1 Peter 3:15 says ...Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect...
As a Christian, I have a duty to be prepared to give an answer about why I believe in Jesus Christ, as does every other Christian. The part that some Christians forget is the last seven words of this passage. Gentleness and respect are necessary when telling others about our faith as Christians. Its too bad some Christians have "bashed" people with their faith. Telling someone they are "going to hell" is not being gentle (on top of the fact that we don't know who is going to hell, only God does). I would venture a guess that many a person has been turned away by a "well meaning Christian" who said something that was harsh rather than gentle. My heart aches for those who are turned away from God by angry, defensive Christians.
As far as praying at the gym... If it were my gym, I would make sure that the participants knew UP FRONT that I run my gym with Christian values and we will pray before/after every practice and before/after every competition. You would know that coming in and it would not be up for debate. I would ask you to respect my beliefs as the owner before you asked me to respect your beliefs as the customer. If you did not want accept my system, then you would be free to find another gym.