Latest research in football - week 7 - 2021

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 Shared Situational Awareness in a Professional Soccer Team: An Explorative Analysis of Post-Performance Interviews 

Reference: Int J Environ Res Public Health. 2020 Dec 9;17(24):E9203. doi: 10.3390/ijerph17249203. 

Authors: Gaute S Schei, Rune Giske

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Summary: Sport science research has done little to elaborate on the cognitive factors that turn a collection of individual players into a coordinated elite team. The purpose of this paper is to clarify if the players and coach of an elite soccer team express shared situational awareness. Ten players and one coach were exposed to twelve video pictures from a previous soccer match, and their statements for each picture were recorded and analyzed using a qualitative approach. Two of five game situations were with ball possession and three out of seven were without ball possession; the player statements are contradictory, with a high threat for inadequate coordination. In seven of the twelve game situations, the players' statements coincided and expressed a shared situational awareness, with good opportunities for adequate defensive and offensive coordination. In two of the game situations, there was a high threat for inadequate coordination. There was consensus among 9 out of 10 players, but the player with the divergent statement was central in the situation. The procedure followed in the study could be used to elucidate if a team has shared situational awareness and clarify in which situations there exists discrepancies and data that can be used to improve team coordination on and off the field. 



#2 The moderating impact of maturation on acute neuromuscular and psycho-physiological responses to simulated soccer activity in academy soccer players

Reference: Eur J Sport Sci. 2020 Dec 14;1-11. doi: 10.1080/17461391.2020.1851775. Online ahead of print. 

Authors: Jamie Salter, Mark B A De Ste Croix, Jonathan D Hughes

Summary: Resource constraints complicate load monitoring practices in some academies, which is problematic based on load-injury associations surrounding periods of rapid non-linear growth. Limited research has explored relationships between maturation and perceived psycho-physiological response to activity and associated neuromuscular performance changes. This study aimed to quantify neuromuscular and psycho-physiological responses to standardised activity and analyse whether dose-responses were moderated by maturation. Fifty-seven male soccer players (age: 14.1 ± 0.9 years; stature: 165 ± 10 cm; body mass, 57 ± 9 kg; percentage of predicted adult height 92.7 ± 5%) from two Elite Player Performance Plan (EPPP) academies completed the youth soccer-specific aerobic fitness test (Y-SAFT60). Countermovement jump (CMJ), reactive strength index (RSI), absolute (ABS) and relative leg stiffness (REL) were measured pre-post the Y-SAFT60 with playerload (PL), heart rate (HR), total distance (TDist) and differential ratings of perceived exertion (dRPE) used as markers of load and intensity. A moderation model was employed to analyse interactions of maturation as a continuous variable. Analysis indicated no significant interaction (p <0.05) between maturation and neuromuscular performance but RPE-Technical demonstrated significant interactions (p = 0.01). Slope analysis indicated four variables (PL, RSI, ABS and REL) that demonstrated significance at various stages of maturation, most notably aligning with peak height velocity (87-96% PAH). Tentatively, we propose that maturational developments in the neuromuscular system offer some mechanistic explanation to the varied dose-responses observed. It is therefore important that maturation is habitually considered within prescription of training programmes and that further empirical studies are completed to determine maturity specific dose-responses. Components of both neuromuscular performance and psycho-physiological response to simulated soccer was influenced by maturity status. Individuals more biologically developed are more capable of 'coping' with the biomechanical load of simulated soccer activity resulting in more favourable neuromuscular responses. The period surrounding peak height velocity appears to influence whole body load-response pathways resulting in altered movement patterns during this period. To minimise the impact of maturity status, practitioners can restrict activities that elicit high biomechanical load and introduce biologically categorised training activities. 



#3 Effects of soccer training in muscular strength: a comparative study in trained youth soccer players and untrained boys of the same biological age 

Reference: J Sports Med Phys Fitness. 2020 Dec 14. doi: 10.23736/S0022-4707.20.11822-X. 

