The body adapts to what you repeatedly ask of it, including inactivity.

Bodies respond to whatever they are asked to do repeatedly, including being asked for nothing. Sitting still is a request, and the body honours it by becoming good at sitting still, losing what it does not use. Nothing is being punished; the same adaptive process runs in both directions.

Ask what your daily pattern is training you for. Then add one small demand you would like to keep answering in ten years. Standing, walking, lifting something. Regularity matters more than intensity.