Latest research in football - week 37 - 2023

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 Prevalence of lower limb pain and disability in football, hockey, and floorball players

Reference: J Back Musculoskelet Rehabil. 2023 Aug 19. doi: 10.3233/BMR-230048. Online ahead of print.

Authors: Magdaléna Hagovská, Alena Buková, Peter Takáč

Summary: Currently there are not enough studies that compared frequent types of collective sports with regard to the prevalence of pain and disability of the lower limb. The aim was to determine the prevalence of lower limb pain and disability in team sports players. 388 athletes with average age 27.26 ± 4.69, from sports clubs at the national level were included in the study. The Oxford Hip Score was used to determine the prevalence of hip pain. The International Knee Documentation Committee was used to determine the prevalence of knee pain. The Foot and Ankle Disability Index was used to determine the prevalence of ankle pain. Hockey players had a prevalence of hip pain of 97.2% and a 14.3 times higher risk of developing hip pain compared with football and floorball players. Floorball players had a 81.9% prevalence of knee pain, with a 3.8 times higher the risk of knee pain compared with football and hockey. Floorball players had a 62.3% prevalence of ankle pain and a 1.8 times higher the risk of developing ankle pain compared with football and hockey players. The highest percentage of knee 81.9% and ankle 62.3% pain, as well as the greatest risk of pain, was found among floorball players. Hockey players had the highest prevalence (97.2%) and risk of developing hip pain.



#2 The effect of COVID-19 on home advantage in high- and low-stake situations: Evidence from the European national football competitions

Reference: Psychol Sport Exerc. 2023 Nov;69:102492. doi: 10.1016/j.psychsport.2023.102492. Epub 2023 Jul 19.

Authors: Merim Bilalić, Mario Graf, Nemanja Vaci

Summary: The Covid-19 pandemic has significantly altered the way sporting events are observed. With the absence or limited presence of spectators in stadiums, the traditional advantage enjoyed by home teams has diminished considerably. This underscores the notion that the support of home fans can often be considered a key factor of the home advantage (HA) phenomenon, wherein teams perform better in front of their own supporters. However, the impact of reduced attendance on games with higher stakes, as opposed to low-stakes friendly matches, remains uncertain. In this study, we investigate the recently concluded European football championship (EURO 20), wherein several teams had the advantage of playing at home in high-stakes games with only one-third of the stadium capacity filled. Firstly, we demonstrate that the Covid-19 restrictions, leading to reduced fan attendance, resulted in a nearly 50% decrease in HA compared to the HA exhibited by the same teams during the qualification stage preceding EURO 20, even after accounting for team strength. Secondly, we show that while low-stakes friendly matches generally exhibit a smaller overall HA compared to high-stakes games, the absence of fans led to a similar reduction in HA during the low-stakes matches. Utilizing the recently developed Home Advantage Mediated (HAM) model (Bilalić, Gula, & Vaci, 2021, Scientific Reports, 21558), we were able to attribute the reduction in both high- and low-stakes games to poorer team performance, with no significant contribution from referee bias.



#3 The obligation to succeed when it matters the most-The influence of skill and pressure on the success in football penalty kicks

Reference: Psychol Sport Exerc. 2023 Mar;65:102369. doi: 10.1016/j.psychsport.2022.102369. Epub 2022 Dec 20.

Authors: Michel Brinkschulte, Fabian Wunderlich, Philip Furley, Daniel Memmert

Summary: In order to gain a more comprehensive understanding of the influence of skill and pressure on the success in football penalty kicks, we analyzed 1711 penalties taken over a 15-year period in major international tournaments. We conducted a multiple correspondence analysis in order to reduce six variables that are associated with skill and pressure to two dimensions that reflect our target concepts. Then, we used these two factors as independent variables in a logistic regression and fit different models using three binary dependent variables. The results show that high situational pressure significantly increases the probability of missing the goal entirely by about 6%, independent of the player's skill level. The probability that the goalkeeper saves a penalty significantly decreases by roughly 4% when a highly skilled player takes the shot. In general, high situational pressure decreases the probability of scoring a penalty kick. Furthermore, the probability to score a penalty increases if a highly skilled player takes the kick which indicates that a high skill level can act as a kind of buffer against debilitating effects caused by performance pressure.