Authors: Athanasios Mandroukas, Thomas I Metaxas, Yiannis Michailidis, Kosmas Christoulas, Jan Heller

Summary: It is not clear if soccer training affected the development of muscle strength positively in children. We hypothesize that soccer training could positively affect the isokinetic concentric muscle strength and anthropometric characteristics in different ages of adolescents of the same biological age. A total of one-hundred and twenty-six (n=126) young soccer players (n=66) and untrained boys (n=60) throughout the developmental ages of 12, 14 and 16 years volunteered to participate in the study. Sexual maturation was classified according to Tanner's stages. Soccer players, except from their school's physical education program, participate also in a soccer training program. All participants underwent anthropometric measurements. The isokinetic-concentric peak torque values of the hamstrings (H) and quadriceps (Q), as well as the conventional strength ratios of H:Q, were measured on an isokinetic dynamometer at angular velocities of 60, 180, and 300°·s-1. Anthropometric differences in the same age group, between trained and untrained, were presented only for 12 year-olds (height, p<0.001 and BMI, p<0.01). Between groups, differences were observed in almost all anthropometric measurements, probably as result of development. The absolute isokinetic-concentric muscle strength was significantly higher (p<0.001) in the 12 and 16 years old trained group, compared to untrained, for the knee-flexors and knee-extensors. However, no significant differences were found between the 14 years old trained and untrained, for the muscle groups of Q and H. The H:Q strength ratios did not differ between groups at all angular velocities. The results of this study showed that systematic soccer training has a positive effect in the peripheral system, expressed as an increased lower limb muscle strength; specifically, Q and H. 



#4 Rethinking training in elite soccer players: comparative evidence of small sided games and official match play in kinematic parameters

Reference: J Sports Med Phys Fitness. 2020 Dec 14. doi: 10.23736/S0022-4707.20.11400-2. 

Authors: Cristian Savoia, Ferdinando Iellamo, Giuseppe Caminiti, Dominic A Doran, Samuel Pullinger, Mario Innaurato, Giuseppe Annino, Vincenzo Manzi  

Summary: The aim of this study was to compare kinematics parameters among official matches and SSGs of an Italian premier league soccer team. Eighteen elite professional male soccer players (4 central defenders, 4 wide defenders, 3 central midfielders, 3 box-to-box midfielders, 2 wingers and 2 strikers) took part in the study. Players were monitored during four months of full training (including pre-season and in-season) and over 26 matches (14 Serie A matches, 9 Europa League matches, and 3 friendly matches), from July 2017 until November 2017. The kinematic parameters during official matches and SSGs were evaluated through Video Match Analysis. The kinematic data analysis shows that the metabolic power, that constitutes an integrated measure of acceleration and velocity, fails to reflect what occurs during actual matchplay. An increased attention should be place in planning SSGs during training to better reproduce actual match situations. 



#5 Muscle Activity Asymmetry of The Lower Limbs During Sprinting in Elite Soccer Players

Reference: J Hum Kinet. 2020 Oct 31;75:239-245. doi: 10.2478/hukin-2020-0049. eCollection 2020 Oct. 

Authors: Przemysław Pietraszewski, Artur Gołaś, Aleksander Matusiński, Sylwia Mrzygłód, Aleksandra Mostowik, Adam Maszczyk

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Summary: The analysis of movement patterns through EMG activity provides the opportunity to identify the muscle groups most involved in a particular exercise, and to determine the scope of inter-limb deficiencies. The aim of the present study was to investigate the effects of a side-to-side muscle activity asymmetry between the left and the right lower limb during sprinting in soccer players. Sixteen professional soccer players took part in the study. Their age, body mass and body height equaled 23.7 ± 7.6 years, 81.2 ± 10.8 kg and 179.3 ± 12.2 cm, respectively. The sprint test consisted of two maximal sprints over 30 m with a 5-min rest interval between each sprint. EMG was recorded bilaterally from the quadriceps, hamstrings and gluteal muscles. Regression analysis revealed a significant effect of a side-to-side average muscle activity asymmetry between the left and right hamstring (LH/RH) muscles during the speed tests at 5 m (p = 0.044), and 30 m (p = 0.045), as well as the left and right glutes (LG/RG) at 5 m (p = 0.044) and 30 m (p = 0.043). Our results indicate that hamstring and glute muscles should be selectively and additionally activated during resistance training in soccer players to prevent injuries and improve sprint performance. 



