Latest research in football - week 20 - 2019

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 Relationship between Change of Direction Tests in Elite Youth Soccer Players
Reference: Sports (Basel). 2019 May 14;7(5). pii: E111. doi: 10.3390/sports7050111.
Authors: Kadlubowski B, Keiner M, Hartmann H, Wirth K, Frick U
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Summary: Change of direction (COD) is a performance-limiting factor in team sports. However, there are no exact definitions describing which physical abilities limit COD performance in soccer. Nevertheless, different COD tests are used or have been recommended as being equally effective in the professional practice of measuring COD performance. Therefore, the aim of this study was to evaluate the relationship between different COD tests, and to test the independence and generalizability of these COD tests in soccer. As such, 27 elite youth soccer players were randomly recruited and were tested in different COD tests (i.e., Illinois agility test (IAT), T agility test (TT), 505 agility test (505), Gewandtheitslauf (GewT), triangle test (Tri-t), and square test (SQT)). Bivariate Pearson correlation analysis was used to assess the relationships between the COD tests. The Benjamini-Hochberg method was used to control for the false discovery rate of the study at 0.05. This investigation calculated explained variances of 10% to 55% between performances in the different COD tests. This suggested that the tests covered different aspects or task-specific characteristics of the COD. Therefore, coaches and sport scientists should review and select different tests with a logical validity, based on the requirement profiles of the corresponding sport.

#2 Does soccer headgear reduce the incidence of sport-related concussion? A cluster, randomised controlled trial of adolescent athletes
Reference: Br J Sports Med. 2019 May 14. pii: bjsports-2018-100238. doi: 10.1136/bjsports-2018-100238. [Epub ahead of print]
Authors: McGuine T, Post E, Pfaller AY, Hetzel S, Schwarz A, Brooks MA, Kliethermes SA
Summary: There have been no large randomised controlled trials to determine whether soccer headgear reduces the incidence or severity of sport-related concussion (SRC) in US high school athletes. We aimed to determine whether headgear reduces the incidence or severity (days out from soccer) of SRCs in soccer players. 2766 participants (67% female, age 15.6±1.2) (who undertook 3050 participant years) participated in this cluster randomised trial. Athletes in the headgear (HG) group wore headgear during the season, while those in the no headgear (NoHG) group did not. Staff recorded SRC and non-SRC injuries and soccer exposures. Multivariate Cox proportional hazards models were used to examine time-to-SRC between groups, while severity was compared with a Wilcoxon rank-sum test. 130 participants (5.3% female, 2.2% male) sustained an SRC. The incidence of SRC was not different between the HG and NoHG groups for males (HR: 2.00 (0.63-6.43) p=0.242) and females (HR: 0.86 (0.54-1.36) p=0.520). Days lost from SRC were not different (p=0.583) between the HG group (13.5 (11.0-018.8) days) and the NoHG group (13.0 (9.0-18.8) days). Soccer headgear did not reduce the incidence or severity of SRC in high school soccer players.

#3 Maximum acceleration performance of professional soccer players in linear sprints: Is there a direct connection with change-of-direction ability?
Reference: PLoS One. 2019 May 14;14(5):e0216806. doi: 10.1371/journal.pone.0216806. eCollection 2019.
Authors: Loturco I, A Pereira L, T Freitas T, E Alcaraz P, Zanetti V, Bishop C, Jeffreys I
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Summary: The purpose of this study was to examine the selective influences of the maximum acceleration capability on change of direction (COD) speed, COD deficit, linear sprint speed, sprint momentum, and loaded and unloaded vertical jump performances in forty-nine male professional soccer players (24.3 ± 4.2 years; 75.4 ± 5.4 kg; 177.9 ± 6.4 cm). Soccer players performed the assessments in the following order: 1) squat and countermovement jumps; 2) 20-m sprinting speed test; 3) Zigzag COD ability test; and 4) bar-power outputs in the jump squat exercise. Athletes were divided, using a median split analysis, into two different groups according to their maximum acceleration rates from zero to 5-m (e.g., higher and lower ACC 0-5-m). Magnitude-based inference was used to compare the differences in the physical test results between "higher" and "lower" acceleration groups. A selective influence of the maximum acceleration ability on speed-power tests was observed, as the higher acceleration group demonstrated likely to almost certain higher performances than the lower acceleration group in all measurements (effect sizes varying from 0.66 [for sprint momentum in 20-m] to 2.39 [for sprint velocity in 5-m]). Conversely, the higher acceleration group demonstrated a higher COD deficit when compared to the lower acceleration group (ES = 0.55). This indicates compromised efficiency to perform COD maneuvers in this group of players. In summary, it was observed that soccer players with higher maximum acceleration rates are equally able to jump higher, sprint faster (over short distances), and achieve higher COD velocities than their slower counterparts. However, they appear to be less efficient at changing direction, which may be related to their reduced ability to deal with greater entry and exit velocities, or counterbalance the associated mechanical consequences (i.e., greater inertia) of being faster and more powerful.

