Latest research in football - week 42 - 2020

#1 The Immediate Effect of Spinal Manipulation on Ball Velocity and Neuromuscular Function During an Instep Kick in Former Varsity Soccer Players: A Feasibility Study
Reference: J Strength Cond Res. 2020 Aug 18. doi: 10.1519/JSC.0000000000003720. Online ahead of print.
Authors: Melissa Corso, Carmen Liang, Steve Tran, Scott Howitt, John Srbely, Silvano A Mior
Summary: Spinal manipulation (SM) has been shown to increase ball velocity (BV) in soccer players. Evidence suggests that SM modulates responses at spinal or cortical levels to enhance force production in asymptomatic populations. No studies have explored the underlying neuromuscular mechanisms contributing to changes in BV post-SM in soccer players. We assessed the feasibility of measuring change in BV and neuromuscular function after SM in former Varsity level soccer players with a pre-post study design. Three to 5 maximal instep kicks were performed before and after SM at the L3-5 level. Ball velocity was measured using high-speed camera. Activation of lower limb and trunk musculature was recorded with electromyography. Outcomes included ease of recruitment, scheduling and data capture, as well as expectation and perception of SM effect and adverse events (AE). Fifteen potential subjects were recruited over 1.5 months. Eleven were scheduled (24-31 years; 8 females, 3 males). Two subjects reported mild AE after maximal voluntary isometric contraction testing. A significant increase in BV (mean change: 1.75 m·s [95% confidence interval: 0.5-3.0]) and a trend to increased peak-activation of knee extensors (90.7%) were observed post-SM. Findings suggest that our recruitment strategy and methodology are feasible in a larger trial with some modifications. Our preliminary findings support previous research by suggesting that increased BV may be mediated through increased activation of knee extensors during the kick. Our findings may offer additional insight into the underlying neuromuscular mechanisms contributing to immediate change in BV post-SM.


#2 Importance of anthropometric features to predict physical performance in elite youth soccer: a machine learning approach
Reference: Res Sports Med. 2020 Aug 23;1-12. doi: 10.1080/15438627.2020.1809410. Online ahead of print.
Authors: Tindaro Bongiovanni, Athos Trecroci, Luca Cavaggioni, Alessio Rossi, Enrico Perri, Giulio Pasta, F Marcello Iaia, Giampietro Alberti
Summary: The present study aimed to determine the contribution of soccer players' anthropometric features to predict their physical performance. Sixteen players, from a professional youth soccer academy, were recruited. Several anthropometric features such as corrected arm muscle area (AMAcorr), arm muscle circumference (AMC) and right and left suprapatellar girths (RSPG and LSPG) were employed in this study. Players' physical performance was assessed by the change of direction (COD), sprint (10-m and 20-m), and vertical jump (CMJ) tests, and Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IRT1). Using an extra tree regression (ETR) model, the anthropometric features permitted to accurately predict 10-m sprint, 20-m sprint and Yo-Yo IRTL 1 performance (p < 0.05). ETR showed that upper-body features as AMAcorr, and AMC affected 10-m and 20-m sprint performances, while lower-body features as RSPG and LSPG influenced the Yo-Yo IRTL 1 (Overall Gini importance ≥ 0.22). The model predicting COD and CMJ presented a poor level of prediction, suggesting that other factors, rather than anthropometric features, may concur to predict their changes in performance. These findings demonstrated that the upper- and lower-body anthropometric features are strictly related to sprint and aerobic fitness performance in elite youth soccer.


