Training Cycles: BT1--What does it mean?

Great question in the comment section: what does BT1 BT2 BT3 mean?
BT refers to "base transition," which is the cycle of training that we're in. Every aspect of the training has an objective, categorized by major "cycles" of training. These cycles, ideally, are put together for an entire year, but they can also be used for a block of training with a specific objective. For this block Base Transition refers to the time of laying the foundation for training, doing a little bit of speed or hill work, but only in short bursts to get the legs to turn over. The rest of the time serves to build up your foundation. You need to build up a solid foundation of endurance for your joints, ligaments, and muscles to withstand the additional mileage required for a half marathon.
There is a time and a reason for everything! :)
-Cami