#6 Tactical Behaviour of Youth Soccer Players: Differences Depending on Task Constraint Modification, Age and Skill Level

Reference: J Hum Kinet. 2020 Oct 31;75:225-238. doi: 10.2478/hukin-2020-0051. eCollection 2020 Oct. 

Authors: João Cláudio Machado, Daniel Barreira, Israel Teoldo, Jaime Serra-Olivares, Alberto Góes, Alcides José Scaglia

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Summary: This study aimed to investigate: i) how Small-Sided and Conditioned Games based on different representation and exaggeration modification strategies, from the Teaching Games for Understanding pedagogical principles, affected team performance and exploratory behaviour; and ii) how teams and players of different ages and skill levels were affected by the use of these different modification strategies. In total, forty-eight youth male soccer players participated in the study (U15, n = 24 mean age = 13.06 ± 1.53 years; U17, n = 24 mean age = 16.89 ± 0.11 years). In both categories, players were organized into three groups according to their tactical efficiency level (Group 01 = High Skilled Players (HSP), Group 02 = Intermediate Skilled Players (ISP), and Group 03 = Low Skilled Players (LSP)). The HSP and LSP groups performed two types of Gk+4vs4+Gk Small-Sided and Conditioned Games (SSCGs) based on different representation and exaggeration modification strategies. The first type of SSCGs was modified by structural constraints (Structural SSCG) and the second type was modified by rule manipulation (Manipulation SSCG). Team performance and exploratory behaviour were analysed through the Offensive Sequences Characterization System and Lag Sequential Analysis, respectively. SSCG modification strategies affected differently tactical performance and exploratory behaviour of teams composed of players of different skill levels. It was found that SSCG modification strategy through rule manipulation provided players and teams with a higher level of difficulty, compromising their performance and inhibiting exploratory behaviour. This information is crucial to practitioners wishing to apply more appropriate pedagogical strategies to improve a specific tactical problem using a player-centred and game-based approach. 



#7 Match and Training High Intensity Activity-Demands Profile During a Competitive Mesocycle in Youth Elite Soccer Players

Reference: J Hum Kinet. 2020 Oct 31;75:195-205. doi: 10.2478/hukin-2020-0050. eCollection 2020 Oct. 

Authors: José María Oliva-Lozano, Carlos David Gómez-Carmona, José Pino-Ortega, Víctor Moreno-Pérez, Manuel Antonio Rodríguez-Pérez

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Summary: The monitoring of the high intensity activity-demands profile during official matches (OMs) and training sessions (TSs) provides a deeper understanding of the relationship between training and competition loads as well as players' fitness characteristics. The aims of this study were to: 1) describe the training and match high intensity activity-demands profile in U-19 soccer players; 2) compare the profile depending on the type of session (OM or TS) throughout match-weeks; and 3) differentiate between profiles depending on the match location (home or away). Twenty-five U-19 Spanish soccer players were monitored during TSs and OMs for a one-month competitive period using a WIMU PROTM wearable inertial device. The variables of the study were: high speed running distance (HSRD), total sprints (SPs), maximum speed (MS) and player load (PL). OMs required higher demands than TSs in HSRD (460.99 ± 206.18 vs. 315.45 ± 180.12 m; p < 0.01; d = 0.75), SPs (10.86 ± 6.64 vs. 7.23 ± 4.82; p < 0.01; d = 0.69), MS (29.99 ± 2.54 vs. 28.50 ± 2.4 km/h; p < 0.01; d = 0.59) and PL (103.08 ± 24.15 vs. 83.18 ± 17.96 a.u.; p < 0.01; d = 0.94). The interaction between the type of session and mean week's demands presented differences with medium effect size in MS (p < 0.01; ωp 2 = 0.06) and small effect size in HSRD (p = 0.04; ωp 2 = 0.03), and SP (p = 0.05; ωp 2 = 0.03), but there were no differences in PL (p = 0.18; ωp 2 = 0). Finally, no differences were found in the match location comparison (p > 0.33; d = 0.22-0.33). Therefore, the profiles presented could be useful for future scientific purposes and serve as valid information for coaches trying to optimize performance. 



