In the past, when I have gone to a gym on a regular basis, I have always found that I am sick more often than not. It doesn't happen if I am active outside or in my own house. I came to the conclusion that all the shared perspiration and heavy breathing spreads germs too easily. So, I try to stay away from gyms, unless there is one in a hotel where I am staying-they never seem to have too many folks in them!
You see if you feel the same if you do the same exercise outside-that might give you more to think about anyway!
Good luck-I loathe sickness!
Imagine the possibilities...and Happy, Happy, Happy!