There are two forms of exercises for building strength, isotonic and isometric exercises. Isotonic exercises are those where your muscles are working against resistance, such as that supplied by gravity, water, weights, rubber bands, or your own body weight.
In isometric exercise, muscles are contracted and relaxed without movement of the joints. An example is when you place your palms together in front of you (in a prayer position) and push them together. Isometric exercises are very useful for RA patients who are limited by disability and pain.
Your PT will help you develop a program of isometric and/or isotonic strength exercises that are appropriate to your needs and abilities.