When I started to read this post I did not have any idea what isometric even was.  I was surprised to find out that it was exercise.  This sounds like something that I can do. My brother who broke his knee possibly can do this isometric also. It is just lifting a book and holding it with outstretched arm and holding it there for 7 seconds and then repeat it 6 times. I know that this will help the strength in both of them. I do not have a lot of arm strength. I can do this with my legs also to strengthen them up also. For more information check out http://www.isometricsexercises.com/2008/12/30/improve-your-health-with-isometic-exercise.html