yoga !
There are many benefits to body and mind of yoga, and they have
nothing at all to do with whether you are naked or not. Start with
a wikipedia article on yoga and go from there. It is certainly
pleasurable to do it naked if you are a nudist but seeking out nude
yoga with no fundamental interest in the practice is sort of
pointless. On the occasions that I can get to a nude yoga class I
do enjoy it. And when I practice alone it is nude. But then so is
making the coffee and balancing the check book :)
Unlike many who practice yoga, I began doing some poses for a very specific reason, to strengthen my lower back muscles. I had strained a back muscle many years ago and the restraining of it was happening more frequently. When researching exercises to strengthen the lower back, many were yoga poses.
As far as nude yoga versus clothed, when nude there is no restrictions to movement. Also, being nude allows one to completely feel the exercise and muscles.