Latest research in football - week 7 - 2022

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 Training load responses to football game profile-based training (GPBT) formats: effects of locomotive demands manipulation

Reference: Biol Sport. 2022 Jan;39(1):145-155. doi: 10.5114/biolsport.2021.102919. Epub 2021 Mar 9.

Authors: Antonio Dello Iacono, Viswanath Unnithan, Tzlil Shushan, Michael King, Marco Beato

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Summary: The aim of this study was to compare internal and external load profiles of different game profile-based training (GPBT) formats among elite young football players. Twenty-one participants (age: 18.7 ± 0.6 years) performed three sessions of three GPBT formats, which were matched for training volume but structured with different high-speed running and sprint demands: i) performed along linear paths (GPBT-L); ii) performed as repetitive actions of short distance including many multi-directional changes of direction (GPBT-S) and, iii) a combination of the other two protocols, that is linear high-speed runs and sprint efforts with a single change of direction (GPBT-M). External load outputs were collected using GPS units, physiological and perceptual responses were monitored with heart rate (HR) monitors, and ratings of perceived exertion (RPE), respectively. While no differences were found between formats for HR and RPE, distinct external load profiles were observed for high-speed running (HSD) and sprint distances (SD), (GPBT-L > GPBT-M > GBPT-S, all p < 0.05), and high-intensity acceleration and deceleration efforts (HIE), (GPBT-S > GPBT-M > GPBT-L, all p < 0.05). Moreover, the GPBT-S format was characterized by greater intra-session variability for HSD, SD, and HIE (CV% = 24.2%, 16.5% and 20.4%, respectively) and inter-session variability for HSD and SD (CV% = 10% and 15.7%, respectively) compared to the other two formats. Considering their load profiles and the associated reliability scores, football practitioners can implement GPBT formats interchangeably to elicit necessary internal load responses and selectively to prioritize specific external load outputs.



#2 The diagonal positioning of the goals modifies the external training load and the tactical behaviour of young football players

Reference: Biol Sport. 2022 Jan;39(1):135-144. doi: 10.5114/biolsport.2021.102929. Epub 2021 Mar 9.

Authors: Albert Canton, Carlota Torrents, Bruno Gonçalves, Angel Ric, Filippo Salvioni, Juliana Exel, Jaime Sampaio

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Summary: The aim of this study was to identify how positioning the goals in diagonal configurations on the pitch modifies the external training load and the tactical behaviour of young football players during small-sided games. Four teams of five outfield players and a goalkeeper played six small-sided games of five minutes' duration in three different scenarios: 1) Control: goals placed one in front of the other; 2) Right diagonal goals: goals placed in the right-hand corner of the offensive half-pitch; and 3) Left diagonal goals: goals placed in the left-hand corner of the offensive half-pitch. The positioning-derived data from each player were collected with 10-Hz GPS units and were used to compute external load and tactical variables. Regarding the external load variables, differences were mainly focused on distance covered while walking in defence and game pace (variability), with higher values for the diagonal scenarios. Also, the length/width ratios in offence and defence were most likely lower in diagonal scenarios. In conclusion, the results showed that players' adaptations to the environmental constraints of positioning the goals diagonally were the enhancement of the width team variable and the variability of the length.



#3 Accumulative weekly load in a professional football team: with special reference to match playing time and game position

Reference: Biol Sport. 2022 Jan;39(1):115-124. doi: 10.5114/biolsport.2021.102924. Epub 2021 Mar 4.

Authors: David Casamichana, Andrés Martín-García, Antonio Gómez Díaz, Paul S Bradley, Julen Castellano

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Summary: The aim of this study was to compare weekly accumulative load during the in-season competitive period by professional soccer players according to the amount of time played in official matches (90-min, >60-min, <60-min, and 0-min) regarding the players' position. Twenty-four professional outfield football players were monitored by GPS devices during training sessions and official matches and the accumulative weekly load were calculated for the following external load variables: total distance (TD; m), high speed running (HSR; >19.8 km·h-1), sprint meters (SPR; >25.2 km·h-1), high metabolic load distance (HMLD; >25.5 W·kg-1), number of accelerations (ACC; >3 m·s-2) and decelerations (DEC; <-3 m·s-2). This study revealed that players (as a whole o per demarcation) with more match playing time had a higher accumulative weekly load for most of the variables, but particularly at TD and HMLD (90-min and >60-min vs. <60-min and 0-min), HSR (90-min vs. <60-min and 0-min) and SPR (90-min vs. <60-min and 0-min). In addition, less positional variation was observed in relation to the competition requirements. This information would allow coaches to refine the required load with the objective of optimizing performance to soccer players.



