Main Set Friday - Grows Slowly

A simple practice that starts very easy, but as the distance increases, the intervals decrease.

This can be started as a warm-up and based on how far you take the progression, can turn into a very serious practice.  The only constraint is how much time you have.

Main Set (short course yards)
 - 10 x 25 on :30 - 30 seconds per 25
 - 10 x 50 on :55 - 27.5 seconds per 25
 - 10 x 75 on 1:15 - :25 seconds per 25
 - 10 x 100 on 1:30 - 22.5 seconds per 25
 - 10 x 125 on 1:40 - :20 seconds per 25

Continue the progression as able.  ;)