#4 The causal impacts of empty stadiums on women's sports activities: Evidence from European football leagues

Reference: Psychol Sport Exerc. 2023 May;66:102385. doi: 10.1016/j.psychsport.2023.102385. Epub 2023 Jan 11.

Authors: Dávid Zoltán Szabó, Péter Kerényi

Summary: This paper examines the effect of spectators on women's football games. COVID-19 and related restrictions provide a unique opportunity with an adequate sample size to test the effect of lockdown on sports activities. Studies have recently exploited this opportunity for men's football to better understand the potential causes of home advantage and, more specifically, assess the psychological consequences when matches are played without supporters. Despite the increased scientific interest, there was only one paper that focused on women's football. Therefore, we aim to contribute to this research field by considering matches from four major European women's football leagues. The findings suggest that for three of these leagues, lockdown has a statistically significant effect on the sanctioned yellow cards by either reducing the number of yellow cards sanctioned to the away teams or increasing the number of yellow cards sanctioned to the home teams. Nonetheless, lockdown does not affect any final match outcomes; therefore, it does not significantly affect the magnitude of home advantage for women's games.



#5 Using video docuseries to explore male professional football head coaches' well-being experiences throughout a season

Reference: Psychol Sport Exerc. 2023 Nov;69:102488. doi: 10.1016/j.psychsport.2023.102488. Epub 2023 Jul 8.

Authors: Andrew J Higham, James L Rumbold, James A Newman, Joseph A Stone

Summary: Football coaches have disclosed how their work environment is unpredictable and demanding, comprising a multitude of stressors which can impede well-being. Additionally, the masculine culture within football often promotes suppression of voice, causing internalisation of thoughts and isolation. Due to professional football head coaches being a seldom-heard group, little is known about how they experience well-being within their given context (i.e., ecological niche). The present study utilised football docuseries and a bioecological framework to explore how four male professional head coaches experienced well-being whilst working in one of the top European football leagues (Premier League, La Liga). Four docuseries were sampled and resulted in the analysis of 31 episodes (Mduration = 46.6 min, SD = 4.5 min). The study implemented an adapted interpretative phenomenological analysis approach to illuminate convergences and divergences in contextual accounts. These accounts resulted in five group experiential themes: 'I belong to the game'; 'he belongs to the game'; 'you need the right people around you'; 'it's difficult to describe the manager without describing the person'; and 'people are trying to stab you'. The findings indicate that football coaches may experience identity conflicts and become deeply absorbed in their work. This impacts not only their well-being but also their family's, who they often turn to for social support. Consequently, by unveiling nuanced challenges to coaches' well-being, organisations may be better informed to offer more aligned and bespoke well-being support systems.



#6 Association between back-leg-chest muscle strength and kicking speed in soccer players: an observational study

Reference: J Sports Med Phys Fitness. 2023 Sep 15. doi: 10.23736/S0022-4707.23.15183-8. Online ahead of print.

Authors: Arijit Debnath, Vandana Esht, Aksh Chahal, Faizan Z Kashoo, Mohammed M Alshehri, Mohammad A Shaphe, Ghufran Jaleel, Masood Khan, Ahmad H Alghadir

