CSS Training For Absolute Beginners

When it comes to becoming a better swimmer, your stroke technique is very important but so too is your fitness. Without a good level of swimming fitness you won't be able to sustain your stroke technique over distance, leading to that horrible feeling of your stroke 'falling apart'.

The key to developing fitness specific to swimming is to introduce the right sort of training so that you can simultaneously improve your stroke technique and fitness at the same time. And the best way to do that is using something called Critical Swim Speed (CSS) training which we're going to explain in this blog post.

CSS sets can be swum in a squad but equally you can do them
by yourself or with a few friends.

Even if you are relatively new to swimming freestyle, don't be afraid to introduce some CSS sets into your swimming routine, your swimming will come on leaps and bounds!

Your Swimming Week

If you are swimming three times per week a good way to structure things is to focus each of your sessions in the following way:

Session 1. Stroke Technique Development
Session 2. Open Water Skills (see here)
Session 3. Threshold / CSS Training

CSS training is Swim Smooth's preferred form of fitness training set for distance swimmers and triathletes. It gives you the biggest bang for your training buck and also has a strong focus on developing your pacing skills - which are critical to swimming as fast and efficiently as possible.

Swimmers moving from conventional masters training to CSS sets normally see improvements in their distance performances after just a few weeks, which is very motivating in its own right.

What Is CSS Training?

CSS training focuses on developing something called your lactate threshold, which is a physiological marker which indicates when your body is at the limit of its aerobic system. CSS training has you swimming at lactate threshold speed ('CSS pace') in order to get faster at that intensity. If we can improve your lactate threshold speed then you are pretty much guaranteed to swim faster in your races.

Don't worry if that previous paragraph read like mumbo-jumbo, simply perform the CSS test below, try the training sessions and notice how you get progressively faster as the weeks go by!

CSS training focuses on your ability to sustain a strong pace
over your race distance.

The CSS Test

The first thing you need to do is find your CSS pace using the CSS test:

1) Perform a thorough warmup, progressively bringing your heart rate up.

2) Time yourself over a 400m swim, swimming as quickly as you can. Make sure you pace it out well but go as hard as you can - this is a time-trial!

3) Then take 5 to 10 minutes to recover, swimming some very easy laps to help flush waste products from your muscles.

4) Now time yourself over another time-trial, this time 200m. Go as hard as you can again!

5) Swim an easy cool-down to recover before hitting the showers.

Finding Your CSS Pace

The first thing to check is that you swam the 200m at a faster time per 100m than the 400m. This should always be the case as it is a shorter distance. This is essential or the calculation will not work!

Then take your 200m and 400m times and use the free calculator here to find your CSS pace: www.swimsmooth.com/csscalc

Or use SS Coach Steve Casson's excellent Swimulator+ iOS app: itunes.apple.com/us/app/swimulator+/id527165536?mt=8

Both of these will give you your CSS pace per 100m which you then need to train at. If you're using a Tempo Trainer Pro to help set this pace accurately (see below), also take note of the time per lap the calculator gives you so you can set that in the beeper.

Simply put your 200m and 400m times into the The Swimulator+ app and
it spits out the CSS pace to go in your tempo trainer - neat!

We recommend you re-test yourself every 4 to 6 weeks to see how you're improving. Improvements of 1 or 2 seconds per 100m are significant in well trained swimmers but for those new to fitness training, taking off 5 or 10 seconds per 100m is quite normal (or in some cases even more than that).

Using A Finis Tempo Trainer Pro

At Swim Smooth we're big fans of using a Tempo Trainer Pro to help pace you accurately through CSS sessions. You simply set it to your target pace per lap, pop it under your swim cap and then stay with the beep as you swim.
Simply take the time per length from
the calculator and set it in the beeper.

For example if you want to target 2:00/100m in a 25m pool you set it to beep every 30 seconds, then simply set off on a beep and make sure you turn and push-off on each beep. Stay with it and you're guaranteed to accurately swim at 2:00/100m with perfect pacing.

