In tai chi you must always remain within your natural range of movement.
Any stretching is done subtly and never forced; the body is allowed to open
by itself, rather than be forced.
By encouraging the joints to be free, mobility increases radically and the
body can move more comfortably.
Tai chi should never strain or hurt the body.
Some movements may feel
uncomfortable if you have bad postural habits and this is to be expected -
your body is already used to set patterns of movement and poise - and the
tai chi is gently changing these.