#8 Relationships Between Measures of Functional and Isometric Lower Body Strength, Aerobic Capacity, Anaerobic Power, Sprint and Countermovement Jump Performance in Professional Soccer Players

Reference: J Hum Kinet. 2020 Oct 31;75:161-175. doi: 10.2478/hukin-2020-0045. eCollection 2020 Oct. 

Authors: Michał Boraczyński, Tomasz Boraczyński, Robert Podstawski, Zbigniew Wójcik, Piotr Gronek

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Summary: The purpose of this study was to assess a wide range of physiological and performance variables and investigate whether and to what extent these variables are associated with each other in soccer. Twenty-five male soccer players (25.1 ± 4.56 years; body mass, 75.2 ± 5.92 kg; body height, 180.6 ± 5.45 cm) performed: 5- and 30-m sprints (T5m and T30m, respectively), 1-repetition-maximum (1RM) half squat, maximal voluntary isometric contraction (MVIC) of the knee extensors, countermovement jump (CMJ) to obtain vertical jump height (CMJheight) and power output (CMJpower), the 10-s Wingate Anaerobic Test (WAnT) to obtain peak power (Pmax), and the 20-m multi-stage shuttle run test (MST) to evaluate aerobic capacity. 1RM, MVIC, and Pmax were normalized to body mass. Large negative correlations were found between sprint times and 1RM half back squat/BM (r = -0.510 to -0.570, r2 = 0.260-0.325, both p < 0.01) and Pmax/BM (r = -0.501, r2 = 0.251, p < 0.01). T30m most strongly and negatively correlated with CMJheight (r = -0.744, r2 = 0.554, p < 0.001). WAnT-determined Pmax showed a very large correlation between absolute Pmax and knee-extensor MVIC (r = 0.827, r2 = 0.684, p < 0.001) and large correlations between absolute Pmax and 1RM half squat (r = 0.674, r2 = 0.454, p < 0.001) and CMJpower (r = 0.579, r2 = 0.335, p < 0.01). We also identified a large inverse relationship between CMJheight and T30m (r = -0.744, r2 = 0.554, p < 0.001) and large positive correlation between CMJheight and MVIC/BM (r = 0.702, p < 0.001). The results demonstrate that elite soccer players with greater lower body strength (quantified by the MVIC of the knee extensor and the 1RM half squat) show better sprint and CMJ performance, suggesting the incorporation of soccer-specific resistance training to develop lower body musculature and therefore maximize sprinting ability. The higher correlation coefficients found between T30m and the physiological and athletic measures compared with T5m promote the use of this sprint distance when assessing performance. The use of relative measures (normalized to body mass) is advisable when comparing strength variables with sprint and CMJ performance or anaerobic power. Considering the correlations of WAnT-determined Pmax versus CMJpower, coaches should administer tests that assess jumping and linear sprint performance rather than the cycling-specific WAnT. 



#9 The Relationship Between Repeated-Sprint Ability, Aerobic Capacity, and Oxygen Uptake Recovery Kinetics in Female Soccer Athletes 

Reference: J Hum Kinet. 2020 Oct 31;75:115-126. doi: 10.2478/hukin-2020-0042. eCollection 2020 Oct. 

