Latest research in football - week 10 - 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 Intra and inter-tester reliability of a novel device to assess gluteal muscle strength in professional football players

Reference: Res Sports Med. 2020 Dec 30;1-13. doi: 10.1080/15438627.2020.1868466. Online ahead of print. 

Authors: V Moreno-Pérez, M Beato, J Del Coso, J L Hernández-Davó, A Sole, M Peñaranda-Moraga, M Madruga-Parera, D Romero-Rodríguez

Summary: The aim of this study is to investigate inter-tester and intra-tester reliability of a novel clam test (CLAMT) for the measurement of gluteal muscle strength and to detect possible differences between CLAMT values in football players with and without a history of groin injuries. Twenty male football players participated in the test-retest and sixty-two male professional football players participated in the case-control study. Hip abductor maximal muscle strength was evaluated either using CLAMT or in a supine position with the hip in a neutral pose. For CLAMT, intraclass correlation coefficient (ICC) for inter-tester-intra-day reliability was 0.80 (95% CI: 0.60-0.90), with a standard error of measurement of 34.2 N. The intra-tester-intra-day ICC was 0.92 (95% CI: 0.87-0.95), with a standard error of measurement of 23.6 N. The inter-week ICC was 0.96 (95% CI: 0.92-0.98), with a standard error of measurement of 18.9 N. CLAMT showed lower (but not significant) strength values in football players with a history of groin injuries to non-injured players. CLAMT showed good to excellent levels of reliability, intraday and inter-week, with low standard errors of measurement while it was effective (possible) to identify residual weakness in players with previous groin injuries. 



#2 Assessment of Biomechanical Response to Fatigue through Wearable Sensors in Semi-Professional Football Referees 

Reference: Sensors (Basel). 2020 Dec 24;21(1):E66. doi: 10.3390/s21010066. 

Authors: Luigi Truppa, Michelangelo Guaitolini, Pietro Garofalo, Carlo Castagna, Andrea Mannini

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Summary: Quantifying muscle fatigue is a key aspect of everyday sport practice. A reliable and objective solution that can fulfil this task would be deeply important for two main reasons: (i) it would grant an objective indicator to adjust the daily training load for each player and (ii) it would provide an innovative tool to reduce the risk of fatigue-related injuries. Available solutions for objectively quantifying the fatigue level of fatigue can be invasive for the athlete; they could alter the performance or they are not compatible with daily practice on the playground. Building on previous findings that identified fatigue-related parameters in the kinematic of the counter-movement jump (CMJ), this study evaluates the physical response to a fatigue protocol (i.e., Yo-Yo Intermittent Recovery Test Level 1) in 16 football referees, by monitoring CMJ performance with wearable magneto-inertial measurement units (MIMU). Nineteen kinematic parameters were selected as suitable indicators for fatigue detection. The analysis of their variations allowed us to distinguish two opposites but coherent responses to the fatigue protocol. Indeed, eight out of sixteen athletes showed reduced performance (e.g., an effective fatigue condition), while the other eight athletes experienced an improvement of the execution likely due to the so-called Post-Activation Potentiation. In both cases, the above parameters were significantly influenced by the fatigue protocol (p < 0.05), confirming their validity for fatigue monitoring. Interesting correlations between several kinematic parameters and muscular mass were highlighted in the fatigued group. Finally, a "fatigue approximation index" was proposed and validated as fatigue quantifier. 



#3 Technical match actions and plasma stress markers in elite female football players during an official FIFA Tournament 

Reference: Scand J Med Sci Sports. 2020 Dec 29. doi: 10.1111/sms.13878. Online ahead of print. 

