Why do you stand ? Are you trying to reduce the impact forces of touchdown ?

You greatly increase you risk of a head impact by standing than reducing any risk of a hard landing. Plus, you become a projectile if there was a severe turbulence event.

You would be better sitting with your seatbelt fastened with your head forward as if you are trying to hug your knees. This is standard crash or impact position because it reduces the forces to the head from a hard landing.

When you head and shoulders are forward, the spine will bend to absorb most of any jarring force. Just hunching your head and shoulders forward will reduce the forces transmitted through the spine.