Latest research in football - week 11 - 2018

#1 The reliability and validity of a video-based method for assessing hamstring strength in football players
Reference: J Exerc Sci Fit. 2017 Jun;15(1):18-21. doi: 10.1016/j.jesf.2017.04.001. Epub 2017 Apr 28.
Authors: Lee JWY, Li C, Yung PSH, Chan KM
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5812858/pdf/main.pdf
Summary: Evaluating hamstring strength by isokinetic dynamometry is limited by various practical issues such as time and cost. A video-based Nordic hamstring exercise is introduced as an alternative option. The aims of this study are to evaluate 1.) the between-session reliability and 2.) concurrent validity of the testing method compared to a standardized isokinetic dynamometry. Thirty male elite footballers were recruited for the study. From the Nordic hamstring exercise, the video-analysis-determined Nordic break-point angles where the participant could no longer withstand the force of the fall (eccentric mode) and the number of seconds that the player could hold at 30° forward flexion angle (isometric mode) were measured. Intra-class correlation coefficients for between-session reliability, Pearson r correlations between the current method and isokinetic dynamometry were calculated. The reliability of the eccentric mode was moderate (ICC (2,1) = 0.82) while that of isometric mode was poor (ICC (2,1) = 0.57). The Nordic break-point angle of the eccentric mode significantly correlated with the concentric and eccentric hamstring peak torque (r = 0.48 and 0.58, p < 0.001), while the isometric was not (r = 0.02 - 0.07, p > 0.05). The eccentric mode of the video-based hamstring strength test was a moderately reliable and valid method to measure the eccentric hamstring strength in elite football players.


#2 Activity profile and physiological responses of Korean amateur football referees during matches
Reference: J Phys Ther Sci. 2018 Feb;30(2):351-354. doi: 10.1589/jpts.30.351. Epub 2018 Feb 28.
Authors: Choi Y, Roh J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5851381/pdf/jpts-30-351.pdf
Summary: The present study aimed to analyze and compare the activity profile and physiological responses of amateur football referees during competitive matches of high school and college students. Thirty referees (high school, 15; college, 15) were included in this study. The total distance covered, movement speed, and heart rate were measured using a global positioning system-enabled wireless heart rate monitor. The blood lactate concentration was measured immediately after the first and second half. College football referees covered a higher total distance than did their high school counterparts (7,547 m vs. 6,719 m). The maximal heart rate of college football referees was low in the first half alone, and the percentage of the heart rate within the "maximum" range was low throughout the game.  Refereeing imposes a significantly high physical load on the body while tracking player and ball movement. The present study suggests the need for developing and distributing physical training programs tailored for refereeing.


#3 Influence of Football on Physiological Cardiac Indexes in Professional and Young Athletes
Reference: Front Physiol. 2018 Feb 28;9:153. doi: 10.3389/fphys.2018.00153. eCollection 2018.
Authors: Francavilla CV, Sessa F, Salerno M, Albano GD, Villano I, Messina G, Triolo F, Todaro L, Ruberto M, Marsala G, Cascio O, Mollica MP, Monda V, Cibelli G, Valenzano A, Zammit C, Monda M, Messina A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835836/pdf/fphys-09-00153.pdf
Summary: After long-term intensive training, considerable morphological and functional heart changes occur in professional athletes. Such changes arise progressively and regress upon interruption of the physical activity. Morphological and functional alterations on heart are known as "Athlete's heart" condition. This study aims to compare echocardiographic parameters in two different groups of professional athletes. Furthermore, a prospective study is performed analyzing the echocardiographic changes occurring in 12 professional players in 3 years of follow-up. 78 football players were examined from July 2011 to May 2016 (40 enrolled in Group A and 38 in Group B). Twelve players of GROUP A were followed for 3 consecutive seasons. The general clinical examination, the cardiopulmonary evaluation, the ECG, the ergometer stress test, the spirometric examination and the standard cardiac eco color doppler test were recorded. Left ventricle dimensions, left atrium dimensions, and interventricular septum dimensions were higher in A players than in B players. Moreover, following up 12 players for 3 years, a statistically significant increase of such values was observed. In A players, higher dimensions of the left chambers and the interventricular septum were observed, compared to B players. No statistically significant difference was found regarding the ejection fraction. The 3 years follow-up showed a statistically significant increase of both left chambers and interventricular septum dimensions, particularly in the second and third year. These findings demonstrated that A players have higher echocardiographic parameters respect to B players. The results of this study support the scientific theory that long-term intensive training influences heart function, inducing "athlete's heart" with morphological adaptations. No significant echocardiographic variation within the examined sample was observed for different roles (goalkeeper, defender, midfielder, or attacker) or skills of individual players.