Authors: Susana Póvoas, António Ascensão, Josė Magalhães, Pedro Silva , Håvard Wiig, Truls Raastad, Carlo Castagna, Helena Andersson 

Summary: This study analyzed the impact of performing four consecutive football matches separated by 48-72 hours during a FIFA tournament on physical load, technical performance and plasma markers of redox state, muscle damage and inflammation in elite female players. Forty-eight players from three national teams were evaluated at seven time points: before (baseline) and throughout the tournament (after each match and before two training sessions). Only data from players who played all matches were included in the analyses (N = 13). The players were divided into high-rank (N = 6) and low-rank (N = 7) team players according to FIFA standards. Plasma creatine kinase (CK), C-reactive protein (CRP), total antioxidant status (TAS), and uric acid (UA) were analyzed at the selected time points. Technical performance and physical load were also quantified according to team rank. Players from low-rank teams played significantly more time than high-rank players (85 ± 10 vs 67 ± 15 minutes; P = .02; d = 1.51). Low-rank team players presented higher values in technical performance actions than the high-rank team players, but most of the differences were explained by the longer match time played. UA content differed across the matches, increasing from baseline (F(4,40) = 3.90; P = .01) and more in the high-rank team players (F(1,10) = 20.46; P = .001), while CRP only differed across the matches (F(4,36) = 2.66; P = .05), also increasing from baseline. A large time effect was shown for UA only in the high-rank players (η2 p = 0.50; P = .02). Four consecutive matches did not result in considerable alterations in plasma stress markers, physical load, and technical performance in elite female football players from distinct rank levels. 



#4 Delayed peroneal muscle reaction time in male amateur footballers during a simulated prolonged football protocol 

Reference: Res Sports Med. 2020 Dec 29;1-9. doi: 10.1080/15438627.2020.1868467. Online ahead of print. 

Authors: Wei Sun, Edwin C H Chan, Daniel T P Fong

Summary: Peroneal muscle fatigue could result in ankle inversion sprain injuries. This study investigated the peroneal muscle reaction time during a simulated prolonged football protocol. Nine male footballers completed a 105-minute simulated prolonged football protocol. The peroneal muscle reaction time to an ankle inversion perturbation was measured every 15 minutes by a surface electromyography system sampling at 1000 Hz. One-way repeated ANOVA with post-hoc paired t-test showed a steady upward trend starting from 48.9 ms at baseline to 57.1 ms at the end of the first half, followed by a recovery back to 50.9 ms at the start of the second half and a further delay in the last 30 minutes to 60.2 ms at the end of the protocol. Delayed peroneal muscle reaction was found after 30 minutes of the first half and 15 minutes of the second half of a football match. The risk of ankle sprain could increase in the latter minutes in each half protocol. Thus, prevention injury training strategies should focus on these specific durations in football matches. 



#5 The Football Association Injury and Illness Surveillance Study: The Incidence, Burden and Severity of Injuries and Illness in Men's and Women's International Football 

Reference: Sports Med. 2020 Dec 28;1-20. doi: 10.1007/s40279-020-01411-8. Online ahead of print. 

Authors: Bradley Sprouse, Jon Alty, Steve Kemp, Charlotte Cowie, Ritan Mehta, Alicia Tang, John Morris, Simon Cooper, Ian Varley  

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Summary: The aim was to determine the incidence and characteristics of injury and illness in English men's and women's senior and youth international football. Time-loss injuries and illnesses, alongside match and training exposure, were collected across 8 seasons (2012-2020) in youth (U15, U16, U17, U18, U19) and senior (U20, U21, U23, senior) English men's and women's international teams. Analysis of incidence, burden, and severity of injury and illness was completed. Sex-specific comparisons were made between the senior and youth groups, and across the 8 seasons of data collection. In men's international football, 535 injuries were recorded (216 senior; 319 youth) during 73,326 h of exposure. Overall, match injury incidence (31.1 ± 10.8 injuries/1000 h) and burden (454.0 ± 195.9 d absent/1000 h) were greater than training injury incidence (4.0 ± 1.0 injuries/1000 h) and burden (51.0 ± 21.8 d absent/1000 h) (both P < 0.001). In women's international football, 503 injuries were recorded (senior: 177; youth: 326) during 80,766 h of exposure and match injury incidence (27.6 ± 11.3 injuries/1000 h) and burden (506.7 ± 350.2 days absent/1000 h) were greater than training injury incidence (5.1 ± 1.8 injuries/1000 h) and burden (87.6 ± 32.8 days absent/1000 h) (both P < 0.001). In women's international football, a group × season interaction was observed for training injury incidence (P = 0.021), with the senior group recording a greater training injury incidence during the 2015-2016 season compared to the youth group (14.4 vs 5.7 injuries/1000 h; P = 0.022). There was no difference in injury severity between match and training for men's (P = 0.965) and women's (P = 0.064) international football. The findings provide a comprehensive examination of injury and illness in English men's and women's senior and youth international football. Practitioners will be able to benchmark their team's injury and illness incidence and characteristics to the match-play and training information provided in the present study. 



