Critical Swim Speed (CSS)

Including:- Constant, Varied, Shuttling and Endurance Sessions.

We appreciate that some terms in swimming can be confusing - here we have a glossary to explain them.  If you feel any are missing, please let your coach know and we will update the page.  This is more effective than having them on the session descriptions in TP as we would need to update hundreds of sessions.  

Below is the description of this specific session type, the aim, how to execute them etc

Intensity

We keep intensity simple in swimming.  It can be overly complicated.  

Easy (Ez): Warm-up or active recovery.  This should be a very comfortable intensity.  

Extensive Endurance (Ext End): Describes most intensities below your CSS.  STEADY in the description means an easier aerobic effort; TEMPO is a stronger effort akin to your 60-70min swim pace. 

Critical Swim Speed (CSS) : Threshold swim pace. Derived from a CSS test session, this equates to your 20-30min best effort. 

VO2max (VO2): Describes your ~5-minute best pace.  For convenience, we refer to this as 200, 300 or 400PB time, ie if it takes you 5min to swim 300m, your VO2 pace is 1’40. if it takes you 5m30s to swim 300 its 1’50.

Speed (Sp): Describes a pace above VO2max, roughly 50 -100m best-effort pace. 

Max is self-evident.  The fastest you can go. 

Descend - get faster rep to rep.

Build - pace accelerates within every rep. 

Varied - the pace within a rep varies sharply, unlike build, where it gradually accelerates. 

Other terms

Fc-Bk = Mix free and backstroke. 

SKPS = Skim/kick/pull/swim in equal measure

P&P = pull and paddle

B3 (or another number) = breathe every 3 strokes

PBA = Pull Buoy between Ankles 

CSS +2s (or another number) = 2s per 100m slower than CSS

CSS -2s (or another number) = 2s per 100m faster than CSS

Rolling = within a rep, there will be faster and easier efforts.  The fast will roll through the reps - i.e. 4 x 100 rolling 25 Fast  - in rep 1 the fast is the first 25m, and the rest of the 100 is easier.  In rep 2, the first 25 is easier, then the fast 25, then 50 easier.  And so on.

Watch or no watch?

Here at ITT, we love our data just as much as we love hearing from you. Except in swimming! Swim data from watches is not like data from a power meter or GPS watch. Training Peaks doesn’t really handle it very well (no other platform does either). Small errors in timing are common but significant.

If you want to wear the watch, wear it; it can help you to perform the session, but if you don’t want to wear a watch, don’t. We like to hear your view on how the session went, the ballpark times you hit on significant parts, and how you found it. As coaches, this means much more to us.

Learning to use a pace clock can be more effective and enjoyable experience for your sessions.

CSS Session Types

  • Constant

    In these CONSTANT sessions, you are aiming for a pace that is consistent through the session, no matter the length of the rep or the number of them.

    The main set pace in this session is going to be largely at or slightly above CSS.

    Don’t try to beat these sessions; swimming too hard is counterproductive. The pace in the initial stages should feel controlled; remember CSS is a pace you can hold for 20+ minutes consistently.

    Fatigue should start to make it harder and harder to maintain the pace, and this is where you will need to concentrate.

    You can count strokes to ensure the quality of your stroke is maintained. An increase in stroke count, even if the time is the same, shows a degradation in technique.

    Sessions will range from 2000 - 4500m, with the main set portion aiming to take approximately 35 - 40-min.

    The longer sessions are more advanced and may include other aspects for more conditioned swimmers.

  • Variable

    VARIABLE sessions are still aimed at around CSS pace, but they may include harder or easier reps to create variation in pace, so you dont get stuck at one pace and for a change in physiological stimulus.

    When performing these sessions, ensure you do change pace. Without the change you will not reap the full benefit of the session. It is very common to see swimmers swimming the EASY to hard and the harder parts not hard enough.

    In the early stages of the session the paces should come relatively easy, this is the danger time when you can fooled into swimming too fast, and then by the end of the session fatigue creeps up and you can no longer hit the times.

    It is the end of the session that counts the most, not the beggining.

    Sessions will range from 2000 - 4500m, with the main set portion aiming to take approximately 35 - 40-min.

    The longer sessions are more advanced and may include other aspects for more conditioned swimmers.

  • Shuttling

    SHUTTLING session use a short block of work above CSS followed by a longer continuous block of work, easier than CSS. The aim is to increase O2 cost, lactates, etc, then have an active endurance block to train the body to manage this better, improving your recovery and driving up CSS.

    To make the most of this session you MUST ensure the block slower than CSS is slow and controlled enough, otherwise you are just driving fatigue. Unless otherwise stated it is OK to use FINS, Snorkels, or PULL BUOYS to help manage this block.

    In the higher intensity parts, you need to commit, but not over commit, its not about beating PB or the session, its about pace and effort control.

    Sessions will range from 2000 - 4500m, with the main set portion aiming to take approximately 35 - 40-min.

    The longer sessions are more advanced and may include other aspects for more conditioned swimmers.

  • Endurance

    CSS ENDURANCE sessions are designed and intended to build your fatigue resistance at CSS pace, not specifically to improve the CSS pace.

    The execution is similar to CONSTANT sessions, but these reps are usually longer and/or with much shorter rest.

    Somtimes you may be asked to build the session, ie. start slightly slower and build the pace rep by rep. It will likely only be by a few seconds as the idea is to hold a pace very close to CSS for a longer time than you could in one continuous block, but you will accumulate much more distance.

    Sessions are often very simple in nature i.e 10×200m or 10 × 300m all at the same pace. No toys, not much variation. It might not be sexy, but it works!

    Sessions will range from 2000 - 5000m, with the main set portion aiming to take approximately 35 - 40-min.

    The longer sessions are more advanced and may include other aspects for more conditioned swimmers.