Here is an easy exercise for the back. Practice it daily.
Cross and Open
Starting position: Arms straight, reaching toward the knees, palms down, wrists crossed.
Step 1: Uncross wrists, turn palms up, and bring the hands even with the front of the chair seat.
Step 2: Cross wrists in front again, BUT this time, open and bring the hands even with the middle of the chair seat (palms up).
Step 3: Cross wrists a third time, BUT this time, open and bring hands toward the back of chair, turning palms up as much as possible. Squeeze shoulder blades together.
Relax and repeat several times.