#6 Prospective Study of Muscle Injuries in Three Consecutive Seasons of the Brazilian Football Championship 

Reference: Rev Bras Ortop (Sao Paulo). 2020 Dec;55(6):687-694. doi: 10.1055/s-0040-1712988. Epub 2020 Sep 24. 

Authors: Gabriel Furlan Margato, Edilson Ferreira Andrade Júnior, Paulo Henrique Schmidt Lara, Jorge Roberto Pagura, Moisés Cohen, Gustavo Gonçalves Arliani

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Summary: The aim was to perform a prospective evaluation of muscle injuries that occurred during the matches of series A and B of the Brazilian Men's Football Championship from 2016 to 2018. A prospective-cohort study with data collection regarding muscle injuries that occurred during the official matches of the first and second divisions of the Brazilian Men's Soccer Championship in the 2016, 2017 and 2018 seasons. The total number of muscle injuries was of 577 throughout the 3 seasons, with a gradual and annual reduction in the incidence of injuries (219 injuries in 2016, 195 in 2017, and 163 in 2018), with a statistically significant difference between the 2016 and 2018 seasons. Muscle injuries represented approximately 35% of the total lesions. The incidence of muscle injuries was of 7.66 per 1,000 hours of play. During the 3 seasons (2016 to 2018), the most common injury was of the hamstring muscle (41.1%, 40.5%, and 33.7% respectively). Wingers were the most affected players, and the most common injury severity scale was moderate (8 to 28 days). The moment of the match with the highest incidence of injuries was in the period between 61 and 75 minutes, with an index of 19.9%, with no statistical difference in relation to the other periods of the match. There was an incidence of muscle injuries of 7.7 /1,000 h, and they occurred predominantly in home games, in defenders (wingers and centre-backs), with an average age of 28 years, mainly involving the hamstring muscles, with a moderate mean time of absence (8 to 28 days). 



#7 FIFA Sudden Death Registry (FIFA-SDR): a prospective, observational study of sudden death in worldwide football from 2014 to 2018

Reference: Br J Sports Med. 2020 Dec 23;bjsports-2020-102368. doi: 10.1136/bjsports-2020-102368.

Authors: Florian Egger, Jürgen Scharhag, Andreas Kästner, Jiří Dvořák, Philipp Bohm, Tim Meyer

Summary: The aim was to investigate the underlying causes and regional patterns of sudden death in football (soccer) players worldwide to inform and improve existing screening and prevention measures. From 2014 to 2018 cases of sudden cardiac death (SCD), survived sudden cardiac arrest (SCA) and traumatic sudden death were recorded by media monitoring (Meltwater), a confidential web-based data platform and data synchronisation with existing national Sudden Death Registries (n=16). Inclusion criteria were met when sudden death occurred during football-specific activity or up to 1 hour afterwards. Death during other activities was excluded. A total of 617 players (mean age 34±16 years, 96% men) with sudden death were reported from 67 countries; 142 players (23%) survived. A diagnosis by autopsy or definite medical reports was established in 211 cases (34%). The leading cause in players >35 years was coronary artery disease (76%) and in players ≤35 years was sudden unexplained death (SUD, 22%). In players ≤35 years the leading cause of SCD varied by region: cardiomyopathy in South America (42%), coronary artery anomaly in North America (33%) and SUD in Europe (26%). Traumatic sudden death including commotio cordis occurred infrequently (6%). Cardiopulmonary resuscitation (CPR) resulted in a survival rate of 85% with the use of an automated external defibrillator (AED) compared with 35% without. Regional variation in SCD aetiology should be verified by expansion of national registries and uniform autopsy protocols. Immediate access to an AED at training and competition sites, as well as CPR training for players, coaches and staff members, is needed to improve survival from SCA. 



