Latest research in football - week 47 - 2020

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 Monitoring Cardiorespiratory Fitness in Professional Soccer Players: Is It Worth the Prick?
Reference: Int J Sports Physiol Perform. 2020 Oct 1;1-5. doi: 10.1123/ijspp.2019-0911. Online ahead of print.
Authors: Martin Buchheit, Ben M Simpson, Mathieu Lacome
Summary: The aim was to compare between-tests changes in submaximal exercise heart rate (HRex, 3 min, 12 km/h) and the speed associated with 4 mmol/L of blood lactate (V4mmol) in soccer players to get insight into their level of agreement and respective sensitivity to changes in players' fitness. A total of 19 elite professional players (23 [3] y) performed 2 to 3 graded incremental treadmill tests (3-min stages interspersed with 1 min of passive recovery, starting speed 8 km/h, increment 2 km/h until exhaustion or 18 km/h if exhaustion was not reached before) over 1.5 seasons. The correlation between the changes in HRex and V4mmol was examined. Individual changes in the 2 variables were compared (>2 × typical error considered "clear"). The changes in HRex and V4mmol were largely correlated (r = .82; 90% confidence interval, .65-.91). In more than 90% of the cases, when a clear individual change in HRex was observed, it was associated with a similar clear change in V4mmol (the same direction, improvement, or impairment of fitness) and conversely. When it comes to testing players submaximally, the present results suggest that practitioners can use HRex or V4mmol interchangeably with confidence. However, in comparison with a field-based standardized warm-up run (3-4 min, all players together), the value of a multistage incremental test with repeated blood lactate samplings is questionable for a monitoring purpose given its time, labor, cost, and poorer player buy-in.

#2 Birth sex ratio in the offspring of professional male soccer players: influence of exercise training load
Reference: Hum Reprod. 2020 Oct 2;deaa225. doi: 10.1093/humrep/deaa225. Online ahead of print.
Authors: D Vaamonde, A C Hackney, J M Garcia Manso, E Arriaza Ardiles, M Vaquero
Summary: This is the first study assessing the influence of exercise training load on the offspring sex ratio of children from male professional athletes, observing a bias toward more females being born as a result of both high-intensity and high-volume loads, with intensity having the greatest effect. There is a relatively constant population sex ratio of males to females among various species; however, certain events and circumstances may alter this population sex ratio favoring one sex over the other. Seventy-five male professional soccer players from First Division soccer teams. Offspring variables were sex of the offspring, number of children and order of birth. Exercise training variables were volume and intensity. Total offspring was 122 children (52 males (42.6%), 70 females (57.4%)). Analysis revealed that increase in either the volume (P < 0.001) or intensity (P < 0.001) of training by the players shifted the birth offspring ratio more toward females. Within the sample of females born, more births (i.e. number) were observed as a consequence of training at the highest intensity (45 out of 70; P < 0.001), no such pattern occurred within males (P > 0.05). When female versus male births were compared within each intensity, only the high-intensity comparison was significant (45 (75%) females vs 15 (25%) males, P < 0.001). While this is the first study assessing differences in the sex ratio of the offspring of male athletes (i.e. soccer players), we acknowledge there are limitations and confounders within our approach; e.g. small sample size, ethnic background and variations in the timing of intercourse relative to ovulation as well as in sex hormone levels. As such, we propose that future research is needed to confirm or refute our findings. It is recommended that such work expand on the measurements obtained and conduct direct assessment of sperm characteristics. The findings of the study support the fact that different stressors on the body may alter the sex of the offspring. While in the present study the stressor is the excessive training load of soccer players, other events may lead to similar results. The bias in offspring sex ratio may have important implications for demography and population dynamics, as well as genetic trait inheritance.