#4 Reference values for collective tactical behaviours based on positional data in professional football matches: a systematic review

Reference: Biol Sport. 2022 Jan;39(1):110-114. doi: 10.5114/biolsport.2021.102921. Epub 2021 Mar 6.

Authors: Markel Rico-González, José Pino-Ortega, Julen Castellano, José M Oliva-Lozano, Asier Los Arcos

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Summary: Match collective tactical behaviours can be used as a reference to design and select training strategies to improve individual and team performance in professional football. The aim of the systematic review was to cluster the collective tactical variables used to highlight and compare male soccer teams' collective behaviour during professional official matches, providing reference values for each of them. A systematic review of relevant articles was carried out using three electronic databases (PubMed, SPORTdiscus and Web of Science). From a total of 1,187 studies initially found, 13 original articles were included in the qualitative synthesis. The articles found concerned studies carried out on the Spanish, Portuguese, English and Brazilian 1st divisions and during the European UEFA Champions League. The team length and width ranged from 31 to 46 m and from 35 to 48 m, respectively. The distance from a defending team's goalkeeper to the nearest teammate ranged from 9 ± 6 to 30 ± 7 m, the goal line-recovery location from 27 to 37 m, and the opponent's goal line from 42 to 50 m. The stretch index ranged from 7 to 16 m. Mean team area was ~900 m2 and the area of the pitch which included all outfield players divided by the 20 outfield players ranged from 79 ± 15 to 94 ± 16 m2. All studies provided greater distance and area values during the team-possession phase in comparison to the non-possession one. The ball location on the pitch determined the collective tactical behaviour of the teams. The differences between halves in the distance and area values were contradictory. Further studies should assess the effect of the interaction between the contextual factors on the collective tactical behaviour to obtain more accurate references. This could help football coaches in the design of suitable training tasks to optimize tactical performance.



#5 Utilisation of performance markers to establish the effectiveness of cold-water immersion as a recovery modality in elite football

Reference: Biol Sport. 2022 Jan;39(1):19-29. doi: 10.5114/biolsport.2021.103570. Epub 2021 Feb 18.

Authors: Jill Alexander, Chris Carling, David Rhodes

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Summary: Optimal strategies for recovery following training and competition in elite athletes presents ongoing debate. The effects of cold-water immersion (CWI) compared to passive recovery (PR) though a triad of performance measures after fatiguing exercise within a normal micro-cycle, during mid-competitive training cycle, in elite male footballers were investigated. Twenty-four elite footballers (age 20.58 ± 2.55 years; height 179.9 ± 5.6 cm; weight 75.7 ± 7.5 kg; body fat 6.2 ± 1.7%) were randomly assigned to CWI or PR following a fatiguing training session. Objective measures included eccentric hamstring strength, isometric adductor strength, hamstring flexibility and skin surface temperature (T sk ). Subjective measures included overall wellbeing. Data were collected at match day+3, immediately post-training, immediately post-intervention and 24 hrs post-intervention. Physiological, biomechanical and psychological measures displayed significant main effects for timepoint for eccentric hamstring strength, T sk , overall wellbeing, sleep, fatigue, stress and group for eccentric hamstring strength, T sk and sleep (groups combined). Group responses identified significant effects for timepoint for CWI and PR, for eccentric hamstring strength peak force, sleep, fatigue, and muscle soreness for CWI. Significant differences were displayed for eccentric hamstring strength (immediately post-intervention and immediately post-training) for peak force and between CWI and PR eccentric hamstring strength immediately post-intervention. Linear regression for individual analysis demonstrated greater recovery in peak torque and force for CWI. CWI may be useful to ameliorate potential deficits in eccentric hamstring strength that optimise readiness to train/play in elite football settings. Multiple measures and individual analysis of recovery responses provides sports medicine and performance practitioners with direction on the application of modified approaches to recovery strategies, within mid-competitive season training cycles.



#6 Can we evidence-base injury prevention and management in women's football? A scoping review

Reference: Res Sports Med. 2022 Feb 14;1-16. doi: 10.1080/15438627.2022.2038161. Online ahead of print.

