Sitting for long periods of time can worsen a herniated disc because it puts additional pressure on the spine. When you sit, the weight of your upper body is concentrated on your lower back, and this can put a significant amount of pressure on the discs in your spine.    If you already have a herniated disc, sitting for extended periods of time can exacerbate your symptoms, such as pain, tingling, or numbness in your legs or back. In some cases, sitting may even cause a herniated disc to worsen or make it more likely for a new herniation to occur.