Authors: Bruno Archiza, Daniela K Andaku, Thomas Beltrame, Cleiton A Libardi, Audrey Borghi-Silva

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Summary: This study investigated the relationship between repeated-sprint ability, aerobic capacity, and oxygen uptake kinetics during the transition between exercise and recovery (off-transient) in female athletes of an intermittent sport modality. Eighteen professional soccer players completed three tests: 1) a maximal incremental exercise test; 2) a constant speed time-to-exhaustion test; and 3) a repeated-sprint ability test consisting of six 40-m sprints with 20 s of passive recovery in-between. Correlations between time-to-exhaustion, repeated-sprint ability, and oxygen uptake kinetics were calculated afterwards. The level of significance was set at p < 0.05. A performance decrement during repeated-sprint ability was found to be related to: 1) time-to-exhaustion (e.g., exercise tolerance; r = -0.773, p < 0.001); 2) oxygen uptake recovery time (r = 0.601, p = 0.008); and 3) oxygen uptake mean response time of recovery (r = 0.722, p < 0.001). Moreover, the best sprint time (r = -0.601, p = 0.008) and the mean sprint time (r = -0.608, p = 0.007) were found to be related to maximal oxygen uptake. Collectively, these results reinforce the relation between oxygen uptake kinetics and the ability to maintain sprint performance in female athletes. These results may contribute to coaches and training staff of female soccer teams to focus on training and improve their athletes' aerobic capacity and recovery capacity to improve intermittent exercise performance. 



#10 Unilateral Plyometric Training is Superior to Volume-Matched Bilateral Training for Improving Strength, Speed and Power of Lower Limbs in Preadolescent Soccer Athletes

Reference: J Hum Kinet. 2020 Aug 31;74:161-176. doi: 10.2478/hukin-2020-0022. eCollection 2020 Aug. 

Authors: Vasileios Drouzas, Christos Katsikas, Andreas Zafeiridis, Athanasios Z Jamurtas, Gregory C Bogdanis

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Summary: This study compared the effects of unilateral and bilateral plyometric training on strength, sprint performance and lower limb power. Sixty-eight preadolescent soccer athletes were randomly assigned to a unilateral plyometric training group (n=23), a bilateral plyometric training group (n=23) and a control group (n=22). Both plyometric training groups trained with equal volumes of unilateral or bilateral exercises for 15 minutes in each session, at which time the control group performed soccer-specific drills. Plyometric exercises were executed twice weekly for 10 weeks during the competitive season. The following tests were performed before and after the intervention: single-leg and double-leg countermovement jump, squat jump, horizontal jumps in different directions, maximal isometric strength of quadriceps and hamstrings, sprint performance, agility and balance. Unilateral plyometric training resulted in greater improvements compared to the control group in the following variables: hamstrings strength (ES: 0.91, p=0.037), 5m sprint time (ES: 0.93, p=0.004), single-leg countermovement jump (ES: 0.90, p=0.006), single- and double-leg squat jump (ES: 0.87, p=0.030 and ES: 0.73, p=0.067, respectively) and single-leg hop performance (ES: 1.01, p=0.004). The only tests where there was an improvement of BPT compared with the CG were the single-leg and double leg SJ (ES: 0.76, p=0.026; ES: 0.70, p=0.050). Quadriceps strength, side hop test, double-leg horizontal jump test, flamingo balance test and modified agility T-test were equally improved in all three groups (p<0.001). In conclusion, unilateral lower-limb plyometric training is more effective in increasing muscle strength and power in preadolescent soccer players when compared to bilateral training or soccer training alone. 



#11 Effectiveness and time-course adaptation of resistance training vs. plyometric training in prepubertal soccer players

Reference: J Sport Health Sci. 2020 Dec;9(6):620-627. doi: 10.1016/j.jshs.2016.07.008. Epub 2016 Jul 16. 