Authors: K Okholm Kryger, A Wang, R Mehta, Fm Impellizzeri, A Massey, M Harrison, R Glendinning, A McCall

Summary: This review aimed, as part of a larger FIFA project aiming to steer women's football research, to scope literature on any level of competitive football for women, to understand the current quantity of research on women's football injuries. The study reviewed all injury-related papers scoped by a recent scoping review mapping all published women's football research with an updated search performed on 23 February 2021. Eligibility criteria assessment followed the recent scoping review with injury-specific research focus. A total of 497 studies were scoped. Most studies contained an epidemiological (N = 226; 45%) or risk factors assessment (N = 105; 21%). Less assessed areas included financial burden (N = 1; <1%) and injury awareness (N = 5; 1%). 159 studies (32%) assessed injuries of the whole body. The most common single location assessed in the literature was the knee (N = 134, 27%), followed by head/face (N =108, 22%). These numbers were, however, substantially lowered, when subdivided by playing level and age-group. The volume of research focuses especially on descriptive research and specific body locations (head/face and knee). Although information can be taken from studies in other sports, more football-specific studies to support management and prevention of injuries are warranted.



#7 High rate of muscle injury despite no changes in physical, physiological and psychophysiological parameters in a professional football team during a long-congested fixture period

Reference: Res Sports Med. 2022 Feb 13;1-12. doi: 10.1080/15438627.2022.2038159. Online ahead of print.

Authors: G S Pinheiro, R C Quintão, J G Claudino, C Carling, M Lames, B P Couto

Summary: This study aimed to analyse match availability, participation, and muscle injury incidence and to compare the effect of time intervals between matches (3-4 versus 6-7 days) on physical, physiological, and psychophysiological parameters in a professional football team during a prolonged congested fixture period. Thirteen professional male football players (29.2 ± 4.8 years old; 78.5 ± 8.3 kg; 179.3 ± 8.8 cm;) participated. Data were collected during 17 consecutive weeks for 35 official matches separated by an average interval of ≤ 3.5 days. Results showed a player availability of 84.8 ± 16.1% while match participation was 68.8% ± 6.4%. Muscle injury incidence was 19.0/ 1,000 hours of match exposure. These injuries occurred after individual players participated in sequences of 8.3 ± 3.3 consecutive matches with intervals of 3.8 ± 0.8 days. No differences were observed in physical performance or in fatigue-related parameters irrespective of the time interval between matches. A high player availability rate was observed. No differences were observed in physical, physiological, and psychophysiological indices of performance when comparing shorter and longer time intervals between consecutive matches.Prolonged exposure to fixture congestion resulted in an high risk of incurring muscle injury.



#8 Inhibition and Calendar Age Explain Variance in Game Performance of Youth Soccer Athletes

Reference: Int J Environ Res Public Health. 2022 Jan 20;19(3):1138. doi: 10.3390/ijerph19031138.

Authors: Florian Heilmann, Rainer Wollny, Franziska Lautenbach

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Summary: The assessment of core executive functions (EFs; i.e., inhibition, working memory, cognitive flexibility) has often been presented as a diagnostic tool for evaluating cognitive functions in recent publications. For example, EFs are essential in soccer because players must quickly adapt, change strategies, and inhibit responses in rapidly changing game situations. Previous research has shown relations between (subjectively rated) game performance and the EFs of soccer players. Nevertheless, the previous studies' samples were heterogeneous in their performance level (experts vs. amateurs), and the ratings were rather unsystematic (no validated rating protocol). Therefore, the current study aimed to predict soccer players' game performance (i.e., systematically rated by coaches) with the help of EF performance. Therefore, we assessed the game performance (small-sided game, Game Performance Assessment Instrument [GPAI]) and EFs (inhibition: flanker task; working memory: 3-back task; cognitive flexibility: number-letter task) of 94 male soccer players (12-19 years old) from Germany's highest competitive level. Multiple regression model results indicate that inhibition (i.e., flanker effect) and calendar age explain ~18% of players' game performance variance. Results have to be interpreted with regard to the age-dependency of game performance and EFs. In conclusion, even though the results are based on a cross-sectional study, it appears that calendar age needs to be considered when assessing EFs.



#9 Impact of Prolonged Absence of Organized Training on Body Composition, Neuromuscular Performance, and Aerobic Capacity: A Study in Youth Male Soccer Players Exposed to COVID-19 Lockdown

Reference: Int J Environ Res Public Health. 2022 Jan 20;19(3):1148. doi: 10.3390/ijerph19031148.

