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Limited positive effects on jump-landing technique in girls but not in boys after 8 weeks of injury prevention exercise training in youth football
Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.ORCID iD: 0000-0002-1533-6872
Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Department of Orthopaedics, Hässleholm-Kristianstad Hospitals.
Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Medicine and Health Sciences.ORCID iD: 0000-0001-9116-8156
Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.ORCID iD: 0000-0002-6883-1471
2019 (English)In: Knee Surgery, Sports Traumatology, Arthroscopy, ISSN 0942-2056, E-ISSN 1433-7347Article in journal (Refereed) Epub ahead of print
Abstract [en]

PURPOSE: To evaluate changes in jump-landing technique in football-playing boys and girls after 8 weeks of injury prevention training.

METHODS: Four boys' and four girls' teams (mean age 14.1 ± 0.8 years) were instructed to use either the original Knee Control injury prevention exercise programme (IPEP) or a further developed IPEP, Knee Control + , at every training session for 8 weeks. Baseline and follow-up testing of jump-landing technique included drop vertical jumps (DVJ), assessed subjectively and with two-dimensional movement analysis, and tuck jump assessment (TJA).

RESULTS: Only minor differences in intervention effects were seen between the two IPEPs, and results are therefore presented for both intervention groups combined. At baseline 30% of the boys showed good knee control during the DVJ, normalised knee separation distances of 77-96% (versus hip) and a median of 3 flaws during the TJA. Among girls, 22% showed good knee control, normalised knee separation distances of 67-86% and a median of 4 flaws during the TJA. At follow-up, boys and girls performed significantly more jumps during TJA. No changes in jump-landing technique were seen in boys, whereas girls improved their knee flexion angle at initial contact in the DVJ (mean change + 4.7°, p < 0.001, 95% CI 2.36-6.99, d = 0.7) and their TJA total score (- 1 point, p = 0.045, r = - 0.4).

CONCLUSION: The study showed small positive effects on jump-landing technique in girls, but not in boys, after 8 weeks of injury prevention training.

LEVEL OF EVIDENCE: Level II.

TRIAL REGISTRATION: Clinical Trials gov identifier: NCT03251404.

Place, publisher, year, edition, pages
2019.
Keywords [en]
Effect mechanisms, Movement quality, Neuromuscular training
National Category
Sport and Fitness Sciences
Identifiers
URN: urn:nbn:se:liu:diva-160777DOI: 10.1007/s00167-019-05721-xPubMedID: 31541293OAI: oai:DiVA.org:liu-160777DiVA, id: diva2:1358275
Available from: 2019-10-07 Created: 2019-10-07 Last updated: 2019-12-03
In thesis
1. Injury Prevention in Youth Football Players: Training Effects and Programme Implementation
Open this publication in new window or tab >>Injury Prevention in Youth Football Players: Training Effects and Programme Implementation
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background With 17–35% of all 14-year-olds in Sweden being active in football, injuries do occur, most frequently during match play. Based on knowledge of injury mechanisms and risk factors, different injury prevention exercise programmes (IPEPs) have been developed. In this thesis, the Swedish IPEP Knee Control was used as a model for injury preventive training.

Aim The overall aim of this thesis was to improve our understanding of the effects of the Knee Control injury prevention exercise programme on sports performance and jump-landing technique, as well as exploring programme implementation and coach experiences of using the programme in youth football.

Methods Studies I and IV were cluster-randomised trials focusing on the performance effects of Knee Control. Study I included four teams with 41 female youth football players (mean age 14). The intervention group used Knee Control twice weekly for 11 weeks, whereas the control group teams did their usual training. Knee Control includes six different exercises at four levels of difficulty and with partner exercises and is meant to be used during warm-up at every training session. Performance was tested using a battery of balance, agility, jump and sprint tests at baseline and follow-up at an indoor venue. Study IV had a similar set-up but included two different interventions: Knee Control and a new, further-developed version of the programme, Knee Control+, which were studied during an eight-week intervention involving eight youth football teams, four male, four female (mean age 14), with 77 players. Similar, but not identical, performance tests were used in Study IV, along with drop vertical jumps and tuck jump assessment to assess jump-landing technique.

Studies II and III focused on the implementation context. Study II was questionnaire based, using the RE-AIM framework covering the reach, effectiveness, adoption, implementation and maintenance of Knee Control. Coaches for female youth teams (n=352), one representative of the national football association and representatives of eight district football associations responded to web-based questionnaires. Data collection was performed two years after the nation-wide implementation of Knee Control started. Study III was a qualitative study that followed up on the results of Study II. Interviews were conducted with 20 coaches for female football teams and analysed using qualitative content analysis. The interviews focused on factors that affected the adoption and use of Knee Control. All 20 coaches had experience of Knee Control.

Results Limited positive effects were seen on jump-landing technique in girls, with the total tuck jump assessment score improving, as well as two separate criteria, the number of jumps accomplished during the 10-second test and additionally an increased knee-flexion angle upon landing from a drop vertical jump. No improvements on the performance tests were found in either Study I or Study IV. Both studies, however, suffered from low player compliance with the IPEPs and as a result low training dosage. No major differences in results were seen between Knee Control and Knee Control+ in Study IV.

Study II showed that 91% of the responding coaches were familiar with Knee Control, they perceived the programme to be effective, 74% had started to use it, and it was fairly well maintained over time. However, only one third of the coaches used the programme every week and few used the whole programme. There were no formal policies for programme implementation and use in the district football associations and clubs. Study III showed that the coach was vital for programme use but needed social support, buy-in from players, resources and a feasible programme to facilitate programme adoption and use. When facing challenges with Knee Control implementation and use, the coaches did their best to work around these obstacles; for example, by modifying the programme content or dosage.

