Determining Your Swim Zones

This is the first in our series on figuring out your training zones.  We’ll start with your swim zones.

  • CSS TEST INSTEAD OF 1000 TT: Instead of a 1000 yard swim TT (which people always seemed to skip), we test our threshold/ CSS (“critical swim speed”) based on a 200 & 400 TT.  We’ll test this about once every 6 weeks.  DO NOT put the test off until you feel “ready” – just do it when it’s on your schedule!  It’s not the end all and be all and you don’t have to tattoo the results on your arm.  It’s just to help us set your training paces.  The details of the workout are in your training plan.  Enter your 200 & 400 tt times into the form on this page at swimsmooth to find your CSS.
  • “Swim Lanes” Based on your 400 TT time we determine your swim “lane.”   Some of our swim workouts have separate “lanes.”  Lane 1 = 400 tt time of 7:15 to 11:00 (yards) or 7:45 to 12:00 (meters); Lane 2: 5:30 to 7:15 (yards) or 6:00 to 7:40 (meters); Lane 3: sub 5:30 (yard), sub 6 (meters).
  • To determine your zones, enter your CSS into this spreadsheet (you’ll need to save a copy first).


Swimmin’ Sally does her CSS test- she does the 400 tt in 6:00 and her 200tt in 2:53.  She enters them into this swimsmooth calculator and gets a CSS of 1:33 / 100 (yards).

Sally’s 6:00 400tt puts her in “lane 2,” so she know’s she’ll follow the directions for lane 2 in her swim workouts (lane 2 workouts are typically a focused 2500 yards once the season is in full swing).

She then visits this spreadsheet, saves a copy for herself, then enters her CSS to get her swim zones, which are displayed below.    Now she knows how fast she should go when her workout calls for 200 at threshold or 400 steady.

The video below will show you  how to set your swim zones in more detail.

Advanced- using a Tempo Tempo Trainer or Wetronome.

You can use your css to do workouts with a tempo trainer or wetronome– devices that you can set to beep every X number of seconds.

Sally’s CSS is 1:33 / 100, which is  23.25 seconds per 25 yards.  So if she wants to do a CSS workout we’ll have her set her tempo trainer to beep every 23 seconds so it will beep every time she finishes a lap.  (NOTE: if the decimal is .25 you can round down, if it’s .5 or .75 ALWAYS round up!).  For most athletes you can just add an extra beep (4 seconds/ 100) to be at your tempo pace, yet another beep (4 seconds / 100) to be at your steady pace and another beep to be at your easy pace. 

Now she can, e.g.,  do 200s at her CSS pace (pushing off the wall every time the tempo trainer beeps) with 1 beep (23 seconds) recovery in between.  Or she can do 300s at CSS pace with 2 beeps recovery (46 seconds) recovery.   If this is her first workout with a tempo trainer she’ll quickly learn that she’s going out too hard in her first 50 (she’ll be ahead of the beep) then she gets slower each lap.  She learns to even out her pacing and finds that it helps her hold her pace.    The tempo trainer becomes both a warning to ease off early in a workout and a tough task master later in the workout.  It’s a great way to learn pacing and to add some variety to your intervals.

If you’re interested in improving your swimming I highly recommend the 2 following DVDs (we use the drills from the DVDs as suggested drills in our team workouts).

swim smooth's amazing new dvd: CATCH MASTERCLASS

Swim Smooth's DVD Boxset

About Coady

Lucky to be coaching some really awesome & fun people!
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