Effects of trunk and neck extensor muscle activity on the bridging exercise according to knee joint angle

Abstract

[Purpose] The aim of this study was to determine the optimal knee joint angle for minimizing cervical muscle tension and maximizing the muscle activity of the trunk during the bridging exercise for trunk stabilization. [Subjects] The subjects of this study were 45 healthy adults in their 20s and 30s. [Methods] The bridging exercise in this study included four forms of the exercise having knee joint flexion angles of 120°, 90°, 60°, and 45°. The posture of the bridging exercise was as follows. To prevent the increase of lumbar hyperlordosis during the bridging exercise, the exercise was practiced after maintaining the lumbar neutral position in the posterior pelvic tilting exercise. [Results] During the bridging exercise, muscle activity increased as the flexion angle decreased. For the knee joint flexion angle of 120°, muscle activity was 102.88 ± 0.69. It was 102.61 ± 0.69 for 90°, 105.57 ± 0.85 for 60°, and 106.24 ± 0.88 for 45°. According to the post hoc results, muscle activity was significantly higher for 60° and 45° than for 120° and 90°. [Conclusion] The knee joint angle affected the muscle activity of the neck muscle. The greater the knee joint angle was, the lower the load placed on the neck muscle. In contrast, the load increased as the knee joint angle decreased. In addition, the muscle activity of the neck muscle and trunk muscle increased as the knee joint angle decreased.