Exercise while sitting down

Slightly unstick your back from the chair to remove the support. 

Shift your pelvis in the center position (no inside or outside arch).

Make yourself as tall as possible while lengthening and strengthening your back pulling your head to the ceiling, and sucking in your stomach. Your glutes tighten. You feel the pressure from your upper body releasing the lower back and the back unfolding, the body feels lighter, suspended by your dorsals, abs and shoulders. 

Hold as long as possible.

Repeat as long as possible.