Summary: Several studies have been performed on soccer kicks and stressed the significance of strength/power and coordination between the agonist and antagonist muscles of the lower limb. Along with accuracy, speed is also an important factor in a successful kick. It is reported that trunk musculature, hip and knee extensors of the non-kicking extremity, and hip adductors of the kicking side have a role in increasing the foot velocity while kicking. Since muscles do not work in isolation while kicking and several muscle groups of the leg and trunk have been reported to have a role in high-speed kicks, therefore measuring the combined strength of the leg, trunk, and arm muscles will be an appropriate method to examine their association with the kicking speed. The aim of this study was to examine the association of the combined strength of the lower extremities, back, chest, and arm muscles with the kicking speed of soccer players. Forty male soccer players (mean age 15.7 years) participated in the study. The back-leg-chest (BLC) dynamometer (Baseline, New York, NY, USA) and the mobile camera measured isometric muscle strength and kicking speed, respectively. The BLC dynamometer measured the isometric strength of the knee, hip, back extensors, and arm muscles. The kicking speed was measured by asking participants to kick a football in three directions - right, middle, and left - from 11 meters. Significant (P<0.001) negative correlations of isometric strength of the back, leg, chest, and arm muscles and kicking speeds were found in all three directions. In all three correlations, Pearson's correlation coefficient was -0.989. Simple linear regression results showed that 97.8% (adjusted R2) of the variance observed in kicking speed (KS; RT), KS (MD), and KS (LT), was explained by the movement in BLC muscle strength values. Kicking speeds in the right, middle, and left directions were negatively associated with the isometric strengths of the back, leg, chest, and arms muscles, measured using the BLC dynamometer, in participating soccer players.



#7 Predicting Injury and Illness with Machine Learning in Elite Youth Soccer: A Comprehensive Monitoring Approach over 3 Months

Reference: J Sports Sci Med. 2023 Sep 1;22(3):476-487. doi: 10.52082/jssm.2023.476. eCollection 2023 Sep.

Authors: Nils Haller, Stefan Kranzinger, Christina Kranzinger, Julia C Blumkaitis, Tilmann Strepp, Perikles Simon, Aleksandar Tomaskovic, James O'Brien, Manfred Düring, Thomas Stöggl

Summary: The search for monitoring tools that provide early indication of injury and illness could contribute to better player protection. The aim of the present study was to i) determine the feasibility of and adherence to our monitoring approach, and ii) identify variables associated with up-coming illness and injury. We incorporated a comprehensive set of monitoring tools consisting of external load and physical fitness data, questionnaires, blood, neuromuscular-, hamstring, hip abductor and hip adductor performance tests performed over a three-month period in elite under-18 academy soccer players. Twenty-five players (age: 16.6 ± 0.9 years, height: 178 ± 7 cm, weight: 74 ± 7 kg, VO2max: 59 ± 4 ml/min/kg) took part in the study. In addition to evaluating adherence to the monitoring approach, data were analyzed using a linear support vector machine (SVM) to predict illness and injuries. The approach was feasible, with no injuries or dropouts due to the monitoring process. Questionnaire adherence was high at the beginning and decreased steadily towards the end of the study. An SVM resulted in the best classification results for three classification tasks, i.e., illness prediction, illness determination and injury prediction. For injury prediction, one of four injuries present in the test data set was detected, with 96.3% of all data points (i.e., injuries and non-injuries) correctly detected. For both illness prediction and determination, there was only one illness in the test data set that was detected by the linear SVM. However, the model showed low precision for injury and illness prediction with a considerable number of false-positives. The results demonstrate the feasibility of a holistic monitoring approach with the possibility of predicting illness and injury. Additional data points are needed to improve the prediction models. In practical application, this may lead to overcautious recommendations on when players should be protected from injury and illness.



#8 Quantitative Analysis of Ball-Head Impact Exposure in Youth Soccer Players

Reference: J Sports Sci Med. 2023 Sep 1;22(3):591-596. doi: 10.52082/jssm.2023.591. eCollection 2023 Sep.

