MA, Cyrino ES, Valente-Dos-Santos J, Ribeiro AS, Silva DR, Ohara D, Coelho-E-Silva MJ, Ronque ER
Summary: This study compared maturation, body composition and physical fitness between youth soccer athletes with different technical skills levels. Sixty-two young athletes (11-17 years) were categorized dichotomously in more skilled (n=31) and less skilled (n=31) groups based on 3 specific technical tests (Dribbling Speed Test [DST], Shuttle Dribble Test [SDT] and Slalom Dribble Test [SLDT]). Chronological and skeletal age, time of practice, body composition and 4 physical fitness tests were performed for comparisons. As expected, the 3 technical tests were correlated (r=0.47-0.54, P<0.05). More skilled subjects in DST and SDT showed (respectively) higher time of practice (effect size [ES]=0.72 and 0.90), and greater performance sit-ups (ES=1.23 and 0.81), squat jump (ES=1.10 and 1.08), countermovement jump (ES=1.11 and 1.10), and Yo-Yo test (ES=1.17 and 1.40) compared to the less skilled subjects (P<0.05). However, more skilled subjects in SLDT showed greater performance (P<0.05) only in the squat jump (ES=0.67) and Yo-Yo tests (ES=0.83). The results suggest that technical performance is associated with greater time of practice and some physical capabilities. Moreover, the DST and SDT tests seem to be good options to discriminate technical performance in youth soccer athletes.


#11 Preferred Hip Strategy During Landing Reduces Knee Abduction Moment In Collegiate Female Soccer Players
Reference: J Sport Rehabil. 2017 Mar 24:1-19. doi: 10.1123/jsr.2016-0026. [Epub ahead of print]
Authors: Nguyen AD, Taylor JB, Wimbish TG, Keith JL, Ford KR
Summary: Hip focused interventions are aimed to decrease frontal plane knee loading related to anterior cruciate ligament (ACL) injuries. Whether a preferred hip landing strategy decreases frontal plane knee loading is unknown. The objective was to determine if a preferred hip landing strategy during a drop vertical jump (DVJ) is utilized during a single leg landing (SLL) task and whether differences in frontal plane knee loading are consistent between a DVJ and a SLL task. Participants were dichotomized into a hip (HIP, n=9) or knee/ankle (KA, n=14) strategy group based on the percentage distribution of each lower extremity joint relative to the summated moment (% distribution) during the DVJ. Separate one-way ANOVAs examined the differences in joint specific % distribution and external knee abduction moment between the HIP and KA groups. The HIP group had significantly greater % distribution of hip moment and less % distribution of knee moment compared to the KA group during the DVJ and SLL. External knee abduction moment was also significantly less in the HIP group compared to the KA group during the DVJ. Female soccer athletes who land with a preferred hip strategy during a DVJ also land with a preferred hip strategy during a SLL. The preferred hip strategy also resulted in less external knee abduction moments during the DVJ.

#12 Effects of Bout Duration on Players' Internal and External Loads During Small-Sided Games in Young Soccer Players
Reference: Int J Sports Physiol Perform. 2017 Mar 24:1-23. doi: 10.1123/ijspp.2016-0584. [Epub ahead of print]
Authors: Koklu Y, Alemdaroglu U, Cihan H, Wong DP
Summary: This study investigated the effects of different bout durations on internal and external loads of young soccer players during different small-sided games (SSGs). Fifteen male young soccer players (average age 17 ± 1 years) participated in 2 vs 2, 3 vs 3 and 4 vs 4 SSGs. All games lasted 12 min playing time in total, but each SSG format further consisted of four bout durations: continuous (CON: 1 bout x 12 min) or interval with short (SBD: 6 bouts x 2 min), medium (MBD: 3 bouts x 4 min) or long (LBD: 2 bouts x 6 min) bout durations. During the SSGs, heart rate (HR) responses, and distance covered in different speed zones - walking, low-intensity, moderate-intensity and high-intensity running were measured. Rating of Perceived Exertion (RPE) and blood lactate (La-) were determined at the end of each SSG. The SBD format elicited significantly lower %HRmax responses compared to LBD and CON in all formats (p<0.05). The SBD format also showed significantly shorter distances covered in walking and greater distances covered in moderate-intensity running as well as significantly greater total distance covered compared to LBD and CON in all formats (p<0.05). In addition, LBD produced significantly lower La- and RPE responses than SBD and CON in all formats (p<0.05). These results suggest that coaches and sports scientists who want to achieve higher internal loads could use SBD and CON timing protocols, while those who want to achieve higher external loads might prefer to use SBD and MBD when planning to all SSG formats.


American Football

#1 The effect of repetitive subconcussive collisions on brain integrity in collegiate football players over a single football season: A multi-modal neuroimaging study
Reference: Neuroimage Clin. 2017 Mar 21;14:708-718. doi: 10.1016/j.nicl.2017.03.006. eCollection 2017
Authors: Slobounov SM, Walter A, Breiter HC, Zhu DC, Bai X, Bream T, Seidenberg P, Mao X, Johnson B, Talavage TM
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Summary: The cumulative effect of repetitive subconcussive collisions on the structural and functional integrity of the brain remains largely unknown. Athletes in collision sports, like football, experience a large number of impacts across a single season of play. The majority of these impacts, however, are generally overlooked, and their long-term consequences remain poorly understood. This study sought to examine the effects of repetitive collisions across a single competitive season in NCAA Football Bowl Subdivision athletes using advanced neuroimaging approaches. Players were evaluated before and after the season using multiple MRI sequences, including T1-weighted imaging, diffusion tensor imaging (DTI), arterial spin labeling (ASL), resting-state functional MRI (rs-fMRI), and susceptibility weighted imaging (SWI). While no significant differences were found between pre- and post-season for DTI metrics or cortical volumes, seed-based analysis of rs-fMRI revealed significant (p < 0.05) changes in functional connections to right isthmus of the cingulate cortex (ICC), left ICC, and left hippocampus. ASL data revealed significant (p < 0.05) increases in global cerebral blood flow (CBF), with a specific regional increase in right postcentral gyrus. SWI data revealed that 44% of the players exhibited outlier rates (p < 0.05) of regional decreases in SWI signal. Of key interest, athletes in whom changes in rs-fMRI, CBF and SWI were observed were more likely to have experienced high G impacts on a daily basis. These findings are indicative of potential pathophysiological changes in brain integrity arising from only a single season of participation in the NCAA Football Bowl Subdivision, even in the absence of clinical symptoms or a diagnosis of concussion. Whether these changes reflect compensatory adaptation to cumulative head impacts or more lasting alteration of brain integrity remains to be further explored.

#2 Changes in Creatine Kinase and Hormones over the Course of an American Football Season
Reference: J Strength Cond Res. 2017 Apr 4. doi: 10.1519/JSC.0000000000001920. [Epub ahead of print]
Authors: Stone JD, Kreutzer A, Mata JD, Nystrom MG, Jagim AR, Jones MT, Oliver JM.
Summary: The purpose of this study was to examine changes in creatine kinase and hormones over the course of an entire season of American football. A secondary purpose was to determine differences between starters and non-starters. Fasting blood samples were obtained from nineteen National Collegiate Athletic Association Division I (n = 19; 20 ± 1 years) football athletes over the course of a season beginning prior to the start of summer off-season conditioning (T1), before (T2) and after pre-season (T3) football camp, with remaining samples taken throughout the competitive season (T4-T8). A magnitude-based inference approach was used to define outcomes. Testosterone was higher in starters prior to the start of the season (T1, Effect Size [ES] = 0.8) and during pre-conference (T4; ES = 0.7). Post-Camp (T3) testosterone was lower in all players, though greater in starters (starters, 0.0%/0.3%/99.7%; non-starters, 0.2%/2.9%/96.9%). An increase cortisol relative to baseline (T1) was observed in starters early in season (T4, ES = 0.7; T5, ES = 0.5). Creatine kinase was elevated at all time-points in all athletes, with starters having higher circulating levels throughout season. These data demonstrate that changes in hormonal markers may be experienced over a season of football and differ by playing status. Differences between starters and non-starters may be indicative of greater damage and stress experienced by starters, which may result from a greater number of repetitions.

#3 Influence of Glenoid Defect Size and Bone Fragment Size on the Clinical Outcome After Arthroscopic Bankart Repair in Male Collision/Contact Athletes
Reference: Am J Sports Med. 2017 Apr 1:363546517700864. doi: 10.1177/0363546517700864. [Epub ahead of print]
Authors: Nakagawa S, Mae T, Yoneda K, Kinugasa K, Nakamura H
Summary: The usefulness of arthroscopic Bankart repair for collision/contact athletes has varied in previous reports. The purpose of the study was to investigate the influence of glenoid rim morphologic characteristics on the clinical outcome after arthroscopic Bankart repair without additional reinforcement procedures in male collision/contact athletes, including athletes with a large glenoid defect. Eighty-six athletes (93 shoulders) followed for a minimum of 2 years were retrospectively investigated. The sports were rugby (36 shoulders), American football (29 shoulders), and other collision/contact sports (28 shoulders). Preoperative glenoid defect size, bone fragment size, and bone union after bony Bankart repair were investigated regarding factors influencing postoperative recurrence. Postoperative changes in glenoid defect size and bone fragment size were investigated as well as their influence on the clinical outcome. Postoperative recurrence of instability was noted in 22 shoulders (23.7%). The recurrence rate was 33.3% in rugby, 17.2% in American football, and 17.9% in other collision/contact sports. The recurrence rate was only 7.1% in 28 shoulders without a preoperative glenoid defect, but it increased to 43.8% in 16 shoulders that did not have a bone fragment even though there was a preoperative glenoid defect. Additionally, the recurrence rate was 7.7% in 26 shoulders with bone union after arthroscopic bony Bankart repair but rose to 45% in 20 shoulders without bone union. In the shoulders with bone union, the mean bone fragment size increased from 8.2% preoperatively to 15.2% postoperatively, while the mean glenoid defect size decreased from 18.0% to 2.8%, respectively. The recurrence rate was 8.3% in shoulders with a final glenoid defect 5% or less versus 38.1% in shoulders with a defect greater than 5%. While the recurrence rate was low among athletes other than rugby players with a final defect of 10% or less, it was low in only the rugby players with a defect of 0%. In male collision/contact athletes, while the overall clinical outcome was unsatisfactory, a favorable outcome was achieved in athletes without a preoperative glenoid defect and athletes with bone union. The glenoid defect decreased in size postoperatively due to remodeling of the united bone fragment, and the recurrence rate was low when the final glenoid defect size was 5% or less.

#4 Epidemiology of Knee Sprains in Youth, High School, and Collegiate American Football Players
Reference: J Athl Train. 2017 Apr 17. doi: 10.4085/1062-6050-52.3.09. [Epub ahead of print]
Authors: Clifton DR, Onate JA, Schussler E, Djoko A, Dompier TP, Kerr ZY
Summary: Variations in knee-sprain incidence among competition levels are unclear but may help inform prevention strategies in American football players. The purpose of the study was to describe the epidemiology of knee sprains in youth, high school, and collegiate football players. Injury and athlete-exposure (AE) data were collected from 3 injury-surveillance programs at the youth, high school, and collegiate competition levels. Data from 310 youth, 184 high school, and 71 collegiate football team-seasons were collected during the 2012 through 2014 seasons. Knee-sprain rates and risks were calculated for each competition level. Injury rate ratios (IRRs) and risk ratios (RRs) compared knee-sprain rates by competition level. Injury proportion ratios (IPRs) compared differences in surgery needs, recurrence, injury mechanism, and injury activity by competition level. Knee-sprain rates in youth, high school, and collegiate football were 0.16/1000 AEs, 0.25/1000 AEs, and 0.69/1000 AEs, respectively. Knee-sprain rates increased as the competition level increased (high school versus youth: IRR = 1.60; 95% confidence interval [CI] = 1.12, 2.30; collegiate versus high school: IRR = 2.73; 95% CI = 2.38, 3.96). Knee-sprain risk was highest in collegiate (4.3%), followed by high school (2.0%) and youth (0.5%) athletes. Knee-sprain risk increased as the competition level increased (high school versus youth: RR = 3.73; 95% CI = 2.60, 5.34; collegiate versus high school: RR = 2.14; 95% CI = 1.83, 2.51). Collegiate football had the lowest proportion of knee sprains that were noncontact injuries (collegiate versus youth: IPR = 0.54; 95% CI = 0.31, 0.95; collegiate versus high school: IPR = 0.59; 95% CI = 0.44, 0.79) and the lowest proportion that occurred while being tackled (collegiate versus youth: IPR = 0.44; 95% CI = 0.26, 0.76; collegiate versus high school: IPR = 0.71; 95% CI = 0.51, 0.98). Knee-sprain incidence was highest in collegiate football. However, level-specific variations in the distributions of knee sprains by injury activity may highlight the need to develop level-specific policies and prevention strategies that ensure safe sports play.

