Staid on the treadmill is often used to describe someone who is consistently doing the same thing without variation. Alternative synonyms for this phrase could include "stuck in a rut," "monotonous," "unchanging," "repetitive," or simply "boring." When someone is staid on the treadmill, they may lack excitement or enthusiasm in their life. Other related words include "routine," "tedious," and "uninspired." To avoid becoming staid on the treadmill, it's important to mix things up and try new activities to keep life interesting and fresh.