Authors: Sümer Alvurdu, Cihan Baykal, Zeki Akyildiz, Ömer Şenel, Ana Filipa Silva, Daniele Conte, Filipe Manuel Clemente

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Summary: The aim of this study is to examine how physical performance has changed after 15 weeks (109 days) long-term absence of organized training in youth soccer players imposed by the stay at home orders. A total of sixty-eight young male soccer players from different age categories (U15, U16, U17 and U19) voluntarily participated in the prospective cohort study. Body fat percentage (BF%), counter-movement jump (CMJ), 30 m sprint, change-of-direction (COD) and yo-yo intermittent recovery test level-1 (YYIRTL-1) were evaluated twice (before and after the detraining period). Subsequently, 2 × 2 repeated measures ANOVA was used to investigate group and time differences in repeated measurements. A significance level of p < 0.05 was implemented. CV and SWC values were calculated to test the reliability of the tests performed at different times. Statistical analysis was performed using the IBM SPSS statistics software (v.25, IBM, New York, NY, USA). Significant increments in BF%, 30 m sprint, and COD (left and right), and also significant decrements in CMJ and YYIRTL-1, were found after the detraining period. A long-term detraining period due to the stay at home orders has a detrimental effect on body composition, neuromuscular performances, and aerobic capacity in youth soccer players.



#10 Automatic Markerless Motion Detector Method against Traditional Digitisation for 3-Dimensional Movement Kinematic Analysis of Ball Kicking in Soccer Field Context

Reference: Int J Environ Res Public Health. 2022 Jan 21;19(3):1179. doi: 10.3390/ijerph19031179.

Authors: Luiz H Palucci Vieira, Paulo R P Santiago, Allan Pinto, Rodrigo Aquino, Ricardo da S Torres, Fabio A Barbieri

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Summary: Kicking is a fundamental skill in soccer that often contributes to match outcomes. Lower limb movement features (e.g., joint position and velocity) are determinants of kick performance. However, obtaining kicking kinematics under field conditions generally requires time-consuming manual tracking. The current study aimed to compare a contemporary markerless automatic motion estimation algorithm (OpenPose) with manual digitisation (DVIDEOW software) in obtaining on-field kicking kinematic parameters. An experimental dataset of under-17 players from all outfield positions was used. Kick attempts were performed in an official pitch against a goalkeeper. Four digital video cameras were used to record full-body motion during support and ball contact phases of each kick. Three-dimensional positions of hip, knee, ankle, toe and foot centre-of-mass (CMfoot) generally showed no significant differences when computed by automatic as compared to manual tracking (whole kicking movement cycle), while only z-coordinates of knee and calcaneus markers at specific points differed between methods. The resulting time-series matrices of positions (r2 = 0.94) and velocity signals (r2 = 0.68) were largely associated (all p < 0.01). The mean absolute error of OpenPose motion tracking was 3.49 cm for determining positions (ranging from 2.78 cm (CMfoot) to 4.13 cm (dominant hip)) and 1.29 m/s for calculating joint velocity (0.95 m/s (knee) to 1.50 m/s (non-dominant hip)) as compared to reference measures by manual digitisation. Angular range-of-motion showed significant correlations between methods for the ankle (r = 0.59, p < 0.01, large) and knee joint displacements (r = 0.84, p < 0.001, very large) but not in the hip (r = 0.04, p = 0.85, unclear). Markerless motion tracking (OpenPose) can help to successfully obtain some lower limb position, velocity, and joint angular outputs during kicks performed in a naturally occurring environment.



#11 Match Physical and Physiological Response of Amateur Soccer Referees: A Comparison between Halves and Match Periods

Reference: Int J Environ Res Public Health. 2022 Jan 24;19(3):1306. doi: 10.3390/ijerph19031306.

