If your body is too old for it you'll know soon enough. I'm sure a lot of people think Lance Armstrong and Brett Favre are too old to compete but they still find a way to win. A lot of people probably think I'm too old to be so immature but I don't let that bother me.
30 is not an old age. Many people couldn't enter into college or pro sports at 20 or 25 or 30. But if someone has the abilty and talent and stamina to enter the sports world at age 30, I say more power to them. It's not something I could have done but I say go for it, if it's something you're capable of doing.