#5 Long-Term Cognitive and Neuropsychiatric Consequences of Repetitive Concussion and Head-Impact Exposure
Reference: J Athl Train. 2017 Mar;52(3):309-317. doi: 10.4085/1062-6050-52.1.14.
Authors: McAllister T, McCrea M
Summary: Initially, interest in sport-related concussion arose from the premise that the study of athletes engaged in sports associated with high rates of concussion could provide insight into the mechanisms, phenomenology, and recovery from mild traumatic brain injury. Over the last decade, concerns have focused on the possibility that, for some athletes, repetitive concussions may raise the long-term risk for cognitive decline, neurobehavioral changes, and neurodegenerative disease. First conceptualized as a discrete event with variable recovery trajectories, concussion is now viewed by some as a trigger of neurobiological events that may influence neurobehavioral function over the course of the life span. Furthermore, advances in technology now permit us to gain a detailed understanding of the frequency and intensity of repetitive head impacts associated with contact sports (eg, football, ice hockey). Helmet-based sensors can be used to characterize the kinematic features of concussive impacts, as well as the profiles of typical head-impact exposures experienced by athletes in routine sport participation. Many large-magnitude impacts are not associated with diagnosed concussions, whereas many diagnosed concussions are associated with more modest impacts. Therefore, a full understanding of this topic requires attention to not only the effects of repetitive concussions but also overall exposure to repetitive head impacts. This article is a review of the current state of the science on the long-term neurocognitive and neurobehavioral effects of repetitive concussion and head-impact exposure in contact sports.


Australian football

#1 Competition Sleep Is Not Compromised Compared To Habitual In Elite Australian Footballers
Reference: Int J Sports Physiol Perform. 2017 Apr 19:1-23. doi: 10.1123/ijspp.2016-0776. [Epub ahead of print]
Authors: Lalor BJ, Halson SL, Tran J, Kemp JG, Cormack SJ
Summary: The purpose was to assess the impact of match start time and days relative to match compared to the habitual sleep characteristics of elite Australian Football (AF) players. 45 elite male AF players were assessed during the pre-season (habitual) and across four home matches during the season. Players wore an activity monitor the night before (-1), night of (0), one night after (+1), and two nights (+2) after each match and completed a self-reported rating of sleep quality. A two-way ANOVA with Tukey's post hoc was used to determine differences in sleep characteristics between match start times and days relative to the match. Two-way nested ANOVA was conducted to examine differences between competition and habitual phases. The Effect size ± 90% confidence interval (ES ± 90% CI) was calculated to quantify the magnitude of pairwise differences. Differences observed in sleep onset latency (ES=0.11 ± 0.16), sleep rating (ES=0.08 ± 0.14) and sleep duration (ES=0.08 ± 0.01) between competition and habitual periods were trivial. Sleep efficiency (%) was almost certainly higher during competition than habitual, however this was not reflected in the subjective rating of sleep quality. Elite AF competition does not cause substantial disruption to sleep characteristics compared to habitual sleep. Whilst match start time has some impact on sleep variables, it appears that the match itself is more of a disruption than the start time. Subjective ratings of sleep from well-being questionnaires appear limited in their ability to accurately provide an indication of sleep quality.

#2 The association between fundamental athletic movements and physical fitness in elite junior Australian footballers
Reference: J Sports Sci. 2017 Apr 13:1-6. doi: 10.1080/02640414.2017.1313996. [Epub ahead of print]
Authors: Woods CT, McKeown I, Keogh J, Robertson S
Summary: This study investigated the associations between fundamental athletic movement and physical fitness in junior Australian football (AF). Forty-four under 18 players performed a fundamental athletic movement assessment consisting of an overhead squat, double lunge, single leg Romanian deadlift and a push up. Movements were scored on three assessment criterions using a three-point scale. Additionally, participants performed five physical fitness tests commonly used for talent identification in AF. A Spearman's nonparametric correlation matrix was built, with correlation coefficients being visualised using a circularly rendered correlogram. Score on the overhead squat was moderately positively associated with dynamic vertical jump height on left (rs = 0.40; P ≤ 0.05) and right (rs = 0.30; P ≤ 0.05) leg take-off, stationary vertical jump (rs = 0.32; P ≤ 0.05) and negatively associated with 20-m sprint time (rs = -0.35; P ≤ 0.05). Score on the double lunge (left/right side) was moderately positively associated with the same physical fitness tests as well as score on the multistage fitness test. Results suggest that improvements in physical fitness qualities may occur through concurrent increases in fundamental athletic movement skill, namely the overhead squat and double lunge movements. These findings may assist with the identification and development of talent.





Latest research in football - week 13 - 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 The effects of menstrual cycle phase on physical performance in female soccer players

Reference: PLoS One. 2017 Mar 13;12(3):e0173951. doi: 10.1371/journal.pone.0173951. eCollection 2017.

Authors: Julian R, Hecksteden A, Fullagar HH, Meyer T

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Summary: Female soccer has grown extensively in recent years, however differences in gender-specific physiology have rarely been considered. The female reproductive hormones which rise and fall throughout the menstrual cycle, are known to affect numerous cardiovascular, respiratory, thermoregulatory and metabolic parameters, which in turn, may have implications on exercise physiology and soccer performance. Therefore, the main aim of the present study was to investigate potential effects of menstrual cycle phase on performance in soccer specific tests. Nine sub elite female soccer players, all of whom have menstrual cycles of physiological length; performed a series of physical performance tests (Yo-Yo Intermittent endurance test (Yo-Yo IET), counter movement jump (CMJ) and 3x30 m sprints). These were conducted at distinct time points during two main phases of the menstrual cycle (early follicular phase (FP) and mid luteal phase (LP)) where hormones contrasted at their greatest magnitude. Yo-Yo IET performance was considerably lower during the mid LP (2833±896 m) as compared to the early FP (3288±800 m). A trend towards significance was observed (p = 0.07) and the magnitude based inferences suggested probabilities of 0/61/39 for superiority/equality/inferiority of performance during the mid LP, leading to the inference of a possibly harmful effect. For CMJ (early FP, 20.0±3.9 cm; mid LP 29.6±3.0 cm, p = 0.33) and sprint (early FP, 4.7±0.1 s; mid LP, 4.7±0.1 s, p = 0.96) performances the results were unclear (8/24/68, 48/0/52, respectively). The results of this study are in support of a reduction in maximal endurance performance during the mid LP of the menstrual cycle. However, the same effect was not observed for jumping and sprint performance. Therefore, consideration of cycle phase when monitoring a player's endurance capacity may be worthwhile.



#2 A low-dose, 6-week bovine colostrum supplementation maintains performance and attenuates inflammatory indices following a Loughborough Intermittent Shuttle Test in soccer players

Reference: Eur J Nutr. 2017 Mar 11. doi: 10.1007/s00394-017-1401-7. [Epub ahead of print]

Authors: Kotsis Y, Mikellidi A, Aresti C, Persia E, Sotiropoulos A, Panagiotakos DB, Antonopoulou S, Nomikos T

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 Summary: The aim of the study was to investigate the effect of a 6-week, low-dose bovine colostrum (BC) supplementation on exercise-induced muscle damage (EIMD) and performance decline in soccer players following the Loughborough Intermittent Shuttle Test (LIST) during a competitive season period. In a double-blind, randomized, placebo-controlled design, two groups of soccer players were allocated to a 3.2 g/day of whey protein (WP, N=8) or BC (N=10) and performed a pre- and a post-supplementation LIST. Maximum isometric voluntary contraction, squat jump (SQJ), countermovement jump, muscle soreness, blood cell counts, creatine kinase (CK), C-reactive protein (CRP) and interleukin-6 (IL-6) were monitored for 2, 24, 48, 72 h post-LIST. LIST induced transient increases in leukocytes, granulocytes, CK, muscle soreness, CRP, IL-6 and declines in lymphocytes and performance indices. Supplementation resulted in a faster recovery of SQJ, CK and CRP compared to pre-supplementation kinetics (trial × time: p=0.001, 0.056, 0.014, respectively) and lower incremental area under the curve (iAUC) for IL-6, only in the BC group [pre-: 31.1 (6.78-46.9), post-: 14.0 (-0.16 to 23.5) pg h/ml, p=0.034]. Direct comparison of the two groups after supplementation demonstrated higher iAUC of SQJ [WP: -195.2 (-229.0 to (-52.5)), BC: -15.8 (-93.2 to 16.8) cm h, p=0.034], a trend for lower iAUC of CK in the BC group [WP: 18,785 (4651-41,357), BC: 8842 (4807-14,802) U h/L, p=0.081] and a significant intervention × time interaction for CRP (p=0.038) in favor of BC. Post-exercise EIMD may be reduced and performance better maintained by a low dose of BC administration following LIST in soccer players.



#3 Developing Evidence for Football (Soccer) Reminiscence Interventions Within Long-term Care: A Co-operative Approach Applied in Scotland and Spain

Reference: J Am Med Dir Assoc. 2017 Apr 1;18(4):355-360. doi: 10.1016/j.jamda.2017.01.013. Epub 2017 Mar 7.

Authors: Coll-Planas L, Watchman K, Domenech S, McGillivray D, O'Donnell H, Tolson D

Summary: Loneliness is a common experience within long-term care and, to promote well-being and quality of life among people with dementia, it is important to draw upon a repertoire of strategies that provide social stimulation, companionship, and enjoyment. This paper describes and reflects on a program of co-operative social participatory research that sought to introduce football-focused (ie, soccer-based) reminiscence based in 4 community settings within Spain and Scotland. Findings are reported and inform an original conceptual model that supports the introduction of sustainable approaches to the development of football-focused reminiscence with and for people with dementia.



#4 Kinesio taping does not alter muscle torque, muscle activity or jumping performance in professional soccer players: A randomized, placebo-controlled, blind, clinical trial

Reference: J Back Musculoskelet Rehabil. 2017 Mar 3. doi: 10.3233/BMR-160556. [Epub ahead of print]

Authors: Dos Santos Gloria IP, de Oliveira Gonzalez T, de Oliveira Gonzalez T, Junior EC, de Paula Gomes CA, Herpich CM, Antonialli FC, Serenza F, de Souza Calheira L, Arruda EE, Lucareli PR, Biasotto-Gonzalez DA

 Summary: Kinesio taping consists of the attachment of a thin elastic tape over specific muscles, the thickness of which is similar to that of the epidermis. The aim of the present study was to compare the effect of Kinesio taping and placebo taping on muscle torque, muscle activity and jumping performance soccer players.Thirty athletes were randomly allocated to two groups (Group A: Kinesio taping and Group B: placebo taping). The participants were instructed to perform the Hop test's and were submitted to an isokinetic evaluation of the knee extensors as well as an electromyographic evaluation of the retus femoris muscle of the dominant lower limb. Next, Kinesio taping was performed for the activation of the rectus femoris muscle in Group A and placebo taping was performed in Group B. The participants were reevaluated 30 minutes after taping and 24 hours after the first evaluation using the same tests. Intra-group and inter-group comparisons were made considering the three evaluation times. No statistically significant differences were found between groups at any evaluation time regarding the Hop test's, root mean square of the electromyographic signal or peak torque of the knee extensors of the dominant lower limb (p>0.05). Kinesio taping for the activation of the rectus femoris muscle has no effect on peak muscle torque, muscle activity or jumping performance among soccer players.



#5 Changes of the psychophysical state and feeling of wellness of professional soccer players during pre-season and in-season periods

Reference: Res Sports Med. 2016 Oct-Dec;24(4):375-386. Epub 2016 Aug 30.