Authors: Eñaut Ozaeta, Uxue Fernández-Lasa, Inmaculada Martínez-Aldama, Ruth Cayero, Daniel Castillo

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Summary: The aim of this paper was to examine the differences in the external and internal load in amateur match officials between the 1st and 2nd half and among different 15 min periods. Twenty-three field referees (FRs) and 46 assistant referees (ARs) from the Spanish División de Honor participated in this study. Match external and internal loads were monitored showing that FRs recorded a lower Powermean, Speedmean, Cadencemean and Stiffnessmean (p < 0.05; d = 0.52 to 0.57) during the 2nd half and they also recorded a lower HRmean, and HRpeak, and spent less time in zone 5 (p < 0.05; d = 0.50 to 0.62). The FRs' match load decreased during the match but they performed higher Powermean and covered more distance in the last 15 min of the match (p < 0.01; d = 0.87 to 4.28). The ARs external load did not show significant variations between halves, but ARs recorded a lower HRmean and spent less time in zone 5 (p < 0.01; d = 0.41 to 0.63), and the highest values of Powermean, Speedmean, Cadencemean and Vertical oscillationmean during the first 15 min of the match (p < 0.05; d = 0.45 to 0.75). The highest values of HRmean and distance covered were in the 0-15 min period. Results suggest that match load decreases as the match progresses because of the neuromuscular fatigue but increases in the last 15 min.



#12 Sprint Performance and Mechanical Force-Velocity Profile among Different Maturational Stages in Young Soccer Players

Reference: Int J Environ Res Public Health. 2022 Jan 27;19(3):1412. doi: 10.3390/ijerph19031412.

Authors: Luis Miguel Fernández-Galván, Pedro Jiménez-Reyes, Víctor Cuadrado-Peñafiel, Arturo Casado

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Summary: The aim of the present study was to determine the influence of maturation status on the components of the sprint force-velocity (F-V) profile in young soccer players. Sixty-two young male soccer players from the same professional soccer academy took part in the present study. A cross-sectional design was implemented to compare the main components of the sprint F-V profile (i.e., maximal theoretical force (F0), velocity (V0), power (Pmax), and ratio of horizontal-to-resultant force (RFpeak), and decrease in the ratio of horizontal-to-resultant force (DRF)) and sprint performance (5, 20, and 30 m sprint time) among participants' maturation stages (i.e., pre-, mid- and post-peak height velocity (PHV) groups). The results show that the ES of differences in 5 min sprint performance, F0, and RFpeak (i.e., strength- and acceleration-related components of the sprint F-V profile) were greater between pre- and mid-PHV groups than those between mid- and post-PHV groups (i.e., large and very large effects (1.24 ≤ ES ≤ 2.42) vs. moderate, small, and zero effects (0 ≤ ES ≤ 0.69), respectively). However, the ES of differences in V0 and DRF (i.e., peak speed-related components of the sprint F-V profile) were greater between mid- and post-PHV groups than those between pre- and mid-PHV groups (i.e., large effects (1.54 ≤ ES ≤ 1.92) vs. moderate effects (-0.59 ≤ ES ≤ 1), respectively). Once the strength development is achieved to a great extent from the pre- to mid-PHV groups, specific strength training methods may be used for young soccer players to improve their sprint performance.



#13 Variations in the physical demands and technical performance of professional soccer teams over three consecutive seasons

Reference: Sci Rep. 2022 Feb 14;12(1):2412. doi: 10.1038/s41598-022-06365-7.

Authors: Zeki Akyildiz, Hadi Nobari, Francisco Tomás González-Fernández, Gibson Moreira Praça, Hugo Sarmento, Aytek Hikmet Guler, Esat Kaan Saka, Filipe Manuel Clemente, António J Figueiredo

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Summary: The purpose of this study was twofold: (i) to analyze the seasonal variations in the physical demands of Turkish Super League teams considering their status in the final rankings and (ii) to analyze the seasonal variations in the technical performance of Turkish Super League teams considering their status in the final rankings. This study followed an observational analytic retrospective design. In the last three seasons of the Turkish Super League (2015-2016, 2016-2017 and 2017-2018), 918 football matches, 54 teams, 25,029 observations were made. The Sentio Sports optical tracking system was used to quantify the physical demands and technical execution of players in all matches. No significant differences of external load were found between seasons analyzed (p > 0.05). The number of lost balls, ball touches in the central corridor, and goals from set pieces increased from season one to the others (p < 0.05), while the number of successful dribbles reduced over time (p < 0.05). As conclusion, it seems not occurred a progressive change in external load over the seasons, while an evolutionary trends regarding technical variables were observed.



#14 Changes in circulating microRNAs following head impacts in soccer

Reference: Brain Inj. 2022 Feb 16;1-12. doi: 10.1080/02699052.2022.2034042. Online ahead of print.