You can also use it to time your recovery between swims. To do that finish a swim and touch the wall on the beep, then wait until the next beep and immediately set off again on the next swim. We call that 'one beep recovery'.

Tempo Trainers are brilliant training partners and a lot simpler than using the pace clock! More information here: Finis Tempo Trainer Pro

The Goldilocks Set

There's plenty of examples of CSS sets to follow in the Swim Smooth Book and our Waterproof Training Plans but here's a good first session to try, the classic Goldilocks Set.

After a thorough warmup, swim the following straight through, all at your CSS pace:

Baby Bear
2x 100m + 20 seconds rest (or 1 beep)*
1x 200m + 20 seconds rest (or 1 beep)

Mama Bear
2x 100m + 20 seconds rest (or 1 beep)*
1 x 300m + 20 seconds rest (or 1 beep)

Papa Bear
2x 100m + 20 seconds rest (or 1 beep)*
1 x 400m + 20 seconds rest (or 1 beep)

* to create a longer set, increase to 3 or 4x 100m.

You may find CSS pace quite easy at first but stick with it, it will get harder and you should be feeling the pace over the 300m and 400m swims! Don't go faster than CSS pace on the 100s - the temptation will be there - but control your pace instead and in doing so develop your pace judgement skills.

If you find you cannot sustain the pace for the whole set then rather than taking additional rest, swim very slightly slower to keep things manageable. Don't take things too easy though, you should be working really hard in the second half of the set!

CSS vs. Traditional Masters Training

Compared to traditional master swim sets, CSS training involves swimming at a slightly (only slightly!) slower pace but with much shorter recoveries between each swim. This keeps things focused on developing your aerobic system, which is what you need to become a better distance swimmer.

The problem with sprinting hard and then recovering is that it focuses much more on your anaerobic system, which is great for sprinters but far from ideal for distance swimmers and triathletes.

For more information see our classic blog post Becoming A Diesel Engine and the main CSS article on the Swim Smooth website: www.swimsmooth.com/css

Meet Mega Megan!

She looks innocent enough but Mega Megan's rapidly
become a swimming machine... and she's not done yet.
As a great example of what CSS training can do, watch out for a forthcoming blog we're writing featuring SS Perth squad swimmer Megan Surrette.

Over the past 18 months Megan has gone from a complete beginner in the pool to swimming the mighty 19.7km Rottnest Channel swim!

The mainstay of her training? Consistent CSS training sets week in, week out which have increased her CSS pace from 2:18/100m to 1:36/100m. A fantastic level of improvement!

18 months ago she would never have considered this sort of training thinking it 'too advanced' for her but quite the opposite was true, she needed consistent CSS training to build her swimming engine - which for her was even more important than for an established swimmer.

More about Megan's experiences and exploits are coming in a few weeks time...

Swim Smooth!


Anonymous said...

What do you recommend as a thorough warm-up?
Thank you -

Anonymous said...

A question regarding the recovery time ; if for e.g. CSS Pace is 2min /100 metres , and one is swimmimng in a 50 metres pool , so the beeper is set every 30 seconds so it will beep at each end of the pool and the halfway 25 metres mark - then the one beep recovery is 30 seconds rather than the 20 seconds recovery as suggested in Cinderella set for e.g. , doesnt this.adversely affect ones improvement compared to a 20 secs recovery?
I know you can press the relevantl button on the Finis Temp trainer to reset but this seems a bit fiddly and difficult as its under the swim cap.?
Would love to know the answer to this, thanks .

Adam Young said...

Hi Anonymous1,

Between 600 and 1000m with a mix of continuous swimming and drills. You might like to do a mini-build towards the end to bring the speed up towards the 400m TT pace.

Hi Anonymous2,

Yes the rest with a beeper is slightly longer than ideal in the case of 100m intervals, this is a small disadvantage of using the beeper.

