Latest research in football - week 41 - 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 Isometric Posterior Chain Peak Force Recovery Response Following Match-Play in Elite Youth Soccer Players: Associations with Relative Posterior Chain Strength
Reference: Sports (Basel). 2019 Oct 1;7(10). pii: E218. doi: 10.3390/sports7100218.
Authors: Constantine E, Taberner M, Richter C, Willett M, Cohen DD
Download link:
Summary: The purpose of this study was to determine changes in two tests of lower limb isometric posterior chain force (IPC-F) following 90 min of match-play in elite youth soccer players and the interaction between relative strength and recovery profile. 14 players (age: 16 ± 2 years) performed 3 × 3 second IPC-F tests unilaterally at 30° and 90° of knee and hip flexion pre- and post-match, +24 h, +48 h, and +72 h post-match. Peak force was recorded for both limbs, combined and expressed relative to bodyweight (N/kg). A two-way repeated measures analysis of variance was performed to determine differences in force output between joint angles, time intervals and subjects. As there was no interaction between angle and time (p = 0.260), we report the change between timepoints as mean Δ in 90° + 30° IPC-F. Relative to pre-match IPC-F, there were significant decreases post (Δ = -18%; p > 0.001) and at +24 h (Δ = -8%; p = 0.040), no significant difference at +48 h (Δ = 0%; p = 0.992) and a significant increase at +72 h (Δ = +12%; p = 0.005). There was a large inter-individual variability in recovery profile at both angles and substantial differences between post-match deficits at 90° (-10.8%) compared to 30° (-20.7%). Higher pre-match IPC-F was correlated with the magnitude of IPC-F deficits at both angles and all time points (r = 0.56 to 0.70, p = < 0.01) except for post-match 90°. Regular IPC-F monitoring to determine the magnitude of match-induced fatigue and track recovery may help inform decision-making regarding modifications to individual players training load, particularly as there is a large inter-individual variability in response to competition. Further research is warranted to better understand and address the finding that stronger players showed larger force deficits and slower recovery following match-play.

#2 Investigating the Clinical Effect of Kinesio Tape on Muscle Performance in Healthy Young Soccer Players - A Prospective Cohort Study
Reference: Clinics (Sao Paulo). 2019 Sep 26;74:e1158. doi: 10.6061/clinics/2019/e1158. eCollection 2019.
Authors: Alrawaili SM
Download link:
Summary: Kinesio tape (KT) is a visible adhesive restorative tape that has typically been utilized for injury prevention, recovery, and even performance improvement, but limited studies have assessed the effect of KT on muscle performance. The purpose of this study was to investigate the clinical impact of KT on muscle performance in healthy young soccer players. Between 25 March and 21 April 2017, sixteen healthy soccer players with a mean age of 20±2.17 were enrolled in this prospective cohort study. All participants were selected from the college football team of Prince Sattam Bin Abdulaziz University. The muscle performance of the players was evaluated with an isokinetic dynamometer for the following three conditions: without tape, immediately after applying KT, and 8 hrs post-KT application while the tape remained on the same site. The differences in peak torque and total work among the three conditions were nonsignificant (p>0.05). Additionally, applying KT to the thigh muscles did not decrease or increase the performance of non injured healthy soccer players (p>0.05). KT does not lead to beneficial outcomes of muscle performance in healthy young soccer players.

