Background: Recently, many studies focus attention on trunk muscles activity during daily performance or sports activities. However, the pattern of trunk muscles activity during the turning movement is not clear. Objective: To elucidate the pattern of trunk muscles activity during a one-legged turn of the body while swinging the free leg. Methods: Subjects are 7 female collegiate rhythmic gymnastics players (age, 19.3±1.7 years; height, 157.8±10.0 cm; weight, 47.5±5.4 kg). Electromyographic data were bilaterally obtained from rectus abdominis (RA), external oblique, internal oblique (IO), and erector spinae muscles. The Subjects performed the "passé pivot." which is the basic pivot in rhythmic gymnastics. The pivot is a turn wherein the toe of the free leg is placed at the knee of the standing leg. The subjects turned as possible as they could. The left leg was the standing leg and the subjects turned towards the right means posteriorly. We analyzed the first turn, and we divided the pivot into 3 phases; namely, the preparation phase (Pp), the early phase (Ep), and the later phase (Lp). The Pp lasts from the 0.5 seconds before the free leg leaves the floor to the time the leg leaves the floor, the Ep lasts from when the leg leaves the floor till the time the subjects turns 180°, and the Lp lasts from the 180° point to the 360°point. The muscle activity (%MVC) was compared between muscles and phases by using repeated two-way analysis of variance (p < .05) Results: As the results of the two-way ANOVA, there is no interaction. IO activities on both sides were high in all phases. The IO activity on the free leg side for each phase was 87.5 %MVC during the Pp, 60.5 %MVC during the Ep, and 69.7 %MVC during the Lp, respectively. Additionally, the IO activity on the standing leg side for each phase was 51.2 %MVC during the Pp, 58.2 %MVC during the Ep, and 87.3 %MVC during the Lp. A major finding during the comparison of the muscles was that the activity of the IO on the standing side was significantly higher than the RA of the free leg. Discussion: The IO muscle activity was highest among all the other muscles and was high value in all the phases. Therefore, the IO may have a significantly affect postural maintenance in turning. The IO activity in the free leg was higher value from the preparation. It is suggested that the IO of the free leg contributed by providing the necessary power for the turn. Although the IO activity in the free leg was high during Pp, the IO activity in the standing leg was higher than that in the free leg during Lp. The results might suggest that the IO in the standing leg provides postural maintenance that prevents the body being pulled in the direction of the free leg by the centrifugal force. Conclusions: This study indicated that the IO showed higher activation than the other trunk muscles during the pivot movement. There is the possibility that the IO of the free leg provided the power for the turn, and the IO of the standing leg provides postural control.
© 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.