This topic has come up before, so maybe you can check in past forums. But, as a 54-year old male whose core strength has diminished over time, I find that my Achilles tendons are probably the most common to be aching or hurting if I am not careful. So I am sure to stretch those out significantly prior to a lesson or dance. I usually just put my foot up against a wall and and lean forward, but not too far, to get a good stretch. My wife teaches aerobics and toning classes and she contends that yoga stretches and core work common in some pilates moves is really helpful. I would think the older folks amongst us find a painful twinge in the knee on occasion. I have been extremely lucky to have never experienced bad back pain. I have found yoga to be great in keeping that in check.