Original research Impact of the FIFA 11þ on the structure of select muscles in adolescent female soccer players Jackie L. Whittaker a, b, * , Carolyn A. Emery a, b a Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada T2N 1N4 b The Alberta Children's Hospital Research Institute for Child & Maternal Health, Faculty of Medicine, University of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada T2N 1N4 article info Article history: Received 23 July 2014 Received in revised form 3 October 2014 Accepted 29 October 2014 Keywords: Injury prevention Inter-recti distance Soccer Sonography abstract Objectives: To determine the impact of an injury prevention program (FIFA11þ) on the structure of select trunk and leg muscles in adolescent female soccer players. Design: Exploratory analysis. Setting: University Sport Medicine Centre. Participants: 23 female soccer players (aged 14e16) recruited from a FIFA11 þ implementation trial grouped by high and low 11 þ exposure. Main outcomes: Pre and post-season sonographic measures of the rectus abdominis, external and in- ternal oblique, transversus abdominis, inter-recti distance (IRD), lumbar multifidus, gluteus medius and minimus, and vastus medialis. Mean (95% confidence intervals; CI) were calculated for pre, post and pre- post season change of all parameters and univariate analyses used to compare groups (a ¼ 0.001). Results: Both low (mean ¼ 149 ± 9 exercises/year) and high (mean ¼ 314 ± 15 exercises/year) 11 þ exposure groups demonstrated significant post-season decreases in IRD at rest (p < 0.001) and during a leg lift (p < 0.001). No other between or within group differences existed. Conclusions: Levels of FIFA11 þ exposure were not associated with differential changes in the morphology of investigated muscles. As the IRD of participants in both exposure groups decreased it is possible that the protective mechanism of the FIFA11 þ may be associated with alterations in neuro- muscular control that result in abdominal wall adaptations. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction With more than 265 million registered players, soccer is one of the fastest growing and highest participation sports in the world (FIFA, 2007). Given this high participation rate, soccer is estimated to account for more than 10% of all sport-related youth injuries, with an estimated injury rate of 4.45 injuries/1000 player hours (Emery & Meeuwisse, 2006). Knee and ankle joint injuries are the most common injuries recorded in soccer (35e40%), occurring in females more frequently than males (Emery, Meeuwisse, & McAllister, 2006), and are associated with increased risk of early onset osteoarthritis (OA) and OA later in life (Roos, 2005). Further, these injuries are linked to long-term health consequences as young athletes that sustain an injury reduce their sport participation, which contributes to obesity and results in not only an increased risk of onset and progression of OA, but more serious long-term health consequences such as cardiovascular disease (Maffulli, Longo, Gougoulias, Loppini, & Denaro, 2010). Accordingly, strategies for prevention of these injuries are of great importance (Emery & Meeuwisse, 2010; Soligard et al., 2008). Many team physical therapists are proponents of injury pre- vention strategies in light of the high risk of injury in soccer. The FIFA11þ is a neuromuscular injury prevention warm-up program that was developed by the Federation Internationale de Football Association (FIFA) Medical Assessment and Research Centre (Junge et al., 2011). The program takes approximately 20 min to complete and is intended to be incorporated into the warm-up preceding soccer training and matches. The 11 þ consists of three parts; running exercises combined with active stretching, controlled partner contacts, planting and cutting movements (parts 1 and 3) as well as conditioning exercises that incorporate strength, agility and balance (part 2). In addition to these exercises, emphasis is placed upon proper technique, lower extremity alignment such as * Corresponding author. Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, 2500 University Dr. NW, Calgary, Alberta, Canada T2N 1N4. Tel.: þ1 403 220 2252. E-mail address: j.whittaker@ucalgary.ca (J.L. Whittaker). Contents lists available at ScienceDirect Physical Therapy in Sport journal homepage: www.elsevier.com/ptsp http://dx.doi.org/10.1016/j.ptsp.2014.10.007 1466-853X/© 2014 Elsevier Ltd. All rights reserved. Physical Therapy in Sport xxx (2014) 1e8 Please cite this article in press as: Whittaker, J. L., & Emery, C. A., Impact of the FIFA 11þ on the structure of select muscles in adolescent female soccer players, Physical Therapy in Sport (2014), http://dx.doi.org/10.1016/j.ptsp.2014.10.007