Authors: Yassine Negra, Helmi Chaabene, Thomas Stöggl, Mehréz Hammami, Mohamed Souhaiel Chelly, Younés Hachana

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Summary: This study aimed to assess the effectiveness and time course for improvements in explosive actions through resistance training (RT) vs. plyometric training (PT) in prepubertal soccer players. Thirty-four male subjects were assigned to: a control group (n = 11); an RT group (5 regular soccer training sessions per week, n = 12); a PT group (3 soccer training sessions and 2 RT sessions per week, n = 11). The outcome measures included tests for the assessment of muscle strength (e.g., 1 repetition maximum half-squat test), jump ability (e.g., countermovement jump, squat jump, standing long jump, and multiple 5 bounds test), linear speed (e.g., 20 m sprint test), and change of direction (e.g., Illinois change of direction test). The RTG showed an improvement in the half-squat (Δ = 13.2%; d = 1.3, p< 0.001) and countermovement jump (Δ = 9.4%; d = 2.4, p< 0.001) at Week 4, whereas improvements in the 20-m sprint (Δ = 4.2%; d = 1.1, p < 0.01); change of direction (CoD) (Δ = 3.8%; d = 2.1, p < 0.01); multiple 5 bounds (Δ = 5.1%; d = 1.5, p < 0.05); standing long jump (Δ = 7.2%; d = 1.2, p < 0.01); squat jump (Δ = 19.6%; d = 1.5, p < 0.01); were evident at Week 8. The PTG showed improvements in CoD (Δ = 2.1%; d = 1.3, p< 0.05); standing long jump (Δ = 9.3%; d = 1.1, p< 0.01); countermovement jump (Δ = 16.1%; d = 1.2, p< 0.01); and squat jump (Δ = 16.7%; d = 1.4, p< 0.01); at Week 8 whereas improvements in the 20-m sprint (Δ = 4.1%; d = 1.3, p < 0.01); and multiple 5 bounds (Δ = 7.4%; d = 2.4, p< 0.001); were evident only after Week. The RT and PT groups showed improvements in all sprint, CoD, and jump tests (p< 0.05) and in half-squat performance, for which improvement was only shown within the RTG (p< 0.001). RT and PT conducted in combination with regular soccer training are safe and feasible interventions for prepubertal soccer players. In addition, these interventions were shown to be effective training tools to improve explosive actions with different time courses of improvements, which manifested earlier in the RTG than in the PTG. These outcomes may help coaches and fitness trainers set out clear and concise goals of training according to the specific time course of improvement difference between RT and PT on proxies of athletic performance of prepubertal soccer players. 



#12 Morphological changes of the lateral abdominal muscles in adolescent soccer players with low back pain: A prospective cohort study 

Reference: J Sport Health Sci. 2020 Dec;9(6):614-619. doi: 10.1016/j.jshs.2018.02.002. Epub 2018 Mar 7. 

Authors: Pawel Linek, Pardis Noormohammadpour, Mohammad Ali Mansournia, Tomasz Wolny, Damian Sikora

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Summary: Most papers examining the lateral abdominal muscles (LAMs) and low back pain (LBP) are cross-sectional, with groups of participants being divided into a control and an LBP group. We hypothesized that morphological measurements of the LAMs in adolescent soccer players may predict future LBP incidence. The aim of this study was to examine the associations between the morphology of LAMs and LBP incidence rate among adolescent soccer players. Ninety-seven adolescent male soccer players with no LBP at baseline were recruited into the prospective cohort study. The thickness of the LAMs was measured at baseline by ultrasound imaging in a supine rest position. Nine cases of LBP occurred during the follow-up 6-month observation. An obliquus internus (OI) asymmetry was related to increasing LBP risk (odds ratio = 19.99; 95%CI: 2.4-167.9). Spearman correlation also showed a linear relationship between OI asymmetry value and duration of LBP (R = 0.75, p = 0.02). An OI side-to-side difference greater than 1.25 mm suggests possible LBP incidence in the 6-month observation among adolescent soccer players. The morphological changes of the OI may be related to LBP's incidence in adolescent soccer players. The presence of OI asymmetry increases the odds of LBP by at least 2.4 times. Hypertrophy of the OI on one side of the body may contribute to trunk muscle imbalance. 



