Limited positive effects on jump-landing technique in girls but not in boys after 8\xa0weeks of injury prevention exercise training in youth football

Hanna Lindblom,Siw Carlfjord,Markus Waldén,Martin Hägglund

doi:10.1007/s00167-019-05721-x

Abstract

PurposeTo evaluate changes in jump-landing technique in football-playing boys and girls after 8 weeks of injury prevention training.MethodsFour 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).ResultsOnly 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).ConclusionThe study showed small positive effects on jump-landing technique in girls, but not in boys, after 8 weeks of injury prevention training.Level of evidenceLevel II.Trial registrationClinical Trials gov identifier: NCT03251404

Highlights

Anterior cruciate ligament (ACL) injury is a severe injury that has both short-term consequences, with long lay-off from sports and secondary injuries, and long-term consequences, such as early onset osteoarthritis [10, 12]
Jump-landing technique was evaluated during drop vertical jumps (DVJ) and tuck jump assessment (TJA) at baseline and at follow-up after approximately 8 weeks of injury prevention training
A sample size calculation was done for the analyses of performance effects of the Knee Control injury prevention exercise programmes (IPEP) and not for the analyses of jump-landing technique presented in the current paper

Summary

Introduction

Anterior cruciate ligament (ACL) injury is a severe injury that has both short-term consequences, with long lay-off from sports and secondary injuries, and long-term consequences, such as early onset osteoarthritis [10, 12]. A number of IPEPs, such as Knee Control, the 11 + and 11 + Kids programmes have been developed for use in the warm-up before football practice. These IPEPs have been efficacious in preventing injuries in both boys’ [35, 38] and girls’ football [38, 40]. A qualitative study among coaches revealed that they wanted better programme fit and higher buy-in from the players [22] This feedback and knowledge led the research group to develop the original Knee Control IPEP further into Knee Control + , which was evaluated in this study. The aim of the study was to evaluate changes in jumplanding technique in football-playing boys and girls after 8 weeks of injury prevention training

Materials and methods

Participants

Ethics approval and consent to participate

Results

Compliance with ethical standards