#8 Injury patterns differ with age in male youth football: a four-season prospective study of 1111 time-loss injuries in an elite national academy 

Reference: Br J Sports Med. 2020 Dec 23;bjsports-2020-103430. doi: 10.1136/bjsports-2020-103430. 

Authors: Eirik Halvorsen Wik, Lorenzo Lolli, Karim Chamari, Olivier Materne, Valter Di Salvo, Warren Gregson, Roald Bahr

Summary: The purpose was to describe age group patterns for injury incidence, severity and burden in elite male youth football. Prospective cohort study capturing data on individual exposure and time-loss injuries from training and matches over four seasons (2016/2017 through 2019/2020) at a national football academy (U13-U18; age range: 11-18 years). Injury incidence was calculated as the number of injuries per 1000 hours, injury severity as the median number of days lost and injury burden as the number of days lost per 1000 hours. We included 301 players (591 player-seasons) and recorded 1111 time-loss injuries. Overall incidence was 12.0 per 1000 hours (95% CI 11.3 to 12.7) and burden was 255 days lost per 1000 hours (252 to 259). The mean incidence for overall injuries was higher in the older age groups (7.8 to 18.6 injuries per 1000 hours), while the greatest burden was observed in the U16 age group (425 days; 415 to 435). In older age groups, incidence and burden were higher for muscle injuries and lower for physis injuries. Incidence of joint sprains and bone stress injuries was greatest for players in the U16, U17 and U18 age groups, with the largest burden observed for U16 players. No clear age group trend was observed for fractures. Injury patterns differed with age; tailoring prevention programmes may be possible. 



#9 The Size and Prevalence of Bony Hip Morphology Does Not Differ Between Football Players With and Without Hip and/or Groin Pain: Findings From the FORCe Cohort 

Reference: J Orthop Sports Phys Ther. 2020 Dec 25;1-43. doi: 10.2519/jospt.2021.9622. Online ahead of print. 

Authors: Joshua Heerey, Rintje Agricola, Anne Smith, Joanne Kemp, Tania Pizzari, Matthew King, Peter Lawrenson, Mark Scholes, Kay Crossley

Summary: The aim was to compare the size and prevalence of bony hip morphology in football players' hips with and without hip and/or groin pain. 184 (290 hips; 20% women) football players (soccer and Australian football) with self-reported hip and/or groin pain (>6 months duration) and a positive FADIR test and 55 (110 hips; 25% women) control football players (no pain, negative FADIR) were recruited. For bony hip morphology, alpha angle and lateral-center-edge-angle (LCEA) were determined from anteroposterior pelvis and Dunn 45° radiographs. The alpha angle and LCEA were analyzed as continuous measures (size) and dichotomised using threshold values to determine the prevalence of bony hip morphology (cam, large cam, pincer and acetabular dysplasia). Regression analyses estimated differences in the size and prevalence of bony hip morphology between football players with and without pain. In all football players and in men, the size and prevalence of bony hip morphology did not differ between hips with and without hip and/or groin pain. In football players, cam morphology was evident in 63% hips without pain and 71% of hips with hip and/or groin pain. Women with hip and/or groin pain had larger alpha angle values than women without on the Dunn 45° view (5.9°; 95% CI: 1.2°, 10.6°, P = .014). The size and prevalence bony hip morphology appears similar in football players with and without hip and/or groin pain.



#10 Applying a holistic hamstring injury prevention approach in elite football: 12 seasons, single club study

Reference: Scand J Med Sci Sports. 2020 Dec 31. doi: 10.1111/sms.13913. Online ahead of print. 