#3 Myositis Ossificans of the Adductor Longus in a Soccer Player
Reference: J Orthop Sports Phys Ther. 2020 Oct;50(10):586. doi: 10.2519/jospt.2020.9573.
Authors: Michael Zarro, Kathleen Tamberrino, E McKenzie Bane
Summary: A 20-year-old male collegiate soccer goalkeeper presented to an athletic trainer during the season complaining of right (dominant kicking leg) groin pain. The athletic trainer identified a mass and hematoma and suspected myositis ossificans. The patient was referred to the team physician, who ordered radiographs and magnetic resonance imaging to confirm the diagnosis and rule out other injuries. Imaging demonstrated an adductor longus muscle strain with myositis ossificans.

#4 Prevalence of concomitant knee injuries associated with anterior cruciate ligament tear in kabaddi and football players
Reference: J Clin Orthop Trauma. 2020 Oct;11(Suppl 5):S784-S788. doi: 10.1016/j.jcot.2020.05.037. Epub 2020 Jun 6.
Authors: Ravi Gupta, Anil Kapoor, Gladson DavidMasih
Summary: There is little literature available about the type of sports and concomitant knee injury. The aim was to help in better prediction of concomitant knee injuries in football and kabaddi players. Five hundred and seventeen male athletes [Football (n = 226) and Kabaddi players (n = 291)] aged between 16 and 35 years were enrolled in the study. These were categorized into five groups depending upon the time interval between injury and surgery (0-3 months, 3-6 months, 6-9 months, 9-12 months, 12-18 months and 18-24 months). Meniscal and chondral damage present at the time of ACL reconstruction was documented. The overall incidence of meniscal tear was more in kabaddi players (220/291) as compared to football players (144/226; p = 0.003). The incidence of both menisci tear was more in kabaddi as compared to football (p = 0.02). Incidence of lateral meniscus tear (147/291) in kabaddi was more as compared to football (84/226; p = 0.002). The incidence of condylar damage was comparable in both groups. Medial femoral condyle was more commonly injured in both the sports irrespective of time frame. The chances of meniscus injuries were more in kabaddi players compared to football players in ACL deficient knee. The time interval between injury and surgery had a direct correlation with meniscus and chondral injuries.

#5 Accuracy of maturity prediction equations in individual elite male football players
Reference: Ann Hum Biol. 2020 Jun;47(4):409-416. doi: 10.1080/03014460.2020.1783360.
Authors: Jan Willem Ajw Teunissen, Nikki Rommers, Johan Pion, Sean P Cumming, Roland Rössler, Eva D'Hondt, Matthieu Lenoir, Geert J P Savelsbergh, Robert M Malina
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Summary: Equations predicting age at peak height velocity (APHV) are often used to assess somatic maturity and to adjust training load accordingly. However, information on the intra-individual accuracy of APHV in youth athletes is not available. The purpose of this study is to assess the accuracy of predication equations for the estimation of APHV in individual youth male football players. Body dimensions were measured at least every three months in 17 elite youth male football players (11.9 ± 0.8 years at baseline) from the 2008-2009 through the 2011-2012 seasons. APHV was predicted at each observation with four suggested equations. Predicted APHV was compared to the player's observed APHV using one-sample-t-tests and equivalence-tests. Longitudinal stability was assessed by comparing the linear coefficient of the deviation to zero. Predicted APHV was equivalent to the observed APHV in none of the players. A difference with a large effect size (Cohen's d > 0.8) was noted in 87% of the predictions. Moreover, predictions were not stable over time in 71% of the cases. None of the evaluated prediction equations is accurate for estimating APHV in individual players nor are predictions stable over time, which limits their utility for adjusting training programmes.

