1 NEUROMUSCULAR ADAPTATIONS TO BALANCE AND TECHNIQUE TRAINING DURING SIDESTEPPING: IMPLICATIONS FOR ACL INJURY RISK Cyril Donnelly 1 , Bruce Elliott 1 , Tim Doyle 1,2 , Caroline Finch 3 , Alasdair Dempsey 1,4 and David Lloyd 1,4 The School of Sport Science, Exercise and Health, University of Western Australia, Perth, Australia 1 ; Defence Science and Technology Organisation, Victoria, Australia 2 ; Accident Research Centre, Monash University, Victoria, Australia 3 ; Musculoskeletal Research Program, Griffith Health Institute, Griffith University, Australia 4 . This study investigated the influence of balance and technique training (BTT) on external knee joint loading and the activation of muscles crossing the knee during anticipated (AnSS) and unanticipated (UnSS) sidestepping. Twenty-eight males participated in a 28 week training intervention implemented adjunct to their regular season training. Twelve completed BTT and 16 completed a ‘sham’ training (ST) intervention. Knee moments and the activation of 8 muscles crossing the knee were collected during AnSS and UnSS prior to and following training. BTT did not influence the activation of the muscles crossing the knee during AnSS or UnSS. Increases in muscle activation were not proportional to increases in valgus knee moments during UnSS in both groups. Unanticipated sport tasks should be identified as distinct factors associated with ACL injury risk. KEY WORDS: neuromuscular, ACL, injury, prevention, training, balance. INTRODUCTION: The majority of non-contact anterior cruciate ligament (ACL) injuries occur during change-of-direction or sidestep sport tasks (Cochrane et al., 2007). Externally applied valgus, internal rotation and flexion knee moments increase in-vivo ACL strain (Markolf et al., 1995). Biomechanical analysis of sidestepping show that both valgus and internal rotation knee moments are elevated relative to straight line running (Besier et al., 2001; Cochrane et al., 2010; Dempsey et al., 2009). Two principles can be used to reduce external knee loading and subsequent ACL injury risk. First, reduce the loads applied to the ACL (Lloyd, 2001) by changing an individual’s posture or technique during sidestepping (Dempsey et al., 2009). Second, increase the activation of muscles with moment arms capable of supporting the ACL from external knee loading when peak external forces act on the ligament (Lloyd, 2001). Previous literature has shown that technique (Dempsey et al., 2009) and balance (Cochrane et al., 2010) training can be used to reduce valgus knee moments during sidestepping. Neuromuscular training, which contains both balance and technique training components, has been used to increase the activation of muscles supporting the knee from external loading during sidestepping (Zebis et al., 2008). Few studies however have analyzed how training influences the activation of muscles crossing the knee and external knee moments simultaneously. The purpose of this investigation was to determine if balance and technique training (BTT) implemented adjunct to normal training influences the activation of muscles crossing the knee during anticipated (AnSS) and unanticipated (UnSS) sidestepping. An additional focus of this investigation was to determine if neuromuscular changes following BTT are proportional to changes in external knee loading. METHODS: Eight amateur level Australian Rules Football (ARF) teams (N ≈ 560) volunteered to participate in either 28 weeks of BTT (Figure 1) or a ‘sham’ training (ST) intervention adjunct to their regular season training. The ST intervention was designed help athletes improve their acceleration during running and served as the experimental control group.