In the Goldilocks set the 100s are really about dialling in the pace with the business end of things being the 200, 300 and 400m efforts. The pacing advantage of the beeper for this outweighs the disadvantage of a slightly long recovery.

Once you're swimming 200, 300 or 400+ the 30 seconds rest is just fine as the work/rest ratio is good, it's really only on 100s it's a touch long.

Hope that answers your questions,


Anonymous said...

Looking for clarity!
My understanding from the comments is that when using the Tempo Pro to improve my pace I should aim at a recover time of 20secs.
Presently I have my Tempo Pro set at 28secs. 28@25m, 56@50m, 84@75m & 112@100m.
So is your suggestion that to improve my fitness session I should rest for 20secs?
I get this however the tempo beep will be 28 not 20. Or do you suggest I re calibrate my session and aim for 20@25m, 40@50m etc.
Thanks for assisting.......

Adam Young said...

Hi Patrick, I think my answer to anonymous2 above answers your question?

Cheers, Adam

Anonymous said...

Hi Adam
I have just done the time trial for my CSS , (25m pool) 400- 7.35 and 200- 3.34 wich gives me a CSS of 29.50. This is slower than my average time for the 400 m. Is this correct as I was expecting it to be somewhere between the 200 and 400 times.
Thank you
Confused in Brisbane

Cyndy@swimsmooth said...

Hi Anonymous 3,

Your CSS pace is all about the rate of drop off. The calculation looks at not only how fast you are but how much you are slowing down between the 200 and 400m distances and assumes this drop off will continue, therefore it is your approximate maximum speed over 1500m.

Think of this as whether someone has a bias for sprinting or distance swimming. The sprinter will be faster over shorter distances but fall away over longer ones – really this has to be the case or the 100m world record holder would also hold the 1500m record.

There’s a little more about this in our classic blog post here: http://www.feelforthewater.com/2013/01/becoming-diesel-engine.html

I hope that helps explain the result?
All the best with your swimming and races!

Neil said...

My CSS is 1.51 per 100m. I'm using the Finis Tempo a 27 sec/25m which is a little faster than my CSS, but ok. I think I'll be ready to aim for a faster CSS fairly soon, but am a bit daunted by the fact that the Tempo only allows me to reduce the 25m time by a minimum of 1 sec - i..e a step up from 1.48 to 1.44 per 100m! Any advice on how to handle this?


Paul said...

Hi Neil, is it the yellow Tempo Trainer Pro? If so, use it in Mode 1 as this is programmable to 1/100th second precision - sweet!


Neil said...

Got it Paul - thanks!

Anonymous said...

Hello. I train in 2 pools - one is 25m long and heated, the other 91m and unheated (currently 17 celcius, I don't use a wetsuit). Will CSS tests done in one pool work for the other, or should I test in both?


Anonymous said...

Do you have any thoughts/advice for CSS pacing i OW sessions?

Anonymous said...

I train primarily for Open Water events(distances between 2,5 and 10K). Should I do CSS(Test and swim sessions in the pool) with sighting, which is the real condition in OW and it impacts the speed?

Cyndy@swimsmooth said...

Hi Anonymous,

Generally your CSS sessions will be in the pool, so it's great to make your testing specific for that so you know what speed to train in the pool environment. One nifty way you could use CSS training in the open water is to set your GPS watch to beep every 100m, and your tempo trainer at your CSS pace, and see if you can swim getting the beeps to synchronise. Give it a go!

Unknown said...

This is cool to learn about. I loved swimming since I first started training. I was on the swim team in high school, and then I stopped swimming for many years. I want to get back into it now, so I'm thinking about CCS. http://brisbanebaysideswimsquad.com.au/swimming-squad-times

michael b said...

hello got my tempo trainer pro today and think its great
did 12x100 to test out at CSS
(my 400/200 time trial gives me a CSS 2:19 and 35sec/25yd.)
QUESTION- i rested one beep - 35s as suggested in one of the workouts on the site for convenience
but the workout specifically says rest 10 sec.
1- will i lose any benefit if rest interval too long? 10sec vs 35sec
2- how do i stay on 35 sec pace if i am only resting 10 sec of the 35 sec recovery interval and the device is under my hat and i don’t pull it out to manipulate?
thanks for any advice!
michael b

Adam Young said...

