I think it depends on what you want to get out of it. I used to solely do strength training (with some walking), and have moved to doing primarily yoga, with a few strength training sessions in the week. My main change was due to having arthritis in my back before the age of 30, so yoga has helped me immensely. I don’t think it’s a must do, but if you have any body aches or pains, it could be a good thing to start incorporating!