#6 The Influence of Recruitment Age and Anthropometric and Physical Characteristics on the Development Pathway of English Academy Football Players
Reference: Int J Sports Physiol Perform. 2020 Sep 29;1-9. doi: 10.1123/ijspp.2019-0534. Online ahead of print.
Authors: Mark R Noon, Emma L J Eyre, Matthew Ellis, Tony D Myers, Rhys O Morris, Peter D Mundy, Ryan Penny, Neil D Clarke
Summary: The purpose was to investigate the influence of recruitment age on retention and release across the development pathway and to explore the influence of anthropometric and physical characteristics on retention and release at different ages throughout the development pathway and the likelihood of obtaining a professional contract. Following receipt of ethics approval, a cross-sectional study tracking 4 cohorts of players over 5 years assessed 76 male youth football players (11-16 y) from an English football academy on 3 occasions annually in anthropometry, countermovement jump height, and linear (30 and 15 m) and multidirectional sprint time. Players were categorized based on their start and release date. Starting early (ie, before U12) in an academy was a key indicator of obtaining a professional contract, representing 87% of the players signed. Bayesian regression models suggest that the majority of differences in physical characteristics between players that were released and retained are trivial, small, and/or uncertain. Players who attained a professional contract at 18 had slower 15- and 30-m sprint times at U13 to U15 (P > 0 = .87-.99), slower multidirectional sprint times at U14 (P > 0 = .99), and lower countermovement jump height at U13 to U16 (P > 0 = .88-.99) compared with players who did not gain a contract. Players recruited early have an increased likelihood of gaining a professional contract. Physical assessments lack utility when used in isolation as a talent-identification tool.

#7 Football spectatorship and selected acute cardiovascular events: lack of a population-scale association in Poland
Reference: Kardiol Pol. 2020 Sep 21. doi: 10.33963/KP.15606. Online ahead of print.
Authors: Jenny E Simon, Łukasz A Małek, Andrzej Śliwczyński, Witold Śmigielski, Karol Korczak, Wojciech Drygas
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Summary: The status of football spectatorship-induced emotional stress as a risk factor for acute cardiovascular (CV) events remains in dispute. Aims: To examine the relation between football spectatorship and the incidence of selected acute CV events across the Polish male population. Events occurring in male patients aged 35 and older across Poland during three tournaments (the 2012 and 2016 European Championships - EC and the 2018 World Cup - WC) were retrospectively analysed through hospital admission codes obtained from the National Health Fund. Of interest were the following primary diagnoses: acute myocardial infarction (AMI, I21), sudden cardiac arrest (SCA, I46), sudden arrhythmias (SA, I47 - I49). The same dates in the years before and after the tournaments constituted the reference periods. A total of 255,383 patients were included in this study. There were no significant differences in the incidence of events between the combined exposure and reference periods: RR = 1.05 (95% CI 0.97 to 1.14, P = 0.20) for AMI, RR = 1.08 (95% CI 0.87 to 1.35, P = 0.47) for SCA, and RR = 1.02 (95% CI 0.98 to 1.06, P = 0.32) for SA. Individual tournament analyses revealed a higher incidence of AMI (RR = 1.20, 95% CI 1.12 - 1.30, P < 0.001) during WC. However, day-by-day analysis of WC did not find a higher incidence of AMI on match vs. match-free days. The emotional stress evoked by football spectatorship is insufficiently potent to precipitate a population-scale increase in selected acute CV events.

#8 Comparing football bettors' response to social media marketing differing in bet complexity and account type - An experimental study
Reference: J Behav Addict. 2020 Sep 26. doi: 10.1556/2006.2020.00056. Online ahead of print.
Authors: Scott Houghton, Mark Moss
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Summary: The current study aimed to assess how sports bettors respond to advertised bets on social media and whether this differs dependent upon bet complexity and social media account type. Employing a 3 × 2 repeated measures design, 145 regular football bettors were recruited to take part in an online study requiring them to rate bets advertised upon social media, providing indications of their likelihood to bet, confidence in the bet and how much they would stake on the bet. Advertised bets differed in terms of complexity (low, medium and high) and each bet was presented separately on both an operator account and an affiliate account. Data analysis highlighted a significant interaction between bet complexity and account type, with bettors rating themselves as being more likely to bet and more confident in bets which were presented on an affiliate account for medium complexity bets but not for low or high complexity bets. This study provides initial evidence that affiliate marketing of sports betting increases bettor's confidence in certain types of bets. This heightens previously addressed concerns around affiliate marketing, given that affiliates are financially incentivised to attract custom toward gambling operators. Future research should explore risk factors for increased uptake of affiliate marketing, and the impact on gambling behaviour.

