[livi]

First of all, if Ibuprofen is needed every time you exercise - your body (knees) does not approve of the training. As a response to trauma it produces an inflammation in order to heal. Ibuprofen counteracts that inflammatory response as well as it has a direct pain killing effect. Both of which will make your knees less of a problem.

Secondly and however, as long as your stomach can handle it, so can the rest of your organs - kidneys included. Just as long as you do not take higher daily doses than prescribed. Many children (and adults) with rheumatic and autoimmune diseases need to take large doses every day for years with no adverse effects.

But as I started out, the actual need for an anti inflammatory agent after each training is proof a your knees disapproval of that specific exercise. A general rule of thumb is that feeling pain is a signal from your body that you should rest in order to avoid further damage. At least if keeping up a pain producing exercise for a long time.