#3 Injuries according to the percentage of adult height in an elite soccer academy
Reference: J Sci Med Sport. 2020 Aug 11;S1440-2440(20)30736-2. doi: 10.1016/j.jsams.2020.08.004. Online ahead of print.
Authors: X Monasterio, S M Gil, I Bidaurrazaga-Letona, J A Lekue, J Santisteban, G Diaz-Beitia, I Martin-Garetxana, E Bikandi, J Larruskain 
Summary: This study aimed to ascertain if there is a defined pattern of injury related to the percentage of attained adult height and classify injuries according to maturity status bands. From 1998-2019, 63 elite male soccer players of at least the U12 category from a Spanish LaLiga club's academy were followed until reaching their final height. Medical staff recorded injuries following the FIFA consensus and measured height 2-3 times per season. The percentage of adult height at which each injury occurred was calculated using the player's closest height to the injury and his final adult height. Injuries were classified in maturity bands, pre-peak-height-velocity (PHV) <88%, circa-PHV 88%-96%, and post-PHV >96%. There were 509 injuries among the 63 players. Growth-related injuries occurred at a median (IQR) of 91.2% (86.7%-95.2%) of adult height, predominating in pre-PHV and PHV bands. Muscle injuries predominantly occurred at post-PHV, with 77.78% of those conditions occurring within that time frame and at 98.7% (96%-99.5%) of adult height. Likewise, knee and ankle joint/ligament injuries predominated at post-PHV (87% and 65% of total cases, respectively) occurring at 99.0% (97.9%-99.9%) and 98.4% (89.2%-99.4%) of adult height, respectively. Injuries follow a specific pattern according to the percentage of adult height.


#4 Predicting Maximal Lactate Steady State from Carminatti's Shuttle Run Test in Soccer Players
Reference: Int J Sports Med. 2020 Aug 25. doi: 10.1055/a-1224-3985. Online ahead of print.
Authors: Lorival José Carminatti, Bruna Nunes Batista, Juliano Fernandes da Silva, Artur Ferreira Tramontin, Vitor Pereira Costa, Ricardo Dantas de Lucas, Fernando Klitzke Borszcz
Summary: The objective of the present study was to determine the validity of Carminatti's shuttle run incremental test-T-Car derived parameters in estimating the maximal lactate steady state determined in shuttle run format. Eighteen soccer players performed a T-Car test, and several trials to determine the maximal lactate steady state. From T-Car were derived the heart rate deflection point, peak speed, maximal heart rate and parameters resulting from percentage of peak measures. The validity was accessed by Bland-Altman plots, linear regressions, and two one-sided tests of equivalence analysis. The results showed the speed at 80.4% of T-Car peak speed, the heart rate deflection point and the 91.4% of maximal heart rate were equivalent to maximal lactate steady state (Mean difference; ±90% compatibility interval; -0.8; ±1.5%, -0.4; ±1.1%, and 0.0; ±2.7%, respectively). Additionally, peak speed during the T-Car test was a stronger predictor of maximal lactate steady state (MLSS [km/h]=2.57+0.65 × sPeak; r=0.82 [90% CI; 0.62-0.92], standard error of the estimate=3.6%; 90% CI ×/÷1.4). Therefore, soccer players can use the T-Car derived parameters as a noninvasive and practical alternative to estimate the specific maximal lactate steady state for soccer.


#5 Relationships between Linear Sprint, Lower-Body Power Output and Change of Direction Performance in Elite Soccer Players
Reference: Int J Environ Res Public Health. 2020 Aug 22;17(17):E6119. doi: 10.3390/ijerph17176119.
Authors: Monika Papla, Michal Krzysztofik, Grzegorz Wojdala, Robert Roczniok, Marcin Oslizlo, Artur Golas
Download link: https://www.mdpi.com/1660-4601/17/17/6119/pdf
Summary: The aim of this study was to investigate the relationship between linear sprint, power output obtained during a squat and change of direction (COD) performance. Fifteen elite soccer players participated in this study (age = 21.7 ± 0.72 years, body mass = 74.9 ± 9.11 kg, body height = 180.4 ± 7 cm, training experience = 9 ± 1.5 years). To examine these correlations a following battery of tests were carried out: 20-m linear sprint, one-repetition maximum (1RM) squat strength, peak power output obtained during a squat at 50% 1RM and time obtained in two 20-m COD tests with different angles of direction change (90° and 135°). In addition, COD deficits (90°-CODDEF and 135°-CODDEF) for both COD tests were calculated. The Spearman's rank order correlation showed a nearly perfect statistical relationship between the 90°-COD and the 90°-CODDEF (r = 0.9; p < 0.001). In the case of 90°-CODDEF, there was a large statistical relationship with 135°-CODDEF (r = 0.59; p = 0.021). Moreover, there was a nearly perfect statistical relationship between 135°-COD and 135°-CODDEF (r = 0.91; p < 0.001). The statistically insignificant (p > 0.05) relationship between 20-m linear sprint time, power output obtained during a squat at 50% 1RM, 1RM squat strength level and both COD test, as well as both COD deficits were found. Results of the present study showed that 20-m linear sprinting speed, 1RM squat strength, power output obtained during squat at 50% 1RM and COD ability at 90° and 135° angles, are separate physical qualities. Moreover, it seems that COD deficit provides a more isolated measure of COD ability than the COD tests alone and does not must be limited to a specific angle, but provides knowledge about the COD ability in a range of other angles, at least concerning 90° and 135° COD angles.