Authors: Victoria E Wahlquist, Thomas A Buckley, Jaclyn B Caccese, Joseph J Glutting, Todd D Royer, Thomas W Kaminski

Summary: Since the implementation of the US Soccer heading guidelines released in 2015, little to no research on ball-head impact exposure in the United States youth soccer population has been conducted. The purpose was to compare ball-head impact exposure across sex and age in youth soccer players over a weekend tournament. Ten male and female games for each age group (Under-12 [U12], U13, and U14) were video recorded at a weekend tournament for a total of 60 games. Ball-head impact exposure for each game was then coded following a review of each recording. Male players were 2.8 times more likely to have ball-head impacts than female players, (p < 0.001) particularly in the U14 age group when compared to the U12 age group (p = 0.012). Overall 92.4% of players experienced 0-1 ball-head impacts per game with the remaining players experiencing 2+ ball-head impacts per game. Ball-head impact exposure levels are low in the youth players. Most youth soccer players do not head the soccer ball during match play and those that did, only headed the ball on average once per game. Overall, the difference in ball-head impact exposure per player was less than 1 between all the groups, which may have no clinical meaning.



#9 Strategic analysis of body composition indices and resting platelet ATP levels in professional soccer players for better platelet-rich plasma therapy

Reference: Front Bioeng Biotechnol. 2023 Aug 30;11:1255860. doi: 10.3389/fbioe.2023.1255860. eCollection 2023.

Authors: Takashi Ushiki, Tomoharu Mochizuki, Katsuya Suzuki, Masami Kamimura, Hajime Ishiguro, Tatsuya Suwabe, Satoshi Watanabe, Go Omori, Noriaki Yamamoto, Tomoyuki Kawase

Summary: Autologous platelet-rich plasma (PRP) therapy is ambiguously thought to be more effective in elite athletes than in sedentary patients, although the possible importance of recipient responsiveness remains poorly understood. To address this issue, along with the well-known PRP quality, in this initial study, we evaluated two candidate biomarkers: body composition indices (BCIs), which reflect systemic physical conditions, and resting platelet ATP levels, which reflect platelet energy expenditure and the mass of energy generation units. In this cross-sectional cohort study, blood samples were collected from male professional soccer players (PSPs) on a local professional team during the off-season and platelet ATP levels were quantified using an ATP luminescence assay kit. BCIs were measured using the body mass impedance method. Age-matched male sedentary participants were used as the controls. Among the BCIs, the body mass index, basal metabolic rate (BMR), and skeletal muscle weight levels were higher in the PSPs than in the controls. The platelet ATP levels in the PSPs group were significantly lower than those in the control group. The correlation between BMR and platelet ATP levels was moderately negative in the control group, but weakly positive in the PSPs group. Owing to regular physical exercise, PSPs had higher BMR levels and lower platelet ATP levels without a significant mutual correlation compared to sedentary controls. This study did not indicate the influence of these biomarkers on the success of PRP therapy but provided evidence for a better understanding of PRP therapy, particularly for elite athletes.



#10 Relationship between Relative age Measured Through Decimal age, physical variables and anthropometry in elite youth soccer players

Reference: Phys Sportsmed. 2023 Sep 12. doi: 10.1080/00913847.2023.2258768. Online ahead of print.

Authors: Iván Asín-Izquierdo, Marcos Chena 1, Vicente de Dios-Álvarez 3, Carlos Galiano 2

Summary: Age differences between athletes born in the same year, as well as an over-representation of older players, are known as the Relative Age Effect (RAE). Players born at the beginning of the selection year have a physical and anthropometric advantage over their younger peers. Experts keep looking for new prediction variables for talent identification. The aim of the study is to correlate anthropometric, strength and power variables with the relative age (RA) and the level of the teams in which players played in each age category. All players (N = 366) from an elite soccer academy of a Spanish club volunteered to participate in the study (U23-U10). There was a significant correlation between the RA of the players and the level of the team in which they played in each age category but no correlation between trimester of birth and level of the team. We found significant correlations between the players' physical capacities, anthropometry, RA and the level of the team in which they played for the same age category, mainly from U16 to U10. U23 did not show any correlation between RA and physical or anthropometric variables. Coaches should be cautious of choosing players based only on anthropometric or physical attributes.



