Basics - Centerline

Correct posture and a strong centerline are essential in Yoshinkan Aikido.
Of course your back leg and spine, but also the back of your neck.

Don't let there be any space between your neck and the collar of your dogi.
This commonly happens, especially during forward movements such as cutting down or throwing.

Don't raise your shoulders or pull your chin in too tightly. Relax your upper body, keeping your chest open and your shoulders naturally rolled back.

My Canadian Sensei once said "Think of a hat just a centimeter above your head and try to extend your centerline into that hat."

The Japanese believe correct posture through a straight centerline is a welcoming path for the Gods to enter your core.