Conclusions In conclusion, limited positive effects on jump-landing technique were seen in girls, potentially affecting risk factors for injury positively. No clinically meaningful effects from Knee Control or Knee Control+ were seen on performance tests as measured in the studies in either boys or girls. This may be related to the low training dosage. The high programme reach, perceived effectiveness, adoption and fairly high maintenance of Knee Control were positive. The modifications of programme content and/or dosage were concerning but will hopefully decrease with a more user-friendly programme.

Abstract [sv]

Bakgrund I och med att 17–35% av alla 14-åringar i Sverige är aktiva inom fotboll så uppkommer en del skador, oftast i samband med matcher. Utifrån kunskap om skadesituationer och riskfaktorer för skador har olika skadeförebyggande träningsprogram utvecklats. I denna avhandling användes det svenska skadeförebyggande programmet Knäkontroll som modell för skadepreventiv träning.

Syfte Det övergripande syftet var att öka förståelsen för effekterna av Knäkontroll på prestationsförmåga och hopp-landningsteknik, programmets implementering och tränarnas erfarenheter av att använda programmet inom svensk ungdomsfotboll.

Metod Studie I och Studie IV var klusterrandomiserade studier som undersökte effekterna på prestationsförmågan av att träna Knäkontroll. Studie I inkluderade 41 flickfotbollsspelare (genomsnittsålder 14 år). Interventionsgruppen använde Knäkontroll två gånger per vecka i 11 veckor, medan kontrollgruppen tränade som vanligt. Knäkontroll involverar sex olika övningar på fyra svårighetsgrader och med tillhörande parövningar och ska användas vid uppvärmningen inför varje fotbollsträning. Prestationsförmågan testades inomhus med ett batteri av olika tester för balans, snabbhet, hopp- och sprintförmåga vid baslinje och uppföljning. Studie IV hade ett likartat upplägg men inkluderade två olika interventioner: Knäkontroll och en vidareutvecklad version av programmet, Knäkontroll+. Studien pågick åtta veckor i åtta fotbollslag (fyra pojk-, fyra flicklag) med 77 spelare (genomsnittsålder 14 år). Liknande test för prestationsförmåga användes som i studie I, men även drop vertical jumps och tuck jumps för att bedöma hopp-landningsteknik.

Studie II och Studie III fokuserade på implementeringskontexten, det vill säga implementeringen av Knäkontroll ute i fotbollslag. Studie II var en enkätstudie som med hjälp av ramverket RE-AIM (reach, effectiveness, adoption, implementation and maintenance) utvärderade implementeringen av Knäkontroll. Tränare för flickfotbollslag (n=352), en representant för Svenska Fotbollförbundet och representanter för åtta distriktsförbund besvarade de webbaserade enkäterna. Datainsamlingen gjordes två år efter att den nationella implementeringen av Knäkontroll startade. Studie III var en kvalitativ studie som fördjupade resultaten av Studie II. Intervjuer genomfördes med tjugo tränare för flick- och damfotbollslag och analyserades med kvalitativ innehållsanalys. Intervjuerna fokuserade på faktorer som påverkade tränarnas upptag och användning av Knäkontroll. Alla tränare hade erfarenhet av Knäkontroll sedan tidigare.

Resultat Begränsad positiv effekt sågs på hopp-landningsteknik bland flickorna i studie IV, med en förbättrad totalpoäng på tuck jumps, på två kriterier i tuck jump, ökat antal hopp under testets 10 sekunder samt en ökad knäflexionsvinkel vid landning från drop vertical jumps. Ingen förbättring av prestationsförmågan sågs i Studie I eller Studie IV. I båda studierna var spelarnas närvaro på fotbollsträningar låg, vilket även gav en låg träningsdos av Knäkontroll. Inga större skillnader i resultat sågs mellan Knäkontroll och Knäkontroll+ i Studie IV.

Studie II visade att 91% av tränarna kände till Knäkontroll, att tränarna upplevde att programmet var effektivt, 74% hade också börjat använda programmet och användandet bibehölls också förhållandevis väl över tid. Däremot använde endast 1/3 av tränarna programmet varje vecka och få använde hela programmet. Det saknades riktlinjer för programmets implementering och användning inom distriktsförbund och klubbar. Studie III visade att tränaren var oumbärlig för programmets användning men behövde mer socialt stöd, intresse från spelarna och resurser utöver ett användarvänligt program för att underlätta det preventiva arbetet. När tränarna ställdes inför utmaningar gjorde de sitt bästa för att kringgå problemen, till exempel genom att modifiera programmets innehåll eller dosering, för att ändå kunna använda programmet.

Konklusion Sammanfattningsvis sågs begränsade positiva effekter på hopplandningsteknik hos flickorna, vilket möjligen påverkar riskfaktorerna för skada positivt. Inga kliniskt meningsfulla effekter av Knäkontroll eller Knäkontroll+ sågs på prestationstesterna hos varken pojkar eller flickor. Detta kan vara relaterat till den låga träningsdosen. Knäkontrollprogrammets stora spridning, högt skattade effektivitet, höga upptag och förhållandevis goda bibehållande var positivt. De modifieringar av programmets innehåll och/eller dosering som sågs var oroväckande men kan förhoppningsvis minska av ett mer användarvänligt program.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. p. 105
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1694
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:liu:diva-160778 (URN)10.3384/diss.diva-160778 (DOI)9789176850190 (ISBN)
Public defence
2019-11-08, Berzeliussalen, Building 463, Campus US, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2019-10-08 Created: 2019-10-08 Last updated: 2019-10-08Bibliographically approved

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