There is time. People who say you can't never made it a priority. I was able to hit the gym for minimum an hour a day, every day, throughout UPT. I fully believe it actually helps performance to take that time, not worry about studying, and take care of yourself. The key is being smart with your time. If you aren't able to go during the duty day due to Formal Release, use those 12 hours to do all your studying. I promise you, after 12 hours in the books, there is no additional benefit studying at home.
Life only gets more hectic for pilots after UPT. Get in a good habit now and it will have huge payoffs down the road.