Abstract.[Purpose] The purpose of this research was to determine the effect of Flexi-Bar exercise with vibration on trunk muscle thickness and balance in university students in their twenties. [Subjects and Methods] This research evaluated 26 university students in their twenties, equally and randomly divided into two groups. Both the experimental and control groups used an ordinary pole for exercise. In addition, the experimental group exercised by using a Flexi-Bar. Ultrasonic imaging was used to measure the changes in trunk muscle thickness. A balance measuring equipment was used to measure balance ability.[Results] The thickness of the transversus abdominis and the multifidus muscles in the experimental group increased, and the experimental group showed increased thickness in the transversus abdominis muscle compared to the control group. After 6 months of exercise, there was an improvement in the blind Romberg test and center of pressure moving distance with one-leg standing. [Conclusion] These results indicate that the Flexi-Bar exercise is effective in increasing trunk muscle thickness and improving balance.

[Purpose] This study aimed to determine if the velocity of mechanical horseback-riding training can improve spinal alignment in young adults. [Subjects and Methods] Thirty-six subjects were enrolled in this study. The subjects were randomly allocated into high-, moderate-, and low-velocity mechanical horseback-riding training groups. All participants completed one 20-minute session per day, 3 days per week, for 6 weeks. The evaluation was performed before and 6 weeks after the training intervention. The spinal alignment was measured by a Formetric III device. The measurement items were kyphotic angle, lordotic angle, trunk inclination, pelvic torsion, pelvic rotation, and lateral deviation. The data were analyzed using analysis of covariance to determine the statistical significance. [Results] The kyphotic angle and trunk inclination were significantly different among the groups. The kyphotic angles of the high- and moderate-velocity groups were significantly lower than that of the low-velocity group after the intervention. The trunk inclination of the high-velocity group was significantly lower than that of the low-velocity group after intervention. [Conclusion] Higher-velocity mechanical horseback-riding training is more effective than lower-velocity mechanical horseback-riding training for improving spinal alignment.