Authors: Stian Bahr Sandmo, Katarina Matyasova, Peter Filipcik, Martin Cente, Inga Katharina Koerte, Ofer Pasternak, Thor Einar Andersen, Truls Martin Straume-Næsheim, Roald Bahr, Igor Jurisica 

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Summary: The purpose was to explore the short-term effects of accidental head impacts and repetitive headers on circulating microRNAs, accounting for the effects of high-intensity exercise alone. Blood samples were collected from professional soccer players at rest. Repeat samples were drawn 1 h and 12 h after three conditions: (1) accidental head impacts in a match, (2) repetitive headers during training, and (3) high-intensity exercise. 89 samples were screened to detect microRNAs expressed after each exposure. Identified microRNAs were then validated in 98 samples to determine consistently deregulated microRNAs. Deregulated microRNAs were further explored using bioinformatics to identify target genes and characterize their involvement in biological pathways. Accidental head impacts led to deregulation of eight microRNAs that were unaffected by high-intensity exercise; target genes were linked to 12 specific signaling pathways, primarily regulating chromatin organization, Hedgehog and Wnt signaling. Repetitive headers led to deregulation of six microRNAs that were unaffected by high-intensity exercise; target genes were linked to one specific signaling pathway (TGF-β). High-intensity exercise led to deregulation of seven microRNAs; target genes were linked to 31 specific signaling pathways. We identified microRNAs specific to accidental head impacts and repetitive headers in soccer, potentially being useful as brain injury biomarkers.



#15 Impact of Long-Haul Travel to International Competition on Sleep and Recovery in Elite Male and Female Soccer Athletes

Reference: Int J Sports Physiol Perform. 2022 Feb 16;1-10. doi: 10.1123/ijspp.2021-0165. Online ahead of print.

Authors: Michelle Biggins, Helen Purtill, Peter Fowler, Kieran O'Sullivan, Roisin Cahalan

Summary: The aim was to investigate the impact of eastward travel across 7 time zones on sleep, jet lag, and recovery in elite soccer athletes. Twenty-one male and 20 female athletes (21.5 [1.7] y) traveled from Ireland to Taiwan to represent their national team at the World University Games 2017. Daily monitoring via actigraphy and subjective sleep and well-being measures were obtained for 1 week in Ireland (baseline), and for the duration of an international soccer tournament (days 1-5 [precompetition] and days 6-18 [competition]). Sleep duration (P = .028) and time in bed (P = .006) were significantly lower at precompetition compared with baseline. Sleep quality (P < .001) was significantly decreased in precompetition compared with baseline and competition. Subjective jet lag symptoms continued for up to 13 days posttravel. Athletes reported significantly greater fatigue during precompetition compared with competition (P = .005); however, there were no significant differences for recovery (P = .35) and readiness to train (P = .35). Sleep hygiene changed significantly during precompetition and competition compared with baseline in relation to reduced electronic device use (P = .005) and reduced caffeine intake (P < .001). Females reported significantly greater presleep tension-anxiety compared with males at all timepoints (P = .02). Long-haul eastward travel across 7 time zones has a significant impact on sleep duration and quality, likely related to changes in sleep patterns and jet lag. Athletes report changes in sleep hygiene posttravel; however, sleep remained negatively impacted for up to 5 days. Despite significant sleep disturbance and jet lag symptoms, young healthy athletes appear to recover well from long-haul travel; however, it is unknown if this interferes with training and competition performance.



#16 Effect of alterations in whole-body cryotherapy (WBC) exposure on post-match recovery markers in elite Premier League soccer players

Reference: Biol Sport. 2022 Jan;39(1):31-36. doi: 10.5114/biolsport.2021.102931. Epub 2021 Mar 1.

Authors: James J Malone, Daniel Hodges, Craig Roberts, Jonathan K Sinclair, Richard M Page, Robert Allan

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Summary: The use of whole-body cryotherapy (WBC) as a recovery intervention is prevalent amongst elite soccer players. However, there is a distinct lack of data available around chronic WBC use and post-match recovery markers in elite soccer. The aim of this study was to investigate the impact of different levels of WBC exposure on subjective and objective measures of post-match recovery in elite soccer players during a chronic exposure period. Sixteen male senior professional outfield soccer players participated in this study over two seasons. K means cluster analysis was used to classify low (-114 ± 2°C for 133 ± 2 s), medium (-121 ± 1°C for 173 ± 2 s) and high (-133 ± 1°C for 181 ± 2 s) cryotherapy exposure indexes (CEI). Salivary markers (immunoglobulin A (IgA) and alpha amylase (AA)) and subjective wellness scores (perceived fatigue, sleep quality, general muscle soreness and stress) were collected post-match across both seasons. Training load (session-RPE) was collected and used as a covariate to control for the load amongst groups. No differences were seen in perceived measures of wellness and salivary AA. Significantly lower IgA concentrations were observed in the medium CEI group (255 ± 32 µg∙ml-1) compared to the low (328 ± 38 µg∙ml-1) and high (306 ± 32 µg∙ml-1) groups. Therefore, increasing the level of chronic WBC exposure appears to have no additional benefit on subjective recovery and alpha amylase response post-match. However, there appears to be an optimal chronic WBC dose with regards to IgA response.



