Definitely. 'Flex - Funnies' is a good one as it combines the idea of flexing muscles with something funny. 'Squat Shenanigans' can be used as squats are a common gym exercise and 'shenanigans' implies some sort of mischief or fun. 'Bench Press Banter' is also suitable as when people are bench pressing, there can be a lot of chatting and joking around.
One time at the gym, I saw a guy trying to lift weights way too heavy for him. He grunted and strained so hard that his face turned bright red. Then, suddenly, he lost his grip and the weights dropped with a loud clang. Everyone in the gym turned to look, but instead of being embarrassed, he just started laughing hysterically. It was so funny that soon the whole gym was laughing with him.
FitFolks' Secret. This name gives the idea that it's about the private fitness journey of the people in the gym. It has a sense of community within the privacy.