Hi Michael,

Yes 35 seconds is a bit long recovery for 100s, you really need to keep it short if you can.

You can reset the beeper, causing it to beep immediately, by pressing the top button. If you position it carefully under your cap with the top upwards you should be able to feel it with your fingers and press the top button through your cap. Time the 10 seconds using the pace clock at the pool and press the button and you should be away!

I hope that helps,


Bryant said...

Hi Adam,

One year of on and off self coached swimming under my belt, swim around 1000-1600 per workout, 3 times a week. Just bought swim smooth book and did the CSS. Interestingly, the CSS ended up being 2:07 (400 7:58, 200 3:45), which is slower than my easy warm up pace (normally I hit easy 50's in around 59 seconds with 5-10 seconds rest, a 200 in around 4 minutes, a few quick (for me) 25's in 18 to 20 seconds). It feels very difficult to keep alignment and tautness in the water at the 2 minute pace, which may be a function of only using a 2 beat kick (working on 6 beat after reading the book). My question is, should I even worry about CSS sets at this point, or just do easy technique sets until my yardage is 2000/swim?

Thanks much,

Unknown said...

Hi Bryant,

Are you getting a good balance to your training? It's worth bearing in mind that you need a mix of technique and fitness work, particularly threshold work, which these shorter distances you're faster over aren't since they're not aerobic. You should be able to start increasing your volumeto 2000 yds now, which will help you train to maintain good form over the longer distances too. This article might explain in more detail for you: http://www.feelforthewater.com/2014/05/mega-megan-going-from-212-to-132-100m.html and http://www.swimsmooth.com/training.html hope that helps!

Dean said...

Hi All,

A question about the CSS test, I have basically just started swimming and have almost completed the Boot camp, now I have to do the CSS test, but I cant swim 400m without stopping.
So my question is, can the test still be performed with a small (10-20 breath) rest? I can do the 200m with out stopping, so I should be ok there.
I realize the CSS pace that I get will not be totally accurate, but will it be ok to use as a starting point until my endurance improves?
Absolutely loving the "app", very clear and loads of information, great job SS!!!!

Unknown said...

Hi Dean,

My advice would be to pace yourself from the start to avoid needing to take a rest at all, and ensure that you are constantly exhaling. If you do this then really you shouldn't feel that much different as you carry on past the first 200m mark! If you need to pause, just try and keep it as short as possible. I hope that helps!

Anonymous said...

Hi Swim Smooth this is awesome thank you! I have a question regarding something you will probably like. Someone who is swimming 5-6x a week! Can you please give me an idea of what that might look like? 2 CSS swims? 2 long continuous? 2 short interval swims faster than CSS? Thank syou!

Anonymous said...

I was explaining a Goldilocks set to my daughter (nearly 8) and after I'd explained the 3 Bears, she asked "But where is Goldilocks?"

Adam Young said...

LOL, you mean she bear-ly understood? :)


@crispinswims said...

Great post, as always. I'm training for a Rotto solo and have started incorporating CSS into my training.
Did test at weekend, which gave me a 1'57" CSS. Doing the Goldilocks set (4x100 sets and baby, mama and papa) I was pacing carefully...but wasn't too stretched even in the 400 at the end. Was more than 10s ahead of the beep in the final swim. Should I return to the test again? Or keep training with same CSS for a bit longer. Thanks!

Paul said...

