Often in your training plan, you'll see shorthand used to describe various parts of your set. While these may make sense to athletes that have been training all their lives, not all of us have done that, so this section describes the various terminology that you might not be sure of. Remember, for a lot of the swimming terminology, be sure to check out the 'swim drills' page for videos of how to perform the drill correctly!
Build: Get faster through the swim. For example, '100 build' means that your effort and pace should increase throughout the 100m, with each 25 slightly faster than the one before it.
C/D: The cool-down section of the session. Effort and pace should gradually decrease to 'very easy.'
Descend (or 'Desc'): Descend the speed of each rep (get faster each time.) For example, '8 x 100m Desc' means to swim each of the 100m reps slightly faster (1-3 seconds) faster than the one before it.
Desc 2-2-2-2: Descend the speed of each pair of reps. So '8 x 100 Desc 2-2-2-2' means swim the first 2 reps at a particular speed, the next 2 reps slightly faster, etc.
Even / Odd: This means to perform one kind of drill on the ODD reps (1,3,5 etc) , and another kind of drill on the EVEN reps (2,4,6) etc.
Free / FS : Freestyle
Fast: As fast as you can swim for that particular rep.
Negative Split: The second half of the rep is faster than the first part of the rep.
Pull: Swim with a pull buoy between your legs. This isolates the arms and gives you a more 'muscular endurance' workout for your upper body.
RI: Rest interval. Shorthand 'on 20s' or 'on 20s RI' means the same thing - you get 20 seconds rest before the next rep.
CSS: 'Critical Swim Speed' - this pace (for swimming) is analogous to 'threshold' speed on the bike or run. It's a good marker for a pace to aim for during your repeats. This pace will be worked out after undertaking a 'CSS test'. It is expressed as pace per 100m, so a CSS pace might be 1.50 (1 minute 50 seconds per 100m)
CSS+4: Sometimes pace guidance will be given like this. 'CSS+4' means 'CSS pace plus 4 seconds per 100m.' If your CSS pace was 1.50, CSS+4 would be 1.54.