#13 The professional contribution of chiropractors to Danish elite football clubs: a qualitative exploration of role and perceived value in an interprofessional service provision context

Reference: Chiropr Man Therap. 2020 Dec 18;28(1):69. doi: 10.1186/s12998-020-00358-x. 

Authors: Joachim Hostrup, Anders Koza, Corrie Myburgh

Summary: Interprofessional team-based care has been widely adopted in elite level athletic health and performance practice. Chiropractors can claim some penetration as health care service providers in high level sport. However, their position as valued members of interprofessional health care teams, especially those built around traditional medical organisational structures, is unclear. This investigation sought to explore the perceived role and value of chiropractors as service providers in elite Danish football clubs. A comparative qualitative case study was conducted. Six Danish premiere league (Superliga) clubs were purposively sampled to compare and contrast instances where chiropractors were both present and absent from the health care team. Triangulated responses were solicited from healthcare coordinators, chiropractors and athletes within each club's organization through semi-structured individual interviews. The audio-recorded responses were transcribed verbatim and thematically analyzed using a framework approach. Data were collected September and November 2019. A coding framework of 14 codes and 4 code families emerged, centering around the role of chiropractors, benefits of utilizing chiropractic care and facilitators and barriers to interprofessional practice. From this framework, three themes were abstracted, these being: "Broadening horizons", "In-house preferred to take-away" and "Already covered, or even necessary?" In this practice context, chiropractors fill the role of musculoskeletal health care service providers. Their perceived value stems from additional expert disciplinary knowledge, improved diagnostic triage and increased treatment flexibility. However, where not utilized, the role of a spinal health expert is questioned and when acknowledged, is limited to that of a technician/therapist. It is unclear from this investigation whether chiropractors can claim core provider status. Further exploration of this interesting context of interprofessional practice is warranted. 



#14 The Relationships between Internal and External Load Measures for Division I College Football Practice

Reference: Sports (Basel). 2020 Dec 15;8(12):E165. doi: 10.3390/sports8120165. 

Authors: Eric J Sobolewski

Summary: The aim of this study is to explore the relationships between internal and external load measures in American football. Thirty football players wore a portable integrated monitor unit for 10 weeks during the fall football season. Relationships between internal and external load measurements were determined. Internal load consisted of heart rate zones and heart rate-derived measures and session Ratings of Perceived Exertion (sRPE). External load consisted of distance in different speed zones, total distance traveled, and accelerations. There were many significant positive relationships, but the meaningful relationships (r > 0.5) were between heart rate-derived measures of load (Training Impulse and heart rate reserve) and low-intensity movement and total distance. Only accelerations between 1 and 1.99 m·s-2 were moderately correlated to heart rate-derived internal load. RPE values alone did not correlate strong enough with any of the measure but sRPE training load (sRPE-TL) correlated to most external values. Overall, moderate correlations were present between heart rate-derived internal load to total distance and lower intensity movement. sRPE-TL values had high correlations but were highly dependent on duration, not perceived exertion. When addressing load in American football, duration of the session is a key component in determining internal load as HR data and sRPE alone do not correlate highly with external loads. 



#15 Association of high profile football matches in Europe with traffic accidents in Asia: archival study

Reference: BMJ. 2020 Dec 16;371:m4465. doi: 10.1136/bmj.m4465. 

