| Summary: | 碩士 === 明志科技大學 === 工業工程與管理系碩士班 === 103 === This study recruited 15 male participants and collected their muscle activations on lower back, leg, and buttocks, as well as lumbosacral angle (LSA) and pelvic angle under 16 posture combinations by 4 trunk angles (0°, 60°, 75°, and 90°), 2 lumbar postures (lordosis and kyphosis), and 2 knee positions (with and without screw-home mechanism, SHM), to understand the flexion-relaxation phenomenon (FRP) of erector spinae. The results showed that trunk angle, lumbar posture, and knee position had different effects on various muscle groups. The erector spinae was affected by trunk angle and lumbar posture variables, whereas the gluteus medius and quadriceps femoris were affected by trunk angle and knee position variables (all p<0.01). As a whole, FRP occurred early as torso forward bending reached 75°. During stance, the erector spinae activation was more significant when bending with lordosis than with kyphosis (23.3:13.6%MVC). With a trunk position of 90°, the average erector spinae activation dropped to 11.7%MVC, which was far lower than those of erect trunk. Furthermore, the LSA and pelvic angle may be used to explain the muscle activations of various body regions. The interaction among the trunk angle, lumbar posture, and knee position was extremely complex and needed further clarification.
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