Pool pacing
Pool pacing
Training > Swim

How to pace pool-based swims

Understanding your lactate threshold and Critical Swim Speed is key when there's no-one to pace yourself against, and can deliver big gains in speed efficiency

Have you decided to enter a pool-based triathlon but are wondering how to pace yourself on race day? Fiona Ford explains how becoming familiar with your individual 'race pace' will ensure you don't burn out early.

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Pace judgement is one of those key skills in swimming or multisport, and distinguishes experienced or elite swimmers from intermediate and amateur swimmers. The best way to approach pool-based swims is to understand your individual lactate threshold, in terms of pace per 100m. Train systematically at or slightly below your lactate threshold to develop confidence and ability to set and maintain a strong race pace.

Start by identifying your Critical Swim Speed (CSS). Do a timed swim over 400m and 200m as fast as you can sustainably manage, taking a short rest in between. CSS is your lactate threshold speed, expressed as pace per 100m. 

Implement sets of 100m, 200m and 400m at CSS with short recoveries as your ‘quality’ swim session every week. Aim to swim the set evenly and challenge yourself to maintain pace towards the end of the session. Avoid over-pacing the early part of the set and suffering the disproportionate drop-off in speed towards the end.

Practising sustaining CSS in training will lead to impressive improvements in speed efficiency. Additionally, you’ll become familiar with ‘race pace’ and confident judging your sustainable speed over a given distance, independently of other competitors in pool-based events.

(Main image: Jonny Gawler)

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I understand the need to calculate CSS but the article doesn't give details of how to do this. Is it the average pace of the 200 & 400m sustainable speed swims expressed as pace per 100m?


Take your 200m time away from your 400m time and that gives you your CSS over 200m. Divide by 2 and you get your CSS per 100m

CSS should be challenging or at least  sustainably hard. Don' try & put time in the bank during a CSS session -keep the pace even throughout. Try and do one session per week. Reduce your CSS by 0.25 to 0.5sec every week to improve but monitor how you are doing as you may improve quickly or not


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