Purpose: The purpose of this study is to investigate the effects of healthy persons performing a plank exercise with hip abduction and use of sling on trunk muscle activity. Methods: Twenty-three subjects participated in this study. Muscle activities of the multifidus, rectus abdominis, external oblique and internal oblique were assessed with electromyography (EMG) while the subjects performed 6 various types of plank exercises in random order. Results: There was a significant difference in

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... ifidus and internal oblique on the supported side and the multifidus, external oblique, and internal oblique on the elevated side (p< 0.05), and differences in plank methods were significantly higher in the multifidus, rectus abdominis, external oblique, internal oblique of the supported side and the rectus abdominis, external oblique and internal oblique on the elevated side (p< 0.05). In addition, post-hoc analysis of the various plank methods showed that muscle activity was significantly higher during the general plank exercise compared with the knee-supported-in-sling plank exercises (p < 0.05), and was significantly higher with the ankle-supported-in-sling plank exercises compared with the general plank exercise. Conclusion: There was greater trunk muscle activity with plank exercises performed with the ankle-supported-in-sling and hip abduction plank exercises compared with the general or knee-supported-in-sling plank exercises. Through this study, various plank exercises have been discovered that can be selected at different intensities for core muscle training purposes based on trunk muscle strength. and maintain balance due to changes in inclination. 11 Slings are effective and can easily be used to perform exercises to promote muscle strength, neuromuscular control, and stabilization. 12 This is an Open Access article distribute under the terms of the Creative Commons Attribution Non-commercial License (Http:// creativecommons.org/license/by-nc/4.0.) which permits unrestricted non-commercial use, distribution,and reproduction in any medium, provided the original work is properly cited. J KPT Elevating lower extremity and hip abduction are used in many ways when exercising on mats. The bridge exercise, similar to plank exercise, promotes muscle activity when Elevating lower extremity and hip abduction. 13 Likewise, the bridge exercise combined with sling and hip abduction shows higher muscle activity than that of general bridge exercise with sling. 14 Although there are several recent studies on the effects of changes in lower extremity positions during plank exercises, studies investihttps://doi.org/10.18857/jkpt.2017.29.3.128 J KPT pending on the plank exercise methods, muscle activities of the multifidus, rectus abdominis, external, and internal oblique of the supported side and the rectus abdominis, external, and internal oblique of the elevated side were significant. In addition, post-hoc analysis of the various plank exercise methods showed that muscle activity was significantly increased with the general plank compared to the knee-supported-in-sling plank position, and with the ankle-supported-in-sling plank compared with the general plank exercise method. These results are compatible with the results from previous studies. A study by Lee 7 compared the general plank versus a plank exercise performed on an unstable surface and found that muscle activi-