#6 Nine typical injury patterns in German professional male football (soccer): a systematic visual video analysis of 345 match injuries
Reference: Br J Sports Med. 2020 Aug 26;bjsports-2019-101344. doi: 10.1136/bjsports-2019-101344. Online ahead of print.
Authors: Christian Klein, Patrick Luig, Thomas Henke , Hendrik Bloch, Petra Platen
Summary: We aimed to systematically analyse the videos of acute injuries in professional men's football and describe typical injury patterns. Injuries were registered with the German statutory accident insurance for professional athletes as part of occupational accident reporting. Following each season (2014-2017), video footage of the two highest divisions in German male football was searched for moderate and severe acute match injuries. Two raters then independently assessed the injuries for: game situation, player and opponent behaviour, referee decision, and injury mechanisms. The total data set included 7493 acute injuries. Of these, 857 (11%) were moderate or severe match injuries. The video search yielded 345 (40%) clearly identifiable injuries and of those 170 (49%) were contact injuries. We describe nine typical injury patterns: one each for head and shoulder injuries, two for thigh and ankle, and three for knee injuries. The nine patterns are called: (1) Head-to-head injury. (2) Collision-and-fall shoulder injury. (3) Sprinter's thigh injury. (4) Perturbation-and-strain thigh injury. (5) Tackle knee injury. (6) Tackle-and-twist knee injury. (7) Non-contact knee injury. (8) Attacked ankle injury. (9) Collision-and-twist ankle injury. Thigh injuries occurred primarily in non-contact situations (44/81), mostly while the player was sprinting (23/44). Knee injuries were often caused by direct external impact (49/84)-mainly suffered by the tackler during a tackle (17/49). The nine common injury patterns in football differed substantially in their mechanisms and causes.


#7 Intra-Individual and Seasonal Variation of Selected Biomarkers for Internal Load Monitoring in U-19 Soccer Players
Reference: Front Physiol. 2020 Aug 4;11:838. doi: 10.3389/fphys.2020.00838. eCollection 2020.
Authors: Manuel Becker , Billy Sperlich  3 , Christoph Zinner  4 , Silvia Achtzehn  5   6
Affiliations
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7417431/pdf/fphys-11-00838.pdf
Summary: The aim of this study was to investigate inter-day and -week as well as intra- and inter-individual variation of selected biomarkers in high-performance youth soccer players to assist practitioners interpreting player's internal load to counteract underperformance and unwanted health risks. Eleven male youth soccer players were tested multiple times during two 3-week periods at midpoint (3-wkmid) and at the end (3-wkend) of the first half of a German under-19 1. Bundesliga season. The levels of creatine kinase (CK), urea, and C-reactive protein (CRP) were measured during 3-wkmid and 3-wkend each Monday, Wednesday, and Friday. In 3-wkmid the CK median was 14% higher (241 vs. 212 U/L) compared to 3-wkend (P = 0.26, ES = 0.16). Overall, the medians of CK, urea (P = 0.59, ES = 0.08), and CRP (P = 0.56, ES = 0.10) during 3-wkmid did not differ to the values of 3-wkend. Daily coefficient of variations (CVs) ranged from 22 to 71% (CK), 17 to 37% (urea), and 9 to 164% (CRP). Individual medians ranged from 101 to 350 U/L (CK), 23 to 50 mg/dL (urea), and 0.6 to 1.1 mg/L (CRP). High intra-individual variability was demonstrated by large intra-individual CVs (medians: CK 50%, urea 18%, and CRP 45%). Our data show (i) large inter-day and inter-week variability of all biomarkers, depending on the external load and (ii) considerable inter- and intra-individual parameter variations. Creatine kinase concentrations could sensitively reflect soccer-specific loads during the season.