Authors: Fessi MS, Nouira S, Dellal A, Owen A, Elloumi M, Moalla W

Summary: Perceived changes due to training monotony, strain, sleep, stress, fatigue, muscle soreness and the influence of specific training sessions on the affective valence were explored in professional soccer players. Seventeen players completed the Hooper questionnaire, the ratings of perceived exertion and feeling scale (FS) every training/match day before and during the soccer season. Higher players' training loads were recorded during pre-season when compared with in-season period (2558.1 ± 262.4 vs. 1642.8 ± 169.3 a.u., p < 0.01; respectively). The ratings of sleep, stress, fatigue and muscle soreness in pre-season were higher than those observed during in-season (p < 0.01) whereas the feeling score was lower (p < 0.01). Furthermore, training sessions, including technical/tactical work, induced an improved feeling score but linked with a lower training load when compared with sessions focus on physical emphasis (p < 0.01). Pre-season period of training induces a significantly more strenuous and exhausting demands on professional soccer players compared with the in-season period at the elite level.



#6 Longitudinal changes in linguistic complexity among professional football players

Reference: Brain Lang. 2017 Mar 16;169:57-63. doi: 10.1016/j.bandl.2017.02.003. [Epub ahead of print]

Authors: Berisha V, Wang S, LaCross A, Liss J, Garcia-Filion P

Summary: Reductions in spoken language complexity have been associated with the onset of various neurological disorders. The objective of this study is to analyze whether similar trends are found in professional football players who are at risk for chronic traumatic encephalopathy. We compare changes in linguistic complexity (as indexed by the type-to-token ratio and lexical density) measured from the interview transcripts of players in the National Football League (NFL) to those measured from interview transcripts of coaches and/or front-office NFL executives who have never played professional football. A multilevel mixed model analysis reveals that exposure to the high-impact sport (vs no exposure) was associated with an overall decline in language complexity scores over time. This trend persists even after controlling for age as a potential confound. The results set the stage for a prospective study to test the hypothesis that language complexity decline is a harbinger of chronic traumatic encephalopathy.



#7 Safety regulation in professional football: Empirical evidence of intended and unintended consequences

Reference: J Health Econ. 2017 Jan 29;53:87-99. doi: 10.1016/j.jhealeco.2017.01.004. [Epub ahead of print]

Authors: Hanson A, Jolly NA, Peterson J

Summary: In response to increasing public awareness and negative long-term health effects of concussions, the National Football League implemented the "Crown-of-the-Helmet Rule" (CHR). The CHR imposes penalties on players who initiate contact using the top of the helmet. This paper examines the intended effect of this policy and its potential for unintended consequences. We find evidence supporting the intended effect of the policy- a reduction in weekly concussion reports among defensive players by as much as 32% (34% for all head and neck injuries), but also evidence of an increase in weekly lower extremity injury reports for offensive players by as much as 34%.



#8 Walking football as sustainable exercise for older adults - A pilot investigation

Reference: Eur J Sport Sci. 2017 Mar 19:1-8. doi: 10.1080/17461391.2017.1298671. [Epub ahead of print]

Authors: Reddy P, Dias I, Holland C, Campbell N, Nagar I, Connolly L, Krustrup P, Hubball H

Summary: The health benefits of playing football and the importance of exercise and social contact for healthy ageing are well established, but few older adults in the UK take enough exercise. Football is popular, flexible in format and draws players into engrossing, effortful and social exercise, but the physical demands of play at full speed may make it unsustainable for some older adults. Restricted to walking pace, will play still be engaging? Will health benefits be retained? Will physical demands remain manageable? This pilot study aims to investigate: (1) the experience of older adults playing walking football every week, is it sustainable and rewarding, (2) the intensity and locomotor pattern of walking football, (3) the scale and nature of walking football health benefits and (4) possible cognitive benefits of playing walking football through measures of processing speed, selective and divided attention and updating and inhibition components of executive function.
 'Walking football' and 'waiting list' groups were compared before and after 12 weeks of one-hour per week football. Walking football was found to be engaging, sustainable for older adults and moderately intensive; however, selective health and cognitive benefits were not found from this brief intervention.



#9 Evaluating erroneous offside calls in soccer

Reference: PLoS One. 2017 Mar 23;12(3):e0174358. doi: 10.1371/journal.pone.0174358. eCollection 2017.

Authors: Huttermann S, Noel B, Memmert D

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Summary: The ability to simultaneously attend to multiple objects declines with increases in the visual angle separating distant objects. We explored whether these laboratory-measured limits on visual attentional spread generalize to a real life context: offside calls by soccer assistant referees. We coded all offside calls from a full year of first division German soccer matches. By determining the x-y coordinates of the relevant players and assistant referee on the soccer field we were able to calculate how far assistant referees had to spread their visual attention to perform well. Counterintuitively, assistant referees made fewer errors when they were farther away from the action due to an advantageous (smaller) visual angle on the game action. The pattern held even when we accounted for individual differences in a laboratory-based attentional spread measure of ten of the assistant referees. Our finding that errors are linked to smaller visual angles may explain the complaints of fans in some situations: Those seated directly behind the assistant referee, further from the players, might actually have it easier to make the right call because the relevant players would form a smaller visual angle.



#10 The Effect of Standard Strength vs. Contrast Strength Training on the Development of Sprint, Agility, Repeated Change of Direction, and Jump in Junior Male Soccer Players

Reference: J Strength Cond Res. 2017 Apr;31(4):901-912. doi: 10.1519/JSC.0000000000001815.

Authors: Hammami M, Negra Y, Shephard RJ, Chelly MS

Summary: The aim was to compare the impact of 2 differing strength training (ST) programs on the athletic performance of junior male soccer players at a critical phase during their competitive season. Participants aged 16.0 ± 0.5 years were randomly assigned between control (C, n = 12), standard ST (n = 16), and contrast strength training (CST, n = 16), each performed twice a week. Athletic performance was assessed before and after the intervention using 8 tests: 40-m sprint, 4 × 5-m sprint (S4 × 5), 9-3-6-3-9 m sprint with 180° turns (S180°), 9-3-6-3-9 m sprint with backward and forward running (SBF), repeated shuttle sprint ability (RSSA), repeated change of direction (RCOD), squat jump (SJ), and countermovement jump (CMJ). The control group's (CG) performance tended to improve in some tests and decrease in others, but these changes were not statistically significant. Both training programs enhanced all sprint performances relative to controls (p ≤ 0.05). The strength training group (SG) and the CST group (CSG) increased significantly in S180°, SBF, and S4 × 5 relative to CG, although the S4 × 5 also increased in CSG relative to SG (p ≤ 0.05). No intergroup difference of RSSA performance was observed. The RCOD parameters increased significantly in CSG relative to both SG and CG (p ≤ 0.05). The SJ and CMJ height increased significantly in both experimental groups (p < 0.000). We conclude that during the competitive season, some measures of athletic performance in male soccer players were increased more by 8 weeks of CST than by ST.



#11 Beetroot Juice Supplementation Improves High-Intensity Intermittent Type Exercise Performance in Trained Soccer Players

Reference: Nutrients. 2017 Mar 22;9(3). pii: E314. doi: 10.3390/nu9030314.

Authors: Nyakayiru J, Jonvik KL, Trommelen J, Pinckaers PJ, Senden JM, van Loon LJ, Verdijk LB

Summary: It has been shown that nitrate supplementation can enhance endurance exercise performance. Recent work suggests that nitrate ingestion can also increase intermittent type exercise performance in recreational athletes. We hypothesized that six days of nitrate supplementation can improve high-intensity intermittent type exercise performance in trained soccer players. Thirty-two male soccer players (age: 23 ± 1 years, height: 181 ± 1 m, weight: 77 ± 1 kg, playing experience: 15.2 ± 0.5 years, playing in the first team of a 2nd or 3rd Dutch amateur league club) participated in this randomized, double-blind cross-over study. All subjects participated in two test days in which high-intensity intermittent running performance was assessed using the Yo-Yo IR1 test. Subjects ingested nitrate-rich (140 mL; ~800 mg nitrate/day; BR) or a nitrate-depleted beetroot juice (PLA) for six subsequent days, with at least eight days of wash-out between trials. The distance covered during the Yo-Yo IR1 was the primary outcome measure, while heart rate (HR) was measured continuously throughout the test, and a single blood and saliva sample were collected just prior to the test. Six days of BR ingestion increased plasma and salivary nitrate and nitrite concentrations in comparison to PLA (p < 0.001), and enhanced Yo-Yo IR1 test performance by 3.4 ± 1.3% (from 1574 ± 47 to 1623 ± 48 m; p = 0.027). Mean HR was lower in the BR (172 ± 2) vs. PLA trial (175 ± 2; p = 0.014). Six days of BR ingestion effectively improves high-intensity intermittent type exercise performance in trained soccer players.






Borussia Dortmund UEFA Champions League Pre-Match Warm-Up

Due to a good friend I was able to visit the UEFA Champions league match of Borussia Dortmund against AS Monaco.


Unfortunately, and due to the bomb-attacks on the team bus I had to travel to the Signal-Iduna-Park at Dortmund twice.


Despite (and probably especially due) the terrible incidents the day before, the BVB fans tried to have a "normal" CL game and pushed their team the entire game.



The stadium was sold out and AS Monaco won the game.



As usual when visiting a football match, I filmed the warm-up of both teams and the one of Borussia Dortmund can be seen below.






Latest research in football - week 12 - 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 Pneumomediastinum in a College-Aged Soccer Player: A Case Report
Reference: Curr Sports Med Rep. 2017 Mar/Apr;16(2):71-73. doi: 10.1249/JSR.0000000000000338.
Authors: Zarandy E, Counts S, Clemow C.
Download link:|ExpireAbsolute;source|Journals;ttl|1489387698829;payload|mY8D3u1TCCsNvP5E421JYK6N6XICDamxByyYpaNzk7FKjTaa1Yz22MivkHZqjGP4kdS2v0J76WGAnHACH69s21Csk0OpQi3YbjEMdSoz2UhVybFqQxA7lKwSUlA502zQZr96TQRwhVlocEp/sJ586aVbcBFlltKNKo+tbuMfL73hiPqJliudqs17cHeLcLbV/CqjlP3IO0jGHlHQtJWcICDdAyGJMnpi6RlbEJaRheGeh5z5uvqz3FLHgPKVXJzdtavZhyL1R7GZ07U38xM5S/usr4L5LXmcxbNZRxgtepo=;hash|fhHlEk29gZDjZAC0saV15A==

#2 Proximal Neuromuscular Control Protects Against Hamstring Injuries in Male Soccer Players
Reference: Am J Sports Med. 2017 Mar 1:363546516687750. doi: 10.1177/0363546516687750. [Epub ahead of print]
Authors: Schuermans J, Danneels L, Van Tiggelen D, Palmans T, Witvrouw E
Summary: With their unremittingly high incidence rate and detrimental functional repercussions, hamstring injuries remain a substantial problem in male soccer. Proximal neuromuscular control ("core stability") is considered to be of key importance in primary and secondary hamstring injury prevention, although scientific evidence and insights on the exact nature of the core-hamstring association are nonexistent at present. The authors hypothesize that the muscle activation pattern throughout the running cycle would not differ between participants based on injury occurrence during follow-up. Sixty amateur soccer players participated in a multimuscle surface electromyography (sEMG) assessment during maximal acceleration to full-speed sprinting. Subsequently, hamstring injury occurrence was registered during a 1.5-season follow-up period. Hamstring, gluteal, and trunk muscle activity time series during the airborne and stance phases of acceleration were evaluated and statistically explored for a possible causal association with injury occurrence and absence from sport during follow-up. Players who did not experience a hamstring injury during follow-up had significantly higher amounts of gluteal muscle activity during the front swing phase ( P = .027) and higher amounts of trunk muscle activity during the backswing phase of sprinting ( P = .042). In particular, the risk of sustaining a hamstring injury during follow-up lowered by 20% and 6%, with a 10% increment in normalized muscle activity of the gluteus maximus during the front swing and the trunk muscles during the backswing, respectively ( P < .024). Muscle activity of the core unit during explosive running appeared to be associated with hamstring injury occurrence in male soccer players. Higher amounts of gluteal and trunk muscle activity during the airborne phases of sprinting were associated with a lower risk of hamstring injuries during follow-up. Hence, the present results provide a basis for improved, evidence-based rehabilitation and prevention, particularly focusing on increasing neuromuscular control of the gluteal and trunk muscles during sport-specific activities (eg, sprint drills, agility drills).