Authors: Luis Suarez-Arrones, Fábio Yuzo Nakamura, Rafael A Maldonado, Nacho Torreno, Valter Di Salvo, Alberto Mendez-Villanueva

Summary: The aim was to investigate the preventive effect of a complex training program based on holistic hamstring health understanding in elite professional soccer players. This study involved an elite club in Europe and was conducted over 12 seasons. The last 2 seasons were the intervention period and the others were the control seasons. During the intervention period, players performed a complex program organized into different interventions throughout the week having as a priority the player health. Hamstring injuries, absenteeism, injury rates, and injury burden between the control and intervention seasons were compared using a rate ratio (RR) with 95% CI. Players had a mean exposure of 333.5±18.6 hours per season with no significant differences between the intervention and control seasons. The overall injury rate was 3 times lower during the two intervention seasons than during the previous seasons (p<0.01); the match injury rate was 2.7 times lower (p<0.01) and the training rate 4.3 times (p<0.01). Injury burden was almost 4 times lower during the two intervention seasons than during the previous seasons (p<0.01) and recurrences in the control group were 10% vs. 0% in the intervention group. Hamstring injuries were reduced ~3 times during the seasons in which elite football players were exposed to multicomponent, complex prevention training with individual approaches based on player needs, management of training load, individualized physiotherapy treatment, and planned staff communication, in comparison to the control seasons without a clearly defined and structured injury prevention intervention. 



#11 A four-week training program with the Nordic hamstring exercise during preseason increases eccentric strength of male soccer player

Reference: Int J Sports Phys Ther. 2020 Aug;15(4):571-578. 

Authors: Nathalia Trevisol de Oliveira, Thales Menezes Medeiros, Karoline Baptista Vianna, Gabriel Dos Santos Oliveira, João Breno de Araujo Ribeiro-Alvares, Bruno Manfredini Baroni

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Summary: The Nordic hamstring exercise (NHE) is an effective strategy to prevent hamstring strain injuries in soccer players. The current literature recommends a 10-week training program with three sessions per week, but the short preseason period and the congested schedule make difficult for high-performance soccer teams to apply the NHE as recommended. The purpose of this study was to examine the effect of a pragmatic NHE training program during a four-week preseason period on eccentric knee flexor strength of high-performance soccer players. This study included 25 under-20 male soccer players from a premier league club. They performed eight sessions of NHE (3 sets of 6-10 repetitions, twice a week) during the four-week preseason period. The eccentric knee flexor strength was evaluated during the NHE execution on a custom-made device, before and after the training program. The NHE training program significantly increased the players' eccentric knee flexor strength in both right (Δ = 13%; p<0.001; effect size = 0.97) and left limbs (Δ = 13%; p<0.001; effect size = 0.92). Individual analysis identified 76% of the players as responders to the NHE training program (Δ = 16%; effect size = 1.60), and 24% as non-responders (Δ = 3%; effect size = 0.24). A four-week training program with NHE performed twice a week is feasible in the real-world of high-performance soccer clubs and increases the eccentric knee flexor strength of male soccer players. 



#12 Association of Low Energy Availability and Suppressed Metabolic Status in Korean Male Collegiate Soccer Players: A Pilot Study

Reference: Am J Mens Health. Nov-Dec 2020;14(6):1557988320982186. doi: 10.1177/1557988320982186. 

Authors: Sihyung Lee, Moto Kuniko, Seungah Han, Taewoong Oh, Motoko Taguchi

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Summary: Low energy availability (EA) can impair physiological function in athletes. The purpose of this study was to investigate EA status, metabolic status, and bone metabolism with biochemical analysis in Korean male soccer players. Twelve male athletes (18-20 years) completed the study. Body composition and bone mineral density were measured using dual energy X-ray absorptiometry (DXA), while VO2 max was determined by an incremental exercise test. Blood samples were taken for bone marker and hormone analyses. Resting energy expenditure (REE) was measured using the Douglas bag method and predicted using the DXA method. Food diaries and heart rates (HR) during training were recorded, and the Profile of Mood States 2 and Eating Attitude Test 26 were completed. Group differences between low EA (LEA <30 kcal/kg FFM/d, n = 5) and high EA (HEA ≥30 kcal/kg FFM/d, n = 7) were evaluated. The mean EA of the all participants was 31.9 ± 9.8 kcal/kg FFM/d with only two participants having an EA above 45 kcal/kg FFM/d. LEA showed suppressed REE (LEA: 26.0 ± 1.7 kcal/kg/d, HEA: 28.8 ± 1.4 kcal/kg/d, p = .011) with a lower REEratio (LEA: 0.91 ± 0.06, HEA: 1.01 ± 0.05, p = .008) as well as a lower insulin-like growth factor 1 (IGF-1) level (LEA: 248.6 ± 51.2 ng/mL, HEA: 318.9 ± 43.4 ng/mL, p = .028) compared to HEA. There were no group differences in bone markers or other hormone levels. Korean male athletes exhibited low EA status with suppressed metabolism, but there was limited evidence on the effect of EA on bone metabolism, endocrine system, and psychological parameters. 