#8 TacticUP Video Test for Soccer: Development and Validation
Reference: Front Psychol. 2020 Aug 4;11:1690. doi: 10.3389/fpsyg.2020.01690. eCollection 2020.
Authors: Guilherme Machado, Israel Teoldo da Costa
Download links: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7422863/pdf/fpsyg-11-01690.pdf
Summary: This study aims to expand the process of tactical assessment of soccer players through the development and validation of a video-based test based on core tactical principles of play. The TacticUP video test for soccer is composed of offensive and defensive video sequences of 11vs11 soccer situations. Participants should choose the most appropriate solution for each video sequence. Content validity was established based on a panel of nine experts from four different countries. Construct validity was assessed through the comparison between players with distinct expertise levels. Comparisons between groups' final scores showed statistical differences (p < 0.05) in 10 out of the 15 variables assessed, in which the expert group displayed higher values compared to the non-expert group. Face validity examined the acceptability and suitability of the test by players. Reliability was determined through the test-retest method for each video sequence, and Cohen's Kappa values ranged from 0.622 to 1.0. Therefore, the TacticUP video test showed adequate content, construct, and face validity and was a reliable measure of perceptual-cognitive and decision-making skills in soccer. We overcame limitations from previous video-based tests in soccer by introducing situations concerning off-the-ball movements in both offensive and defensive phases. The practical applications of this test are: (i) it can be used to monitor players' perceptual-cognitive and decision-making skills; (ii) the test is based on players' response selection in a video-based test, which enables the measurement of their perceptual-cognitive and decision-making skills based on the core tactical principles of play; (iii) generate players' tactical profile considering their perceptual-cognitive and decision-making skills based on core tactical principles of play; and (iv) measure the effectiveness of intervention/training programs on the development of perceptual-cognitive and decision-making skills.


#9 On-Field Perceptual-Cognitive Training Improves Peripheral Reaction in Soccer: A Controlled Trial
Reference: Front Psychol. 2020 Aug 7;11:1948. doi: 10.3389/fpsyg.2020.01948. eCollection 2020.
Authors: Nils Schumacher, Rüdiger Reer , Klaus-Michael Braumann
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7427441/pdf/fpsyg-11-01948.pdf
Summary: Abilities such as peripheral reaction are of special importance in soccer. Whether these abilities can be improved by sport-specific on-field interventions remains unclear. The aim of the present controlled trial was to investigate the effect of a soccer-specific perceptual-cognitive on-field training on peripheral reaction of highly talented soccer players aged 12-13 years. N = 38 male elite athletes from young talent centers were allocated to an intervention (n = 19) and a control group (CG) (n = 19). Computer-based peripheral perception tests were conducted before and after intervention. Combining a sport-specific and a juggling task, the intervention was performed once a week (8 weeks, 20 min per week) in addition to team training. The CG exclusively underwent usual team training. Analyses show significant differences between the two groups for peripheral reaction time (PRT), with significant improvements for the intervention group and none for the CG. Furthermore, results indicate that improvements in peripheral reaction might be due to changes in the reaction time of right-footed players. Future studies should be conducted to clarify the effect of sport-specific on-field training approaches on PRT. These analyses should consider the influence of lateralization on effectivity of perceptual-cognitive on-field training approaches.


