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
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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.

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