#4 Age-Predicted Maximal Heart Rate Equations Are Inaccurate for Use in Youth Male Soccer Players
Reference: Pediatr Exerc Sci. 2018 Mar 15:1-5. doi: 10.1123/pes.2017-0281. [Epub ahead of print]
Authors: Cicone ZS, Sinelnikov OA, Esco MR
Summary: The purpose of this study was to compare the differences between measured (MHRobt) and predicted (MHRpred) maximal heart rate (MHR) in youth athletes. In total, 30 male soccer players [14.6 (0.6) y] volunteered to participate in this study. MHRobt was determined via maximal-effort graded exercise test. Age-predicted MHR (MHRpred) was calculated for each participant using equations by Fox, Tanaka, Shargal, and Nikolaidis. Mean differences were compared using Friedman's 2-way analysis of variance and post hoc pairwise comparisons. Agreement between MHRobt and MHRpred values was calculated using the Bland-Altman method. There were no significant differences between MHRobt and MHRpred from the Fox (P = .777) and Nikolaidis (P = .037) equations. The Tanaka and Shargal equations significantly underestimated MHRobt (P < .001). All 4 equations produced 95% limits of agreement of ±15.0 beats per minute around the constant error. The results show that the Fox and Nikolaidis equations produced the smallest mean difference in predicting MHRobt. However, the wide limits of agreement suggests that none of the equations adequately account for individual variability in MHRobt. Practitioners should avoid applying these equations in youth athletes and utilize a lab or field testing protocol to obtain MHR.


#5 Laterality-Specific Training Improves Mental Rotation Performance in Young Soccer Players
Reference: Front Psychol. 2018 Feb 27;9:220. doi: 10.3389/fpsyg.2018.00220. eCollection 2018.
Authors: Pietsch S, Jansen P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5835319/pdf/fpsyg-09-00220.pdf
Summary: This study investigates the influence of specific soccer training with the non-dominant leg on mental rotation performance of 20 adolescent soccer players between 10 and 11 years of age. While the experimental group performed soccer specific tasks only with the non-dominant foot once a week for 10 weeks, the control group absolved the same exercises with the dominant foot for the same period of time. Both groups performed a mental rotation task and shot, dribbling and ball control tests before and after the 10 week intervention. The most relevant result was that the experimental group showed a significantly larger increase in mental rotation ability than the control group.


#6 The Influence of Task Conditions on Side Foot-Kick Accuracy among Swedish First League Women's Soccer Players
Reference: J Sports Sci Med. 2018 Mar 1;17(1):74-81. eCollection 2018 Mar.
Authors: Carlsson T, Isberg J, Nilsson J, Carlsson M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5844211/pdf/jssm-17-74.pdf
Summary: The purpose of this study was to investigate the influence of the task conditions on 20-m side foot-kick accuracy among Swedish first league women's soccer players. Twenty-three players performed three side foot-kick tests under different task conditions: stationary ball using match-relevant ball speed (SBRS) and maximal ball speed (SBMS) and a 5-m run with the ball from different approach angles (0°, 30°, and 60°) to a predetermined position, where passing of the ball on the move was executed using match-relevant ball speed (RBRS). With each test, the players performed 30 side-foot kicks, alternating between kicking legs with the aim of hitting a target stick. The accuracy was determined using video analysis. The side foot-kick accuracy was significantly greater for SBRS, compared to RBRS and SBMS. For all three test variables, the preferred leg displayed greater accuracy. The preferred leg's accuracy was greater for the approach angle of 30° compared to both 0° and 60°. A significant deviation from the target stick was found for the straight-ahead approach, in which the right-foot and left-foot kicks deviated to respectively the left and right of the stick; in contrast, for the approach angle of 60°, the deviation from the target stick was on the opposite side of the approach side for both legs.


#7 Effect of 8 Weeks Soccer Training on Health and Physical Performance in Untrained Women
Reference: J Sports Sci Med. 2018 Mar 1;17(1):17-23. eCollection 2018 Mar.
Authors: Ortiz JG, da Silva JF, Carminatti LJ, Guglielmo LGA, Diefenthaeler F
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5844205/pdf/jssm-17-17.pdf
Summary: This study aims to analyze the physiological, neuromuscular, and biochemical responses in untrained women after eight weeks of regular participation in small-sided soccer games compared to aerobic training. Twenty-seven healthy untrained women were divided into two groups [soccer group (SG = 17) and running group (RG = 10)]. Both groups trained three times per week for eight weeks. The variables measured in this study were maximal oxygen uptake (VO2max), relative velocity at VO2max (vVO2max), peak velocity, relative intensity at lactate threshold (vLT), relative intensity at onset of blood lactate accumulation (vOBLA), peak force, total cholesterol, HDL, LDL, triglycerides, and cholesterol ratio (LDL/HDL). VO2max, vLT, and vOBLA increased significantly in both groups (12.8 and 16.7%, 11.1 and 15.3%, 11.6 and 19.8%, in SG and RG respectively). However, knee extensors peak isometric strength and triglyceride levels, total cholesterol, LDL, and HDL did not differ after eight weeks of training in both groups. On the other hand, the LDL/HDL ratio significantly reduced in both groups. In conclusion, eight weeks of regular participation in small-sided soccer games was sufficient to increase aerobic performance and promote health benefits related to similar aerobic training in untrained adult women.


