Prolonged sitting can significantly affect posture by leading to muscle imbalances and structural misalignment. When seated for long periods, certain muscle groups, like hip flexors and pectoral muscles, tend to become tight, while others, such as the glutes and abdominals, weaken. This imbalance can result in a slouched appearance, vertebral issues, and back pain. Regular breaks to stand, stretch, or engage in movements can counteract these effects and promote better postural alignment.