Coaching, Training, Camps.

 “That Which You Measure You Can Improve!”

Swim Faster by Building Your Aerobic Engine – Here’s how!

By Coach Stacee Seay

Want to swim faster?

A sure fire way to improve your swimming, once you have developed a good stroke technique is to work on your swim fitness through CSS training.  Critical Swim Speed training focuses on developing your lactic threshold or the point in your swimming where you switch from using your aerobic engine to your anaerobic engine. Improving fitness aerobically will ensure faster times in any endurance sport. That’s a fact!

Developing this CSS fitness to hold your technique over time leads to efficiency. Efficiency is defined for this article as: doing a given task and expending the least amount of energy for the duration of the task.  So if we swim efficiently we will decrease our swim times over time.  It’s just that simple.


Know your CSS Pace?

Critical Swim Speed is calculated by using this CSS Test Protocol.

To figure out your Critical Swim Speed (CSS) Pace Do this Simple Swim Test

WU:     400-600m swim that may include some drills or short sprint work to get your heart rate up and settle into a comfortable pace.

MS:      400 Time Trial and time yourself. Knowing what you first 100m split is also helpful!

Then: steady or recovery swim for 5-10mins followed by

200m Time Trial and time yourself as well.

CD:      swim an easy cool down of your choice

Then plug these numbers into this handy CSS Calculator:

The Calculator will give you your CSS Pace. Use this pace with a Finis Tempo Trainer Pro or Platysens Marlin pacer unit to help you hone and perfect your pacing skills.

Take your CSS pace, convert to seconds and divide by 4 to set the beepers to beep on the walls for your CSS pace.

What Does this Measurement Mean?


The results are your projected 100 pace for a distance of 1500m.  This pace is a little more accurate than your T-Pace for distances greater than 1500m.  If you train at this pace or slightly slower you are assured faster overall swim times by developing your aerobic fitness base.

What to do with it?

Now that you know your CSS pace, here is how to develop that aerobic fitness. Choose or alternate between these a simple CSS and Red Mist Swim workouts weekly. Depending on your race distance or swim fitness choose one of the following swim workouts.

Classic CSS Goldilocks Set using this formula to set the beeper – (CSS/4) = Set to Mode 1 on the Tempo Trainer. Beep on each 25m wall.

(Stay with the beep for perfect pacing)

After a good warm up do this Main Set Swim using your favorite pacing tool.

Baby Bear

  • 2x 100m + (1 beep recovery)
  • 1x 200 + (1 beep recovery)

Mama Bear

  • 2x 100 (1 beep recovery)
  • 1x 300 (1 beep recovery)

Papa Bear

  • 2x 100 (1 beep recovery)
  • 1x 400 (1 beep recovery)

CD: Choice

Classic Red Mist Set(s)

choose distance based on fitness or race distance – (CSS/2) Set to Mode 2 on the Tempo Trainer. Beep every 50m

(Beat the beep for your recovery)

  • 10x 200 (+1 full beep between each 200 set)
  • 10x 300 (+1 full beep between each 300 set)
  • 10x 400 (+1 full beep between each 400 set)

These sets may seem quite comfortable at the beginning but will become increasingly more challenging as the sets progress.  Swim these workouts 1-3x per week to increase your aerobic fitness along with your Technique and Open Water Skills workouts.

Measure or Re-test to Check Your Progress at regular intervals.

Plan to retest or perform the CSS test set every 4-6 weeks to check progress.

Its not new — but it’s the BEST!

The concept of measuring progress is not a new to BEST coaches. We have been doing this through our implementation of Joe Friel’s Periodization Training since its inception. This CSS work is yet another tool to check your progress and measure your fitness regularly to become the well tuned and oiled racing machine you are capable of in the shortest amount of time.  Training Smart to be the BEST Athlete you are capable of is what we do every day.

Coach Stacee Seay is Swim Smooth Certified Coach in the U.S. and regularly holds Chicago based Squad Sessions modeled after the swim squads in Perth Australia.  She also holds swim camps and clinics around the U.S as well as remote and 1-2-1 Swim Video Analysis. Please feel free to contact her with your swim training related questions.