Trunk Movement and Sequential Trunk Muscle Activation During Oscillation Exercises Using Flexible Poles

Objectives: Oscillatory exercises using flexible poles, such as the Flexi-bar, were recommended as rehabilitation programs to increase trunk muscles strength; however, the strategy to enhance the training effects is under investigations. The aim of this study was to characterize the trunk movements and muscle activation patterns when performing an oscillation exercise with flexible poles in different weights. Methods: Twelve healthy male participants performed oscillation exercises with flexible poles of different weights. The center of mass, as well as surface electromyography for 10 trunk muscles were assessed while participants performed oscillation exercises. Results: The participants’ trunks showed rhythmic anterior–posterior movement during oscillation exercises using flexible poles. The center-of-mass movement distances were 20.32 (6.73) mm, 25.33 (5.31) mm, 32.40 (9.94) mm, and 37.28 (21.59) mm for the Flexi-bar, light pole, medium pole, and heavy pole, respectively. Erector spinae, internal obliques, multifidus, and external obliques revealed significant activation levels during oscillation exercises. The participants who could perform steady and smooth oscillation with heavy pole for 30 seconds revealed phasic sequential muscle activation. Conclusion: The present study suggested that oscillation exercises with flexible poles were associated with a concomitant trunk movement in anterior–posterior direction and an effective activation of trunk muscles.