Just listen to your body and do only what you can do without feeling too exhausted. As you are very fit you should theoretically be able to do most things you could do before however you may be surprised at how tired you do get in the first trimester so make sure you don't overdo it. One thing I was told is to not do much raising above your head ie. shoulder press and the like as it can cause your blood pressure to drop and make you feel dizzy.