It seems as though there are a few methods out there to attempt to determine what your anaerobic/aerobic divider zone is for targeting training for distance events. I'm having a bit of trouble determining on my own if I am actually swimming at this "sweet spot". I've tried different methods of calculating...a 30minute swim, the 400/200 test, and the 3x300 on 1:00 rest. Ultimately, they all produce a different threshold pace and the difference of 4 seconds per hundred definitely produces a different feel on a set such as 16x100 hold T-pace on 10s rest. I'm aiming for goal events between 1000y (Pool) and 2.5 miles (open water), so it makes a difference to go hard enough that I can improve but not so hard I'm dragging every day out of the pool. What is threshold or CSS pace really supposed to feel like? Is there one method better than another for estimating your threshold pace? Does it seem reasonable that your threshold pace may actually vary based on the day, so there's a particular feel you need to be going for rather than a time?