#13 Systematic review and meta-analysis of sex-based differences for concussion incidence in soccer 

Reference: Phys Sportsmed. 2021 Jan 7;1-9. doi: 10.1080/00913847.2020.1868955. Online ahead of print. 

Authors: Udit Dave, James Kinderknecht, Jennifer Cheng, Kristen Santiago, Bridget Jivanelli, Daphne I Ling

Summary: The purpose was to compare concussion incidence in male and female soccer players due to the specific concussion-causing activity. PubMed, EMBASE, and Cochrane Library were searched for studies published between January 2000 and February 2020. Search terms included 'sex,' 'gender,' 'sex differences,' 'brain injury,' 'sports,' 'athletes,' 'incidence,' 'epidemiology,' 'symptoms,' and 'injury rate.' Studies that contained data on concussion incidence in soccer and featured comparisons by sex and soccer activity were included. Studies that were not written in English, contained data on non-sports-related concussions, or were conference abstracts were excluded. Six studies were included in this meta-analysis, each of which contributed the number of concussions in males and females for a specific soccer activity. Concussion incidence rates were calculated using athlete-exposures as the denominator and a rate ratio was measured by dividing the concussion rate among female soccer players by the rate among male soccer players. Female soccer players were shown to have a greater rate of concussions from heading [1.65 (95% CI: 1.35, 2.03, p < 0.001)] and goalkeeping [1.63 (95% CI: 1.22, 2.17, p = 0.001)]. There were 3 studies comparing sex differences for general play. While the pooled rate ratio was statistically significant [1.51 (95% CI: 1.12, 2.04), p = 0.007], this result was largely driven by 1 study. Concussion incidence rates were significantly higher in female soccer players compared to male players while heading. There is also some evidence to suggest that the incidence is higher for female goalkeepers. Soccer coaches and health care providers need to recognize this sex difference when coaching or treating players. 



#14 Magnetic resonance imaging of midtarsal sprain: Prevalence and impact on the time of return to play in professional soccer players 

Reference: Eur J Radiol. 2020 Dec 24;135:109491. doi: 10.1016/j.ejrad.2020.109491. Online ahead of print. 

Authors: Miriam T Leiderer, Goetz H Welsch, Isabel Molwitz, Kai-Jonathan Maas, Gerhard Adam, Peter Bannas, Frank Oliver Henes 

Summary: Ankle sprain is a common injury in professional soccer, but to date midtarsal sprain has not been investigated in this context. The purpose of this study was to determine the prevalence of midtarsal sprain by MRI and to assess its impact on the time of return to play in professional soccer players. We included 52 professional soccer players who underwent 59 MRI examinations after acute ankle trauma between January 2012 and September 2019. Images were retrospectively reviewed in consensus by two radiologists for assessment of midtarsal sprain and ankle sprain. Ligaments were graded as i) normal, ii) partial tear, or iii) complete tear. Time to return to play (RTP) for each athlete was retrieved from team medical records. A Kruskal-Wallis test and Dunn's pairwise tests were used to calculate differences in RTP time between groups with i) isolated midtarsal sprain, ii) isolated lateral ankle sprain, and iii) combined midtarsal and lateral ankle sprain. MRI revealed isolated ankle sprain in 24 of 59 MRI examinations (40.6 %). Acute midtarsal ligament injury was present in 15 examinations (25.4 %). Four of the 15 examinations (26.7 %) had isolated midtarsal injuries and eleven of the 15 examinations (73.3 %) had concomitant ankle sprain. RTP time was 39 days (range 9-70 days) for isolated midtarsal sprain. RTP time was significantly higher for athletes with combined ankle and midtarsal sprain (47 days, range 15-74 days) when compared to athletes with isolated ankle sprain (24 days, range 2-59 days) (p = .019). Our MRI study reveals that midtarsal sprain is a frequent injury in professional soccer players with ankle sprain. Midtarsal ligament findings on MRI combined with evidence of lateral ankle sprain is associated with a longer time of return to play compared to isolated lateral ligament injuries. 