#3 Biomechanical mechanisms of jumping performance in youth elite female soccer players
Reference: J Sports Sci. 2019 Oct 1:1-7. doi: 10.1080/02640414.2019.1674526. [Epub ahead of print]
Authors: Jeras NMJ, Bovend'Eerdt TJH, McCrum C
Summary: We aimed to determine key biomechanical parameters explaining age-related jumping performance differences in youth elite female soccer players. Multiple biomechanical parameters from countermovement (CMJ) squat (SJ) and drop (DJ) jump testing of elite female soccer players (n = 60) within the same national training centre were analysed across ages 9-11y, 12-14y and 15-19y. Effects of age group and jump type on jump height were found, with the older jumping higher than the younger groups in all jumps (P < 0.05). For DJ, higher reactive strength index was found for older, compared to each younger group (P < 0.001). For CMJ and SJ, peak power was the most decisive characteristic, with significant differences between each group for absolute peak power (P < 0.0001) and body-weight-normalised peak power in CMJ (57 ± 7W/kg, 50 ± 7W/kg, 44.7 ± 5.5W/kg; P < 0.05) and between the older and each younger group in SJ (56.7 ± 7.1W/kg, 48.9 ± 7.1W/kg, 44.6 ± 6W/kg; P < 0.01). Age-related differences in jumping performance in youth elite female soccer players appear to be due to power production during standing jumps and by the ability to jump with shorter ground contact times during reactive jumps.

#4 Effect of Match Location, Team Ranking, Match Status and Tactical Dimensions on the Offensive Performance in Spanish 'La Liga' Soccer Matches
Reference: Front Psychol. 2019 Sep 12;10:2089. doi: 10.3389/fpsyg.2019.02089. eCollection 2019.
Authors: González-Rodenas J, Aranda-Malavés R, Tudela-Desantes A, Calabuig Moreno F, Casal CA, Aranda R

Download link:
Summary: The aim of this paper was to study the combined effects of tactical and contextual dimensions on achieving offensive performance in open play possessions from Spanish "La Liga" soccer matches. 1860 team possessions from 20 random matches were evaluated by means of multidimensional observation. Multilevel regression models were constructed to predict the probability to achieve offensive performance according to the tactical and contextual dimensions registered in each possession. Performing penetrative actions after recovering the ball (OR = 1.497; 95% CI: 1.022-2.192; P < 0.05), and progressing by fast attacks (OR = 3.588; 95% CI: 2.045-6.294; p < 0.001) or counterattacks (OR = 7.097; 95% CI: 3.530-14.269; P < 0.001) was more effective to create scoring opportunities than performing a non-penetrative action and progressing by combinative attack, respectively. Also, progressing by long possessions (OR = 5.057; 95% CI: 2.406-10.627; p < 0.001) was more effective than progressing by short possessions to create scoring opportunities. As for contextual dimensions, multivariate analyses showed how playing at home and against high-ranked opponents registered more likelihood of achieving offensive penetration, although no associations were found in the production of scoring opportunities. Tactical dimensions as initial penetration, type of attack and possession length played an important role on achieving offensive penetration and goal scoring opportunities in Spanish Soccer "La Liga".

#5 Transformational Leadership, Task-Involving Climate, and Their Implications in Male Junior Soccer Players: A Multilevel Approach
Reference: Int J Environ Res Public Health. 2019 Sep 28;16(19). pii: E3649. doi: 10.3390/ijerph16193649.
Authors: Álvarez O, Castillo I, Molina-García V, Tomás I
Download link:
Summary: Despite the well-known positive consequences of transformational coaches in sport, there is still little research exploring the mechanisms through which coaches' transformational leadership exerts its impact on athletes. Multilevel SEM was used to examine the relationship between coaches' transformational leadership style, a task-involving climate, and leadership effectiveness outcome criteria (i.e., players' extra effort, coach effectiveness, and satisfaction with their coach), separately estimating between and within effects. A representative sample of 625 Spanish male soccer players ranging from 16 to 18 years old and nested in 50 teams completed a questionnaire package tapping the variables of interest. Results confirmed that at the team level, team perceptions of transformational leadership positively predicted teams' perceptions of task climate, which in turn positively predicted the three outcome criteria. At the individual level, players' perceptions of transformational leadership positively predicted teams' perceptions of task climate, which in turn positively predicted teams' extra effort and coach effectiveness. Mediation effects appeared at the team level for all the outcome criteria, and at the individual only for extra effort. Transformational leadership is recommended to enhance task climate, in order to increase players' extra effort, their perceptions of the effectiveness of their coach, and their satisfaction with his/her leadership style.