#3 Who runs the fastest? Anthropometric and physiological correlates of 20 m sprint performance in male soccer players
Reference: Res Sports Med. 2016 Oct-Dec;24(4):341-351. Epub 2016 Aug 22.
Authors: Nikolaidis PT, Ruano MA, de Oliveira NC, Portes LA, Freiwald J, Lepretre PM, Knechtle B
Summary: The aim of the present study was to examine the relationship of 20 m sprint performance with anthropometrical and physiological parameters in male soccer players. A hundred and 81 soccer players from the region of Athens (age 23.4 ± 5.0 yrs, body mass 73.4 ± 7.7 kg, height 180.0 ± 5.9 cm, body fat (BF) 14.4 ± 3.6%), classified into quartiles according to 20 m sprint time (group A, 2.84-3.03 s; group B, 3.04-3.09 s; group C, 3.10-3.18 s; group D, 3.19-3.61 s), participated. Soccer players in group A were younger and had better performance in vertical jumps and in the Wingate anaerobic test (WAnT, p < 0.05). Sprint time correlated to age (r = 0.27), body mass (r = 0.23), body height (r = 0.20), BF (r = 0.23), vertical jumps (-0.58 ≤ r ≤ -0.50) and the WAnT (-0.45 ≤ r ≤ -0.30, p < 0.05). In summary, the magnitude of correlations of sprint time with measures of lower limbs muscle strength and power (WAnT and jumps) was larger than with anthropometric measures (body mass and BF).

#4 The specificity of the Loughborough Intermittent Shuttle Test for recreational soccer players is independent of their intermittent running ability
Reference: Res Sports Med. 2016 Oct-Dec;24(4):363-374. Epub 2016 Aug 22.
Authors: Coratella G, Beato M, Schena F
Summary: The aim of the present study was to evaluate whether or not recreational soccer players (SP) and non-soccer players (non-SP) with similar intermittent-running ability had similar physiological responses to a soccer match-simulation protocol. Twenty-two recreational SP and 19 fitness-matched non-SP participated. Yo-Yo level 1 assessed intermittent-running ability, while the Loughborough Intermittent Shuttle Test served as soccer match-simulation protocol. Heart rate (HR), blood lactate concentration [La-] and rating of perceived exertion (RPE) were recorded after each bout (1-5, plus an exhaustive task). SP had lower HR after the third, fourth and fifth bout, compared to non-SP. Similarly, SP had lower [La-] after the third, fourth and the fifth bout. SP also had lower RPE after the third, fourth and fifth bout. The appropriateness of intermittent-running ability as the main determinant of physical performance in SP was questioned.

#5 Effects of horizontal plyometric training volume on soccer players' performance
Reference: Res Sports Med. 2016 Oct-Dec;24(4):308-319. Epub 2016 Aug 22.
Authors: Yanci J, Los Arcos A, Camara J, Castillo D, García A, Castagna C
Summary: The aim of this study was to examine the dose response effect of strength and conditioning programmes, involving horizontally oriented plyometric exercises, on relevant soccer performance variables. Sixteen soccer players were randomly allocated to two 6-week plyometric training groups (G1 and G2) differing by imposed (twice a week) training volume. Post-training G1 (4.13%; d = 0.43) and G2 (2.45%; d = 0.53) moderately improved their horizontal countermovement jump performance. Significant between-group differences (p < 0.01) in the vertical countermovement jump for force production time (T2) were detected post-training. No significant and practical (p > 0.05, d = trivial or small) post-training improvements in sprint, change of direction ability (CODA) and horizontal arm swing countermovement jump were reported in either group. Horizontal plyometric training was effective in promoting improvement in injury prevention variables. Doubling the volume of a horizontal plyometric training protocol was shown to have no additional effect over functional aspects of soccer players' performance.

#6 The effect of slope on repeated sprint ability in young soccer players
Reference: Res Sports Med. 2016 Oct-Dec;24(4):320-330. Epub 2016 Aug 18.
Authors: Padulo J, Ardigo LP, Attene G, Cava C, Wong DP, Chamari K, Migliaccio GM
Summary: This study aimed to describe a gradient repeated sprint ability (RSA) test in comparison with a standard level one by investigating performance, metabolic demand and muscular jumping performance as a proxy for running mechanics. Eighteen athletes performed two level RSA tests (40 m × 6) - for reliability evaluation - and one ±5% gradient RSA test, second leg downhill (RSAgrad). Rating of perceived exertion (RPE), blood lactate concentration (BLa) concentration, vertical jump heights were assessed as well. Level test measures resulted highly reliable (Intra-class correlation coefficient (ICC) ≥0.96). RSAgrad worsened only first sprints' performance (-2%) but not overall test performance (~45 s). RSAgrad resulted to be less deteriorating in terms of fatigue index (FI) (-36%), BLa (-23%), RPE (-11%), jumping performance (RSAgrad post-/pre-squat jump, countermovement jump heights (CMJh): -3%, -6%, respectively). RSAgrad could be used to diversify common training protocol without stressing excessively athletes' current metabolic-anaerobic capacity. Such physical conditioning procedures could improve acceleration/braking capability.

#7 Physical and technical performances are not associated with tactical prominence in U14 soccer matches
Reference: Res Sports Med. 2016 Oct-Dec;24(4):352-362. Epub 2016 Aug 17.
Authors: Clemente FM, Figueiredo AJ, Martins FM, Mendes RS, Wong DP
Summary: The aim of this study was to analyse the association between physical/technical variables and the tactical prominence variables in U14 soccer matches. Twenty-two young amateur soccer players (13.5 [Formula: see text] 0.5 years old, 5.4 [Formula: see text] 0.5 years of practice, 163.3 [Formula: see text] 9.8 cm in body height) from two teams of the Portuguese regional league volunteered for the study. Our results showed positive and moderate correlation between dribbling test and betweenness centrality (r = 0.324; p = 0.142), and negative moderate correlation between %fatigue index and betweenness centrality (r = -0.390; p = 0.073). Physical and technical variables had no statistical differences among tactical positions. Nevertheless, when tactical prominence of players from four tactical positions were compared, significant differences were found in terms of degree prestige (p = 0.001) and degree centrality (p = 0.002). This pilot study did not find strong correlations between physical/technical levels and tactical prominence in soccer matches.

#8 Predicting football injuries using size and ratio of the multifidus and quadratus lumborum muscles
Reference: Scand J Med Sci Sports. 2017 Apr;27(4):440-447. doi: 10.1111/sms.12643.
Authors: Hides JA, Stanton WR
Summary: Deficits in muscles of the lumbo-pelvic region, such as a relatively small multifidus muscle, have been used to predict lower limb injuries in professional football players. Results have been less consistent for the size of the quadratus lumborum (QL) muscle. Changes in size of the multifidus and QL muscles could be functionally related to each other, and modeling this relationship could improve prediction of lower limb injuries. Ultrasound imaging examinations were performed on male elite football players at the start of the Australian Football League (AFL) pre-season and playing season. Injury data were obtained from records collected by each club. Results indicated that the cross-sectional area of the multifidus muscle was related to the occurrence of an injury in the pre-season (odds ratio [OR] = 2.08/cm2 decrease below the mean; OR for dichotomized measure = 12.2) and in the season (OR = 2.43/cm2 ). The size of the QL muscle was significantly related to an injury in the pre-season (OR = 2.12/cm2 increase above the mean; OR for dichotomized measure = 7.26) but not in the season. A significant link was found between the ratio of the multifidus and QL muscles, and the incidence of pre-season (OR = 14.71) and season injuries (OR = 5.29). The sensitivity and specificity of the model in the pre-season were 75% and 85.7%, respectively; values for the playing season were 88.4% and 62.5%. A model was developed for prediction of lower limb injuries in football players. Combining size measurements of the multifidus and QL muscles improved predictive power. This information may have clinical implications for injury screening and prevention.

#9 Circannual rhythm of plasmatic vitamin D levels and the association with markers of psychophysical stress in a cohort of Italian professional soccer players
Reference: Chronobiol Int. 2017 Mar 17:1-9. doi: 10.1080/07420528.2017.1297820. [Epub ahead of print]
Authors: Lombardi G, Vitale JA, Logoluso S, Logoluso G, Cocco N, Cocco G, Cocco A, Banfi G
Summary: Adequate plasmatic Vitamin D levels are crucial to maintain calcium homeostasis and bone metabolism both in the general population and in athletes. Correct dietary supply and a regular sun exposure are fundamental for allowing the desired and effective fitness level. Past studies highlighted a scenario of Vitamin D insufficiency among professional soccer players in several countries, especially in North Europe, whilst a real deficiency in athletes is rare. The typical seasonal fluctuations of Vitamin D are wrongly described transversally in athletes belonging to teams that play at different latitudes and a chronobiologic approach studying the Vitamin D circannual rhythm in soccer players has not been described yet. Therefore, we studied plasma vitamin D, cortisol, testosterone, and creatin kinase (CK) concentrations in three different Italian professional teams training at the same latitude during a period of two consecutive competitive seasons (2013 and 2014). In this retrospective observational study, 167 professional soccer players were recruited (mean age at sampling 25.1 ± 4.7 years) and a total of 667 blood drawings were carried out to determine plasma 25(OH)D, serum cortisol, serum testosterone and CK levels. Testosterone to cortisol ratio (TC) was calculated based as a surrogate marker of overtraining and psychophysical stress and each athlete was drawn until a maximum of 5 times per season. Data extracted by a subgroup of players that underwent at least 4 sample drawings along a year (N = 45) were processed with the single and population mean cosinor tests to evaluate the presence of circannual rhythms: the amplitude (A), acrophase (Φ) and the MESOR (M) are described. In total, 55 players (32.9%) had an insufficient level of 25(OH)D during the seasons and other 15 athletes (9.0%) showed, at least once, a deficiency status of Vitamin D. The rhythmometric analyses applied to the data of Vitamin D revealed the presence of a significant circannual rhythm (p < 0.001) with the acrophase that occurred in August; the rhythms of Vitamin D levels were not different neither among the three soccer teams nor between competitive seasons. Cortisol, testosterone and TC showed significant circannual rhythms (p < 0.001): cortisol registered an acrophase during winter (February) while testosterone and TC registered their peaks in the summer months (July). On the contrary, CK did not display any seasonal fluctuations. In addition, we observed weak but significant correlations between 25(OH)D versus testosterone (r = 0.29 and p < 0.001), cortisol (r = -0.27 and p < 0.001) and TC (r = 0.37 and p < 0.001). No correlation was detected between Vitamin D and CK. In conclusion, the correct chronobiologic approach in the study of annual variations of Vitamin D, cortisol and testosterone could be decisive in the development of more specific supplementation and injury prevention strategies by athletic trainers and physicians.

#10 Predictors Of Linear And Multidirectional Acceleration In Elite Soccer Players
Reference: J Strength Cond Res. 2017 Mar 13. doi: 10.1519/JSC.0000000000001897. [Epub ahead of print]
Authors: Jonathan N, Russell M, Shearer D, Cook C, Kilduff L
Summary: Linear and multidirectional acceleration underpins success in professional soccer match-play. However, the physical qualities that determine these performance indicators are poorly understood in elite players. English Premier League players (n=26) performed isometric mid-thigh pulls (IMTP), bilateral and unilateral drop jumps (DJ; from 40 and 20 cm, respectively), bilateral and unilateral countermovement jumps (CMJ) and assessments of linear (5-, 10-, 20-m) and multidirectional (left/right pre-planned and reactive) acceleration. Regression analyses highlighted that 21% of variance in 5-m sprint time (1.02±0.07 s) was explained by relative peak power output (PPO) in bilateral CMJ (54.5±5.3 W·kg). A 5.4 W·kg increase in CMJ predicted a 0.03 s decrease in 5-m sprint time (P=0.02). For 10-m sprint time (1.72±0.09 s), 44% of variance was explained by isometric relative peak force (PF; 30.4±4.9 N·kg) and bilateral relative CMJ PPO (54.5±5.3 W·kg). A 5.4 W·kg increase in CMJ predicted reduced 10-m sprint times by 0.04 s (P=0.01). For 20-m sprint time (2.94±0.11 s), 55% of the total variance was explained by isometric relative PF (30.4±4.9 N·kg) and relative CMJ PPO (54.5±5.3 W·kg). Increases of 5.4 W·kg in bilateral CMJ predicted an improvement of 20-m sprint time by 0.06 s (P=0.002). Contributions were insignificant (P>0.05) for pre-planned and reactive multidirectional acceleration. Relativized indices, especially those related to force production during CMJ and IMTP tests, likely underpin linear but not multidirectional acceleration performance in professional soccer players. When linear acceleration is a training focus, practitioners should seek to monitor CMJ and IMTP test performance.