#8 Muscle Strength Is a Poor Screening Test for Predicting Lower Extremity Injuries in Professional Male Soccer Players: A 2-Year Prospective Cohort Study
Reference: Am J Sports Med. 2018 Mar 1:363546518756028. doi: 10.1177/0363546518756028. [Epub ahead of print]
Authors: Bakken A, Targett S, Bere T, Eirale C, Farooq A, Mosler AB, Tol JL, Whiteley R, Khan KM, Bahr R
Summary: Lower extremity muscle strength tests are commonly used to screen for injury risk in professional soccer. However, there is limited evidence on the ability of such tests in predicting future injuries. The purpose of the study was to examine the association between hip and thigh muscle strength and the risk of lower extremity injuries in professional male soccer players. Professional male soccer players from 14 teams in Qatar underwent a comprehensive strength assessment at the beginning of the 2013/2014 and 2014/2015 seasons. Testing consisted of concentric and eccentric quadriceps and hamstring isokinetic peak torques, eccentric hip adduction and abduction forces, and bilateral isometric adductor force (squeeze test at 45°). Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff throughout each season. Univariate and multivariate Cox regression analyses were used to calculate hazard ratios (HRs) with 95% CIs. In total, 369 players completed all strength tests and had registered injury and exposure data. Of these, 206 players (55.8%) suffered 538 lower extremity injuries during the 2 seasons; acute muscle injuries were the most frequent. Of the 20 strength measures examined, greater quadriceps concentric peak torque at 300 deg/s (HR, 1.005 [95% CI, 1.00-1.01]; P = .037) was the only strength measure identified as significantly associated with a risk of lower extremity injuries in multivariate analysis. Greater quadriceps concentric peak torque at 60 deg/s (HR, 1.004 [95% CI, 1.00-1.01]; P = .026) was associated with the risk of overuse injuries, and greater bilateral adductor strength adjusted for body weight (HR, 0.75 [95% CI, 0.57-0.97; P = .032) was associated with a lower risk for any knee injury. Receiver operating characteristic curve analyses indicated poor predictive ability of the significant strength variables (area under the curve, 0.45-0.56). There was a weak association with the risk of lower extremity injuries for 2 strength variables: greater quadriceps concentric muscle strength at (1) high and (2) low speeds. These associations were too small to identify an "at-risk" player. Therefore, strength testing, as performed in the present study, cannot be recommended as a screening test to predict injuries in professional male soccer.


#9 Close Encounter With a Prickly Soccer Ball: An Injury from an Indian Crested Porcupine
Reference: Wilderness Environ Med. 2018 Mar 9. pii: S1080-6032(18)30003-6. doi: 10.1016/j.wem.2018.01.003. [Epub ahead of print]
Authors: Thalgaspitiya SPB, Wijerathne BTB, Thennakoon BDB
Summary: The Indian crested porcupine, Hystrix indica, is a large rodent with the unique feature of long quills. These quills are an integral part of its defense mechanism against predators. Injuries resulting from human contact with quills may cause pain, bleeding, and swelling. Quill-related injuries are common among animals such as dogs, cats, and some wild animals. The mechanism of injury, consequences, and management of injuries to humans from H indica quills are rarely described. In this report, we describe the injuries and management of a man who sustained injury from H indica quills.

#10 Inferior heel pain in soccer players: a retrospective study with a proposal for guidelines of treatment
Reference: BMJ Open Sport Exerc Med. 2018 Feb 7;4(1):e000085. doi: 10.1136/bmjsem-2015-000085. eCollection 2018.
Authors: Saggini R, Migliorini M, Carmignano SM, Ancona E, Russo C, Bellomo RG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5841518/pdf/bmjsem-2015-000085.pdf
Summary: The cause of heel pain among soccer players is multifactorial and is related to repetitive microtrauma due to impact forces involving technical moves, but also the playground, the exercise mode, the recovery time, the climatic conditions and the footwear used. The aim was to investigate the aetiology of plantar heel pain of soccer players with the objective of proposing an example of guidelines for treatment. We investigated the prevalence and characteristics of inferior heel pain of 1473 professional, semiprofessional and amateur players. All evaluated subjects were submitted to a specific rehabilitation protocol that involved advanced physical therapies and viscoelastic insoles depending on the aetiology of pain. Clinical and instrumental examinations revealed that 960 of 1473 athletes had inferior heel pain. These patients were divided into seven groups based on aetiology: sural nerve compression, abductor digiti minimi compression, atrophy and inflammation of the fat pad, plantar fasciitis, stress injury of the heel spur, stress fracture of the heel bone and heel spur. The proposed rehabilitation treatment aims for a reduction of pain and an early return to sports, with excellent results. According to what was observed in the present study, related also to the specific treatment of inferior heel pain, and considering the technological progress achieved in recent years, we can now propose an integrated therapeutic approach to treatment of heel pain, properly differentiated according to specific aetiology.