Threshold
CSS 10 x 100 m on 15 Seconds Rest
10 × (100 m at CSS pace, 15 s rest), 4 × (100 m pull buoy, 15 s rest)
CSS and Threshold Swim Workouts
CSS and threshold swim sets from 10 x 100 to a broken 1500, over-unders and descending 400s, with pace targets from your critical swim speed.
Workouts
12 workouts
Threshold
CSS 5 x 200 m Threshold Set
5 × (200 m at CSS pace, 20 s rest), 400 m pull buoy
Threshold
CSS 3 x 400 m with Fast 50s
3 × (400 m at CSS pace, 30 s rest), 200 m easy freestyle, 8 × (50 m at CSS pace, 15 s rest)
Threshold
Broken 1500 m at CSS in 3 Rounds of 5 x 100 m
5 × (100 m at CSS pace, 5 s rest), 1 min rest, 5 × (100 m at CSS pace, 5 s rest), 1 min rest, 5 × (100 m at CSS pace, 5 s rest), 400 m pull buoy, 4 × (100 m freestyle, 15 s rest)
Threshold
First CSS Set with 50s and 100s for Beginners
8 × (50 m at CSS pace, 20 s rest), 200 m easy freestyle or backstroke, 4 × (100 m at sweet spot, 30 s rest)
Threshold
4 x 200 m Threshold Builder for New CSS Swimmers
4 × (200 m at sweet spot, 30 s rest), 4 × (50 m easy backstroke or breaststroke, 15 s rest)
Threshold
CSS 20 x 100 m in Blocks of Five
5 × (100 m at CSS pace, 10 s rest), 30 s rest, 5 × (100 m at CSS pace, 10 s rest), 30 s rest, 5 × (100 m at CSS pace, 10 s rest), 30 s rest, 5 × (100 m at CSS pace, 10 s rest), 300 m easy backstroke and freestyle
Threshold
4 x 300 m at CSS with Pull Finish
4 × (300 m at CSS pace, 25 s rest), 200 m easy freestyle, 4 × (100 m at tempo, 15 s rest)
Threshold
CSS Over-Under 200s and 100s
4 × (200 m at sweet spot, 10 s rest, 100 m at CSS pace, 30 s rest), 300 m pull buoy
Threshold
Descending 4 x 400 m from CSS Plus 4 to CSS
2 × (400 m at sweet spot, 30 s rest), 400 m at CSS pace, 30 s rest, 400 m at CSS pace, 1 min rest, 200 m easy freestyle, 8 × (100 m pull buoy, 15 s rest)
Threshold
T-Pace Set with 3 x 300 m and 6 x 100 m
3 × (300 m at sweet spot, 30 s rest), 100 m easy freestyle, 6 × (100 m at CSS pace, 15 s rest), 300 m pull buoy
Threshold
10 x 200 m Threshold Swim and Pull Alternating
5 × (200 m at CSS pace, 20 s rest, 200 m at sweet spot, 20 s rest), 300 m easy backstroke and freestyle
Threshold Workouts
Threshold training raises the pace you can hold for a long time, which in swimming means your pace over roughly 1500 m. A widely used way to set that pace is critical swim speed, or CSS, calculated from a 400 m and a 200 m time trial. Threshold sets are swum at or close to CSS with short rest, usually 5 to 30 seconds, so the effort stays high while the stroke stays sharp.
This category covers the familiar CSS formats, 10 and 20 x 100, 5 x 200, 4 x 300 and 3 x 400, as well as a broken 1500 m on five seconds rest, over-under sets that move above and below CSS, descending 400s, swim and pull alternations and a T-pace set based on a 1000 m time trial. Two beginner sessions introduce the pace with 50s, 100s and 200s and generous rest.
Threshold work suits the build and peak phases, typically once or twice a week, after a few weeks of aerobic base. It is demanding, so follow it with an easy or technique session. Choose by experience. If you are new to CSS training, start with the beginner sessions and then 10 x 100 on 15 seconds. Stronger swimmers can work toward 20 x 100 and the broken 1500. Retest your CSS every six to eight weeks so the targets keep up with your fitness.
Questions about Threshold Workouts
What is CSS in swimming?
CSS stands for critical swim speed. It is the pace you can sustain for about 1500 m and serves as the threshold reference for pace training. You calculate it from a 400 m and a 200 m time trial by subtracting the 200 m time from the 400 m time and dividing by two, which gives your pace per 100 m in seconds.
How much rest should I take in CSS sets?
Short rest is what makes a CSS set work. For 50s and 100s, 10 to 15 seconds is typical, for 200s about 20 seconds and for 400s about 30 seconds. Beginners can take a little more. If you need much longer rest to hold the pace, your CSS is probably set too fast, and if the set feels easy on the given rest, it is time to retest.
Can I do threshold sets without a CSS test?
Yes. Swim at an effort that feels comfortably hard, the pace you could just about hold for 1500 m or roughly 20 to 30 minutes. That gets you close. A test makes it precise, though, and pace targets on the watch need a value to work with, so plan a CSS test or a 1000 m time trial within the first few weeks.