A slightly serious reply.
Are you tall, aesthetic, big as a brick shithouse? There is a lot more competition in a gym than out in the world.
Lets look at the odds and social dynamics.
Generally you're looking at a highly skewed M to F sex ratio. Then you take into account, if a gym hottie is single. She probably isn't single for long. I would do a little recon before making a move in the gym. Lots of couples in the gym.
Are you outgoing in the gym? Do you smile and talk to everyone. I call this, the social vulture maneuver. So when said cardio bunny does become single or thinks about it you're probably on her mind. IE, when something dies you're ready to swoop in...lol
At my current gym, there are quite a few men who chat up ANY woman in the place. This behavior is pretty common at commercial gyms.
I go to a gym to lift and reduce stress. Not to talk to women. I do have women hit on me on occasionally. A woman would have to be pretty special for me to take a shit on my front porch.