#6 Inspiratory muscle training improves performance of a repeated sprints ability test in professional soccer players
Reference: J Bodyw Mov Ther. 2019 Jul;23(3):452-455. doi: 10.1016/j.jbmt.2019.01.016. Epub 2019 Jan 30.
Authors: Cavalcante Silva RL, Hall E, Maior AS
Summary: The aim of this study was to investigate the effects of IMT on exercise tolerance, repeated sprint ability (RSA) performance, maximal inspiratory pressure (MIP), and peak inspiratory flow (PIF) in a cohort of professional male soccer players. Twenty-two healthy male professional soccer players (18.3 ± 1.4 years; 174.5 ± 6.1 cm; 70.5 kg ± 4.6 kg; body fat 10.1 ± 4.2%) from a club in the Brazilian first division soccer league participated in this study. IMT consisted of 15 and 30 self-paced inspiratory breaths (each to 50% maximal static inspiratory pressure [P0]) in the 1-and 2-week intervention period, respectively. IMT was performed prior to soccer training (1 sets.d-1; 6 d.wk-1) with repeated sprint ability (RSA) assessed pre- and post- the 2-week period of IMT. Statistical analyses identified a significant (p < 0.001) decrease in sprint time post-IMT. Additionally, RSAbest, RSAmean, total sprint time and percentage of RSA performance decrement (RSA % dec) also showed significant decreases (p < 0.0001) post-IMT. Additional measures including MIP and PIF were also significantly elevated (p < 0.0002) following the 2-week period of IMT. In conclusion, our results raise two important issues. Firstly, IMT demonstrated enhanced inspiratory muscle strength in professional soccer players. Secondly, this increase in inspiratory muscle efficiency led to a decrease in sprint time and improved exercise tolerance. We recommend that a standard training protocol be developed and tested in an experimental and control group with a large representative sample.

#7 Regarding: "Inspiratory muscle training improves performance of a repeated sprints ability test in professional soccer players"
Reference: J Bodyw Mov Ther. 2019 Jul;23(3):443-444. doi: 10.1016/j.jbmt.2019.03.012. Epub 2019 Apr 2.
Authors: Matte DL, Ribeiro GS, Esquivel MS, Karsten M
Summary: The Journal of Bodywork & Movement Therapies recently published an article by Silva et al., entitled "Inspiratory muscle training improves performance of a repeated sprints ability test in professional soccer players" (Silva et al., 2019). After close reading we find that the new findings of Silva et al., (2019) are relevant and provide a promising indication that IMT can improve the performance of young male soccer players. However, some additional important points must be considered when interpreting these positive findings.

#8 Session-To-Session Variations of External Load Measures of Youth Soccer Players in Medium-Sided Games
Reference: Int J Environ Res Public Health. 2019 Sep 26;16(19). pii: E3612. doi: 10.3390/ijerph16193612.
Authors: Clemente FM, Rabbani A, Kargarfard M, Nikolaidis PT, Rosemann T, Knechtle B
Download link:
Summary: The aim of this study was to analyze the variability of time-motion variables during five vs. five games when completed within the same session as, and between, two different sessions. Ten under-19 male soccer players (18.27 ± 0.47 years old) participated in this study. The five vs. five matches (3 × 5 min) were played twice with a 3-day interval of rest in the same week. Moderate between-session variations were observed for TD (total distance) (range coefficient of variation (CV), 6.9; 8.3%, confidence interval (CI), (5.0; 14.0), standardized typical error (STE), 0.68; 1.06, (0.64; 1.75)) and RD (running distance) (range CV, 53.3; 145.7%, (36.6; 338.9), STE, 0.83; 1.09, (0.60; 1.76)). PL (player load) showed small variations (range CV, 4.9; 6.0%, [3.6; 10.1], STE, 0.37; 0.43, (0.27; 0.71)). In within-session analyses for examining the differences between sets, a small decrease was observed in RD in set 3 versus set 2 (-14.8%, 90% CI (-32.1; 6.9%); standardized difference (ES): -0.39 (0.95; 0.16)). TD decreased with moderate (-3.5%, (-6.8; -0.1%); ES: -0.65(-1.30; -0.01)) and large (-8.2%, (-11.4; -4.9%); ES: -1.58(-2.24; -0.92)) effects in sets 2 and 3, respectively, versus set 1. Our results suggest that PL is the most stable performance variable. It was also verified that measures had a progressive decreasing tendency within a session.

