When I first started meditating and journeying, I would get very uncomfortable. My legs would fall asleep and I was constantly fidgeting. I would sink into meditation, then find that leg pain or numbness would distract me.
A Zafu is a meditation Pillow
Before beginning meditation it is helpful to know what posture will be comfortable and what will work best for you. The spine needs to be erect with the arms and legs settled comfortably.
Breathing begins with the physical posturing of the body.
For example: try breathing from a slouched position. Which part of your lungs feels restricted? Diaphragm (belly), rib cage, upper chest? How many seconds can you inhale and exhale? How did you feel when trying to breathe in this way?
Now try this with your spine erect which allows for proper breathing. Leaning forward even slightly can restrict your breathing capacity.
Despite the common vision of a monk sitting as still as a rock for hours on end in meditation, sitting too rigidly can shut off body awareness and can stress the cushioning of bones and muscles.
If you feel any pain or numbness, reposition your body.
Meditation for your Life by Robert Butera, PhD