#4 Relationship Between Resting Heart Rate Variability and Intermittent Endurance Performance in Novice Soccer Players
Reference: Res Q Exerc Sport. 2019 May 13:1-7. doi: 10.1080/02701367.2019.1601666. [Epub ahead of print]
Authors: Pereira LA, Abad CCC, Leiva DF, Oliveira G, Carmo EC, Kobal R, Loturco I
Summary: This study examined the relationships between the Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) and resting heart rate variability (HRV) and submaximal 5'-5' test derived measures in novice male soccer players. Forty players (11.54 ± 0.58 years) from a soccer academy participated in this study, performing physical tests on two different days, separated by 48 h, as follows: (day 1) resting HRV and Yo-Yo IR1 test, and (day 2) anthropometric assessments (for peak height velocity assessment [PHV]) and the 5'-5' test. The Pearson product-moment correlation coefficient was used to determine the correlations between Yo-Yo IR1 performance and the remaining variables. A partial correlation analysis was further performed using age, stature, body mass, distance to PHV, and age at PHV as "confounders." The highest correlation score was observed between Yo-Yo IR1 performance and resting HRV, when the absolute age was used as confounder (r = 0.72; p < .05). We observed that a practical measure of parasympathetic activity at rest is largely associated with performance obtained during a traditional intermittent endurance performance test.

#5 Shorter Small-Sided Game Sets May Increase the Intensity of Internal and External Load Measures: A Study in Amateur Soccer Players
Reference: Sports (Basel). 2019 May 9;7(5). pii: E107. doi: 10.3390/sports7050107.
Authors: Clemente FM, Nikolaidis PT, Rosemann T, Knechtle B
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Summary: The purpose of this study was to compare internal and external load measures during two regimens (6 x 3' and 3 x 6') of a 5 vs. 5 format of play. Moreover, within-regimen changes (between sets) were also tested. Ten amateur soccer players (age: 19.8 ± 1.6 years; experience: 8.3 ± 2.1 years; height: 177.4 ± 3.8 cm; weight: 71.7 ± 4.2 kg) participated in the experiment. Internal load was measured using the CR-10 scale as the rated of perceived exertion (RPE) scale and a heart rate (HR) monitor. The measurements of total (TD), running (RD) and sprinting (SD) distances were also collected using a 10-Hz validated and reliable GPS. Comparisons between regimens revealed that the 3 x 6' regimen was significantly more intense in terms of RPE than the 6 x 3' regimen (p = 0.028; d = 0.351), although no significant differences were found in HR. Significantly greater averages of TD (p = 0.000; d = 0.871) and RD (p = 0.004; d = 0.491) were found in the 6 x 3' regimen. In both regimens, the RPE was significantly lower during the first set than in the remaining sets. On the other hand, the TD was significantly shorter in the last sets than in the earlier. In summary, the present study suggests that shorter sets may be beneficial for maintaining higher internal and external load intensities during 5 vs. 5 formats, and that a drop-in performance may occur throughout the sets in both regimens.