#9 Head impact exposure in youth football - are current interventions hitting the target?
Reference: Scand J Med Sci Sports. 2019 Oct 4. doi: 10.1111/sms.13562. [Epub ahead of print]
Authors: Sandmo SB, Andersen TE, Koerte IK, Bahr R
Summary: Restrictions on heading in youth football have been implemented in some countries to limit head-impact exposure. However, current interventions remain poorly guided by evidence. Our objective was to quantify heading exposure in youth football, assessing the effects of sex and age. Football matches played during an international youth football tournament with no heading restrictions were directly observed, including players from both sexes (11-19 years). The elite senior level was included for comparison, using video analysis. All heading events were registered, classified and assigned to individual players. Heading rates were calculated for each sex and age group. We observed a total of 267 matches, corresponding to 4011 player hours (1927 player hours for females, 2083 player hours for males). Males headed more frequently than females (2.7 vs. 1.8 headers/player hour; p<0.001). Heading rates increased with age (ANOVA, p<0.001), approaching the elite senior level for players 16 years and older. There was substantial variation within teams for all age and sex groups, with the widest range (1-18 headers) observed for girls aged 19. Girls younger than 12 years had the lowest exposure, with an average of less than two players per team heading the ball, each with 1-2 headers. In conclusion, age and sex influence head-impact exposure in youth football, and warrants careful consideration when introducing injury prevention measures. Males are more frequently exposed than females, heading rates increase with age, and there is substantial variation between players. Heading is a rare event in the youngest age groups, especially among females.

#10 Trapezoid Fracture Associated with Scaphoid Fracture in a Football Goalkeeper
Reference: Case Rep Orthop. 2019 Sep 5;2019:7949754. doi: 10.1155/2019/7949754. eCollection 2019.
Authors: Yamamoto T, Matsushita T, Ito K, Matsushima S, Yoshida K, Kuroda R
Download link:
Summary: A 19-year-old male who played as a football goalkeeper visited our hospital with complaints of sustained pain from the right wrist to the hand after punching a ball. Scaphoid fracture was diagnosed on plain radiographs, whereas trapezoid fracture was overlooked. Computed tomography revealed a displaced trapezoid fracture associated with a scaphoid fracture. Both fractures were successfully treated by open reduction and internal fixation using cannulated screws. Almost complete bone union was achieved at 5 months after surgery. The patient returned to play as a football goalkeeper. The simultaneous occurrence of trapezoid and scaphoid fractures has never been reported. Trapezoid fractures are rare and can be overlooked on plain radiographs, as what happened in the present case, because the trapezoid is small and overlaps with other carpal bones on plain radiographs. If there is sustained pain in the wrist and hand after punching, combined trapezoid and scaphoid fractures should be considered as the possible injury.

