A short threshold swim

Yesterday I had a sore throat which made me feel I didn't want to swim. Today it was a little better and having sat at my desk for most of the day I needed some exercise. How about a sharp 20 minutes? So I did a leisurely 200m then 400m and 200m with a bit of effort.

The first half of the 400m was done at around my PB at 4:37 minutes the second 200m in 4:41 minutes, still respectable for me. After a pause I struggled for the final 200m with 4:39 minutes so not great data for a CSS calculation, although a drop off of 0.4% shows a good aerobic system, but little ability to sprint. What's new then?

A month ago in a 25 yard pool I estimated 2:23min/100m so today's result may show a little progress. It's worth noting though that in the interim I've had little success at using the Tempo Trainer for pacing.