#9 Inertial flywheel knee- and hip-dominant hamstring strength exercises in professional soccer players: Muscle use and velocity-based (mechanical) eccentric overload
Reference: PLoS One. 2020 Oct 2;15(10):e0239977. doi: 10.1371/journal.pone.0239977. eCollection 2020.
Authors: Luis Suarez-Arrones, F Javier Núñez, Pilar Lara-Lopez, Valter Di Salvo, Alberto Méndez-Villanueva
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Summary: The primary aim of the present study was to analyze mechanical responses during inertial knee- and hip-dominant hamstring strengthening exercises (flywheel leg-curl and hip-extension in conic-pulley), and the secondary aim was to measure and compare regional muscle use using functional magnetic resonance imaging. Mean power, peak power, mean velocity, peak velocity and time in the concentric (CON) and eccentric (ECC) phases were measured. The transverse relaxation time (T2) shift from pre- to post-exercise were calculated for the biceps femoris long (BFl) and short (BFs) heads, semitendinosus (ST) and semimembranosus (SM) muscles at proximal, middle and distal areas of the muscle length. Peak and mean power in flywheel leg-curl were higher during the CON than the ECC phase (p<0.01). ECC peak power was higher than CON phase (p<0.01) in conic-pulley hip-extension exercise, while mean power was higher during the CON than ECC phase (p<0.01). Flywheel leg-curl showed a higher T2 values in ST and BFs and BFl (p<0.05), while the conic-pulley hip-extension had a higher T2 values in the proximal region of the ST and BFl (p<0.05). In conclusion, ECC overload was only observed in peak power during the conic-pulley hip-extension exercise. Flywheel leg-curl involved a greater overall use of the 4 muscle bellies, more specifically in the ST and BFs, with a selective augmented activity (compared with the conic-pulley) in the 3 regions of the BFs, while conic-pulley hip-extension exercise selectively targeted the proximal and medial regions of the BFl. Physiotherapists and strength and conditioning coaches should consider this when optimizing the training and recovery process for hamstring muscles, especially after injury.

#10 Post-competition recovery strategies in elite male soccer players. Effects on performance: A systematic review and meta-analysis
Reference: PLoS One. 2020 Oct 2;15(10):e0240135. doi: 10.1371/journal.pone.0240135. eCollection 2020.
Authors: Albert Altarriba-Bartes, Javier Peña, Jordi Vicens-Bordas, Raimon Milà-Villaroel, Julio Calleja-González
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Summary: The main aim of the present review was to update the available evidence on the value interest of post-competition recovery strategies in male professional or semi-professional soccer players to determine its effect on post-game performance outcomes, physiological markers, and wellness indicators. A structured search was carried out following the PRISMA guidelines using six online databases: Pubmed, Scopus, SPORTDiscus, Web of Science, CINAHL and Cochrane Central Register of Controlled Trials. The risk of bias was completed following the Cochrane Collaboration Guidelines. Meta-analyses of randomized controlled trials were conducted to determine the between and within-group effects of different recovery strategies on performance, physiological markers and wellness data. Final meta-analyses were performed using the random-effects model and pooled standardized mean differences (SMD). Five randomized controlled trials that used Compression Garments (n = 3), Cold Water Immersion (n = 1), and acute Sleep Hygiene Strategy (n = 1) were included. Greater CMJ values at 48h for the intervention group (SMD = 0.70; 95% CI 0.14 to 1.25; p = 0.001; I2 = 10.4%) were found. For the 20-m sprint and MVC, the results showed no difference either at 24h or 48h. For physiological markers (CK and CRP) and wellness data (DOMS), small to large SMD were present in favor of the intervention group both at 24h (-0.12 to -1.86) and 48h (-0.21 to -0.85). No heterogeneity was present, except for MVC at 24h (I2 = 90.4%; p = 0.0012) and CALF DOMS at 48h (I2 = 93.7%; p = 0.013). The use of recovery strategies offers significant positive effects only in jumping performance (CMJ), with no effects on the 20-m sprint or MVC. Also, the use of recovery strategies offers greater positive effects on muscle damage (physiological markers and wellness data), highlighting the importance of post-match recovery strategies in soccer.

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