Standing tall

does anyone know meaning of expression "standing tall in the saddle?" Doesn't someone normally sit in the saddle? Thanks Guy Andrews

It means having an air of heroic masculine dignity. Yes, people normally sit in the saddle, but they occasionally stand in the stirrups. The expression can be used without "standing": "After reading Western novels all weekend, I felt pretty tall in the saddle myself."

I've only heard the phrase as "standing tall". Is "in the saddle" the rest of it? Are there other endings?