#6 Maximal heart rate assessment in recreational football players. A study involving a multiple testing approach
Reference: Scand J Med Sci Sports. 2019 May 21. doi: 10.1111/sms.13472. [Epub ahead of print]
Authors: Póvoas SCA, Krustrup P, Pereira R, Vieira S, Carneiro I, Magalhães J, Castagna C
Summary: This study aimed at examining the suitability of a standard treadmill test (TT), popular intermittent field tests and small-sided recreational football matches to induce maximal heart rate (HRmax ) in recreational football players. Sixty-six male sedentary untrained subjects (age 39.3±5.8 years, VO2max 41.3±6.2 ml·kg-1 ·min-1 , body mass 81.9±10.8 kg, height 173.2±6.4 cm) were evaluated. On separate occasions, the players were randomly submitted to a progressive VO2max TT, to the Yo-Yo intermittent endurance level 1 (YYIE1) and level 2 (YYIE2) tests, to the Yo-Yo intermittent recovery level 1 (YYIR1) test, and to 7v7 (43x27 m pitch, 83 m2 /player) football matches (45 min; 2-4 matches/player). To ensure data consistency, exercise HR was recorded using the same HR monitors in all the experimental conditions. A total of 73, 24, 18, 17 and 30% of players achieved HRmax during the YYIE1, YYIE2, YYIR1, TT and the small-sided football matches, respectively. The probability of achieving HRmax increased proportionally to test duration, with 7.8 min as the cut-off time. Variations in HRpeak of ±2 b. min-1 should be regarded as of practical relevance. YYIE1 HRpeak provided the most accurate estimation of a subject's individual HRmax and much higher probability of reaching HRmax . Nevertheless, the results of this study suggest caution in considering a reference test for HRmax assessment in this population. The use of confirmation tests is still highly advisable when the test duration is shorter than 7.8 min. In this regard, field tests seem to be suitable and accurate for individual HRmax assessment in recreational football players.

#7 The effect of the change of football turf on knee kinematics of adolescent male football players
Reference: J Sports Med Phys Fitness. 2019 May 20. doi: 10.23736/S0022-4707.19.09774-3. [Epub ahead of print]
Authors: Zhou B, Li B, Bai L
Summary: The aim of this study was to investigate the effect of the change of football turf on knee kinematics of adolescent male football players. Thirteen adolescent male football players were tested by a portable infrared motion analysis system based on markers. The angular displacements of flexion/extension,valgus/ varus and internal/external rotation were calculated respectively when players performed 90° shuttle running on artificial turf and natural turf. The maximum valgus angle and range of valgus/varus were larger when they were changed from artificial turf to natural turf (P<0.05). There were no significant differences in the maximum flexion angle, maximum extension angle,range of flexion/extension,maximum varus angle,maximum internal rotation angle, maximum external rotation angle and range of internal/external rotation(P>0.05). The change of football turf has a significant effect on knee kinematics of adolescent male football players.The risk of noncontact anterior cruciate ligament(ACL) injury is increased when players who are changed from artificial turf to natural turf.

#8 The Relationship Between Cognitive Functions and Sport-Specific Motor Skills in Elite Youth Soccer Players
Reference: Front Psychol. 2019 Apr 25;10:817. doi: 10.3389/fpsyg.2019.00817. eCollection 2019.
Authors: Scharfen HE, Memmert D
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Summary: The aim of the present study was to examine the relationship between basic cognitive functions and sport-specific motor skills in elite youth soccer players. A total of 15 elite youth soccer players aged 11-13 years performed a computer-based test battery measuring the attention window (AW), perceptual load (PL), working memory capacity (WMC), and multiple object tracking (MOT). Another set of tests was used to asses speed abilities and football-specific technical skills (sprint, change of direction, dribbling, ball control, shooting, and juggling). Spearman's correlation tests showed that the diagonal AW was positively associated with dribbling skills (rs = 0.656) which indicates that a broader AW could be beneficial for highly demanding motor skills like dribbling. WMC was positively related to dribbling (rs = 0.562), ball control (rs = 0.669), and ball juggling (rs = 0.727). Additionally, the cumulated score of all cognitive tests was positively related to the cumulated motor test score (rs = 0.614) which supports the interplay of physical and psychological skills. Our findings highlight the need for more, and especially longitudinal, studies to enhance the knowledge of cognition-motor skill relationships for talent identification, talent development, and performance in soccer.