#10 An Acute Bout of Soccer Heading Subtly Alters Neurovascular Coupling Metrics
Reference: Front Neurol. 2020 Jul 24;11:738. doi: 10.3389/fneur.2020.00738. eCollection 2020.
Authors: Jonathan D Smirl, Dakota Peacock, Alexander D Wright, Kevin J Bouliane , Jill Dierijck, Joel S Burma, Michael Kennefick, Colin Wallace, Paul van Donkelaar
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7396491/pdf/fneur-11-00738.pdf
Summary: The current investigation examined how a bout of soccer heading may impact brain function. We used controlled soccer heading. Seven male soccer players (24.1 ± 1.5 years) participated in this study. 40 successful soccer headers were performed in 20 min (25 m, launch velocity ~80 km/h). X2 xPatch recorded linear and rotational head accelerations during each impact. A contact control "sham" condition - ball made body contact, but not by the head; and a no activity time "control" condition were also completed. Posterior and middle cerebral artery (PCA and MCA, respectively), cerebral blood velocity (CBV) was recorded during a visual task (neurovascular coupling: NVC) alongside SCAT3 symptoms scores pre/post a controlled bout of soccer heading. Cumulative linear and rotational accelerations were 1,574 ± 97.9 g and 313,761 ± 23,966 rads/s2, respectively, during heading and changes in SCAT3 symptom number (pre: 2.6 ± 3.0; post: 6.7 ± 6.2, p = 0.13) and severity (pre: 3.7 ± 3.6, post: 9.4 ± 7.6, p = 0.11) were unchanged. In the PCA, no NVC differences were observed, including: relative CBV increase (28.0 ± 7.6%, p = 0.71) and total activation (188.7 ± 68.1 cm, p = 0.93). However, MCA-derived NVC metrics were blunted following heading, demonstrating decreased relative CBV increase (7.8 ± 3.1%, p = 0.03) and decreased total activation (26.7 ± 45.3 cm, p = 0.04). Although an acute bout of soccer heading did not result in an increase of concussion-like symptoms, there were alterations in NVC responses within the MCA during a visual task. This suggests an acute bout of repetitive soccer heading can alter CBV regulation within the region of the brain associated with the header impacts.


#11 No relationship between the nordic hamstring and two different isometric strength tests to assess hamstring muscle strength in professional soccer players
Reference: Phys Ther Sport. 2020 Aug 18;46:97-103. doi: 10.1016/j.ptsp.2020.08.009. Online ahead of print.
Authors: Víctor Moreno-Pérez, Alberto Méndez-Villanueva, Aitor Soler, Juan Del Coso, Javier Courel-Ibáñez
Summary: The aim was to investigate the relationship between one eccentric and two isometric tests commonly used to assess hamstring strength in professional soccer. Twenty male professional soccer players participated in this study. Hamstring force was quantified during 3 tests (Nordic hamstring eccentric, 90:20 isometric posterior-chain strength and isometric 15° knee flexion) using a load cell, a handheld dynamometer and a force platform, respectively. Poor relationships and low concordance were observed between isometric and eccentric tests, showing different ability to discriminate hamstring weakness and asymmetries. The Nordic hamstring test identified between-limb asymmetry >15% in 30% of the players, 25% in the 15° knee flexion and 5% in the 90:20 test. All players obtained different results in the three tests with only one showing asymmetry >15% in two tests. Results obtained in each test cannot inform the others. Mechanical outputs of these tests must be used for particular purposes during the prevention, rehabilitation and monitoring process of hamstring injury. Isometric testing might be preferable during the initial phases of the recovery process of a hamstring injury while the Nordic hamstring test might be used in the last stages or detect muscle weakness/asymmetries in non-injured players.


#12 Ankle laxity affects ankle kinematics during a side-cutting task in male collegiate soccer athletes without perceived ankle instability
Reference: Phys Ther Sport. 2020 Aug 28;46:89-96. doi: 10.1016/j.ptsp.2020.08.012. Online ahead of print.
Authors: Shun Kunugi, Takashi Koumura, Ryota Myotsuzono, Akihiko Masunari, Naruto Yoshida, Shumpei Miyakawa, Naoki Mukai
Summary: The objective was to investigate whether ankle joint laxity alone influences lower limb kinematics during a side-cutting task. In total, 66 male collegiate soccer players with history of ankle sprains with no perceived ankle instability were categorised into three groups: no-laxity copers (n = 26), laxity copers (n = 23), and severe-laxity copers (n = 17). The hip, knee, ankle, rearfoot, midfoot, and forefoot kinematic data during the stance phase (0%-100% indicated initial contact to take-off) of a 45° side-cutting task were analysed using one-dimensional statistical parametric mapping. The horizontal plane kinematics of the rearfoot differed significantly among the three groups during 30%-91% of the stance phase (P < .05). Severe-laxity copers exhibited a greater external rotation angle than no-laxity copers during 6%-14% and 32%-92% of the stance phase (P < .05). Our data suggest that severe ankle joint laxity affects rearfoot horizontal plane kinematics in individuals without perceived ankle instability performing a 45° side-cutting task. These findings could be used by clinicians in developing rehabilitation programs to prevent further ankle sprains in patients with severe ankle joint laxity.