I have been considering for quite a long time now of buying a Wii fit. But I am worried about whether it might be a bit too tough on my joints. Has anyone else used it successfully?

I have played some of the standard Wii games with my daughter and son inlaw, like bowling, boxing, tennis etc... but I just end up getting such sore elbows, wrists and knees. I have been watching about the Wii fit on the TV and thought it might be a great alternative.