Authors: Kai Chi Yam, Joshua Conrad Jackson, Jenson Lau, Xin Qin, Christopher M Barnes, Juin-Kuan Chong

Summary: The aim was to investigate the association between popular football games played in Europe and the incidence of traffic accidents in Asia. Study based on 41 538 traffic accidents involving taxis in Singapore and 1 814 320 traffic accidents in Taiwan, combined with 12 788 European club football games over a seven year period. The largest taxi company in Singapore, with fine grained traffic accident records in a three year span; all traffic accident records in Taiwan in a six year span. Days when high profile football games were played or not played. Number of traffic accidents was choosen as the main outcome measure. Regression based and time series models suggest that days with high profile European football matches were more positively associated with traffic accidents than days with less popular European football matches. For an approximate €134.74m (£120.25m; $159.76m) increase in average market value for matches played on a given day, approximately one extra accident would occur among Singapore taxi drivers, and for an approximate €7.99m increase in average market value of matches, approximately one extra accident would occur among all drivers in Taiwan. This association remained after control for weather conditions, time of the year, weekend versus weekday effects, driver demographics, and underlying temporal trends. It was also stronger for daytime traffic accidents than for night time traffic accidents, suggesting that the association between high profile football matches and traffic accidents cannot be attributed to night time celebration or attention deficits while watching and driving. Annually, this increased rate of traffic accidents may translate to approximately 371 accidents among taxi drivers in Singapore and approximately 41 079 accidents among the Taiwanese public, as well as economic losses of approximately €821 448 among Singapore taxi drivers and approximately €13 994 409 among Taiwanese drivers and insurers. The total health and economic impact of this finding is likely to be much higher because GMT+8 is the most populous time zone, encompassing 24% of the world's population. 

Conclusions: Days featuring high profile football matches in Europe were associated with more traffic accidents in Taiwan and Singapore than were days with lower profile football matches. A potential causal mechanism may be Asian drivers losing sleep by watching high profile European matches, which are often played in the middle of the night in Asia. 



#16 Neurocognitive performance and mental health of retired female football players compared to non-contact sport athletes 

Reference: BMJ Open Sport Exerc Med. 2020 Dec 3;6(1):e000952. doi: 10.1136/bmjsem-2020-000952. eCollection 2020. 

Authors: Annika Prien, Nina Feddermann-Demont, Evert Verhagen, Jos Twisk, Astrid Junge

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Summary: Adverse long-term effects of playing football due to repetitive head impact exposure on neurocognition and mental health are controversial. To date, no studies have evaluated such effects in women. The aim was to (1) compare neurocognitive performance, cognitive symptoms and mental health in retired elite female football players (FB) with retired elite female non-contact sport athletes (CON), and to (2) assess whether findings are related to history of concussion and/or heading exposure in FB. Neurocognitive performance, mental health and cognitive symptoms were assessed using computerised tests (CNS-vital signs), paper pen tests (Category fluency, Trail-Making Test, Digit Span, Paced Auditory Serial Addition Test), questionnaires (Hospital Anxiety and Depression Scale, SF-36v2 Health Survey) and a symptom checklist. Heading exposure and concussion history were self-reported in an online survey and in a clinical interview, respectively. Linear regression was used to analyse the effect of football, concussion and heading exposure on outcomes adjusted for confounders. FB (n=66) performed similar to CON (n=45) on neurocognitive tests, except for significantly lower scores on verbal memory (mean difference (MD)=-7.038, 95% CI -12.98 to -0.08, p=0.038) and verbal fluency tests (MD=-7.534, 95% CI -13.75 to -0.46, p=0.016). Among FB weaker verbal fluency performance was significantly associated with ≥2 concussions (MD=-10.36, 95% CI -18.48 to -2.83, p=0.017), and weaker verbal memory performance with frequent heading (MD=-9.166, 95% CI -17.59 to -0.123, p=0.041). The depression score differed significantly between study populations, and was significantly associated with frequent heading but not with history of concussion in FB. 

Conclusion: Further studies should investigate the clinical relevance of our findings and whether the observed associations point to a causal link between repetitive head impacts and verbal memory/fluency or mental health. 


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