Hi @crispinswims - exciting that you're doing Rotto! Have you seen our full Rotto program? http://www.swimsmoothperth.com/#!rotto-program/cjl8

I'd recommend dropping your CSS down to 1'54" for next week and seeing how you go there. Each time you make it through a CSS session like you've done there, don't be afraid to drop it down a smidgen. 3s is quite a jump - but you can handle that - these margins will get smaller of course as you move towards 27/2/16!

Keep up the good work and make your own luck!


Unknown said...


Bit baffled as to why the CSS becomes quicker for a slower 200m and the same 400m . For example on a recent CSS test I did 9:07 400m and 4.12 200m which gave a CSS of 2:28. However if I keep the same 400m time of 9:07 but put in a SLOWER 400m time of say 4.33 then it give s a FASTER CSS of 2:17.

Why is this so as it doesn't seem to make sense to me?

Unknown said...

ah..... having now read your Becoming a Diesel Engine post it all becomes clear at last!

Adam Young said...

Hi Cheryl, yes it's a bit mind-bending but important to understand!


Anonymous said...

Hi there,

thank you so much for the excellent Swim Smooth site which is a constant source of inspiration and motivation. I read about the css training, understood the concept and bought the Finis Tempo Trainer. Then I did the CSS test which gave me a CSS pace of 2:02.
Today I just wanted to test swimming att CSS pace and got very confused actually. Swimming in a 50 m pool, I needed to hold 61 secs per length which I found very hard to do. I struggled to reduce my speed and ended up with a stroke rate of 45/min which felt very strange and unbalanced. I feel much more comfortable with 60 strokes/min but end up with 45 sec/length which is too fast and which at my current level I definitely couldn’t hold for 1500 m. So what am I missing; what am I doing wrong? I just don’t want to turn into an over glider just to hold the css pace? Any suggestions are very much appreciated.

Kind regards from Sweden!

Adam Young said...

Hi Sven,

Something went wrong with your test!! What were your 200 and 400 times?


Anonymous said...

Hi Adam,

400 m at 7:32
200 m at 3:28

CSS 2:02/100m


Adam Young said...

Thanks Sven. So what's happened in the test is that you swam the 400 at a much slower pace than the 200 - in the business we call this a 'big drop off'. The calculation is predicting this drop off in speed will continue the longer you go until at around 1500m (approx CSS pace) it is around 2 mins/100m.

However, 2 mins/100 or thereabouts sounds too slow for you - so my suspicion is that you can actually swim the 400 at faster than 7:32. How hard did you push during the test? Could you go harder or did you push too soon and blow up a bit?

Let me know!


Anonymous said...

Hi Adam,
thanks a lot for your immediate answers. I guess your analysis is exactly right. I timed myself with a
Garmin device and the recorded lap paces show exactly what you suggest.

50 m pace: 1:39 min/100m
50 m pace: 1:42 min/100m
50 m pace: 1:50
50 m pace: 1:57
50 m pace: 2:00
50 m pace: 2:01
50 m pace: 2:03
50 m pace: 1:56

Well, not exactly a steady pace. I guess the big challenge, especially for relative beginners like me, is to hold a steady pace but at the same time swim at a maximum effort.
What du you suggest? Obviously I have to do the test again. Should I use the tempo trainer to do the test?

Also when performing the 400 m time trail I could not maintain bilateral breathing and my stroke technique suffered quite a lot (this is what i felt at least).

Thanks a lot for your help Adam.


Adam Young said...

HI Sven,

OK yes, definitely set off too fast there!

> I guess the big challenge, especially for relative beginners like me, is to hold a steady pace but at the same time swim at a maximum effort.

Yes this is that pace judgement that you need to develop. It should feel like a gradual crescheno, see: http://www.feelforthewater.com/2013/05/the-gradual-crescendo.html

I'd recommend trying to set off at 1:50/100 for the first 100m (you can set a tempo trainer to that pace), continue until half way and then see what you have left over the second half.

Go for it!


Andy Mac said...