#11 Is Physical Performance a Differentiating Element between More or Less Successful Football Teams?
Reference: Sports (Basel). 2019 Sep 30;7(10). pii: E216. doi: 10.3390/sports7100216.
Authors: Asian Clemente JA, Requena B, Jukic I, Nayler J, Hernández AS, Carling C
Download link:
Summary: This study investigated the time-motion characteristics of football teams in the Spanish first division, in relation to their final competitive level as defined by league position (Champions League, Europa League, Upper mid-table, lower mid-table and relegation). Match observations (n = 9641) were collected using a multiple-camera computerized tracking system during the 2013-2014 competitive season. The following match parameters were analyzed: total distance, relative distance (m·min-1), distance < 14 km·h-1, >14 km·h-1, between 14-21 km·h-1, >21 km·h-1, and >24 km·h-1. Total distance and distance at different velocities (>14, 21, and 24 km·h-1) in and out of ball possession were also analyzed. A repeated analysis of variance and a comparison of effect sizes were carried out to compare the performance of the teams. The analysis of the data showed differences in physical performance characteristics between competitive levels. The volume of distance covered in the variables analyzed did not relate to success in soccer. Both successful and unsuccessful teams presented the same running requirements at higher velocities. These findings provide valuable information about the physical demands of the running requirements according to their final position in the league table.

#12 Community-based football in men with prostate cancer: 1-year follow-up on a pragmatic, multicentre randomised controlled trial
Reference: PLoS Med. 2019 Oct 1;16(10):e1002936. doi: 10.1371/journal.pmed.1002936. eCollection 2019 Oct.
Authors: Bjerre ED, Petersen TH, Jørgensen AB, Johansen C, Krustrup P, Langdahl B, Poulsen MH, Madsen SS, Østergren PB, Borre M, Rørth M, Brasso K, Midtgaard J
Download link:
Summary: Physical exercise has been shown to be effective in relation to fatigue, aerobic fitness, and lower body strength in men with prostate cancer. However, research into the clinically relevant effects of interventions conducted in heterogeneous patient populations and in real-life clinical practice settings is warranted. We conducted a pragmatic, multicentre, parallel randomised controlled trial in 5 Danish urological departments. Recruitment began in May 2015, the first participant was randomised in June 2015, and the last participant was included in February 2017. In total, 214 men with prostate cancer were randomly assigned to either 6 months of free-of-charge football training twice weekly at a local club (football group [FG]) (n = 109) or usual care (usual care group [UG]) (n = 105), including brief information on physical activity recommendations at randomisation. Participants were on average 68.4 (SD 6.2) years old, 157 (73%) were retired, 87 (41%) were on castration-based treatment, 19 (9%) had received chemotherapy, and 41 (19%) had skeletal metastases at baseline. In this 1-year follow-up study, we evaluated the effects of community-based football training on the following outcomes: primary outcome, quality of life; secondary outcomes: continuation of football after 6 months, hip and lumbar spine bone mineral density (BMD), mental health score, fat and lean body mass, and safety outcomes, i.e., fractures, falls, and hospital admissions. Intention to treat (ITT) and per protocol (PP) analyses were conducted. No statistically significant between-group difference was observed in change in prostate-cancer-specific quality of life (ITT: 1.9 points [95% CI -1.9 to 5.8], p = 0.325; PP: 3.6 points [95% CI -0.9 to 8.2], p = 0.119). A statistically significant between-group difference was observed in change in total hip BMD, in favour of FG (0.007 g/cm2 [95% CI 0.004 to 0.013], p = 0.037). No differences were observed in change in lumbar spine BMD or lean body mass. Among patients allocated to football, 59% chose to continue playing football after the end of the 6-month intervention period. At 1-year follow-up in the PP population, FG participants had more improvement on the Mental Component Summary (2.9 [95% CI 0.0 to 5.7], p = 0.048 points higher) than UG participants, as well as a greater loss of fat mass (-0.9 kg [95% CI -1.7 to -0.1], p = 0.029). There were no differences between groups in relation to fractures or falls. Hospital admissions were more frequent in UG compared to FG (33 versus 20; the odds ratio based on PP analysis was 0.34 for FG compared to UG). There were 3 deaths in FG and 4 in UG. Main limitations of the study were the physically active control group and assessment of physical activity by means of self-report. In this trial, participants allocated to football appeared to have improved hip BMD and fewer hospital admissions. Men who played football more than once a week for 1 year lost fat mass and reported improved mental health. Community-based football proved to be acceptable, even when club membership was not subsidised.

The Training Manager -