I watched Michael Mosely in Trust me I'm a doctor this evening. It assessed the health benefits of 12 weeks of Zumba with 12 weeks of Tai Chi. The incredible thing was, Tai Chi was just as effective in increasing heart beat, relaxing blood vessels and all the other things exercise brings to you that supports your health as the much more obviously energetic Zumba.
MM, did a Tai Chi session and said that for such a gentle exercise, he felt he had experienced a real work out, which is exactly what I said in my post of 17.17.50 today. Remember you read it on GN before you heard on tv!!
varian, with pilates, it rather depends on what class you do. Many places run pilates for the over 50s, which is quite gentle, usually done sitting down and does not require lying on the floor, or the quite vigorous stretching a main stream pilates class requires.
Main stream pilates is not practical for anyone with arthritis or has any problem with movement or is frail in any way. I wouldn't choose it as a route back to exercise for someone who hasn't exercised for sometime. I have been doing main stream pilates for several years and still cannot manage some of the exercises.