All I can say is here I am almost 68 years old, overweight and I just finished walking all over Europe. Believe me, it made any time I have spent at WDW seem like a casual stroll. No blisters, no muscle pain. I did at one point tell my sister that this experience was either going to fix whatever problem I have with my leg or make me a cripple. So far... all is good.
FTW, my eye problem has seemed to resolve and I am done with this experience, at least for now. If I get any type of positive news about the cancer thing, I will be scheduling the other eye as soon as possible. I didn't think it would ever clear up, but, it has and I can see well now and don't need glasses for anything other then reading and even that has improved.