Introduction: Muscle weakness is considered a risk factor for ankle injury. Numerous training modalities have been used in an attempt to strengthen the muscles crossing the ankle such as balance training or barefoot running. It is expected that training modalities that successfully strengthen the ankle would elicit increased muscular activity. However, it is unknown how an individual`s ankle strength will influence the muscle activity used during a given task. Therefore this study aimed to analyse the role that ankle strength may play in EMG strategies of the lower leg muscles during static and dynamic training modalities. Methods: 26 participants performed dynamic (shod and barefoot running) and static tasks (squat on ground, squat on a bosu ball) believed to strengthen the muscles surrounding the ankle[1]. Muscle activity of the tibialis anterior, peroneus longus, gastrocnemius lateralis and medialis were measured registering surface EMG and analysed using a non-linearly scaled wavelet analysis. Total muscle activity for each task was obtained by adding up all four muscles EMG. Subjects were divided into a strong and a weak group defined as the 9 individuals with the highest (strong) and 9 individuals with the lowest (weak) normalized, isometric plantar flexion torque. Results: Group differences The strong group used 74% and 76% relatively less muscle activity compared to the weak group during shod and barefoot running, respectively. Stronger participants needed 61% less muscle activity to perform the squats on the ground, whereas no difference was observed between groups during the squat on the bosu ball. Task differences During the running tasks, no difference in EMG was observed between shod and barefoot running. Regarding the unipedal squats, participants needed 71% more muscle activity when performing a squat on the bosu ball compared to a squat on the ground. Discussion: People with stronger ankles need less relative muscle activity to carry out different tasks which have been previously speculated to strengthen the ankle-foot complex structures. Also, dynamic actions (running) elicited higher muscle activity than static actions (squats) and there was a significant effect of training modality on muscle activation level for the weak group, whereas the strong group used similar muscle activity across tasks. We speculate that, for any given task, people with weaker ankles seem to be closer to their physiological limit and, consequently, at greater injury risk when performing any of these situations over time.
© Copyright 2014 19th Annual Congress of the European College of Sport Science (ECSS), Amsterdam, 2. - 5. July 2014. Veröffentlicht von VU University Amsterdam. Alle Rechte vorbehalten.