#11 Groin Problems in Male Soccer Players Are More Common Than Previously Reported
Reference: Am J Sports Med. 2017 Feb 1:363546516687539. doi: 10.1177/0363546516687539. [Epub ahead of print]
Authors: Haroy J, Clarsen B, Thorborg K, Holmich P, Bahr R, Andersen TE
Summary: The majority of surveillance studies in soccer have used a time-;loss injury definition, and many groin problems result from overuse, leading to gradually increasing pain and/or reduced performance without necessarily causing an absence from soccer training or match play. Thus, the magnitude of groin problems in soccer has probably been underestimated in previous studies based on traditional injury surveillance methods. The purpose of the study was to investigate the prevalence of groin problems among soccer players of both sexes and among male soccer players at different levels of play through a new surveillance method developed to capture acute and overuse problems. We registered groin problems during a 6-;week period of match congestion using the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. A total of 240 players from 15 teams across different levels of play and from both sexes were included, and they responded to the weekly questionnaire. We calculated the average weekly prevalence of all groin problems and substantial groin problems. Of the 240 players, 112 male players (59%) and 20 female players (45%) reported at least 1 episode of groin problems. The average weekly prevalence of any groin problem and substantial groin problem for all male players was 29% (range, 23%-32% across different levels) and 10% (7%-13%), respectively. Elite male players had an increased risk of experiencing groin problems (odds ratio: 3.1, 95% CI: 1.5-6.4, P = .03) compared with elite female players. There was no difference in the risk of experiencing groin problems among elite, subelite, and amateur male players. For substantial problems, there was no difference between elite male and elite female players or among levels of play for senior male soccer players. We found a high prevalence of groin problems among male soccer players during a period with match congestion. Time-loss definition as used in previous injury surveillance studies captured only one-;third of the male groin problems registered with the new method. Elite male players had 3 times' higher risk of reporting groin problems as compared with elite female players, while playing level did not influence the risk of reporting a groin problem among males.





Latest research in football - week 11 - 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 Monitoring Elite Soccer Players External Loads Using Real-Time Data
Reference: Int J Sports Physiol Perform. 2017 Mar 2:1-10. doi: 10.1123/ijspp.2016-0516. [Epub ahead of print]
Authors: Barrett S
Summary: The principle aim of the study was to assess the validity of measuring locomotor activities and PlayerLoad using Real-Time (RT) data collection during soccer training. Twenty-nine (n=29) English soccer players participated. Each player wore the same MEMS device (S5, Optimeye, CatapultSports, Melbourne, Australia) during twenty-one training sessions (n= 331 data sets) in the 2015/2016 and 2016/2017 season. A Real-Time receiver (TRX, Catapultsports, Melbourne, Australia) was used to collect the locomotor activities and PlayerLoad data in RT and compared with the post-event downloaded (PED) data. PlayerLoad and locomotor activities (total distance covered, TDC; total high speed running distance covered, >5.5m/s, HSR; total sprinting distance covered, >7m/s, SP; maximum velocity, VEL) were analysed. Correlations were near perfect for all variables analysed (r=0.98-1.00), with a varied level of noise between RT and PED also (0.3-9.7% CV). Locomotor activities and PlayerLoad can be used both RT and PED concurrently to quantify a players physical output during a training session. Caution should be taken with higher velocity based locomotor activities during RT compared to PED.

#2 Long Sprint Abilities in Soccer: Ball vs Running Drills
Reference: Int J Sports Physiol Perform. 2017 Mar 2:1-22. doi: 10.1123/ijspp.2016-0565. [Epub ahead of print]
Authors: Castagna C, Francini L, Póvoas SC, D'Ottavio S
Summary: The purpose of the study was to examine the acute effects of generic (Running Drills, RD) and specific (Small-Sided Games, SSG) Long Sprint Ability (LSA) drills on internal and external load of male soccer-players. Fourteen academy-level soccer-players (mean±SD; age 17.6±0.61 years, height 1.81±0.63 m, body-mass 69.53±4.65 kg) performed four 30s LSA bouts for maintenance (work:rest, 1:2) and production (1:5) with RD and SSG drills. Players' external-load was tracked with GPS technology (20Hz) and heart-rate (HR), blood-lactate concentrations (BLc) and rate of perceived exertion (RPE) were used to characterize players' internal-load. Individual peak BLc was assessed with a 30s all-out test on a non-motorized treadmill (NMT). Compared to SSGs the RDs had a greater effect on external-load and BLc (large and small, respectively). During SSGs players covered more distance with high-intensity decelerations (moderate-to-small). Muscular-RPE was higher (small-to-large) in RD than in SSG. The production mode exerted a moderate effect on BLc while the maintenance condition elicited higher cardiovascular effects (small-to-large). The results of this study showed the superiority of generic over specific drills in inducing LSA related physiological responses. In this regard production RD showed the higher post-exercise BLc. Interestingly, individual peak blood-lactate responses were found after the NMT 30s all-out test, suggesting this drill as a valid option to RD bouts. The practical physiological diversity among the generic and specific LSA drills here considered, enable fitness trainers to modulate prescription of RD and SSG drills for LSA according to training schedule.

#3 Changes in body composition and bone of female collegiate soccer players through the competitive season and off-season

Reference: J Musculoskelet Neuronal Interact. 2017 Mar 1;17(1):386-398.
Authors: Minett MM, Binkley TB, Weidauer LA, Specker BL
Summary: The purpose of the study was to assess body composition and bone changes pre- to post-season (pre-post) and post- to off-season (post-off) in female soccer athletes (SC).
Outcomes were assessed using DXA and pQCT in 23 SC and 17 controls at three times throughout season. SC, non-starters in particular, lost lean mass pre-post (-0.9±0.2 kg, p<0.01; not different from controls, p=0.2) and gained fat mass post-off (1.4±0.3 kg, p<0.01; differed from controls, p=0.01). Baseline femoral neck and hip aBMD were higher in SC than controls (both,p<0.04), but increased in controls more than SC in pre-post and decreased post-off. SC cortical bone mineral content (BMC), cortical area and periosteal circumference increased pre-post (all, p<0.01; differed from controls, p<0.05) and trabecular vBMD decreased post-off (-3.0±1.3 mg/cm3; p=0.02; not different from controls, p=0.4). Both SC and controls increased cortical BMC, cortical area, and thickness post-off (all, p<0.01). Soccer players lost lean mass over the competitive season that was not recovered during off-season. Bone size increased pre- to post-season. Female soccer athletes experience body composition and bone geometry changes that differ depending on the time of season and on athlete's playing status. Evaluations of athletes at key times across the training season are necessary to understand changes that occur.

#4 The assessment of neuromuscular fatigue during 120 min of simulated soccer exercise
Reference: Eur J Appl Physiol. 2017 Feb 28. doi: 10.1007/s00421-017-3561-9. [Epub ahead of print]
Authors: Goodall S, Thomas K, Harper LD, Hunter R, Parker P, Stevenson E, West D, Russell M, Howatson G
Download link:*~hmac=5dd338e5036a46152a7d9f94e33901a365f57c98ec7ccb3aa84adee932e5d4e7
Summary: This investigation examined the development of neuromuscular fatigue during a simulated soccer match incorporating a period of extra time (ET) and the reliability of these responses on repeated test occasions. Ten male amateur football players completed a 120 min soccer match simulation (SMS). Before, at half time (HT), full time (FT), and following a period of ET, twitch responses to supramaximal femoral nerve and transcranial magnetic stimulation (TMS) were obtained from the knee-extensors to measure neuromuscular fatigue. Within 7 days of the first SMS, a second 120 min SMS was performed by eight of the original ten participants to assess the reliability of the fatigue response. At HT, FT, and ET, reductions in maximal voluntary force (MVC; -11, -20 and -27%, respectively, P ≤ 0.01), potentiated twitch force (-15, -23 and -23%, respectively, P < 0.05), voluntary activation (FT, -15 and ET, -18%, P ≤ 0.01), and voluntary activation measured with TMS (-11, -15 and -17%, respectively, P ≤ 0.01) were evident. The fatigue response was robust across both trials; the change in MVC at each time point demonstrated a good level of reliability (CV range 6-11%; ICC2,1 0.83-0.94), whilst the responses identified with motor nerve stimulation showed a moderate level of reliability (CV range 5-18%; ICC2,1 0.63-0.89) and the data obtained with motor cortex stimulation showed an excellent level of reliability (CV range 3-6%; ICC2,1 0.90-0.98). Simulated soccer exercise induces a significant level of fatigue, which is consistent on repeat tests, and involves both central and peripheral mechanisms.

#5 Soccer and head injuries: What is the risk?
Reference: Neurology. 2017 Feb 28;88(9):e74-e77. doi: 10.1212/WNL.0000000000003669.
Authors: Allen B, Karceski S.
Download link:

#6 Lack of eye discipline during headers in high school girls soccer: A possible mechanism for increased concussion rates
Reference: Med Hypotheses. 2017 Mar;100:10-14. doi: 10.1016/j.mehy.2016.12.016. Epub 2017 Jan 5.
Authors: Clark JF, Elgendy-Peerman HT, Divine JG, Mangine RE, Hasselfeld KA, Khoury JC, Colosimo AJ
Summary: The sport of soccer is the fastest growing and most popular sport worldwide. With this growth and popularity, attention needs to be given to this athletic population. Sports related concussions is a topic that has gained attention both in the media and by governmental organizations, with growing initiatives in diagnosis, prevention and treatment. The act of soccer heading is thought to contribute to increased concussion incidence. Current evidence reveals that within the high school soccer athletic population, female athletes incur a higher concussion rate than males. This is often attributed to many things including differing cervical spinal musculature, skull thickness, etc., but a definitive reason has not yet been found. Other behaviors, such as field awareness and eye discipline™ on the field of play, may also be contributing factors that result in females incurring a greater concussion rate than males. For the purposes of this paper we define eye discipline™ as the ability to keep the eyes engaged in sporting activity with high risk potential. We present our hypothesis that high school female soccer players are more likely to have their eyes closed when in position for heading the ball as compared to high school male soccer players and this lack of visual awareness may increase the risk of concussion. Should these differences be substantiated between males and females, it may initiate and promote discussion of the need for vision training in the high school athletic setting. As a tool for injury prevention, vision training may improve specific visual parameters improving athletes' abilities to process the field of play and prepare for or avoid injury causing situations. Through ocular motor and visual conditioning, an athlete may become more eye disciplined™, and more likely to have their eyes open during heading of the ball, and more likely to avoid concussions.

#7 Youth Football Injuries: A Prospective Cohort
Reference: Orthop J Sports Med. 2017 Feb 10;5(2):2325967116686784. doi: 10.1177/2325967116686784. eCollection 2017.
Authors: Peterson AR, Kruse AJ, Meester SM, Olson TS, Riedle BN, Slayman TG, Domeyer TJ, Cavanaugh JE, Smoot MK
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Summary: There are approximately 2.8 million youth football players between the ages of 7 and 14 years in the United States. Rates of injury in this population are poorly described. Recent studies have reported injury rates between 2.3% and 30.4% per season and between 8.5 and 43 per 1000 exposures. Youth flag football has a lower injury rate than youth tackle football. The concussion rates in flag football are lower than in tackle football. Three large youth (grades 2-7) football leagues with a total of 3794 players were enrolled. Research personnel partnered with the leagues to provide electronic attendance and injury reporting systems. Researchers had access to deidentified player data and injury information. Injury rates for both the tackle and flag leagues were calculated and compared using Poisson regression with a log link. The probability an injury was severe and an injury resulted in a concussion were modeled using logistic regression. For these 2 responses, best subset model selection was performed, and the model with the minimum Akaike information criterion value was chosen as best. Kaplan-Meier curves were examined to compare time loss due to injury for various subgroups of the population. Finally, time loss was modeled using Cox proportional hazards regression models. A total of 46,416 exposures and 128 injuries were reported. The mean age at injury was 10.64 years. The hazard ratio for tackle football (compared with flag football) was 0.45 (95% CI, 0.25-0.80; P = .0065). The rate of severe injuries per exposure for tackle football was 1.1 (95% CI, 0.33-3.4; P = .93) times that of the flag league. The rate for concussions in tackle football per exposure was 0.51 (95% CI, 0.16-1.7; P = .27) times that of the flag league. Injury is more likely to occur in youth flag football than in youth tackle football. Severe injuries and concussions were not significantly different between leagues. Concussion was more likely to occur during games than during practice. Players in the sixth or seventh grade were more likely to suffer a concussion than were younger players.

