It's REAL important as most of our unconscious, repetitive movements impact our health as we age. Where we place our thighs, pelvis and lower back while sitting plays a significant role in how our upper spine posture is impacted. We know that sitting puts our hips in flexion which makes our hip flexors tighter and can often lead to lower back pain.
When sitting, you want to make sure that your knees are the same height or slightly lower than your hip bones (the bony parts of the front of your pelvis). This will allow the front hip flexors a bit of slack. Sit on the sits bones, the bones beneath your butt (not on the tailbone) with both feet flat on the floor. As you sit on your sits bones, lift up through the top of your head to lift the rib cage off the pelvis (which will feel like more work for some of us)!
We'd love to hear how this works for you!