Effects of bridge exercise performed on an unstable surface on lumbar stabilizing muscles according to the knee angle

[Purpose] This study aimed to determine the effects of bridge exercise performed on an unstable surface on lumbar stabilizing muscles according to the knee angle. [Subjects] Fifteen healthy adult men were selected for this study. [Methods] The study subjects performed the bridge exercise on an unstable surface and a stable surface, with the knees at different angles (45°, 90°, and 120°). An aero-step device was used as the unstable surface, and the flat ground was used as the stable surface. External oblique, internal oblique, and rectus abdominis muscle activities were assessed and compared using electromyography. [Results] The study results demonstrated that performing the bridge exercise on an unstable surface with a knee angle of 120° led to a greater increase in the external oblique, internal oblique, and rectus abdominis muscle activities than when performed on a stable surface. [Conclusion] The bridge exercise with the knees at a 120° angle was found to be an effective intervention for increasing the external oblique, internal oblique, and rectus abdominis muscle activities.