#8 Football nutrition: time for a new consensus?
Reference: Br J Sports Med. 2017 Mar 2. pii: bjsports-2016-097260. doi: 10.1136/bjsports-2016-097260. [Epub ahead of print]
Authors: Collins J, McCall A, Bilsborough J, Maughan R
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#9 Effect of lifelong football training on the expression of muscle molecular markers involved in healthy longevity
Reference: Eur J Appl Physiol. 2017 Mar 1. doi: 10.1007/s00421-017-3562-8. [Epub ahead of print]
Authors: Mancini A, Vitucci D, Labruna G, Imperlini E, Randers MB, Schmidt JF, Hagman M, Andersen TR, Russo R, Orru S, Krustrup P, Salvatore F, Buono P
Summary: We investigated whether lifelong football training affects the expression of healthy longevity-related muscle molecular markers. Biopsies were collected from the vastus lateralis muscle of 10 lifelong football-trained men (68.2 ± 3.0 years) and of 10 active untrained healthy men (66.7 ± 1.3 years). Gene and protein expression was measured by RTqPCR on RNA and by western blotting on protein extracts from muscle biopsies, respectively. The expression of AMPKα1/α2, NAMPT, TFAM and PGC1α, which are markers of oxidative metabolism, and MyHC β isoform expression was higher in the muscle of football-trained men vs untrained men. Also citrate synthase activity was higher in trained than in untrained men (109.3 ± 9.2 vs 75.1 ± 9.2 mU/mg). These findings were associated with a healthier body composition in trained than in untrained men [body weight: 78.2 ± 6.5 vs 91.2 ± 11.2 kg; body mass index BMI: 24.4 ± 1.6 vs 28.8 ± 4.0 kg m-2; fat%: 22.6 ± 8.0 vs 31.4 ± 5.0%)] and with a higher maximal oxygen uptake (VO2max: 34.7 ± 3.8 vs 27.3 ± 4.0 ml/min/kg). Also the expression of proteins involved in DNA repair and in senescence suppression (Erk1/2, Akt and FoxM1) was higher in trained than in untrained men. At BMI- and age-adjusted multiple linear regression analysis, fat percentage was independently associated with Akt protein expression, and VO2max was independently associated with TFAM mRNA and with Erk1/2 protein expression. Lifelong football training increases the expression of key markers involved in muscle oxidative metabolism, and in the DNA repair and senescence suppression pathways, thus providing the molecular basis for healthy longevity.

#10 Increased Training Volume Improves Bone Density and Cortical Area in Adolescent Football Players
Reference: Int J Sports Med. 2017 Mar 1. doi: 10.1055/s-0042-124510. [Epub ahead of print]
Authors: Varley I, Hughes DC, Greeves JP, Fraser WD, Sale C
Summary: Habitual football participation has been shown to be osteogenic, although the specific volume of football participation required to cause bone adaptations are not well established. The aim of the present study is to investigate tibial bone adaptations in response to 12 weeks of increased training volume in elite adolescents who are already accustomed to irregular impact training. 99 male adolescent elite footballers participated (age 16±0 y; height 1.76±0.66 m; body mass 70.2±8.3 kg). Tibial scans were performed using peripheral quantitative computed tomography immediately before and 12 weeks after an increase in football training volume. Scans were obtained at 4, 14, 38 and 66% of tibial length. Trabecular density (mg/cm3), cortical density (mg/cm3), cross-sectional area, cortical area (mm2), cortical thickness (mm) and strength strain index (mm3) were assessed. Trabecular (4%) and cortical density (14, 38%), cortical cross-sectional area (14, 38%), total cross-sectional area (66%), cortical thickness (14, 38%) and strength strain index (14, 38%) increased following 12 weeks of augmented volume training (P<0.05). Increased density of trabecular and cortical compartments and cortical thickening were shown following an increased volume of training. These adaptive responses may have been enhanced by the adolescent status of the cohort, supporting the role of early exercise intervention in improving bone strength.

#11 Return to play criteria after hamstring muscle injury in professional football: a Delphi consensus study
Reference: Br J Sports Med. 2017 Feb 28. pii: bjsports-2016-097131. doi: 10.1136/bjsports-2016-097131. [Epub ahead of print]
Authors: Zambaldi M, Beasley I, Rushton A
Summary: Hamstring muscle injury (HMI) is the most common injury in professional football and has a high re-injury rate. Despite this, there are no validated criteria to support return to play (RTP) decisions. The purpose was to use the Delphi method to reach expert consensus on RTP criteria after HMI in professional football. All professional football clubs in England (n=92) were invited to participate in a 3-round Delphi study. Round 1 requested a list of criteria used for RTP decisions after HMI. Responses were independently collated by 2 researchers under univocal definitions of RTP criteria. In round 2 participants rated their agreement for each RTP criterion on a 1-5 Likert Scale. In round 3 participants re-rated the criteria that had reached consensus in round 2. Descriptive statistics and Kendall's coefficient of concordance enabled interpretation of consensus. Participation rate was limited at 21.7% (n=20), while retention rate was high throughout the 3 rounds (90.0%, 85.0%, 90.0%). Round 1 identified 108 entries with varying definitions that were collated into a list of 14 RTP criteria. Rounds 2 and 3 identified 13 and 12 criteria reaching consensus, respectively. Five domains of RTP assessment were identified: functional performance, strength, flexibility, pain and player's confidence. The highest-rated criteria were in the functional performance domain, with particular importance given to sprint ability. This study defined a list of consensually agreed RTP criteria for HMI in professional football. Further work is now required to determine the validity of the identified criteria.





Latest research in football - week 10 - 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 Hormonal responses during two different concurrent-training trials in youth elite soccer players: does changing the organisation of training impact the hormonal response to concurrent exercise?
Reference: J Sports Med Phys Fitness. 2017 Feb 22. doi: 10.23736/S0022-4707.17.07198-5. [Epub ahead of print]
Authors: Enright K, Morton J, Iga J, Drust B
Summary: There are no data describing the acute hormonal responses to concurrent- training programmes in youth elite soccer players. Therefore, the aim of this study was to describe the total testosterone (T), cortisol (C), and growth hormone (hGH) responses during two same-day concurrent-training (CT) trials in elite soccer players. Thirteen youth elite players (age: 17.0±0.2 yrs; height, 1.80±0.07 m; body mass, 73.1±5.7 kg; VO2 max, 64.4± from an English premier league soccer club completed two CT trials. 'Trial 1' (CT1); E (10.30h) followed by S (14.00h) and Trial 2 (CT2); strength-training (S) 09.00h followed by a soccer-specific endurance-training session (E) at 10.30h. Venous blood samples were collected at 5 time-points around training and food intake (T1; 08.00h, T2; 09.45h, T3; 12.30h, T4; 13.45h and T5; 15.15h) and analysed for T (nmol/L) and C (nmol/L) and hGH (ug/L). There was no main effects found between exercise conditions for any hormones (T; P=0.22, C; P=0.07, hGH; P=0.21). Effect size analysis revealed a moderate effect for T at T3 (ES=0.63, CT1; 18.4±3.8, CT2; 15.7±4.7 nmol/L-1). A moderate effect for T area under the curve (AUC) was observed between conditions (CT1; 300±76 versus CT2; 244 ± 81 [AU]; ES=0.71). A moderate effect was apparent for C concentrations T4 in (ES=-0.95, CT1; 230±69, CT2; 314±105 nmol/L-1). Moderate effect sizes were observed at T3 and T4 (ES=0.82, CT1; 1.28±1.17, CT2; 0.47±0.75, ES=0.72, CT1; 0.11±0.05, CT2; 0.07±0.06 ug/L-1 respectively). A moderate effect for hGH AUC was observed between trials (CT1; 14±11 versus CT2; 5±9; [AU], ES=-1.08). The organisation of the concurrent-training protocols used in this study has a negligible impact upon the acute T, C and hGH in youth elite soccer players.

#2 The periodization of resistance training in soccer players: changes in maximal strength, lower extremity power, body composition, and muscle volume
Reference: J Sports Med Phys Fitness. 2017 Feb 22. doi: 10.23736/S0022-4707.17.07129-8. [Epub ahead of print]
Authors: Barjaste A, Mirzaei B
Summary: The purpose of this study was to investigate the effect of 12-weeks traditional periodized resistance training on some physical capacities of soccer players. Eighteen amateur soccer players with very little experience in resistance training voluntarily participated in this study. Subjects were assigned into two groups; Experimental (EX) group (n: 10) that conducted a traditional linear periodized resistance training program and a control (C) group (n: 8) that did not participate in any resistance training. Periodized resistance training in two mesocycles was used in this study: general or anatomical adaptation phase (6 wk, 65%-75% of 1RM, eleven exercises in each session) and maximal strength phase (6 wk, 85%-95% of 1RM, three to four exercises in each session). One Repetition Maximum (1RM) strength in lower and upper body, Vertical Jump (VJ) height, Body Composition, and Muscle Volume were measured at three different time points; baseline, after general phase, and after maximal strength phase. The average of the increase in 1RM all exercises in general phase was greater than the maximal strength phase, on average 29.38% and 9.67% respectively (P≤0.05). Also, the Percentage of change in VJ height in general phase was greater than the maximal strength phase (11.93% vs 3.97% respectively) (P≤0.05). The results of this study indicated that muscle strength and explosive performance in players with the little experience in resistance training can be significantly improved with the completion of general phase of resistance training periodization using moderate loads.

#3 Nonlinear sprint performance differentiates professional from young soccer players
Reference: J Sports Med Phys Fitness. 2017 Feb 22. doi: 10.23736/S0022-4707.17.07116-X. [Epub ahead of print]
Authors: Cardoso de Araujo M, Baumgart C, Freiwald J, Hoppe MW
Summary: Linear and nonlinear sprinting activities are relevant physical capacities in soccer. This study aimed (1) to compare linear and nonlinear sprint performance between professional and young soccer players and (2) to investigate relationships between both sprint types. Sixty-eight German male elite field soccer players were grouped based on age as professional (PRO, n = 20), under-23 (U23, n = 16), under-19 (U19, n = 18), and under-17 (U17, n = 14). All players were tested for 30 m linear (split-times at 5, 10, and 20 m) and 22 m nonlinear sprint performance. In linear sprint, PRO players were moderately to very largely faster than U17 players at all distances and also than U19 players at 20 m (effect size [ES] = 0.90-2.06, p ≤ 0.04). U23 players were moderately to largely faster than U17 players at 5 and 10 m (ES = 0.93-1.74, p ≤ 0.04). In nonlinear sprint, PRO players were moderately to largely faster than all other groups (ES = 1.04-1.84, p ≤ 0.02). Moderate to large correlations were found between linear and nonlinear sprint performance for all players (r = 0.48-0.50, p < 0.01). Within groups, moderate to large correlations were evident only for PRO at 5-20 m (r = 0.45-0.61, p ≤ 0.05) and U23 at 30 m (r = 0.55, p = 0.03). The findings indicate that nonlinear sprint performance is a key physical capacity in professional soccer. Therefore, training programs should focus to increase this capacity in younger players. Furthermore, linear and nonlinear sprint performance should be independently tested and trained in elite players.

#4 Sex Differences in Anthropometrics and Heading Kinematics Among Division I Soccer Athletes
Reference: Sports Health. 2017 Mar/Apr;9(2):168-173. doi: 10.1177/1941738116678615. Epub 2016 Nov 15.
Authors: Bretzin AC, Mansell JL, Tierney RT, McDevitt JK
Summary: Soccer players head the ball repetitively throughout their careers; this is also a potential mechanism for a concussion. Although not all soccer headers result in a concussion, these subconcussive impacts may impart acceleration, deceleration, and rotational forces on the brain, leaving structural and functional deficits. Stronger neck musculature may reduce head-neck segment kinematics. The relationship between anthropometrics and soccer heading kinematics will not differ between sexes. The relationship between anthropometrics and soccer heading kinematics will not differ between ball speeds. Division I soccer athletes (5 male, 8 female) were assessed for head-neck anthropometric and neck strength measurements in 6 directions (ie, flexion, extension, right and left lateral flexions and rotations). Participants headed the ball 10 times (25 or 40 mph) while wearing an accelerometer secured to their head. Kinematic measurements (ie, linear acceleration and rotational velocity) were recorded at 2 ball speeds. Sex differences were observed in neck girth ( t = 5.09, P < 0.001), flexor and left lateral flexor strength ( t = 3.006, P = 0.012 and t = 4.182, P = 0.002, respectively), and rotational velocity at both speeds ( t = -2.628, P = 0.024 and t = -2.227, P = 0.048). Neck girth had negative correlations with both linear acceleration ( r = -0.599, P = 0.031) and rotational velocity at both speeds ( r = -0.551, P = 0.012 and r = -0.652, P = 0.016). Also, stronger muscle groups had lower linear accelerations at both speeds ( P < 0.05). There was a significant relationship between anthropometrics and soccer heading kinematics for sex and ball speeds.

