to get a really good figure, you have to go to a lab and be tested. If you want a fairly accurate and much easier way, check in the training and nutrition forum under the first or second thread that's called something like "2 x 20 anerobic threshold test". That's a pretty good way to get your LT for the bike. I am under the impression that it, along with max heart rate, will be different for biking, swimming, and running. I don't see why you could not perform the same test for swimming and running if you wanted to get the most accurate results. good luck