build swim endurance
Credit: James Mitchell
Training > Swim

Swim session: How to build race endurance in the pool

Here's how to introduce longer interval sets in your swim training to build race endurance for every distance

When training in the pool, it’s easy to forget that the tri swim is endurance-based, requiring both an efficient technique and subtle pace awareness/control. So including regular, longer interval sets in your swim training is vital. But how long is long? At what pace? And how can they be made fun?

For sprint/standard-distance racing, repeat intervals could vary from 300m-800m, and for long course 400m-1km, depending on the focus. Pacing for endurance intervals may vary depending on your goal, e.g. swimming a longer interval at an easy aerobic pace allows you to focus on technique,  build base endurance and support active recovery. Whereas swimming closer to race pace over longer intervals challenges pace control and efficiency under fatigue.

Swimming with a similar ability partner or group, as drafted swims and/or inc. ‘Aussie exits’ (climb
out and stand up before re-entering the water safely), can make the challenge of longer intervals great fun. This session has it all!

Richard's top three tips

Draft in training

A challenging and effective way to swim your endurance intervals and keep on pace is to ‘swim on the draft’ in pairs or a group, alternating the lead swimmer.

Record your splits

Analyse your 100m split times over longer intervals to gauge your pace control. Record at which point fatigue kicks in to achieve faster swim average speeds.

Calculate your pace

It’s easy enough to smash out a fast 50m, but endurance swimming requires subtle pace awareness/control, so use training aids to achieve consistent pacing.




200m build swim

30secs rest

4 x 50m kick

15secs rest

4 x 50m as: 25m scull; 25m swim

15secs rest


600m at 95% of your 750/1500m race pace with ‘Aussie exit’
every 200m

1min rest

6 x 100m at 105% of your 750/1500m race pace holding pace

2mins rest

600m at 95% of your 750/1500m race pace with ‘Aussie exit’
every 200m

1min rest

6 x 100m at 105% of your 750/1500m race pace holding pace

20secs rest


200m easy

Mixed strokes

Adapt for beginners

Reduce the long swim intervals down to 300-400m repeats and reduce the number of 100m reps. The % swim paces should reflect your target race-distance pace.

Adapt for Ironman

Increase the long swim intervals up to 800m-1km repeats and increase the number of 100m and/or sets completed. Adjust your % swim paces.


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