What you need to do is swim a 400m and 200m time trial (ie as fast as possible) and then enter those times into the form and it works out your threshold training pace. I did a 7:20 400m and a 3:33 200m and my threshold pace was defined as 1:54 / 100m.
– It’s important to note that this isn’t meant to be your fastest pace, but a pace you can keep to consistently over a longer training session.
I then did my first session using that threshold pace on Tuesday lunchtime. The goal was to swim 20 x 100m at 1:54 with just a 15sec gap between each set. What was interesting was how hard it was to go slow enough to keep to that time at the start (my first 3 or 4 sets were 1:50 or below), but then how hard it was to go fast enough by the end (the 16th or 17th set was a 1:58 because I wasn’t concentrating).
Apart from that though, I like the concept of it and will keep this in my regular training plan.