This is really needed, especially once exercises are in.
Perhaps something like this will do:

"If you have had any recent surgery, muscle or joint problems, please consult a
healthcare professional before using this program."

Eh...
How about "If you have had any recent surgery, muscle or joint problems, please
consult a healthcare professional."

But seriously...
I really don't like the trend to put the most ridiculous disclaimers on all
kinds of stuff, nor the american "claimcultuur" (for lack of a translation) that
causes it. I think we should promote self-responsability.

I think the GPL explicitly disclaims any kind of usability, and the wr
documentation explicitly states that wr helps (but you still should do the work)
and nothing more. People with medical problems should go see a doctor, no matter
what. 

Root cause of this is you pretending to be a healthcare professional, by
offering exercises, and yet you have no training in this area, nor do you know
your patients. That would be a difficult situation for any healthcare
professional, let alone you. I (once again) propose to resolve this problem once
and for all by deciding not to do exercises. At least until we reqruit someone
knowledgeable to our team.

Yesterday, I heard someone mention that cigarettes now have a "best before"
date. I wonder what will happen if you smoke afterwards. Will they kill you?

I disagree. 

Workrave claims to help in RSI prevention and recovery by introducing breaks.
Yet, we do not have a professional medical background, so according to your
logic, we must not claim the Workrave is an RSI tool.

The truth is that even though we do not have a medical background, we do know
from experience, personal study and experts in the field that taking breaks is
helpful. Hence, we software engineers can add "break" support to Workrave and
claim that it helps. We do not invent our own radical new break concepts,
because we are not certified to claim that that would help.

Similarly, we do know from experience, personal study and experts in the field
that taking exercises is helpful. Hence, we software engineers can add exercises
developed by professionals and claim that it is helpful. We do NOT introduce our
own invented exercises, because we do not know if that would help. 

One way or the other, exercises are emminent.

... and, as far as the GPL is concerned, here are the disclaimer parts.
Personally, I feel the text is more oriented towards damage to your computer
while using the program, in contrast to damage to your body. What do you think? 
This bug is about making the damage to your body aspect more explicit.

  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
REPAIR OR CORRECTION.

  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.

ouch...
We're building a healthcare app that may damage your body. I'm beginning to
loose faith here... :-)

Anyway, GPL could be interpreted to mean damage to your body, even though all
examples are suggesting damage to data or hardware. Then again, it is not common
for an app to be able to cause bodily harm, so why put it in the gpl explicitly? :-)

The american thing to do would be to make the bodily damage more explicit.

How about: The exercises in this application were performed by trained experts.
Don't try them at home

Umm, we're already in feature & string freeze for 1.4.0...
(or just think of some other excuse...)

The problem with using the GPL to limit liability is that the user is not
required to accept it. The GPL regulates distribution, not usage; therefore one
can use workrave without accepting the GPL.

As an amateur lawyer (which is to say not a lawyer at all), I would say putting
a disclaimer is wise. We may all disagree with the legal systems that create a
warn-about-everything society, but that does not mean such systems cease to have
power over us.