#5 The effects of "Prevent Injury and Enhance Performance Program" in a female soccer team
Reference: J Sports Med Phys Fitness. 2017 Feb 21. doi: 10.23736/S0022-4707.17.07024-4. [Epub ahead of print]
Authors: Rodriguez C, Echegoyen S, Aoyama T
Summary: The purpose of this study is to evaluate the changes of muscle strength in lower limbs and knee valgus alignment using the Prevent Injury and Enhance Performance Program (PEP program) to prevent ACL injuries in female soccer players during an entire season. A longitudinal and prospective study was done in twenty female soccer players at the Universidad Nacional Autónoma de México, from a senior team. During 24 weeks the training program was applied three times a week as a part of the team workouts. Video analysis of dynamic knee valgus alignment and maximal strength of quadriceps, hamstrings and gastrocnemius were evaluated pre and post training. Quadriceps and hamstring strength increased on the right pelvic limb (p<0.001). In addition the quadriceps/hamstrings ratio decreased from 3.38 to 2.3 in the right side, and from 1.99 to 1.09 in the left side. The mechanics of jump improved in 20% of the female soccer players. Muscle strength in quadriceps and hamstrings increased in right pelvic limb (p<0.001), and the quadriceps/hamstrings ratio decreased from 3.38 to 2.3 in right side and from 1.99 to 1.09 in left side. Although injuries did not decrease during this period no ACL injury was registered. Until now there are no reports about muscle strength and jump technique assessment with the application of the PEP program. The neuromuscular training and muscle balance are important to prevent ACL injuries. We advise that this program is integrated to women ́s soccer training.

#6 Soccer-related performance in eumenorrheic Tunisian high-level soccer players: effects of menstrual cycle phase and moment of day
Reference: J Sports Med Phys Fitness. 2017 Feb 21. doi: 10.23736/S0022-4707.17.06958-4. [Epub ahead of print]
Authors: Tounsi M, Jaafar H, Aloui A, Souissi N
Summary: This study aimed to examine the combined effects of menstrual cycle phase and moment of day on female soccer players' performances in the five-jump test (5JT), the repeated shuttle- sprint ability test (RSSA), and the Yo-Yo intermittent recovery test level 1 (YYIRT1). Eleven eumenorrheic Tunisian high-level soccer players volunteered to participate. Each subject individually participated in three testing periods: one in the early follicular phase (menses), one in the late follicular phase, and another in the luteal phase. In each period, two test sessions were conducted: one at 07:30 h and another at 17:30 h. The testing routines included the 5JT, the RSSA, and the YYIRT1. None of the measured variables were altered due to menstrual cycle phase (all P > 0.05). Mean time during RSSA was significantly lower in the afternoon session compared to the morning session (8.48 ± 0.27 s and 8.77 ± 0.34 s, respectively, P < 0.001), while 5JT performance was significantly higher in the afternoon compared to the morning (9.08 ± 0.58 m and 8.60 ± 0.56 m, respectively, P < 0.001). Soccer-specific endurance as well as jumping and repeated sprinting ability of Tunisian female high-level soccer players are not affected due to menstrual cycle phase neither in the morning nor in the afternoon.

#7 Neuroplus biofeedback improves attention, resilience, and injury prevention in elite soccer players
Reference: Psychophysiology. 2017 Feb 21. doi: 10.1111/psyp.12847. [Epub ahead of print]
Authors: Rusciano A, Corradini G, Stoianov I
Summary: Performance and injury prevention in elite soccer players are typically investigated from physical-tactical, biomechanical, and metabolic perspectives. However, executive functions, visuospatial abilities, and psychophysiological adaptability or resilience are also fundamental for efficiency and well-being in sports. Based on previous research associating autonomic flexibility with prefrontal cortical control, we designed a novel integrated autonomic biofeedback training method called Neuroplus to improve resilience, visual attention, and injury prevention. Herein, we introduce the method and provide an evaluation of 20 elite soccer players from the Italian Soccer High Division (Serie-A): 10 players trained with Neuroplus and 10 trained with a control treatment. The assessments included psychophysiological stress profiles, a visual search task, and indexes of injury prevention, which were measured pre- and posttreatment. The analysis showed a significant enhancement of physiological adaptability, recovery following stress, visual selective attention, and injury prevention that were specific to the Neuroplus group. Enhancing the interplay between autonomic and cognitive functions through biofeedback may become a key principle for obtaining excellence and well-being in sports. To our knowledge, this is the first evidence that shows improvement in visual selective attention following intense autonomic biofeedback.

#8 Relative Age, Maturation and Physical Biases on Position Allocation in Elite-Youth Soccer
Reference: Int J Sports Med. 2017 Feb 20. doi: 10.1055/s-0042-119029. [Epub ahead of print]
Authors: Towlson C, Cobley S, Midgley AW, Garrett A, Parkin G, Lovell R
Summary: This study assessed the contribution of relative age, anthropometry, maturation, and physical fitness characteristics on soccer playing position (goalkeeper [GK], central-defender [CD], lateral-defender [LD], central-midfield [CM], lateral-midfielder [LM], and forward [FWD]) for 465 elite-youth players (U13-U18's). U13-14 CD were relatively older than LD and CM (likely small effects). CD and GK were generally taller and heavier (likely small to very-likely moderate effects) than other players at each developmental stage and were advanced maturers at U13-14 (very-likely small to likely moderate effects). GK had inferior agility (very-likely small to likely moderate effects), endurance (very-likely small to likely moderate effects), and sprint capacities (likely small-moderate effects) vs. outfield positions at U13-14, but deficits in anaerobic phenotypes were diminished in U15-16 and U17-18. Position specific fitness characteristics were distinguished at U15-16 (likely small) and U17-18 (likely moderate), where LM were faster than their central counterparts. In summary, relative age, maturation and anthropometric characteristics appear to bias the allocation of players into key defensive roles from an early development stage, whereas position-specific physical attributes do not become apparent until the latter stages of talent development in outfield players. Given the inter-individual trajectories of physical development according to biological maturation, playing position allocation might be considered 'plastic' by selectors, until complete-maturity is achieved.

#9 The intra- and inter-reliability of the soccer injury movement screen (SIMS)
Reference: Int J Sports Phys Ther. 2017 Feb;12(1):53-66.
Authors: McCunn R, Aus der Funten K, Govus A, Julian R, Schimpchen J, Meyer T
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Summary: The growing volume of movement screening research reveals a belief among practitioners and researchers alike that movement quality may have an association with injury risk. However, existing movement screening tools have not considered the sport-specific movement and injury patterns relevant to soccer. The present study introduces the Soccer Injury Movement Screen (SIMS), which has been designed specifically for use within soccer. Furthermore, the purpose of the present study was to assess the intra- and inter-rater reliability of the SIMS and determine its suitability for use in further research. The study utilized a test-retest design to discern reliablility. Twenty-five (11 males, 14 females) healthy, recreationally active university students (age 25.5 ± 4.0 years, height 171 ± 9 cm, weight 64.7 ± 12.6 kg) agreed to participate. The SIMS contains five sub-tests: the anterior reach, single-leg deadlift, in-line lunge, single-leg hop for distance and tuck jump. Each movement was scored out of 10 points and summed to produce a composite score out of 50. The anterior reach and single-leg hop for distance were scored in real-time while the remaining tests were filmed and scored retrospectively. Three raters conducted the SIMS with each participant on three occasions separated by an average of three and a half days (minimum one day, maximum seven days). Rater 1 re-scored the filmed movements for all participants on all occasions six months later to establish the 'pure' intra-rater (intra-occasion) reliability for those movements. Intraclass correlation coefficient (ICC) values for intra- and inter-rater composite score reliability ranged from 0.66-0.72 and 0.79-0.86 respectively. Weighted kappa values representing the intra- and inter-rater reliability of the individual sub-tests ranged from 0.35-0.91 indicating fair to almost perfect agreement. Establishing the reliability of the SIMS is a prerequisite for further research seeking to investigate the relationship between test score and subsequent injury. The present results indicate acceptable reliability for this purpose; however, room for further development of the intra-rater reliability exists for some of the individual sub-tests.

#10 Effects of a small-sided game-based training programme on repeated sprint and change of direction abilities in recreationally-trained football players
Reference: J Sports Med Phys Fitness. 2017 Feb 21. doi: 10.23736/S0022-4707.17.07044-X. [Epub ahead of print]
Authors: Bujalance-Moreno P, Garcia-Pinillos F, Latorre-Roman PA
Summary: The purpose of the study was to examine the effects of 6-week periodized small-sided game (SSG) training intervention on change of direction [COD], sprint and repeated sprint ability [RSA] in recreational male football players. Twenty-three young football players (age: 20.86 years) were randomized in a control group (n = 11) and an experimental group (n = 12). The SSG programme was included in the experimental group's training sessions. The players completed two variations of a SSG (i.e. 2 vs. 2 and 4 vs. 4 players) during intervention. To examine the changes in physical performance after the 6-week periodized SSG training intervention, all players were tested 6 weeks apart (i.e. pre-test and post-test) in sprint, COD ability test, and RSA shuttle test. A 2x2 ANOVA showed that 6-week SSG training intervention induced significant improvements (P<0.05, ES>0.7) in COD ability test, and variables related to both sprint test and RSA in the experimental group, whereas the control group remained unchanged (P≥0.05, ES<0.4). Regarding the response to the RSA test - in terms of BLa, both the experimental group (P=0.001, ES=1.270) and the control group (P=0.010, ES=0.939) increased BLa after the intervention. The current study indicates that a 6-week SSG-based training programme could improve decisive parameters in performance in football, such as COD, RSA and sprint in recreationally trained football players.

#11 Risk factors of anterior cruciate ligament injury in football players: a systematic review of the literature
Reference: Muscles Ligaments Tendons J. 2016 Feb 12;6(4):480-485. doi: 10.11138/mltj/2016.6.4.480.
Authors: Volpi P, Bisciotti GN, Chamari K, Cena E, Carimati G, Bragazzi NL
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Summary: The ACL lesion represents one of the most dramatic injuries in a sportsman's career. There are many injury risk factors related to intrinsic, or non-modifiable, and extrinsic, or modifiable, factors. In literature at today current evidence suggests that ACL injury risk is multifactorial and involves biomechanical, anatomical, hormonal and neuromuscular factors. The purpose of the study was to perform a systematic review of the literature concerning the ACL injury risk factors in soccer. The injury risk factors show a low level of evidence, further studies in the field are needed.

#12 ACL injury in football: a literature overview of the prevention programs
Reference: Muscles Ligaments Tendons J. 2016 Feb 12;6(4):473-479. doi: 10.11138/mltj/2016.6.4.473.
Authors: Bisciotti GN, Chamari K, Cena E, Carimati G, Volpi P
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Summary: The ACL prevention programs are addressed to the control and/or modification of the so-called "modifiable risk factors". All these programs focus on different intervention strategies aimed to decrease the ACL injury risk, particularly in female athletes population. The purpose of the study was to furnish an overview of the most used ACL injury prevention program through a narrative review. In literature there are many reports on prevention programs whose common denominator is the proper alignment of the lower limb joints and proper motor control during movements that are considered at risk for ACL integrity, as the landing phase after a jump. Nevertheless, some programs would appear more effective than others. In any cases a major problem remains the lack of sufficient compliance in respect of prevention programs. Finally, it is important to remember that the ethiology of ACL injuries is multifactorial. For this reason a prevention program able to prevent all the risk situations is utopian.