#17 Ten-minute warm-up in hot climate best assists thermal comfort, muscular power output, and fatigue, during soccer-specific repeated-sprint ability

Reference: Biol Sport. 2022 Jan;39(1):37-43. doi: 10.5114/biolsport.2021.102808. Epub 2021 Dec 18.

Authors: Nesrine Chaâri, Mohamed Frikha

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Summary: Structuring warm-up (WU) in hot climate conditions before high-intensity efforts is still drawing the attention of researchers and practitioners. The present study investigates the effect of two WU durations (i.e.10 min: WU10 and 20 min: WU20) in a hot climate (~31°C), on thermal comfort, muscular power output and fatigue after a repeated-sprint test (RSA) in soccer players. Twelve amateur soccer players (age = 21.13 ± 1.8 years; height = 172.5 ± 4.6 cm and weight = 70.8 ± 5.1 kg) participated in a cross-over randomized study, and they underwent a soccer-specific RSA test, after two WU durations and on different days. Peak power (PP), mean power (MP) and the fatigue index (FI) were calculated and analysed. Likewise, thermal comfort/discomfort (TC), tympanic temperature (Ttym) and rating of perceived exertion (RPE) were recorded at rest, after WU and after RSA. The ANOVA showed a significant increase in MP after WU10 in comparison to WU20 by 1.9%, while PP remained similar between the two durations. A significant decline in muscular power in WU20 compared to WU10 appeared from the 5th sprinting repetition and continued to the end of the RSA. The WU20, compared to the WU10, produced higher RPE at post-WU (p < 0.001) and post-RSA (p = 0.018), and higher thermal discomfort sensation in both post-WU (p = 0.022) and post-RSA (p = 0.007) point of measures. Larger increases in Ttym were recorded after WU20 compared to WU10. WU10 in a hot climate (~31°C) best assists mean power output during soccer RSA, but not peak power. Extending the WU duration up to 20 min in a hot climate was revealed to be detrimental for muscular power output, inducing excessive thermal discomfort and fatigue. Therefore, it is important that trainers and soccer players carefully consider WU duration prior to competitions and training sessions in a hot climate, to optimize physiological responses.



#18 How does curve sprint evolve across different age categories in soccer players?

Reference: Biol Sport. 2022 Jan;39(1):53-58. doi: 10.5114/biolsport.2022.102867. Epub 2021 Mar 1.

Authors: Alberto Filter-Ruger, Petrus Gantois, Rafael S Henrique, Jesús Olivares-Jabalera, Jose Robles-Rodríguez, Alfredo Santalla, Bernardo Requena, Fabio Y Nakamura

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Summary: Research has shown that soccer players regularly execute curved sprints during matches. The purpose of this study was to determine the age-related effects on curve sprint (CS) performance to both sides, asymmetry, and association with linear sprint (LS). Eighty-four soccer players (aged 16.1 ± 1.6 categorized in U15, U17, and U20) were recruited, who performed CS and LS tests. One-way analysis of variance (ANOVA) and effect size (ES) were used to compare CS performance between age categories, and relationships between physical performance measures were calculated using Pearson's correlation coefficient. The main findings of this study were that: 1) there were significant differences in the "good" side CS among age groups (p < 0.001; ES from moderate to large), but not in the "weak" side CS, 2) curve asymmetry was significantly higher in U20 than U15 (p < 0.05; ES large) and U17 players (p < 0.05; ES moderate), and 3) relationships between CS and LS times decreased with age (from significant and very large [p < 0.001] to non-significant and smallmoderate [p > 0.05]). This study highlights the importance of assessing and training CS in different age categories, an action that becomes less correlated with LS as age increases, with the aim of mitigating the increase in asymmetries as a result of the specialization process, focusing interventions mainly on improving the CS "weak" side.


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