#11 Chronic Beetroot Juice Supplementation Attenuates Neuromuscular Fatigue Etiology During Simulated Soccer Match Play

Reference: Appl Physiol Nutr Metab. 2023 Sep 11. doi: 10.1139/apnm-2023-0179. Online ahead of print.

Authors: Wael Daab, Firs Zghal, George P Nassis, Haitham Rebai, Wassim Moalla, Mohamed Amine Bouzid

Summary: The aim of the present study was to assess the effect of beetroot juice supplementation (BEET) on neuromuscular fatigue etiology during simulated soccer match play. In a randomized, double-blind, crossover design, 13 soccer players completed the Loughborough Intermittent Shuttle Test (LIST). Players received either BEET (2*150ml; ~ 8mmol/l nitrate) or PLA for 7 days (6 days prior to the experimental session and on the day trial, 2h before LIST). Neuromuscular assessments were performed at baseline, 45min (half time: HT) and at 90min (final time: FT) following LIST. Maximal voluntary contraction (MVC) and twitch responses, delivered through electrical femoral nerve stimulation, were used to asses peripheral (quadriceps resting twitch force, Qtw,pot) and central fatigue (voluntary activation, VA). Compared to baseline, MVC Qtw,pot and VA values decreased in PLA and BEET conditions at HT and FT (p<0.05). Compared to PLA, the decrease in MVC and Qtw,potat were significantly attenuated with BEET at HT and FT(p <0.001). Likewise, BEET attenuated the decrease in VA at HT (p <0.001, d = 1.3) and FT (p <0.001, d = 1.5) compared to PLA condition. Chronic beetroot juice supplementation attenuates neuromuscular fatigue development during simulated soccer match and this is due to both central and peripheral factors. Consequently, chronic beetroot may optimize physical performance.



#12 Football and respiratory medicine-Time to start kicking goals

Reference: Respirology. 2023 Sep 10. doi: 10.1111/resp.14600. Online ahead of print.

Authors: Natasha Smallwood

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#13 Menthol mouth rinsing and performance in elite football referees in the heat: A study protocol for a randomized crossover trial

Reference: Contemp Clin Trials Commun. 2023 Aug 22;35:101202. doi: 10.1016/j.conctc.2023.101202. eCollection 2023 Oct.

Authors: Maria Roriz, João Brito, Filipe J Teixeira, Konstantinos Spyrou, Vitor Hugo Teixeira

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Summary: Within professional European competitions, matches can be played in extreme environmental temperatures, ranging from -5 °C to +30 °C in different countries. Furthermore, the World Cups are usually played in the summer months, when temperatures can exceed 35 °C, increasing physiological stress. Practical and cost-effective cooling strategies may be implemented to help players and referees to cope with exercising in the heat. No study has evaluated the effect of non-thermal internal cooling techniques regarding performance responses on elite football referees, so far. This study aims to analyse the effects of a menthol mouth rinse regarding physical, physiological, and perceptual performance in elite male football referees, during a 90-min football protocol in the heat. At least thirteen male football referees will be recruited to perform two intermittent football protocols, separated by no less than 7 days. After passing the eligibility criteria, the participants will be randomly assigned to 1 of 2 beverages: (1) intervention - menthol solution 0.01% and (2) placebo - noncaloric berry-flavored solution, both at room temperature. The beverages will be given before warm-up (pre-cooling) and at the half-time (per-cooling). The trials will follow a randomized counterbalanced crossover design, single blinded, and will take place in indoor facilities, with Wet Bulb Globe Temperature (WBGT) > 30 °C, at the same time of the day to control for circadian variations. The results of this study are expected to determine whether mouth rinsing a menthol solution before and during a football exercise protocol performed in the heat will alter perceptual measures and help ease physiological strain and attenuate performance decrements in elite male football referees, comparing to a non-cooling strategy. Thus, we can be closer to defining nutritional strategies of internal cooling that may be an advantage for the performance of the football referees in the heat.