I love the clear training guide that CSS offers, but just need to check something:

I completed the 400/200 test a couple of months ago and came in at 6:12/3:00 respectively giving a CSS of 1:36/100m.

I've had a pretty decent 8 weeks of CSS training with beeper in hat and repeated the test again today, my times came out as 6:09/2:57 which again results in a CSS of exactly 1:36/100m.

Playing about with the calculator if I'd been slower for the 200 eg 3:02 the CSS time drops markedly to 1:34!

To train in a zone for maximum improvement should I stick with the calculated CSS despite an improvement in both times?



Cyndy@swimsmooth said...

Hi Andy, I think you will find this helps answer your question:


Well done on the improvements!


Andy Mac said...

Link explains all. Thanks!

In essence I should work to the calculated CSS and with the goal over the next couple of months being to narrow the gap between my 400 and 200. Perhaps what's part of what has happened is that I calculated the CSS in the 25m pool and a decent chunk of my sessions have been with the pool at 50m... and I've been pushing too hard to hit the designated CSS times.

I've completed the CSS twice this week... once in the 50m pool and then again in the 25m pool... CSS 2sec slower in the 50m pool... which matches what your describe in the link. As you'd expect I was gutted to be slower than 2 months ago... hence the repeat test and all these questions.

Red mist sessions on the menu...



Adam Young said...

Definitely on the right track now Andy - go for it!


Anonymous said...

Hi, I'm an intermediate swimmer who has swum all my life - not competitively - but just in a pool and the sea for fun. I'm comfortable plodding along for 1-2km. But at 43 I've started training for triathlons and am discovering that the way swimming is taught these days is quite different from when I last had lessons when I was about 8 years ago!
I am enjoying the challenge of trying to learn to swim again - and thanks for all the Swim Smooth advice. I have a finis tempo trainer and am just starting to use it, but I swim in two different pools. One is 25m, and the other is (frustratingly) only 16.5m. Do you know if it will work to simply divide my CSS by 25 and multiple by 16.5 for use in the smaller pool?

Adam Young said...

Hi Tania,

Yes dividing by 25 and multiplying by 16.5 is the starting point for sure.

However, depending on how good your turns are, you might well find that you are able to swim faster in the 16.5m pool as the push off accelerates you at the beginning of each length. If you find this then remove a little off your CSS pace in the shorter pool - it could be you are as much as 3-4 seconds per 100m quicker! We don't have a standard figure to give you here as it will depend on your individual swimming but experiment and see.

Let us know what you find.


Ali said...

Hi - been using CSS with a squad with some really good returns. However I have one guy who hits the same pace for both his 400m and 200m. He is very fit and does a lot of endurance work. I don't believe he is holding back at all on the 400m. But it means his CSS pace is his race pace and he struggles to maintain it over longer sets e.g. golidlocks? Also his pace is not improving.
I am wondering what would be best for him e.g. a different test, what pace to work at for CSS sets etc? Appreciate any help you can offer.

Cyndy said...

I am assuming you meant to say he does not hold back on his 200. There are some swimmers that are such diesel engines they can maintain their pace over a longer distance but have no change in speed with the shorter distances. However doing exactly the same pace as you have seen will affect the outcome on the CSS calculator as most people will have some drop off. One, I would have him working on some more sprints so he does improve on his top end speed. The second thing you can do is just bump up his CSS pace around 3 - 5 seconds per 100 and see how he does on the CSS sets. Then gradually bring it back down as he improves. Let us know how he goes. Regards Cyndy

Ali said...

Thank you Cyndy - I shall try your suggestions and see what happens!

Cyndy said...

Great Ali be sure and let us know how it goes and if you have any other questions. Regards Cyndy

Unknown said...


I have been swimming 6 months now with some coaching, but I am just about able to do 50m, with about a 20 second rest. I just keep grinding away at that and do 2k in bout an hour

Clearly I cant swim the distances you are talking about for your tests, so how can I improve my swim fitness in your opinion?


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