#9 Physical and Physiological Responses during the Stop-Ball Rule During Small-Sided Games in Soccer Players
Reference: Sports (Basel). 2019 May 17;7(5). pii: E117. doi: 10.3390/sports7050117.
Authors: Halouani J, Ghattasi K, Bouzid MA, Rosemann T, Nikolaidis PT, Chtourou H, Knechtle B
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Summary: Small-sided games (SSGs) are a recommended training method for significant performance enhancement, and training efficiency. The stop-ball (SSG-SB) effects on physical responses (e.g., acceleration, deceleration, sprints, total distance, and indicator of workload) have not been investigated yet. This study aimed to investigate the effects of the SSG-SB compared to the small-goals SSG (SSG-SG) on physical and heart rate (HR) responses at high intensity (total distance (>18 km/h)), sprints (>18 km/h), and acceleration and deceleration (>3 m/s²) during a 4 vs. 4 SSG format in youth professional soccer players. Sixteen male elite young soccer players (mean ± SD body height, 176.5 ± 6.3 cm; age, 18.3 ± 0.7 years; body weight, 73.4 ± 7.2 kg) performed two forms of SSGs, i.e., SSG-SB or SSG-SG, for 4 × 4 min with a recovery of 2 min between sets. Data were compared using the t-test. The SSG-SB induced a significantly higher mean HR (180.0 ± 2.0 vs. 173.0 ± 3.0 beats per minute; p < 0.05) compared to the SSG-SG. Likewise, the SSG-SB was significantly higher compared to the SSG-SG for total distance (2580 ± 220.3 vs. 2230 ± 210 m; p < 0.001), player load (98.07 ± 12.5 vs. 89.4 ± 10.5; p < 0.05), sprint distance (7.9 ± 2.3 vs. 5.2 ± 2.0 m; p < 0.05), acceleration (15.6 ± 2.75 vs. 12.5 ± 1.75; p < 0.05), and deceleration (17.3 ± 3.20 vs. 14.4 ± 2.55; p < 0.05). However, no significant difference was found between the SSG-SG and the SSG-SB for maximal velocity, power, and sprints duration. This study provides new information about the effectiveness of the SSG-SB as a training stimulus for soccer.

#10 Comparative Effects of Game Profile-Based Training and Small-Sided Games on Physical Performance of Elite Young Soccer Players
Reference: J Strength Cond Res. 2019 May 27. doi: 10.1519/JSC.0000000000003225. [Epub ahead of print]
Authors: Dello Iacono A, Beato M, Unnithan V
Summary: This study was designed to investigate and compare the effects of game profile-based training (GPBT) and small-sided game (SSG) training on physical performances of elite youth soccer players during the in-season period. Twenty young soccer players (18.6 ± 0.6) were randomly assigned to either GPBT or SSG protocols performed twice a week for 8 weeks. The GPBT consisted of 2 sets of 6-10 minutes of intermittent soccer-specific circuits. The SSG training consisted of 3-5 sets of 5 vs. 5 SSGs played on a 42 × 30-m pitch. Before and after the training program, the following physical performances were assessed: repeated sprint ability, change of direction (COD), linear sprinting on 10 m and 20 m, countermovement jump, and intermittent running (YYIRL1). Significant improvements were found in all the assessed variables after both training interventions (p < 0.05). The GPBT group improved more than the SSG group in the 10-m and 20-m sprint tests by 2.4% (g = 0.4; small effect) and 4% (g = 0.9; large effect), respectively. Conversely, the SSG group jumped 4% higher (g = 0.4; small effect) and resulted 6.7% quicker than the GPBT (g = 1.5; large effect) in completing the COD task. These results suggest both GPBT and SSGs to be effective for fitness development among elite young soccer players during the competitive season. More importantly, these 2 conditioning methodologies may be considered in terms of specificity for selectively improving or maintaining specific soccer fitness-related performances in the latter phase of the season.

#11 The Experiences of Young Men, Their Families, and Their Coaches Following a Soccer and Vocational Training Intervention to Prevent HIV and Drug Abuse in South Africa
Reference: AIDS Educ Prev. 2019 Jun;31(3):224-236. doi: 10.1521/aeap.2019.31.3.224.
Authors: Swendeman D, Bantjes J, Mindry D, Stewart J, Tomlinson M, Rotheram-Borus MJ, Medich M
Summary: Young men in South Africa are at high-risk for HIV, substance abuse, and gender-based violence. This article presents qualitative results from a pilot study testing soccer leagues and vocational training to engage young-adult township men to deliver preventive interventions, including rapid HIV and alcohol/drug testing, shifting attitudes toward gender-based violence, and promoting other prosocial behaviors. Three groups participated in focus groups and in-depth interviews on experiences with the program: (1) a subset of 15 participants, (2) 15 family members, and (3) five intervention coaches. Results suggest that participants first reduced substance use on tournament days and then gradually reduced to practice days and beyond. Families suggested that "keeping young men occupied" and encouragement of prosocial behaviors was critical to risk reduction and led to increased community respect for the men. Coaches noted that behavioral and attitudinal changes were incremental and slow. The use of incentives was problematic and more research is needed to understand how incentives can be used in interventions of this nature.

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