#14 Motivation and goal-pursuit for injury prevention training in amateur football coaches: a cross-sectional study using the Health Action Process Approach

Reference: Inj Prev. 2023 Sep 11;ip-2023-044978. doi: 10.1136/ip-2023-044978. Online ahead of print.

Authors: Hanna Lindblom, Martin Hägglund

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Summary: Adoption of injury prevention exercise programmes (IPEPs) in team sports is contingent on behaviour change among coaches. The aim was to study motivation and goal-pursuit in IPEP use among coaches of amateur football players. A cross-sectional study using web-based questionnaires was administered to coaches in one Swedish regional football district. The study was carried out one season after dissemination of the IPEP Knee Control+. The questionnaire was based on the Health Action Process Approach and covered perceptions and beliefs about using Knee Control+. Questions were rated on 1-7 Likert scales. 440 coaches participated (response rate 32%). Coaches were neutral about injury risks (median 4-5) and knowledge about preventing injuries (median 5) but had positive outcome expectancies of preventive training (median 6). Coaches who had used an IPEP perceived they had more knowledge about preventing injuries than non-users (median 5 vs 4, small effect size d=0.43). Coaches who used Knee Control+ were positive about their practical ability to use it (median 6) and had high intention to prioritise continuous use (median 7). Highly adherent coaches to higher extent believed that specific training may prevent injuries and had plans for how to instruct the players and how to work around barriers compared with low adherent coaches. Coaches need more knowledge and support on IPEP usage and how to structure training. Coaches who had adopted Knee Control+ had high belief in their abilities but may need constructive plans on how to use the programme and to overcome barriers.



#15 Characteristics of brain activation in high-level football players at different stages of decision-making tasks off the ball: an fMRI study

Reference: Front Hum Neurosci. 2023 Aug 28;17:1189841. doi: 10.3389/fnhum.2023.1189841. eCollection 2023.

Authors: Ming-Hao Huang, Jian Lang, Ju Li, Zhe Qin, Ya-Ping Cao

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Summary: This study aimed to examine the neural mechanisms underlying the decision-making process of off-ball movements among high-level football players and ordinary college students, as well as the effect of long-term skill training on these neural mechanisms using functional magnetic resonance imaging (fMRI). The study recruited 20 professional college football players as the expert group (EG) and 20 novice football players with no background in sports-related disciplines as the novice group (NG). The participants performed the motor video observation and button-decision-making tasks, and fMRI data were acquired, pre-processed, and analyzed. During the decision-making process regarding running without the ball, whole-brain fMRI scans were conducted on both the EG and NG. The analysis of these scans revealed noteworthy disparities in brain activity between the two groups. These disparities were observed during tasks involving motor video observation and button-based decision-making. According to the behavioral data, the EG made more correct decisions than the NG (p < 0.05); however, there was no significant difference in their reaction speed (p > 0.05). During video observation, both the EG and NG exhibited simultaneous activation in the frontoparietal cognitive area, primary somatosensory cortex, visual cortex, and insula. However, there were no significant differences between the two groups in terms of activated brain regions [false discovery rate (FDR) corrected to p < 0.05]. Regarding button-press decisions, the areas of the brain that were commonly activated in both the NG and EG were primarily located in the frontoparietal cognitive area, temporal cortex, and cuneus cortex. Notably, the left superior temporal gyrus, left inferior temporal gyrus, and left middle occipital gyrus exhibited greater activation in the NG compared to those in the EG (FDR corrected to p < 0.05). This study demonstrated that during motor video observation, the EG's sports experience and professional knowledge can help them achieve better visual information processing strategies in specific areas of sports. During button decision-making, the EG was more economical, whereas the NG required more brain function activity to process visual information, confirming the "neural efficiency" hypothesis.