#15 Whole and peak physical characteristics of elite youth female soccer match-play 

Reference: J Sports Sci. 2020 Dec 30;1-10. doi: 10.1080/02640414.2020.1868669. Online ahead of print. 

Authors: Alice Harkness-Armstrong, Kevin Till, Naomi Datson, Stacey Emmonds

Summary: This study quantified whole and peak physical characteristics of Under (U)14 and U16 elite youth female soccer, and compared by position and age-group. Data was collected using 10 Hz GPS units from 431 match observations, during 50 matches involving 201 players (U14 n = 93; U16 n = 108) representing Regional Talent Centres in The Football Association's Girl's England Talent Pathway League. Whole match data were reported as absolute and relative; total (TD), high-speed running (HSR; ≥3.46 m·s-1), very high-speed running (VHSR; ≥5.29 m·s-1), and sprinting (SPR; ≥6.26 m·s-1) distance, and maximum velocity. Moving average analysis determined peak data (1-10 minute durations). Linear mixed models established position-specific differences. U16s covered greater; absolute distance at all speeds (small-moderate ESs; p < 0.001); relative VHSR and SPR m·min-1 (small-moderate ESs; p < 0.001); peak TD and HSR m·min-1 (small ESs) across several peak-durations, and VHSR m·min-1 (small ESs; p < 0.001) across all peak-durations compared to U14s. Position-specific differences were observed across all positions between and within both age-groups, identifying whole and peak physical characteristics are age- and position-dependent within elite youth female soccer match-play. Findings may facilitate informed coaching practices and training programme design, talent identification and development processes. 



#16 Concurrent validity, inter-unit reliability and biological variability of a low-cost pocket radar for ball velocity measurement in soccer and tennis 

Reference: J Sports Sci. 2020 Dec 30;1-8. doi: 10.1080/02640414.2020.1868090. Online ahead of print. 

Authors: Alejandro Hernández-Belmonte, Alejandro Sánchez-Pay

Summary: This study aimed to analyse the (i) concurrent validity, (ii) inter-unit reliability, and (iii) biological variability of a low-cost device called Pocket radar. Eleven men recreational soccer players performed 6 kicks to a soccer ball, whereas 13 men recreational tennis players conducted 10 shots to a tennis ball. All executions were simultaneously measured by two Pocket units and the Stalker radar (reference criterion). The within-subject variation among the executions was used for the biological variability analysis. The level of agreement and magnitude of errors included the intraclass correlation coefficient (ICC), Pearson's correlation coefficient (r), bias, and the smallest detectable change (SDC). A good agreement (ICC ≥ 0.98, r ≥ 0.98) and very low magnitude of error (SDC ≤ 7.70 km·h-1, bias ≤ 3.19 km·h-1) were found between both Pocket units and the Stalker, in soccer and tennis. Inter-unit analysis found limited technical errors (SDC ≤ 5.49 km·h-1, bias ≤ -0.93 km·h-1) and nearly perfect agreement (ICC = 0.99, r ≥ 0.98) in both sessions. These technical errors were lower than the variations due to the biological variability, in soccer (SDC = 2.47 km·h-1 vs. SDC ≥ 8.6 km·h-1) and tennis (SDC = 5.49 km·h-1 vs. SDC ≥ 21.95 km·h-1). These findings suggest the Pocket radar as a valid and highly sensitive tool for BV measurement. 


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