Dear Rabbi Simon
Whilst I have realised for a while at my ripe old age that I need to do more exercise, what holds me back is finding the time. Once I get home in the evening, there is always something to do and despite my best efforts I never seem to be able to get these trainers on and get out the house for a jog!
One solution which would really work for me would be to go to the gym next to my office during the working day, I would be able to schedule it in, and hopefully listen to a shiur in the gym too.
Am I right in thinking that as long as one is careful to guard ones eyes that it is okay to go to a mixed gym? (Alas there is no men-only gym nearby.)
The short answer to your question is yes, in view of your circumstances and stage of life, for reasons of improving/maintaining/preserving good health there are grounds to allow attending a mixed gym as per the specifics of your question.
Rabbi Rashi Simon