#16 Plasma myoglobin indicates muscle damage associated with acceleration/deceleration during football

Reference: J Sports Med Phys Fitness. 2023 Sep 15. doi: 10.23736/S0022-4707.23.15203-0. Online ahead of print.

Authors: Yoshitomo Saita, Kazuhiko Hattori, Atsushi Hokari, Tomoko Ohyama, Junya Inoue, Tomoaki Nishimura, Shota Nemoto, Seiji Aoyagi

Summary: Monitoring muscle damage in athletes assists not only coaches to adjust the training workload but also medical staff to prevent injury. Measuring blood myoglobin concentration can help evaluate muscle damage. The novel portable device utilized in this study allows for easy on-site measurement of myoglobin, providing real-time data on the player's muscle damage. This study investigated the relationship between external load (global positioning system parameters) and internal loads (myoglobin concentration and creatine kinase activity) in 15 male professional football players before and after a match. Whole blood samples from participants' fingertips were collected before the match (baseline) and at 2, 16, and 40 h after the match. Myoglobin concentrations were measured using the IA-100 compact immunoassay system. Creatine kinase concentrations were measured in a clinical laboratory, and match loads were monitored using a global positioning system device. The mean myoglobin concentration was significantly higher at 2 h than at the other time points (P<0.05), and decreased to baseline levels within 16 h post-match. The mean creatine kinase concentration increased after the match but did not reach a significant level. Muscle damage monitored by myoglobin after football match-play was strongly associated with acceleration/deceleration metrics rather than the sprint/high-speed running distance. Our findings indicate that myoglobin is a more sensitive marker of muscle damage than creatine kinase after football match-play. Monitoring myoglobin in athletes can aid in determining their recovery status from the previous training load and help practitioners manage the training load.



#17 Health and performance effects of 12 weeks of small-sided street football training compared to grass football training in habitually active young men

Reference: Eur J Appl Physiol. 2023 Sep 15. doi: 10.1007/s00421-023-05308-y. Online ahead of print.

Authors: Morten B Randers, Marie Hagman, Jesper F Christensen, Susana Póvoas, Jens Jung Nielsen, Peter Krustrup

Summary: The purpose of the present study was to investigate the health and exercise performance effects of street football training on very small pitches surrounded by boards in young habitually active men in comparison to small-sided football training on grass. Thirty-nine habitually active men (30.7 ± 6.7 years, 90.9 ± 16.6 kg, 183.8 ± 4.5 cm, 39.6 ± 6.0 mL/min/kg) were randomly assigned to a street football training group (ST) or grass football group (GR) playing small-sided games for 70 min, 1.5 and 1.7 times per week for 12 weeks, respectively, or an inactive control group (CO). Intensity during training was measured using heart rate (HR) and GPS units. Pre- and post-intervention, a test battery was completed. Mean HR (87.1 ± 5.0 vs. 84.0 ± 5.3%HRmax; P > 0.05) and percentage of training time above 90%HRmax (44 ± 28 vs. 34 ± 24%; P > 0.05) were not different between ST and GR. VO2max increased (P < 0.001) by 3.6[95% CI 1.8;5.4]mL/min/kg in GR with no significant change in ST or CO. HR during running at 8 km/h decreased (P < 0.001) by 14[10;17]bpm in ST and by 12[6;19]bpm in GR, with no change in CO. No changes were observed in blood pressure, resting HR, total body mass, lean body mass, whole-body bone mineral density, fasting blood glucose, HbA1c, plasma insulin, total cholesterol(C), LDL-C or HDL-C. Moreover, no changes were observed in Yo-Yo IE2 performance, 30-m sprint time, jump length or postural balance. Small-sided street football training for 12 weeks with 1-2 weekly sessions led to improvements in submaximal exercise capacity only, whereas recreational grass football training confirmed previous positive effects on submaximal exercise capacity as well as cardiorespiratory fitness.



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