#13 Where biomedicalisation and magic meet: Therapeutic innovations of elite sports injury in British professional football and cycling
Reference: Soc Sci Med. 2017 Feb 9;178:136-143. doi: 10.1016/j.socscimed.2017.02.011. [Epub ahead of print]
Authors: Faulkner A, McNamee M, Coveney C, Gabe J
Summary: Injury is a conspicuous feature of the practice and public spectacle of contemporary elite sports. The paper argues that the 'biomedicalisation' thesis (medico-industrial nexus, techno-scientific drivers, medical optimisation, biologisation, the rise of evidence and health surveillance) goes some way to capturing the use in elite sports injury of some highly specialised mainstream therapies and some highly maverick biological therapies, which are described. Nevertheless, these main strands of biomedicalisation do not capture the full range of these phenomena in the contexts of sports medicine and athletes' practices in accessing innovative, controversial therapies. Drawing on multi-method qualitative research on top-level professional football and cycling in the UK, 2014-2016, we argue that concepts of 'magic' and faith-based healing, mediated by notions of networking behaviour and referral systems, furnish a fuller explanation. We touch on the concept of 'medical pluralism', concluding that this should be revised in order to take account of belief-based access to innovative bio-therapies amongst elite sportspeople and organisations.





Latest research in football - week 9 - 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 Injuries of the obturator muscles in professional soccer players
Reference: Knee Surg Sports Traumatol Arthrosc. 2017 Feb 10. doi: 10.1007/s00167-017-4453-6. [Epub ahead of print]
Authors: Wong-On M, Turmo-Garuz A, Arriaza R, Gonzalez de Suso JM, Til-Perez L, Yanguas-Leite X, Diaz-Cueli D, Gasol-Santa X
Summary: Obturator externus and internus muscular tears are uncommon injuries. Only a few case reports exist, mainly in high-level athletes. Our aim is to describe a series of obturator externus and internus muscular tears in professional soccer players. Injury data from four teams from the First Division of the Spanish Soccer League were collected over a total of four seasons. Any soccer player who sustained an injury to either the obturator externus or internus identified on magnetic resonance (MRI) was included. All injured players were treated non-operatively with a goal of returning to play as fast as possible. Sixteen players sustained injuries to the obturator externus and internus during matches or training sessions. The main complaint was anterior hip pain with a physical examination showing pain during internal rotation or external rotation of the flexed hip. The MRI documented 12 muscular tears of the obturator externus, and 4 muscular tears of the obturator internus. All injuries were treated conservatively based on physical therapy, analgesic medications, and underwent a symptoms-based rehabilitation protocol. Mean return to play was 11.5  ±  8.8 days. Although uncommon, tears of the obturator externus and internus occur in professional soccer players. The MRI scan was essential to the location, classification, and evaluation of the injury size. The clinical relevance of our investigation is based on the relatively benign prognosis of these injuries.

#2 Torque-angle-velocity Relationships and Muscle Performance of Professional and Youth Soccer Players
Reference: Int J Sports Med. 2016 Nov;37(12):992-996. Epub 2016 Aug 1.
Authors: Mazuquin BF, Dela Bela LF, Pelegrinelli AR, Dias JM, Carregaro RL, Moura FA, Selfe J, Richards J, Brown LE, Cardoso JR
Summary: Soccer matches consist of a variety of different activities, including repeated sprints. Time to attain velocity (TTAV), load range (LR) and the torque-angle-velocity relationship (TAV3D) represent an important measurement of muscle performance, however there are few related studies. The aim of this study was to compare these outcomes between soccer players of different age category. 17 professional (PRO) and 17 under-17 (U17) soccer players were assessed for concentric knee flexion/extension at 60, 120 and 300°/s. For the extensor muscles, differences were found in favor of the U17 group for TTAV and LR outcomes at 120°/s, however, the PRO group maintained higher torques in both movement directions in comparison to the U17 in TAV3D evaluation. These results suggest that muscle performance of the PRO group is more efficient than the U17 group.

#3 What's in a game? A systems approach to enhancing performance analysis in football
Reference: PLoS One. 2017 Feb 17;12(2):e0172565. doi: 10.1371/journal.pone.0172565. eCollection 2017.
Authors: McLean S, Salmon PM, Gorman AD, Read GJ, Solomon C
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Summary: Performance analysis (PA) in football is considered to be an integral component of understanding the requirements for optimal performance. Despite vast amounts of research in this area key gaps remain, including what comprises PA in football, and methods to minimise research-practitioner gaps. The aim of this study was to develop a model of the football match system in order to better describe and understand the components of football performance. Such a model could inform the design of new PA methods. Eight elite level football Subject Method Experts (SME's) participated in two workshops to develop a systems model of the football match system. The model was developed using a first-of-its-kind application of Cognitive Work Analysis (CWA) in football. CWA has been used in many other non-sporting domains to analyse and understand complex systems. Using CWA, a model of the football match 'system' was developed. The model enabled identification of several PA measures not currently utilised, including communication between team members, adaptability of teams, playing at the appropriate tempo, as well as attacking and defending related measures.The results indicate that football is characteristic of a complex sociotechnical system, and revealed potential new and unique PA measures regarded as important by SME's, yet not currently measured. Importantly, these results have identified a gap between the current PA research and the information that is meaningful to football coaches and practitioners.

#4 Football APP based on smart phone with FES in drop-foot rehabilitation
Reference: Technol Health Care. 2016 Feb 3. doi: 10.3233/THC-160730. [Epub ahead of print]
Authors: Ciou SH, Hwang YS, Chen CC, Luh JJ, Chen SC, Chen YL
Summary: Long-term, sustained progress is necessary in drop foot rehabilitation. The necessary inconvenient body training movements, the return trips to the hospital and repetitive boring training using functional electrical simulation (FES) often results in the patient suspending their training. The patient's drop foot rehabilitation will not progress if training is suspended. A fast spread, highly portable drop foot rehabilitation training device based on the smart phone is presented. This device is combined with a self-made football APP and feedback controlled FES. The drop foot patient can easily engage in long term rehabilitation training that is more convenient and interesting. An interactive game is established on the smart phone with the Android system using the originally built-in wireless communications. The ankle angle information is detected by an external portable device as the game input signal. The electrical stimulation command to the external device is supplemented with FES simulation for inadequate ankle efforts. After six-weeks training using six cases, the results indicated that this training device showed significant performance improvement (p< 0.05) in the patient's ankle dorsiflexion strength, ankle dorsiflexion angle, control timing and Timed Up and Go. Preliminary results show that this training device provides significant positive help to drop foot patients. Moreover, this device is based on existing and universally popular mobile processing, which can be rapidly promoted. The responses of clinical cases also show this system is easy to operate, convenient and entertaining. All of these features can improve the patient's willingness to engage in long term rehabilitation.

#5 A comparison of injuries in elite male and female football players: A 5-Season prospective study
Reference: Scand J Med Sci Sports. 2017 Feb 16. doi: 10.1111/sms.12860. [Epub ahead of print]
Authors: Larruskain J, Lekue JA, Diaz N, Odriozola A, Gil SM
Summary: The aim was to compare the epidemiology of injuries between elite male and female football players from the same club. Injuries and individual exposure time in a male team and a female team, both playing in the Spanish first division, were prospectively recorded by the club's medical staff for five seasons (2010-2015) following the FIFA consensus statement. Total, training and match exposure hours per player-season were 20% higher for men compared to women (P < 0.01). Total, training and match injury incidence were 30-40% higher in men (P ≤ 0.04) mainly due to a 4.82 [95% confidence interval (CI) 2.30-10.08] times higher incidence of contusions, as there were no differences in the incidence of muscle and joint/ligament injuries (P ≥ 0.44). The total number of absence days was 21% larger in women owing to a 5.36 (95% CI 1.11-25.79) times higher incidence of severe knee and ankle ligament injuries. Hamstring strains and pubalgia cases were 1.93 (95% CI 1.16-3.20) and 11.10 (95% CI 1.48-83.44) times more frequent in men, respectively; whereas quadriceps strains, anterior cruciate ligament ruptures and ankle syndesmosis injuries were 2.25 (95% CI 1.22-4.17), 4.59 (95% CI 0.93-22.76) and 5.36 (95% CI 1.11-25.79) times more common in women, respectively. In conclusion, prevention strategies should be tailored to the needs of male and female football players, with men more predisposed to hamstring strains and hip/groin injuries, and women to quadriceps strains and severe knee and ankle ligament injuries.

#6 Hip strength and range of motion: Normal values from a professional football league
Reference: J Sci Med Sport. 2016 Aug 23. pii: S1440-2440(16)30106-2. doi: 10.1016/j.jsams.2016.05.010. [Epub ahead of print]
Authors: Mosler AB, Crossley KM, Thorborg K, Whiteley RJ, Weir A, Serner A, Holmich P
Summary: The objective of the study was to determine the normal profiles for hip strength and range of motion (ROM) in a professional football league in Qatar, and examine the effect of leg dominance, age, past history of injury, and ethnicity on these profiles. Participants included 394 asymptomatic, male professional football players, aged 18-40 years. Strength was measured using a hand held dynamometer with an eccentric test in side-lying for hip adduction and abduction, and the squeeze test in supine with 45° hip flexion. Range of motion measures included: hip internal and external rotation in 90° flexion, hip IR in prone, bent knee fall out and hip abduction in side-lying. Demographic information was collected and the effect on the profiles was analysed using linear mixed models with repeated measures. Strength values (mean±SD) were: adduction=3.0±0.6Nm/kg, abduction=2.6±0.4Nm/kg, adduction/abduction ratio=1.2±0.2, Squeeze test=3.6±0.8N/kg. Range of motion values: internal rotation in flexion=32±8°, external rotation=38±8°, internal rotation in prone=38±8°, bent knee fall out=13±4.4cm, abduction in side-lying=50±7.3°. Leg dominance had no clinically relevant effect on these profiles. Multivariate analysis demonstrated that age had a minor influence on squeeze strength (-0.03N/kg/year), external rotation (-0.30°/year) and abduction range (-0.19°/year) but past history of injury, and ethnicity did not. Normal values are documented for hip strength and range of motion that can be used as reference profiles in the clinical assessment, screening, and management of professional football players. Leg dominance, recent past injury history and ethnicity do not need to be accounted for when using these profiles for comparison purposes.

#7 One ACL injury is enough! Focus on female football players
Reference: Br J Sports Med. 2017 Feb 9. pii: bjsports-2016-097179. doi: 10.1136/bjsports-2016-097179. [Epub ahead of print]
Authors: Faltstrom A

#8 Injury mechanism of midfacial fractures in football causes in over 40% typical neurological symptoms of minor brain injuries
Reference: Knee Surg Sports Traumatol Arthrosc. 2017 Feb 8. doi: 10.1007/s00167-017-4431-z. [Epub ahead of print]
Authors: Krutsch V, Gesslein M, Loose O, Weber J, Nerlich M, Gaensslen A, Bonkowsky V, Krutsch W
Summary: The injury mechanisms of midfacial fractures may be typical causes of concussion, but hardly any scientific data on midfacial injuries sustained in football are available. Head and brain trauma represent frequent injuries in athletes of different sports that require appropriate treatment by sports and trauma physicians. This study investigated the management of midfacial fractures in football and the association of such fractures with concomitant brain injury. In a prospective cohort study lasting 24 months (2012 to 2013), midfacial injuries of football players were analysed with regard to the injury mechanisms, first aid procedures on the field, treatment and return-to-play. To analyse concomitant and potentially overlooked minor brain injuries due to the trauma, we retrospectively investigated the neurological symptoms of the study population. The study included 132 football players (37 semi-professionals and 95 amateurs) with midfacial fractures. The main injury mechanisms were head-to-head and head-to-elbow trauma. The mean period of return-to-play after trauma was 33.5 days, which was significantly shortened if a protective face mask was worn (mean 10.4 days earlier, p = 0.0006). Semi-professional football players returned to play earlier (p = 0.009) and more often used protective face masks (p = 0.001). 55 players (41.6%) had neurological symptoms immediately after trauma as a possible sign of concomitant minor brain injury. 5 of 132 players with concussion had been hospitalised for 24 h, but no persistent neurological symptoms were detected. In football, midfacial fractures represent moderate-to-severe injuries with time away from sports of more than 4 weeks. Over 40% of athletes with a midfacial fracture showed concomitant neurological symptoms as a sign of minor brain injury. Therefore, sports physicians and other staff supervising athletes in daily practice should be aware of the presence of neurological symptoms.